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gitano 10-30-2014 12:40 PM

The .17 Predator on a Savage Axis Action
First, here are the "tags" I used for this thread: ".17 caliber, .17 predator, action wrench, axis, barrel profile, chambering, fire-forming, lathe, mill, obt, ocw, optimal barrel timing, optimal charge weight, savage, switch barrel, threading, wildcat". You can use up to 25, so don't be stingy, but try to use words that describe what the main theme of the thread is. However, no need to use words that are obvious: In this case no need for "making stuff", because this is the "Making Stuff" forum.

So, I am back to the shop, picking up 'dropped' projects. At the top of the list of those projects is making a .17 Predator barrel to put on the Savage Axis rifle I have that is factory-chambered in .223 Rem. The primary reason this project is at the top of the list is that I have all of the "pieces" in hand: 27" .17 caliber barrel blank, .17 Predator chambering reamer, lathe, mill, and action to put the barrel on. Having 'stuff' in hand is no small matter when it comes to prioritizing "to do" lists. There was one small item that I did not have on hand; the full-form inserts for cutting 1"-20 external threads. (I have them for cutting 1"-20 internal threads.) However, those are readily available from Ebay, and they should be in hand today.

In my lexicon, "in hand" can also mean "I can make it". And such is the case here because I did not have a Savage action wrench in hand, but I could certainly make one. Of course they are available commercially, but the cheapest price I could find DELIVERED was $86. I'm not going to pay that when I can make one. What the heck did I buy the mill and lathe for if I'm not gonna use them!

This thread is really going to be more about the "making" aspects of this project - lathe and mill setups, solving problems, and the WORK one has to do when one isn't working in a production shop, than producing a new rifle. The details I provide are NOT to "toot my own horn", but rather to demonstrate a couple of things: 1) If I can do it- a guy with no formal machine training - so can you!, 2) "how can I make a 'work-around' if I don't have exactly what the "doctor ordered"", 3) the significance of "order of operations" in metalwork.

I suppose I should give a little background on the cartridge - .17 Predator. Simply put, it is mostly just a .17/.223 Remington Ackley Improved. It was conceived by a fellow named Dan Clements that wanted a longer-range .17 caliber cartridge that could launch heavier bullets (30 grainers) at muzzle velocities that would allow more energy to be carried out to longer ranges. As for me, I just like small, really fast, bullets. :D I've always been a big fan of the .17 Remington. It's an amazing cartridge. This one just has a little more 'oomph'. Like getting a 25-grain bullet over 4500 f/s at the muzzle. :D

This particular project has a 'snakey' ontogeny. It started with j0e_bl0ggs wanting a .17 caliber barrel, and so we went looking, and found some REALLY cheap ones at Green Mountain. Like $50 cheap! So I bought a few of them. ;) Then there were thoughts of putting the Predator on an AR, but after lots of paper-whipping, it was clear that the AR platform - a semi-auto - is really not the right action for a 'hot-rod'. If not AR, I would have to find a cheap action. I have plenty of Mausers, but that meant bolt-face modifications, and long actions, and "big" magazines. No go. The Savage switch-barrels were a logical choice, and I found a WHOLE rifle, "new-in-the-box" for about $280 delivered. An added plus was that I could use the factory .223 Rem barrel too.

All zounds good, no? Well, recall all the hassle I had getting the barrel off of the Savage 110 I have. I fully anticipated the same with the Axis. I wasn't wrong. I wasn't going through that headache again, so first on the docket was making an action wrench.

I have "made a lot of words" here, so I'll stop that and get to "the good stuff" - Pictures.

Here's a link you can look at to see a commercial action wrench:

Basically, it is two pieces of steel profiled to fit the action. In some cases - including mine - there is an aluminum shim between the wrench and action. This provides greater 'grab' and protects the action from the wrench. Took me at least 8 hours of labor to make the wrench, and - I kid you not - I used it for about 5 seconds!

Remember what I said about "order of operations". Since the aluminum bushing has to fit both the action and the steel jaws, the bushing was the first item to be fabricated. The receiver is 1.350" in diameter at the front. Therefore, the bushing had to be close, but just slightly - about 0.005" - smaller in diameter. The wall thickness could be just about anything that wouldn't crush - I decided on 0.200" - making the overall outside diameter (OD) of the bushing 1.75". I started with some 2" OD aluminum round stock:

Notice the 4-jaw chuck. I'll get back to that. It wasn't necessary for this particular part of the fabrication, but I already had it on the lathe, so it was the one used.

Next, came cutting the inside diameter. This is always a pain to me. The main reasons are that inside cutters have to be "flimsier" than outside cutters are. That means shallower cuts, and constant vigilance for 'chatter' because the flimsy boring tool is extended out so it can reach into the work-piece. Quality boring bars are expensive. I'm a cheap 'bloke', and since I don't do TOO much boring, I have a cheap set of Chinese boring bars. They are right on the edge of usable and useless. As it was, I still had to grind the outside profile so that it wouldn't hit the bushing below the cutter. All of which TAKES TIME not spent making the "thing"! Here is a photo of the start of the boring. First a drill point makes a "hole".

Then the boring bar enlarges it to final dimensions. (You'll see the actual boring bar in future pictures.)

Then some checks for fit.
(Note that all pictures so far were taken with cell phone. Taking photos while working is a pain.)

Once that piece is parted off, it's time to start on the steel jaws. The first order of business is to cut the 'long' bar into two similar pieces. I don't have a power hack saw, and unless you have actually cut some 'larger' steel bar stock, you have no idea how long that takes "by hand". That wasn't gonna happen. I took a small end-mill cutter and milled the 'long' bar into two pieces.

As I approached the full cut, I turned the workpiece over and put the uncut part "up". This held both pieces as the final cut was made.

Next, comes making the two pieces "fit" together. That meant milling both of the faces that mate at the same time, ensuring that they would "mate".

And the last step on the mill was drilling and tapping the holes for the bolts that clamp the jaws together. I didn't take any pictures of that because it's "just" drilling and tapping. But it was tedious. Very tedious. You just can't start drilling with the drill size of the final hole dimension. It took four separate drills to get the DEEP holes - 3" - drilled. The holes in the "top" jaw are larger than the bolt shank and aren't threaded. Only the "lower" jaw holes get threaded. Because of the relatively small size of these jaws - 2 3/4" x 3" - there wasn't room for a bolt larger than 1/4". Doesn't matter. 1/4" is plenty big enough.

After the holes were drilled and tapped, and the jaws bolted together to make sure the mating faces were "dead flush", it was time to bore the hole for the aluminum bushing. You can't center a square object in a 3-jaw chuck. Hence the requirement for using the 4-jaw chuck. For those not familiar with lathe chucks, the jaws on a 3-jaw chuck move in and out in synchrony. The jaws of a 4-jaw chuck move in and out independently. Therefore, centering a workpiece, be it round or not, in a 4-jaw chuck is a pain in the rear. HOWEVER, the alternative is NOT DOING IT. Actually, with square workpieces, it's pretty easy to get centered.

Again, started with a 'drill point'

Then moved out to a 1/2" drill bit, then to a 3/4" drill bit,

Then to the boring bar. Remember that the hole had to be 1 3/4" in diameter.


Once it was close, the aluminum bushing was tried until it 'just' fit.

Almost ready to actually USE it! But not quite.

The bushing needs to be parted so that it can "grab" the receiver. All of the commercial action wrenches I have seen us a two-part bushing. That was my plan, but j0e_bl0ggs had mentioned that he often uses only one slit on crush bushings, and after I made the first slit, it appeared to me that a single slit might be best. It was.

I put the bushing on the barreled receiver,

Put the bushing and receiver in the jaws of the wrench, and tightened the bolts. DANG! Making the hole in the jaws EXACTLY the OD of the bushing meant that when they were closed, there was no "clamping" by the bushing. Couldn't make the hole in the jaws smaller, and couldn't make the bushing larger. The only solution was to take a little off of the mating faces of the jaw(s). It didn't matter which jaw face got reduced, so I chose the top one because the holes weren't threaded. I took 0.010" off. This means that BOTH sides of the jaw were 0.010" "above" the mating face of the lower jaw when the bushing and receiver were inserted. Tipping the upper jaw to one side to 'close the gap' on that side, left a gap on the other side of a little less than 20 thousandths.

I put the assembly together again, and voila'!, it 'grabbed' like I knew what I was doin'.

I slipped the barrel nut wrench on the barrel nut

and inserted the 1/2" drive of the torque wrench in the hole in the barrel nut wrench

and 'gave a yank'.

No joy. :angry:

The blasted thing was so tight that the action wrench slipped in the vise jaws. I "leaned" on the vise jaw handle, tightening them as tight as I was able and gave another pull. SAME RESULT. First, some swearing, then reorient the wrench in the vise so that the torque of turning the barrel was perpendicular to the long axis of the vise jaws. The BARREL came off like 'nuthin'. Notice the all-caps on the "barrel". That's because the @#$%^&*ing nut is on the BARREL so tight that the barrel came out of the receiver - with nut attached - the nut did not loosen from the barrel!

In the above dark picture, the action wrench has the receiver still in it, and the barrel WITH nut still on is laying in front of action and wrench. I will have to clamp the barrel in a vice and remove the nut. "Switch-barrel", aye.:angry:

Next comes barrel work. Stay tuned.


sakorick 10-30-2014 12:45 PM

Re: The .17 Predator on a Savage Axis Action
You've really getting somewhere now.....very nice.

gitano 10-30-2014 01:35 PM

Re: The .17 Predator on a Savage Axis Action
You might want to go back and reread the post, Rick. I hit the "submit" button before I was finished with it. The post is now complete.


sakorick 10-30-2014 02:42 PM

Re: The .17 Predator on a Savage Axis Action
I knew what you up to....a Skype poltergeist told me.:toff:

gitano 10-30-2014 03:50 PM

Re: The .17 Predator on a Savage Axis Action
I should also note that another important "piece" I had in hand was loading dies - sort of. In the absence of actual ".17 Predator" dies, Clements suggests using .17 Mach IV dies and fireforming. So, when I bought the barrels, I found some used Mach IV dies on Ebay. i hope to be fireforming some time next week.


gitano 10-30-2014 08:32 PM

Re: The .17 Predator on a Savage Axis Action
Here's a picture of the .17 Predator beside the .17


j0e_bl0ggs 10-31-2014 08:46 AM

Re: The .17 Predator on a Savage Axis Action
4.5k 25 grain, what is not to like!

gitano 10-31-2014 10:42 AM

Re: The .17 Predator on a Savage Axis Action
By the way, I notice the 'tags' at the bottom of the thread, and that they are "hot links". If you click on one of them the THL search engine will find all threads that have that TAG. Unfortunately, this is currently the only thread with those tags, so only this thread comes up. However, if there were ANY threads with the same tag as the one you click on - say .17 caliber - it would be found. That is VERY cool for finding stuff.


PS - AND LOOK WHAT I JUST FOUND - An "Edit Tags" button, with which one can ADD TAGS! I'm off to see if I can "edit" the tags on those threads that didn't get tagged originally.


gitano 11-02-2014 03:48 PM

Re: The .17 Predator on a Savage Axis Action
Here are some pictures of profiling the barrel. The barrel does not have a "finish" on it yet. I will do that last, then I plan on sending it to sakorick for him to black/blue.

This first picture is out of focus, but I didn't realize it at the time and there's no putting the paper back on after it is unwrapped.

Here it is unwrapped:

The end. I prefer to keep this the breech because it has the ID markings on it. Unfortunately, profiling sometimes removes them. In this case, the caliber - .172 - is not stamped, but the rifling twist (1-8) and type of steel (CM for chrome moly) are.

Here it is in the lathe, 'clocked', and the diameter being reduced to the max diameter (1.050") for the tenon/stub that will be threaded and inserted in the receiver.

Here's the muzzle end starting the profiling.

The profile is a straight taper from a diameter of 1.050", 6" ahead of the breech to 2.5" from the muzzle. At that point the barrel will be 0.625" in diameter. Then an increase back up to 0.750" for the last 2.5" to the muzzle. Ultimately, about half an inch will be cut off of the muzzle to get back to "pristine" bore after all of the machining. I'll go into more detail on the profiling and final profile after the pictures.

In the following pictures, the barrel is at its finished profile, but not its final finish. In the first picture, you can see the difference between the rough finish of the tenon and the finer finish of the profile ahead of the tenon. Since the tenon is going to be 1) threaded, and 2) inside the receiver, there's no need for 'polishing' it.

I'm sure the last two pictures have piqued some interest, and I'll explain that, but let me first explain the process of profiling 22.5" of barrel with only 3.3" of travel on the cross-slide. Since it is a constant taper - no curves or radii - one setup on the cross-slide will 'work' from one end of the barrel to the other. However, while 1.050" at one end, and 0.625" 22.5" later may seem like a lot, in terms of 'angles', it's darned 'skinny'. The actual angle of the taper is 0.55 degrees. It is essentially impossible to adjust the angle of attack of the cross-slide to anything even close to half a degree of precision, let alone 5 HUNDREDTHS of a degree. "So what's the need for 5 hundredths of a degree?" you ask. That 5 hundredths over 22.5 inches means a "step" back at the breech, OR too small an OD. However, there is more than one way to skin a cat, and getting the "angle" set correctly simply involved adjusting the total "displacement" of the cutter from one end of the travel to the other. In other words, once I 'did the math" on what an angle of 0.55 degrees meant in terms of 'displacement' over 3.3", I could set the cross-slide angle of attack such that its total movement equaled that figure. In this case, the cross-slide needed to be 0.032" "closer' to me at the end of the cut, (or farther, depending on which end of the travel the cut started). Adjusting to better than 0.001" of precision is easy.

The proof would be in where, length-wise, the taper 'ran out' back at the breech end of the muzzle. It turned out to 'run out' 0.121" short of where it was predicted to run out. I was 'just fine' with that. ;) However, it was VERY tedious. At the muzzle end (OD = 0.625"), the cut in was 1.100 (rough OD) minus 0.625", or 0.475". At 0.020" per pass, that's 24 passes. In reality, it was more because there are issues at the 'end point' that have to be dealt with, but I'll spare you those details.

Once the proper depth was reached, the cross-slide was moved 3.3" breechward, and the process started again. And so on 'til I "ran out" of barrel to cut. In practice, I didn't cut down to the final diameter on the first pass from end to end. I cut within 0.025", and went back and made 0.005" and 0.001" finish cuts to get to the final diameter. Worked like I knew what I was doin'. I think it took me about 3 hours to finish the profile, not counting setup. The final passes were very slow feed rates. I took 8 minutes to traverse the 3.3" of cross-slide travel. However, that time spent is worth it, as it substantially reduces the hand finishing time.

Now, about that funny-looking muzzle...

Those that have been around THL for a while will know that I am 'committed' to the concepts and theories associated with barrel harmonics and harmonic timing. (AKA Optimal Barrel Timing (OBT) and Optimal Charge Weight (OCW) theories.) in a nutshell, those theories assert that the timing of the bullet's exit from the muzzle relative to the maximum amplitude of the longitudinal wave caused by firing the cartridge, is critical to the rifle's precision. Therefore, dampening the magnitude of that longitudinal wave would have a beneficial effect on precision. Dampening that wave is the whole reason for existence of the barrel "De-resonator" made by Limbsaver. (Personally, I don't like the looks of the "de-resonator" and neither do I like the people at Limbsaver.)

I did some 'back of the envelope' calculations of the wave-length of the longitudinal wave, and the spacing of "destructive" reflective surfaces based on that wavelength, and came up with what you see at the muzzle of this barrel. As the leading edge of the wave hits the first edge of the muzzle swell (hereafter MS), some of its energy will be reflected. (That's not 'theory'.) However, if the MS was uniform in diameter, OR uniformly tapered, the remaining wave energy would continue 'unattenuated' to the muzzle. However, if there are repeating "walls" for it to reflect from, its magnitude would be diminished at each reflection. However, one must always keep in mind 'harmonics' - uniform vibrations - when setting up reflective surfaces. If I made all of the subsequent reflective 'walls' the same distance apart, they could sum together and create another wave of similar amplitude, thereby thwarting my efforts to 'dissipate' and attenuate the primary wave. Therefore, I spaced the subsequent reflective surfaces at sub-integral units of the wavelength, thereby making the reflections out of phase with the primary wave - subtractive instead of additive. You'll note that the grooves also increase in depth as they approach the muzzle. There SHOULD be "all kinds" of 'cancelling' going on in that MS. That's the paper-whipping. It very well may not work. If it doesn't, I left enough 'meat' to reduce the diameter to 0.625" 'smooth'.

All of that said, this looks a little too "Buck Rogers" for my tastes for a 'classic' rifle. However, there are mitigating circumstances here. First and foremost, this barrel is being created for a "hot rod" cartridge, not a "classic" one. Second, it's being installed on a Savage Axis action. That ain't exactly a "classic". Third, at least to start, the stock is a plastic one. FOR ME, plastic and "classic" are polar opposites. Therefore, I am willing, at least until it proves ineffective, to put up with a little "Buck Rogers" in a rifle I would carry into the field.

By the way... being able to "Buck Rogers" - or do anything else that isn't "the norm" - is precisely WHY I bought the lathe and mill. I want things MY way, not the way some "gunsmith" THINKS I 'need' it. Not the way some "gunsmith" SAYS I 'need' it. And not the way some "gunsmith" WANTS to do it. I WANT IT MY WAY, and most of the time, the only way to get that without grief, and money, is to do it yourself!


gitano 11-02-2014 04:22 PM

Re: The .17 Predator on a Savage Axis Action
There is an interesting 'development' with respect to the OBT theory paper-whipping.

The longitudinal wave travels to the muzzle, reflects off of the muzzle face, returns to the action, reflects off of the action, and repeats. Calculations of "barrel timing" determine the transit time from breech to muzzle and back in milliseconds, and provides "node times" when the longitudinal wave is NOT at the muzzle. This time needs to be coordinated with the "exit time" of the bullet. (The exit time is determined by 1) the pressure vs. time curve, 2) the internal velocity of the bullet, and 3) the length of the barrel.

Most common cartridges have exit times that run between the 4th and 6th timing nodes. However, the .17 Remington, and other 'hot rods' like the .17 Predator, are sneaking up on getting out the barrel AHEAD of the first cycle of the longitudinal wave. That's FAST! In the case of the PAPER-WHIPPED .17 Predator and a 20-grain bullet from a 26.5" barrel, it is right on the first timing node - 0.984 msec. While I might get it to go faster - there is some "paper" pressure headroom - doing so would move it off of the THEORETICAL timing node. In my opinion, there is no need to build a hot rod and then load it "down". QuickLOAD predicts that I can get that bullet doing near 4600 f/s at the muzzle from a 26.5" barrel. I like that!:COOLdude::jumpingsmiley::COOLdude: :jumpingsmiley: :COOLdude:

We shall see if QuickLOAD comes close to reality.


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