Higher velocities with annealed brass

[Mickp7]

Finally got my AMP annealer and prepped my first batch of 300 PRC. Lapua brass was twice fired and annealed for the first time before loading. Brass was tumbled and deprimed, then annealed, prepped, and sized.

Load is 79.5 grains Retumbo, CCI 250 primer, 215 Berger .030 off the lands.

1x fired brass velocity was 2940 and shooting under .5 moa at 420 yards.

2x fired brass, prepped same way but annealed was 2290- 3000. Grouped well but about 1.5" higher and 2.5" right at same distance. (Shots with both rounds were in same session)

Barrel is at about 350 rounds, so not a new barrel speeding up.

Have you guys noticed higher velocities like this with annealed brass?

 

[Trm82]

1 x fired brass usually runs less pressure , once fire formed after first firing in my experience you'll see higher pressures which will explain your higher velocity. It probably wouldn't matter whether it was it was annealed or not.

 

[Mickp7]

Thanks Trm82!

Just to make sure I don't mislead, the 2940 fps was brass fired for the 2nd time, not annealed. The 3000 fps was was brass fired for the 3rd time, annealed.

If annealing shouldn't affect the velocity, is it common to tweak the load, or the rifle zero, in loading intervals? Or does the brass/ load settle in after a few loadings?

 

[Fullbore92]

2x fired 2290-3000? Did you mean 2990-3000?

 

[Mickp7]

2x fired 2290-3000? Did you mean 2990-3000?

Yes, sorry for the typo! 710 ES would be a whole other can of worms!

 

[Trm82]

Thanks Trm82!

Just to make sure I don't mislead, the 2940 fps was brass fired for the 2nd time, not annealed. The 3000 fps was was brass fired for the 3rd time, annealed.

If annealing shouldn't affect the velocity, is it common to tweak the load, or the rifle zero, in loading intervals? Or does the brass/ load settle in after a few loadings?

My mistake I read that as you had the higher velocity on second firing plus annealed.

 

[MagnumManiac]

Brass gives higher velocities until fully expanded to chamber dimensions then settles if minimal sizing is done.
One of my 300WM's goes from 3160fps to 3212fps with 3 times fired brass, so the load is adjusted back to the node @ 3160fps.
This is almost universal with all brass running 50,000psi+, lower pressures never really show this until many firings have been cycled through the brass. Annealing doesn't really affect this outcome.
My 6.5x47 gains only 200fps or so once fully formed, so the brass then stays very stable and identical velocities are the norm with this round after that.

Cheers.

 

[Mickp7]

Brass gives higher velocities until fully expanded to chamber dimensions then settles if minimal sizing is done.
One of my 300WM's goes from 3160fps to 3212fps with 3 times fired brass, so the load is adjusted back to the node @ 3160fps.
This is almost universal with all brass running 50,000psi+, lower pressures never really show this until many firings have been cycled through the brass. Annealing doesn't really affect this outcome.
My 6.5x47 gains only 200fps or so once fully formed, so the brass then stays very stable and identical velocities are the norm with this round after that.

Cheers

Thanks MM. The speed up on that 300WM is right in line with what I am seeing.

Fortunately, I was loading this bunch as I shot to confirm all was good. Figured once it was confirmed I'd make a box full. I did start to reduce the load to get back to the lower velocity... it took about 1.5 less grains to get there. I stopped because I wasn't sure what the heck was going on and started the thread right then and there. I may load 3 and shoot a group with the higher velocity... just out of curiosity . Otherwise, I'll reduce the powder and carry on.

Appreciate all the feedback guys.

 

[Hugnot]

My thinking:

Annealing will reduce brass springback, providing additional neck tension & that will increase initial pressures, (steeper slope on pressure vs. time). Crimping bullets will have the same effect with the crimp deforming brass where plastic deformation occurs (beyond elasticity). This will also provide a steeper slope on the pressure vs. time curve.

Increased pressure as shown by a steeper slope in the pressure vs. time curve will provide higher & more uniform velocities. As brass spring back increases due to work hardening neck tension will decrease & velocity variations will increase.

Annealing works real good. I see this on 6.5-06, .20P, & 6 CM from 6.5 CM where brass is necked down with plastic deformation & work hardening occurring. Annealing fixes this real good as shown by slightly increased velocities & lower spreads. Force used to seat bullets is also more uniform.

 

[budlight]

In higher pressure rounds with big case volume you end up with a certain amount of brass flow. I bought the RCBS machine to do inside and outside neck truing along with trimming and chamfering.

 

[Hugnot]

In higher pressure rounds with big case volume you end up with a certain amount of brass flow. I bought the RCBS machine to do inside and outside neck truing along with trimming and chamfering.

View attachment 575225

I have observed this also. Like upon turning necks two or more times, more brass is removed near shoulder than towards front. The little .22-.250 loaded at over 61K psi shows this.

 

[Mickp7]

In higher pressure rounds with big case volume you end up with a certain amount of brass flow. I bought the RCBS machine to do inside and outside neck truing along with trimming and chamfering.

View attachment 575225

How do you like this machine? I am very interested in the most consistent and accurate ammunition development possible. Neck turning would be the last step to add that I am aware of. That said, I have no knowledge of how to do it yet.

 

[budlight]

I was taught that neck turning made all the difference from a person that had the national record for the 30 cal for a short period of time in the 1000 yard meets.

RCBS doesn't sell my exact machine anymore. They broke it into the neck turner/trimer and a separate chamfering inside and out.

It really speeds up things like a minny lathe. I was doing mass quantities for competition.