Brass Sizing and the Savage Barrel Nut Equation

[m12lrs]

Ok, so if the title of this thread caught your interest hopefully you have some good knowledge and understanding of proper brass sizing for precision ammo. This may get a little long winded, but I'll try to keep it simple.

BLUF: This is a research post not really an advice seeking post. I don't plan on changing anything. I know I could get a body die to bump the shoulder further or have the Shell holder or die shaved by a few thou etc. and I will use brass from this barrel as dummy rounds for Jim to do my barrels for next season. Just seeking others experiences with this or other methods of determining sizing specs etc.



First off, my current barrel is a Cryo-Treated XCaliber, 8 Twist Chambered in 6.5x47 Lapua by Jim at Apache Gun Works. (Not a ploy) This has been the most accurate barrel I have had to date. There is no questioning the dope. Groups are always small and I have the reloading equipment to squeeze every ounce on performance out of it.

First My Process after every firing:

1. on my Lee Press: Deprime with Might Armory's "The Pua" die.
2. Dry Tumble in Walnut Media with Flitz and a dryer Sheet
3. Anneal on AMP Annealer with Prescribed Collet and Program
4. On my RCBS Summit Press: Size with Forster Bushing-Bump Die (.287 Bushing) (Will expand here later)
5. Tumble off sizing lube
6. Inspect and Clean Primer Pockets
7. Prime (I use my lee press for this as well)
8. Trim on Giraud Trimmer
9. Run all brass through a Sinclair .262 Carbide Mandrel Die
10. Charge to the Kernel on Auto-Trickler with Auto-Throw Combo
11. Seat on RCBS Summit Press with Forster Competition Seater die with the Stem honed to 140Hybrids.

Results:

Groups avg. .2-.4", SD 2 and ES 8 over 10 shot strings. Velocity 2780fps. Load is Lapua Brass (Obvious), CCI450, 36.6grs Varget (Within .02grs every charge), and 140 Berger Hybrid .035 off the lands.

Now the point of this post. My Forster Sizing die is maxed out. Can not bump the shoulder back any more than current. Obviously the goal is .002-.003 Shoulder bump measured with Calipers and Bump Gauge. Here's the scenario:

Using the Calipers and Bump Gauge I completed the Following measurements:

Go-Gauge: 1.425
No-Go: 1.428
Fired Brass: 1.429
Sized Brass: 1.427

Bolt close is slightly stiff, but not tight, so I know that brass is being worked very lightly. Again Sizing die is maxed out and will not bump the shoulder any further than the 1.427 measurement. Doesn't matter how tight it is... period. The beauty of the Savage barrel-nut and a prefit combo allows you to custom headspace for this all to work out which I took the time to do when setting the barrel up. However, I'd like to know if anyone else shooting 6.5x47 or other cartridges are getting numbers similar to this and are also bottomed out in their sizing die?

sounds like an excellent procedure.

the reason your cases are a little tight is not your shoulder bump. in fact i set my dies up for only a 1 thousandth shoulder bump.

the forster bushing bump die only sizes the neck and bumps the shoulder. it does not size the case body. i would reccomended you either get a body die or a full length bushing die or the forster full length sizing die honed to your neck specifications.

if you do decide to use a body die check your shoulder bump measurement afterwards. brass will probably grow and you will need to run it through your bump die again.