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8mm SLT Swaged Bullet Load Workup
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Old 05-04-2015, 02:39 PM
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Default 8mm SLT Swaged Bullet Load Workup

I've been doing some swaging calcs which got me to thinking about swaging (imagine that), and I decided that I needed to find a "standard" and make that work.

Sparing you the gymnastics of how I arrived at the number, I have decided on a 136.3-grain bullet as my light-for-caliber (LFC) bullet from these jackets. This puts it in the category with the 115-grain 7mm HP and the 130-grain .308 HP bullets that I like so much. I decided to make it a "spitzer" with exposed lead tip. I'm not real happy about that, but I can't get enough bearing surface if I go lighter, and going lighter is required if I want HP unless I change the core material. I swaged up 35 of them.

The bullet weighs 136.3 grains, +or- 0.1 grain.
The bullet is 0.900" long.
The meplat is 0.100" in diameter.
The bearing surface is 0.315" in length, (bore diameter but essentially only 1/3rd of the total length That 8R ogive is a pain).
The theoretical BCs are:
3450 and above: .290
3000 to 3450: .276
2000 to 3000: .270
1000 to 2000: 266

Using 71.3 grains of Reloader-17 in my 8mm SLT, I can get it (theoretically) right on the 3rd timing node at 3350 f/s for the 23.352" barrel with an estimated max pressure of 55k PSI. Here's a picture of the trajectory table specs:


From my perspective, it's 'good'. 3400 ft-lbs at the muzzle is as high as I want to go. In the 11.0 lb rifle, that's not unpleasant. (100 ft-lbs less than my .338 Win Mag shooting 225-grain bullets at 2650 f/s which I find "fine", and the .338 weighs 2 lbs less.)

About an inch and a quarter high at 125 yards, six inches low at 300 yards, and carrying 1500 ft-lbs out to 330 yds. "My kinda bullet/cartridge/rifle."

Considering how well this rifle shoots the 220-grain Sierra, I have SOME hope for this bullet. HOWEVER, this Steyr LONG Throat rifle wasn't "made" to shoot LFC bullets. I have made another rifle, the Steyr SHORT Throat, specifically for shooting LFC bullets. That rifle will, (I have to put a new barrel on it), have a barrel of at least 26" length. If I can get one to 28" I will.

I'm going to get a range report on this as soon as I can. 'The new local range is closed for "renovations" until late June or early July. I might be able to get to a 100+ yard range before then. If I do, I'll 'report' here.

Paul
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8mm slt, 8x57, load work-up, swaged


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