8mm SLT Swaged Bullet Load Workup

[gitano]

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

[gitano]

So I loaded 5 up. Sounds easy, no? First I had to 'make' some cases. All but three of my 8mm SLT cases are currently loaded with 220 Sierras. "Making" cases involves necking down from .376 to .323, a 3-step process - .358, .338, .323. Then they have to be primed, charged with 15 grains of Bullseye, filled with corn meal, tamped down with a wad of toilet paper, and fired. The firing is a bit complicated as the cases won't headspace in the "raw" necked down form. The case has to be held in the bolt as the bolt is closed. Once they're fired, they have to be resized, reprimed, charged and a bullet seated. Which brings me to back to the 8R ogive and this post.

The bullet seat die has a "top punch", (the part of the die that presses the bullet into the case's neck), made for 1) .375 bullets, 2) plastic-tipped bullets or those with ogives less than 8R OR 3) harder bullets. My hand-swaged bullets are extruding the very tip into a recess in the top punch and putting a little "nose" on them. I'm going to need to fabricate another top punch especially for this bullet. I THINK I'm back to the burr reamers. Maybe a tree burr in 3/16ths of an inch.

For the first exercise of testing the top (max) load (72.9 grains of RL-17) these won't be an issue. But ultimately, something will have to be done to mitigate this problem.

Paul

[gitano]

Not too shabby in the 8x57 either:

That's about .112" off the lands in that specific rifle.

Paul

[gitano]

$7.05 and the top punch/bullet seat issue is resolved.

http://www.ebay.com/itm/CARBIDE-BURR-TREE-SHAPE-PLOINTED-END-SG-2DC-5-16-DIAMETER-DAYTONA-/181723114251?pt=LH_DefaultDomain_0&hash=item2a4f8aab0b

Paul

[j0e_bl0ggs (deceased)]

Or a bit of epoxy putty in counter bored punch, put release agent on bullet, stuff it in the punch, let it set - hey presto, custom punch...
Good trick for cast bullets and Lyman RCBS style lubrisizer...