Precision Reloading: .308 Win Example

Started by gitano, August 23, 2009, 11:22:49 PM

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gitano



In another thread, we got to talking about various light-for-caliber (hereafter LfC) .308 Win loads and I mentioned that I was working up some loads for resized pistol bullets weighing from 60 to 90 grains. Egged on by the ever-willing-to-egg-on here at THL, I said I'd start a thread on the matter once I had more to offer than just how to 'squeeze' bullets. While I haven't been to the range yet, (you'll see why soon), I have got a good enough start on the process to start this thread.
 
Since the .308 Winchester is one of my 'most favoritest' cartridges, I thought I might as well wring every last drop of precision I could from this exercise. Knowing that I'd be facing the slings and arrows of nay-sayers and skeptics (not THL folks, but those that might visit), I decided to exercise all the quantitative 'muscle' I could muster. I want the results to be as unambiguous as I can get them. Meaning... I want to minimize the comments about various sources of variability by eliminating as much of the variability as I can and quantifying the rest as much as I can. Strap in, 'cause it's gonna be 'dense'.
 
My desire with the LfC bullets is to get 'good energy' (lethal doses - 1000 ft-lbs minimum for white-tailed deer) down range with as little recoil as possible. I spend much of my time with women, young, and inexperienced shooters, and recoil is a very real issue for them. Almost as significant as recoil is "lethality". My opinion on the matter of lethality is that the less experienced the hunter, the more psychologically importantit is for the animal hunted to be killed with one clean shot and not have to be chased. The 'experience' is not as "good" if the animal is found dead even shortly after having been chased than if it had been killed "in its tracks". Hence the search for a .308 Win load that is "lethal" on the pointy end, yet "friendly" on the blunt end.
 
When reloading, one often starts with bullet selection. In this case the suite of bullets from which I was going to choose was:
 
.312", 60, Hornady HP/XTP 32010 swaged to .3085"
.312", 60, Speer HP GD 3986 swaged to .3085"
.312, 71, Sierra FMJ FN TM RN 8010 swaged to .3085"
.312, 85, Hornady HP/XTP 32050 swaged to .3085"
.312, 90, Sierra JHC 8030 swaged to .3085
.308, 110, Speer SpirePoint 1855
.308, 130, Speer HP 2005
 

 
 
A comprehensive search for the best load for 7 different bullets would be very labor-intensive. (Turns out, it’s pretty darn labor-intensive for “only” 3 of them.) To narrow the list a bit, I started off with QuickLoad (hereafter QL) to see how fast I could get each of them going, and what their trajectories and delivered energies were like. Without boring you with the details of that exercise, the results were that of the resized pistol bullets, only the 85-grain Hornady HP had the ballistic coefficient to 'reach out' to 150-plus yards. I will be going back to fiddle with the others, but for now, the 85-grainer is "it" for the resized pistol bullets.
 
At my recommendation, sakorick has been experimenting with the Speer 130 in his custom .308 Win. Turned out, the 125-grain spitzer shot straighter than the 130 HP for him, so he was going to use the 125 for hunting. I know what that 130 Speer HP can do terminally, so I want to develop a load that is laser-accurate. (I have a ‘good enough’ load, but I haven’t really fine tuned it.) So the 130 is in this mix for this exercise.
 
The third bullet is the 110 Speer Spire Point. It's a good step up from the 85-grainer, and down from the 130-grainer. While not an HP, it will be 'screaming along', and based on my experience with other similar bullets, I expect its terminal performance to be excellent.
 
These loads are being worked up for use in my Ruger M77 with a 22" barrel so I needed to get precise information about the chamber if I was to get the best estimates from QL. The first order of business was fire-forming a case and getting the exact dimensions for creating a "new" cartridge in QL - the ".308 Win My Ruger". (QL allows the user to create new cartridges based on the exact dimensions of a specific case.)
 
That done, I needed to precisely measure the chamber in order to select a seating depth/overall length for each different bullet. For long bullets, I prefer 1 caliber seating depth - for short bullets, I use 67% of 1 caliber. In the case of the .308 caliber, 67% is 0.206", and since these are definitely short bullets, all of them were going to be seated 0.206" deep as long as the chamber would allow it. Using the Hornady (originally Stony Point) Chamber All, I measured the chamber length from the bolt face to the lands. In this rifle it is 2.288". Clearly, all the bullets could be seated 0.206" deep.
 
The special case (I made this one, but they can be purchased in common cartridges, or you send them one of your wildcat cases) next to the Overall Length Gauge.

 
The gauge with the case screwed on.

 
The case showing the rod that extends inside the case and positions the bullet against the lands when the whole contraption is inserted into the chamber.

 
After seating the bullet against the lands, the gauge is removed from the chamber and the length is measured from the head of the cartridge to the where the ogive of the bullet hits the lands. In this case, 2.288". You should measure this distance for each bullet you use, OR measure the ogival length of each of your bullets.

 
Armed with that information, I could get pretty good ‘numbers’ from QL for each bullet. However…
 
As those of you that have been reloading for some time probably know, “serious” reloaders weigh each batch of cases they get and sort them by weight. While it is rarely, if ever, explained WHY they do this, the implication is that those cases that have similar weights will have similar case capacities. Previously, when I have casually looked at this, I have not found the relationship between case weight and case capacity to be predictable. 'Til now, I haven’t performed a comprehensive examination. Now I have, and weighing cases in hopes of getting cases of similar capacity is an exercise in futility. (Here is one place I expect those ‘slings and arrows’ of which I spoke above to start flying.)
 
I used a sample size of 54 cases. There were cases from three “lots”. Two were military surplus, (White City Cartridge 1984 and Lake City 1993), and one was “civilian” (Federal Cartridge .308 Win HE).

 
I have a scale capable of weighing to 0.001 grams (0.01534 grains). To give you some idea of this level of precision, one granule of I3031 weighs approximately 0.003 grams. So I can weigh with a precision greater than one granule of powder. (That's granule not grain.)
 
To do this “right”, each case had to be prepared identically. First, each case was full-length resized in a Lee resizing die. Then each case was trimmed to 2.010” exactly. Because I would be filling each case with water, each case was “primed” with a spent primer. The primer was inserted ‘backwards’ so that what ever variability between the spent primers was, it was not an issue when inverted. The inverted primer sealed the case uniformly regardless of what type of primer was used.
 
The procedure was:
Weigh the empty case and write the weight on the case.
Tare the scale.
Fill the case with water using a pipette.
Wick off the meniscus so that the water was exactly even with the mouth.
Empty the case of water.
Write the weight of water (case capacity in cubic centimeters (cc)) on the case.
 
Here's a picture of what the meniscus looks like.

 
Here it is after wicking off hte meniscus. This may look concave, but that's an illusion. I assure you the level of water is absolutely flat across the mouth.

 
 
Once the weight and capacity in cc was recorded for every case, I entered all of the data in Excel and performed a simple linear regression. The first regression was with all the cases pooled. Then I regressed case weight on case capacity for each separate case group – WCC, LC, and HE. The results are unambiguous – there is NO relationship between case weight and case capacity within a given cartridge. Of course there will be at least two rebuttals to the above statement.
 
First, someone will argue that the sample size is too small. Wrong. Based on internationally accepted statistical standards, a sample size of 54 is sufficient to determine the magnitude of the variability of a sample that demonstrates the variance of this sample.
 
Second, someone will argue that “good” (read “expensive”) cases from “good” manufacturers would render results that show a relationship between case weight and case volume. While I cannot say with certainty that this is not true, until I see THE DATA that PROVES it, I’m sticking with the results from this random selection of case manufacturers. There are two reasons to do so. First, the process of ‘drawing’ a case requires that a mandrel be used for the inside of the case. Therefore, the most uniform dimension of ANY case should be the volume. As a manufacturer, why spend money on weighing cases to the 0.001 grams, when the volume will be determined by a mandrel? Second, one of the many “givens” of reloading, is that military brass is “thicker” and therefore weighs more, and therefore has a smaller case capacity, and therefore causes higher pressures in non-military firearms. This data says exactly the opposite. The WCC cases are lighter and have higher volumes. Exactly the opposite of what common “wisdom” asserts. Therefore, I am completely unconvinced that “good” cases will have a high correlation between case weight and case capacity.
 
In conclusion on the case weight/case capacity relationship: Don’t waste your time weighing cases. Cases with similar weights will not yield cases with similar capacities.
 
Below you can see the graphs in which are plotted the case weights on the horizontal (“x”) axis, and the case volumes on the vertical (“y”) axis.
 
Here is a graph of all 54 of the cases. As you can see from the legend, the WCC mil-surp cases (green) are the lightest and have the highest volumes. Just the opposite of what gunwriters (ptooey) will tell you.

Note also that there is no way to predict capacity based on case weight.
 
Here are the Federal HE cases alone:

 
Here are the Lake City cases alone:

 
Here are the White City Cartridges cases alone:

 
It should be clear that there is no relationship between case weight and case capacity.
 
Once the case capacity for all 54 cases was measured and recorded, I could use QL and find appropriate charges for each bullet. Theoretically, if I adjusted the case capacity every time I calculated a charge that produced a specific chamber pressure for a given bullet, the resulting muzzle velocities and exit timings would be identical. In fact, that was indeed the case.
 
I chose 56,565 PSI for the upper limit. This figure is the CIP (European) standard for the max chamber pressure for Mauser 98 actions – an action I use frequently. This figure is well below, (about -6%), the SAAMI max of 60,191 PSI for the .308 Win cartridge. At the low end, I chose 52,667 PSI. It is the default value used by QL for the .308 Win cartridge as the “safe” ceiling for the .308 Win cartridge. The third value – 54,616 PSI - was simply half way between 56,565 and 52,667.
 
Having chosen the pressure boundaries, I could input each case’s capacity and calculate the charge that gave the exact (within about 20 PSI) chamber pressure I was looking for. It was tedious, but it proved what I was expecting. Namely, by altering the charge appropriate to the case capacity, I could get each case to ‘generate’ the same chamber pressure and therefore MV and bullet exit timing. This means that small changes in case capacity compensated for by charge adjustment, yields uniform velocities and exit timings.
 
From that point it was simply a matter of setting the charge specific to the case capacity to give either 56,565 PSI chamber pressure, 54,616 PSI, or 52,667 PSI. Each case should then theoretically produce the same MV and exit time. Once that was done ‘on paper’ (in QL), I had all the charges I needed to load 6 cartridges each of three charges for three bullets, or a total of 54 cartridges. (6 x 3 x 3 = 54) In the end, this all took about16 hours to accomplish for the 54 cartridges. And this is why I didn’t get to the range today. J
 
In summary:
I loaded 18 cartridges with the 130-grain HP, and a charge of I3031 to yield chamber pressures of 56,565 PSI (6 cartridges); 54,616 PSI (6 carttidges), and 52,667 PSI (6 cartridges).
 
I loaded 18 cartridges with the 85-grain HP, and a charge of I4227 to yield chamber pressures of 56,565 PSI (6 cartridges); 54,616 PSI (6 carttidges), and 52,667 PSI (6 cartridges).
 
I would have loaded 28 cartridges with the 110-grain spitzer, and a charge of I4198 to yield chamber pressures of 56,565 PSI, 54,616 PSI, and 52,667 PSI, but I found out after I did all the paper-whipping that I only had enough I4198 for 2 cartridges. L I’ll have to recalculate for another powder I have on hand.
 
 
Here is part of the table I created that has the proper charge for every case to produce the specific chamber pressure.

 
I used my .308 Win precision bullet seating die for seating every bullet to the exact seating depth of 0.216.
 
 
Here are pictures of the RCBS Precision Bullet Seating Die.

 

 
Here is a picture of the loaded cartridges:

 
I don’t have a .308 Win-chambered rifle fitted with a pressure sensor or I would use it and get chamber pressure data to test if the theoretical estimates (of chamber pressure) made by QL are accurate. I will be measuring muzzle velocity though, and the MVs can be used to estimate chamber pressures. In other words, the MVs that QL estimates are based on the theoretical chamber pressures. Therefore, if the spread of the MVs is as small, it would indicate that the chamber pressures are uniform.
 
The range I use is closed Mondays and Tuesdays so I can't get to the range 'til Wenesday. As soon as I can, I'll give a range report.
 
I expect questions from everyone, and number QC by drinksgin
 
Paul
Be nicer than necessary.

22hornet

WOW! :eek: So far this is starting out to be one really involed experiment. But, for the short time I have been at THL I wouldn't expect anything less.
 
I have to agree with the case weight / capacity issue. In my experiance it makes little difference if one case weighs more or less than another. Maybe it does make a difference, but there are too many other variables to look at that will also have an impact on the final accuracy of the rifle and these variables are often ignored.
 
My main concern is if the rifles twist will support the shorter lighter projectiles. I only ask this as I remember an article years ago where the author tried shooting .311 71gn pistol projectiles in a 7.62x39mm Ruger M77. He said the projectiles shot excellent "patterns". Is there anyway of working this out or have you already done it? That said I shoot cast 84gn .314 pistol projectiles in my .303 and they shoot around 2" at 50 metres without any load work.
 
Have you placed a velocity ceiling on any of the projectiles?
 
 
What were the energy numbers with the 60gn projectiles? How far short of the 1000ftlbs did they go?
"Belief:" faith in something taught, as opposed to "knowledge:" which is awareness borne of experience.

gitano

#2
QuoteMy main concern is if the rifles twist will support the shorter lighter projectiles.

Well... that depends on what you mean by "support". Reality is, that given two bullets in one caliber with one twist rate, the shorter bullet is MORE gyroscopically stabilized. Period. It's the "law" - law of physics. Put another way, you can't spin a bullet "too fast" as far as gyroscopic stability goes.
 
There are those that subscribe (in small arms) to a phenomenon called "precession". Armchair ballisticians call this "over-stabilization". This phenomenon has been demonstrated in large cannons that shoot large projectiles (2000 lb) 25 miles and beyond. "Out there" at 25 miles or so, the change in point of impact can be measured - in meters. It is impossible to measure at small-arms ranges, even REALLY long ranges like 2000 yds.
 
That said, I am not denying that extremely high velocities coupled with high twist rates can lead to 'problems'. First and foremost is the bullet 'flying apart' due to excessive centifugal forces. This is the problem I anticipate the most for the pistol bullets. For example, a 180-grain .308 bullet in a 1:12 twist barrel doing 2800 f/s has a rotational velocity of 168,000 rpm. The 60-grain bullet in that same 1:12 twist barrel but doing 4,000 f/s has a rotational velocity of 240,000 rpm. The centifugal/centripetal forces in the 60-grainer are WAY larger than in the 180-grainer, and MAY pull the bullet apart. Based on personal experience I doubt it, but it is theoretically possible, and has been reportedly observed.
 
The reason people report - myself included - poor precision ("patterns" instead of groups) with LfC bullets, is, I think, due to the long 'jump' to the lands created by a short bullet in a 'standard' chamber. You may recall that I recently made two rifles - both chambered in the wildcat 8mm Steyr (.376 Steyr necked down to 8mm.) One I called the 8mm Steyr Long-Throat (8mm SLT) and one called the 8mm Short-throated Steyr (8mm STS). The chamber of the SLT was cut with a long throat to facilitate shooting the Sierra 220-grain bullets seated only 1 caliber deep in the case. (It shoots them very well by the way.) The STS was cut with a short throat, so that when seated 67% of a caliber deep, the 125-grain bullets are still 'close' to the lands. I haven't had a chance to work up loads for the STS yet. I'm doing that as I do this .308 work.
 
QuoteThat said I shoot cast 84gn .314 pistol projectiles in my .303 and they shoot around 2" at 50 metres without any load work.
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I would expect better than that even if your rifle has a long throat. How's the muzzle on that rifle?
 
QuoteWhat were the energy numbers with the 60gn projectiles? How far short of the 1000ftlbs did they go?
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Here's a picture of the QL output on that bullet in my case:
 

 
Here's the trajectory for the 85 grainer:

 
Jamie.270 sent me a private note correcting some of my math. I appreciate two things about that. First, that he chose to use PM to 'correct' me. Not necessary, as my skin is pretty thick. It is so thick because I make mistakes and it has to be or I'd be a psychological basket-case. Second, I appreciate everyone 'checking the math'. I do this stuff "offline" then redo it all over again in preparing the posts. It is inevitable that I will make some transcription errors, and in some cases even calculation errors. In this case, Jamie caught a transcription error regarding the nature of the max chamber pressures. Specifically:
 
QuoteI chose 56,565 PSI for the upper limit. This figure is the CIP (European) standard for the max chamber pressure for Mauser 98 actions – an action I use frequently. This figure is well below, (about -13%), the SAAMI max of 60,191 PSI for the .308 Win cartridge. At the low end, I chose 52,667 PSI. It is the default value used by QL for the .308 Win cartridge as the “safe” ceiling for the .308 Win cartridge.
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As Jamie observed, 56,565 PSI is NOT 13% down from 61,191 PSI. In fact, it is only about 6% down. It is the 52,667 PSI that is the 13% down from the SAAMI max of 60,191 PSI PSI. I transcribed my "back down" of 56,565 PSI as the 13% (actually only about 6%) instead of QL's "back down" to 52,667 PSI which is the 13% to which I referred.
 
Thanks for checking my math. Usually drinksgin is my math editor, but I think you snuck in before he saw it.
 
Since this exercise is about 'recoil, among other things', here are some recoil numbers.
 
First, recoil for what I call an American "standard". A 180-grain bullet doing 2800 f/s in a rifle weighing in total (scope + rifle) 9.5 lbs.

 
Here are the same calculations for the 60-grain HP:

 
Here for the 85-grainer:

 
Here for the 110-grainer:

 
Here for the 130-grainer:
[/SIZE]
 
There's a lot of "stuff" on this page. I look primarily at the figure for "Energy of Recoiling Mass".
 
Here's a table comparing the "Energy of Recoiling Mass" for each of the above bullets.
 
180 - 19.77 ft-lbs
130 - 11.63 ft-lbs
110 - 8.99 ft-lbs
85 - 7.23 ft-lbs
60 - 6.04 ft-lbs
 
To give another 'ruler' with which you might judge these values, here's a .223 Remington shooting a 55-grain bullet at in a 8.5-lb rifle.

 
The "Energy of Recoiling Mass" is 3.29 ft-lbs.
 
More later.
 
Paul
Be nicer than necessary.

gitano

By the way...

Since the charges are listed in grams, you probably didn't notice that the difference in charge between the lower chamber pressure figure - 52,667 PSI - and the upper one - 56,565 PSI - is about 1 grain. That means that the chamber pressure in the middle is about 0.5 grains from either the high or low. So... of the 18 cartridges per bullet, I have 6 each at half-grain intervals.

I thought it was interesting that charges that produced the QL max (52,667 PSI), were almost (but not quite), exactly one grain less than the charges needed to produce my max pressure of 56,565 PSI. I am hoping therefore, that one of the three loads (lo - medium - high) will be near a timing "sweetspot". That's why you see the "node=" note on the charge table.

Paul
Be nicer than necessary.

sakorick

#4
During my testing of the 125 grain Nosler loads(308), I purposely shot a 6 shot group with both Winchester and Federal Brass. I fired the Federals first and the Winchesters 2d. I was going to keep a detailed analysis until I realized that I just kept putting holes next to each other! I have had similar experience with the '06 and 243. Some rifles just don't care......I call them "not fussy" and so mark in my book.

I can't wait for the results. By the way, the 125's and 130's kick about like a 30-30. Regards, Rick.
Talk to yourself. There are times you need expert advice.

gitano

#5
I've never found a rifle that "liked" a particular make of brass. The only effort I take in that regard is to try to keep the cases to one manufacturer for a given bullet as much possible. The first graph in the first post shows the difference between manufacturers. In this batch of brass, if one mixed the WCC brass with the FC-HE brass, one could see a difference in case capacity of as much as 1 full grain - 53.09 to 54.11 grains. By the same token, if you measure the case capacity of each case, then the manufacturer is immaterial, because you will be keeping together those cases with similar capacities.

Paul
Be nicer than necessary.

Nelsdou

Pretty thought-provoking stuff there Paul.

I don't have any 130 Speer HPs yet, but I have been experimenting with Alliant Reloader 10-X powder. Cranking the numbers through QL with this combo looks promising; I can hit an approximate node on a 600mm mauser barrel at just less than 52 ksi and MV of 2950 with 100% burn.  Not too shabby.  Pretty light recoil to boot.

What numbers caught my eye was the relatively low pressure at the muzzle.  Less than 6.9 ksi.  IMHO the less blast the better, but thinking about effects on accuracy in regard to residual pressure at the muzzle for LFC bullets, any thoughts?  Would high pressure at the muzzle be detrimental to accuracy for LFCs, little effect, or none?

Nels
Put it into perspective; we live on a rock hurtling through space, what could be scarier than that?

gitano

We're on the same page, Nels. Since getting QL, my desire to find loads that exhibit 100% "burned-in-barrel" has always been more about lowering muzzle pressure than getting the most efficiency out of the powder. Like you, it seems to me that the lower the pressure at the muzzle, the 'gentler' the bullet would be pushed from the barrel. That in turn should minimize whatever defects are present at the crown.
 
That said, the most precise rifle/bullet combo I own is my 7x300 Weatherby, and it 'wastes' a lot of powder with the 115-grain HP. I shot that rifle for years before I realized it was blowing unburnt powder out the muzzle. (115-gr HP in 7x300 Weatherby = large case, LfC bullet, and short 24" barrel relative to case capacity.)
 
One day I was at the range and had laid a 4' x 8' sheet of plywood on the ground out in front of the shooting bench to provide a stable base upon which I set a chronograph. After shooting a few rounds, I got up to check the targets. When I walked by the plywood, I noticed a great deal of unburnt powder on it.
 
At that point, I was convinced that I was 'wasting' that powder, and decided to lower the charge. The muzzle velocity went down, and so did the precision. Since that powder was unburnt, it seemed clear to me that it could not be contributing to muzzle velocity and concluded that it was a matter of combustion chamber volume, so I added a variety of inert materials equal in volume to the unburnt powder I was taking out. Nothing I tried restored the MV or the precision. Finally, I gave up and resigned myself to the 'wasted' powder. While it was emotionally disatisfying not to be able to resolve the technical issue logically, to me the 'wasted' powder was small price to pay for the precision of that rifle/bullet combination.
 
All of this is to say that while my thoughts on the subject of muzzle pressure seem to be the same as yours, I can't help but acknowledge that the most precise rifle/bullet combo I own uses a large cased/light-for-caliber cartridge in a relatively short barrel. A combo in which the powder burnt in the barrel is clearly well below 100%.

This experience is by the way, why I do not consider the 7x300 Weatherby to be a "better" cartridge than the 7mm Remington Magnum (from which I also shoot the 115 gr Speer HP). In my opinon, the modest gain in MV is not worth the substantially increased inefficiency. I do acknowledge though, that there are those that would 'waste' 10's of grains of powder to realize 10s of feet per second increases in MV. In such matters, "each to his own" as far as I'm concerned
 
Paul
Be nicer than necessary.

22hornet

Quote from: gitano;95901
I would expect better than that even if your rifle has a long throat. How's the muzzle on that rifle?
Paul

Thats the rifle that I recently tried to fixed the crown on.
 
I load ADI's AP70, 6.5gns, no filler, 84gn cast round nose.  Barrel is now 18" long. Just a simple plinking load. No idea of the velocity or the energy.
"Belief:" faith in something taught, as opposed to "knowledge:" which is awareness borne of experience.

22hornet

Quote from: sakorick;95909By the way, the 125's and 130's kick about like a 30-30. Regards, Rick.

I love those 125gn Nosler's. About as long as a standard 150gn SP, maybe that is one of the reasons why they shoot so well. After using them I will never go back to a 150gn .308 projectile.
"Belief:" faith in something taught, as opposed to "knowledge:" which is awareness borne of experience.

22hornet

Quote from: gitano;95953At that point, I was convinced that I was 'wasting' that powder, and decided to lower the charge. The muzzle velocity went down, and so did the precision. Since that powder was unburnt, it seemed clear to me that it could not be contributing to muzzle velocity and concluded that it was a matter of combustion chamber volume, so I added a variety of inert materials equal in volume to the unburnt powder I was taking out. Nothing I tried restored the MV or the precision. Finally, I gave up and resigned myself to the 'wasted' powder. While it was emotionally disatisfying not to be able to resolve the technical issue logically, to me the 'wasted' powder was small price to pay for the precision of that rifle/bullet combination.
 

If you are getting the desired results then I can hardly say the powder is being wasted. It might not be doing its primary role, but if the end result is increased accuracy is it really a waste?


All the numbers look good so far but I wonder how light a projectile is too light?  The 85gns certainly look better than the 60gns in all respects except for recoil, but the recoil is so light it doesn't matter.
I wonder if you could put a plastic tip on the 85gn projectile? Or at least do something to improve the B.C.?

I do remember an article on the .303 jungle carbine when the author used the 85gn hornady projectile to develop a light load. I'm at work at the moment, when I knock off in the morning I'll look it up and post the load data. I know it's for a .303 but it might be of interest.
"Belief:" faith in something taught, as opposed to "knowledge:" which is awareness borne of experience.

sakorick

I do not believe that putting a plastic tip on a hollow point will improve the BC of the bullet. Paul????? Regards, Rick.
Talk to yourself. There are times you need expert advice.

subsonic

The plastic tips help, but only because they allow a longer bullet without adding much weight. Plastic is lighter than lead. A plastic tipped 180gr boat-tail will be about .150" longer than a regular soft point boat-tail from what I have measured.
 
I'm having trouble getting plastic tipped bullets to shoot in my .308 right now because they add LENGTH to the bullet and force me to seat the bullet deeper if I want it to feed from the mag - resulting in a much larger jump to the rifling than a similar softpoint or hollowpoint, plus less powder capacity (not really an issue).

gitano

#13
Akshully...

The plastic tip does more than just add length. It substantially decreases the amount of air the bullet has to push. However, there's a real trade-off going on here between the greater aerodynamic efficiency (high BC) of the "plastic-tipped bullet" (PTB) and what I call the "hammer effect" of the large-meplatted hollowpoint. (LMHP).

For close to 100 years, 'old codgers' (hunters) have been extolling the "lethality" of blunt-nosed bullets and cursing the 'pointy' ones. This started right after the Germans introduced the "spitzer" ("pointed", or "spired") bullets in the early 1900s. The Germans did A LOT of work on both internal and external ballistics, and among their findings of improvements was the improved aerodynamic efficiency of bullets with "points". What followed was what has happened ever since "gunwriters" (ptooey) first reared their ugly heads. Taking the military "spitzer" out of context by looking ONLY at one component of its performance - trajectory - they extolled (sold) its virtues as a hunting bullet. The result was that big game animals quit 'falling down' when they got shot. Instead, they started running off and then falling down. The "old codgers" hated this, rightly so, and mean-mouthed all "spitzers". With some justification.

The mis-use of a military projectile for hunting arose from the stupidity of gunwriters (ptooey) to recognize the obvious, in favor of "being cool" by touting some new technology. (Nothing has changed by today, has it?.) The purpose of a military projectile is to "poke" the enemy. It doesn't matter if he dies right there or dies a week later or even dies at all. Wounding is almost as good as killing. Therefore, the farther out one could reach the enemy, (higher BC), the better. "Lethality" was not a high priority. The exact opposite is the case for a hunting bullet.

So, true to form, the hunting-bullet industry took it on themselves to "have their cake and eat it too", and started the research on how to make 'pointy' bullets "work" as hunting bullets. That research continues to this day. Among the latest innovations is the development of the "plastic-tipped" bullet, which is essentially a hollow-point in spitzer 'clothing'. It works. However... My question is:

Does the PTB "work" BETTER than the original LMHP from which it was derived?.

I don't think so inside 250 yds. Performance is close, and close enough to be called a "good", maybe even a "very good", hunting bullet. But I truly don't think it provides the DRT (dead right there) results that the actual LMHP (AKA "blunt-nosed") HP does. This conclusion of mine is drawn from field observations on  big game and the results I presented in the thread on "Work".

So here's the trade-off from my perspective:

The PTB gives considerably better trajectory, especially beyond 250 yds, than the same-weighted, LMHP. The PTB's terminal performance - "hammer effect" - while I believe is only slightly less than the LMHP, IS still less, and I believe it is because of the large frontal area of the LMHP at impact. I think my evaluation of the "hammer effect" as a function of "work" explains the slight differences observed in the field on big game between these two bullet types.
 
QuoteAll the numbers look good so far but I wonder how light a projectile is too light?
That's what I'm trying to find out. :)
 
QuoteThe 85gns certainly look better than the 60gns in all respects except for recoil, but the recoil is so light it doesn't matter.
[/SIZE]Again, I agree completely.

However, I have a "feeling" about the "hammer effect" of a projectile that starts out at over 4,000 f/s. This "feeling" is based on what I have personally seen the .17 Rem do to big game at under 150 yds. It is positively jaw-dropping, and the ONLY characteristic it can be tied to is velocity. Of course the REAL characteristic is impact velocity, but... ANY projectile doing over 4000 f/s at the muzzle will still be going VERY fast at impact at ranges less than 150 yds, regardless of BC.

The BC of the .17 caliber 25-grain HP is about 0.181. That's really poor considering most of today's "hunting bullets, yet it is scary what it does to big game animals. In fact, the single firearm I own that I actually am 'afraid' of is the .17 Rem. It is my heart-felt belief that if I accidentally shot myself in the foot, it would kill me 'instantly'. There's something "magic" about that super-high velocity. I've seen it too many times to deny it.

Which is why I continue to pursue super-high velocity loads for various cartridges in spite of the fact that personally I've grown VERY fond of slow, big around, bullets. Here's the explanation for that apparent philosphical 'conflict'.

The super-fast loads are not for me...

They're for all the women and youthful and novice hunters "out there" for whom I think it is critical that fast, clean kills are extremely important if they are to continue hunting long enough to realize that  Hunting is the point, not what some guy on TV tells you is the purpose of "hunting". If they have to chase wounded animals around the woods, or lose a wounded animal, or have the snot kicked out of them by their Dad's "hunting rifle" as their first hunting experience, the odds are that they're not going to ever get to the place where they understand what Hunting truly is. You don't throw a novice pilot in an F-21 fighter, yet that's what we do all too often when teaching new hunters. I've trained my wife, two daughters, and more. I know what goes on in the novice's head. A good "killer" cartridge and rifle are what novices truly need so that Hunting is the point, not the inadequacies or painfulness of "the tool".

The weather's good, so it looks like I"m off to the range today. Range report later this evening or tomorrow.

Paul
[/SIZE]
Be nicer than necessary.

LLANOJOHN (deceased)

#14
Paul,
 
I agree with you 110%...........!
 
1. 22 LR
2. .222 Rem or .223 or .204
3. .243 Win
4. 6.5x55 Swede
5. .308 Win
6. 338x57 MAI
7. 375 H & H
 
8. 500 big bang ear-ger-splittin'loud-en-boomer mit und grossen hole-in-ground-und alles is kaput!!
 
To me that would be the natural progression, but I personally would leave out #8:eek: :hanged: But thats just me...!
 
As usual,
 
Ol' John:Banghead: :sleeping:
Life Member-NRA-TSRA
Riflesmith-Bolt & Lever Centerfires Only
Left-Hand Creek Rifles
Mark Twain was right-"There is no such thing as too much good whiskey!"
My best advice.."Best to stay outta trees and offa windmills!"

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