Shoulder Bump...how much do you???

[Davehc130]

I have mostly bumped my brass 2 thou after firing...starting to rethink my bump...why...well virgin brass seems to be about 5 thou shorter than my chamber and I usually get really good SD/ES talking single digits for both... last batch of 6GT Hornady virgin brass, neck turned and trimmed with my load, I was getting SD of 5 and ES of 9....changed nothing except bumping shoulder back two thou and my SD jumped to 10 and ES to 20.....I was thinking maybe by bumping back to 5 thou the brass might be acting as a shock absorber some what stablizing the velocity to a degree....any thoughts?

 

[Supersubes]

If your neck tension is good with virgin brass, they can produce small spreads. The expanding case is acting like a buffer and preventing spikes. That doesn’t mean you should bump five thou. The fired brass load needs a charge or seating depth tweak.

 

[rockchalk06]

If your neck tension is good with virgin brass, they can produce small spreads. The expanding case is acting like a buffer and preventing spikes. That doesn’t mean you should bump five thou. The fired brass load needs a charge or seating depth tweak.

I did this with 308. Starting with Virgin Lapua, I was getting single digit SD's. After neck sizing and bumping the shoulders back 2-3 thousands, my SD's went up. I had to tweak the seating depth just a tad. I got the desired group and SD I was after, so I never messed with the charge. This is consistent with Virgin v's 1-2-3 times fired brass, so I now have two different loads.

 

[A&8's]

Try annealing your once fired and bumping 2 thou?
Or
Trying annealing your once fired and bumping 5 thou.

It's a process of elimination. IMO, that's the intriguing thing about reloading. I'm still the guy who "shoots to reload." I just like the tinkering side of it.

 

[DIBBS]

IMHO if you bump your shoulders .005 on a regular basis you are going to overwork your brass and your case life will be substantially shortened.

As others have suggested I believe that annealing and adjusting neck tension and tweaking your load... would be a more viable path to success.

Good luck and let us know what you came up with.

 

[Boxerglocker]

308 I start with new Lapua brass which is 0.004-0.005 smaller than my actual chamber. I mandrel it 0.002 undersized, load and once fired bump 0.002 from them on. Honestly, I only seen a slight difference in chrono numbers between new and once fired. I anneal and mandrel every firing thereafter.

 

[Snuby642]

I'm missing something?

308 brass mandrel to .262?

 

[Boxerglocker]

I'm missing something?

308 brass mandrel to .262?

MY bad thinking 0.002 under but 6.5 Creedmore, for 308 I use a standard Sinclair mandrel which is 0.002 undersize

 

[Snuby642]

My Sinclair 308 mandrell (.306) has been on back order for weeks from brownells.

I did get the die, 6.5 and 223 mandrells. And another order is 2 days out still no 308 mandrell.

 

[Davehc130]

IMHO if you bump your shoulders .005 on a regular basis you are going to overwork your brass and your case life will be substantially shortened.

As others have suggested I believe that annealing and adjusting neck tension and tweaking your load... would be a more viable path to success.

Good luck and let us know what you came up with.

only getting 5 reloading on the brass...so no worries of over working...