Question about load velocity and barrel life

[EchoDeltaSierra]

I'm doing the initial load work-up for a Nucleus action and 21" Criterion barrel in 6.5CR. I'm using 140gr ELD pills and H4350 powder. There seem to be two nice nodes; one is at 42.2gr running at about 2645fps, the other is 44.2gr running at 2760fps. Both are single digit SD and grouped well at 100m, the hotter charge only started to flatted BR-2 primers a bit. (note, this was tested at freezing temps - 31.5 F)

When considering barrel life, is there any significant advantage to running at the slower node?

 

[EchoDeltaSierra]

The hive-mind was too slow so I called Criterion. First off, really nice customer support; there feedback was it might be 100~ rounds impact on barrel life thus the recommendation was to go with the faster load.

 

[MtnCreek]

I'd load the same handful of cases several times to see if primer pockets hold up.

FWIW, you're about 0.6 gr over what I can get using Hornady brass and 140 amax.

 

[Sogan]

If you are somewhat flattening primers at 32 degrees then you may want to test again when it get some warmer out. You could be really flattening them then.

 

[Subwrx300]

I'm doing the initial load work-up for a Nucleus action and 21" Criterion barrel in 6.5CR. I'm using 140gr ELD pills and H4350 powder. There seem to be two nice nodes; one is at 42.2gr running at about 2645fps, the other is 44.2gr running at 2760fps. Both are single digit SD and grouped well at 100m, the hotter charge only started to flatted BR-2 primers a bit. (note, this was tested at freezing temps - 31.5 F)

When considering barrel life, is there any significant advantage to running at the slower node?

I run a Criterion 6.5 also but in 26" variety... in summer months, 42 GR H4350 gives me about 2760 fps avg (after 600 rounds through barrel) and factory 140 ELD runs about 2720-2730 fps. Based on the 15 fps per inch, I'd say your barrel is running about the same speed as mine if yours hasn't speed up yet. I didn't see any primer issues at 43gr but it was 2830ish and didn't feel need to push it any further

44.2 of H4350 is quite the charge for that bullet.... It's your gun and brass, but that seems like an awfully hot load to save a mil of drop and ~.1 mil wind at 1k. Especially since load is at freezing temps...I'd be very VERY cautious running 2-3 grains over book max in summer temps even with a temp stable powder like H4350; would never do it with less stable powder.

If barrel is still new (under 300 rounds), it will probably speed up another 40-60fps over next couple hundred rounds. You've probably see this but if not: http://precisionrifleblog.com/2013/07/16/6-5-creedmoor-barrel-length-and-muzzle-velocity/

Is this a match rifle where reliability/extraction in wet conditions is possible? Maybe try the water test: pour bottle of water through your magazine, then load and shoot 4-5 rounds quickly. You may find difficult (or impossible) extraction which would give you your answer on pressure/downside to running the hot charge. If no issues and barrel life is only couple hundred rounds less, then would seem your good to go.

 

[EchoDeltaSierra]

Thanks for the feedback. I was able to test 1000y yesterday. Upon further inspection of the brass, i decided to go with 43.9gr of H4350 on a lot of 50 rounds. Shot a few to validate 100m zero with the suppressor, then measured velocities with the magnetospeed at decided to plug 2750fps into the ballistic calculator as the starting point. I made first round hits at 1000y and with measured 8.5 mils drop and there was no primer flattening (Nosler brass with BR-2 primers at 22 deg F). This trued up muzzle velocity to 2794fps.

I agree that this is hot, but it seems in line with others experiences. It’ll be a while until Minnesota allows me to test in warmer conditions though i plan to re-measure things at 50, 70, and then 90 deg F.

 

[EchoDeltaSierra]

I'd load the same handful of cases several times to see if primer pockets hold up.

That’s my plan. I have a lot of 50 pieces of Nosler brass that I plan to shoot though several time to see how they hold up. The Lapua brass is staying shiny and prepped until I get this dialed in.

 

[Sogan]

I'd load the same handful of cases several times to see if primer pockets hold up.

Question on this in regard to primer pockets: Are you looking for no resistance seating the primer, primer literally falling out, or after firing seeing black around the primer to show that its not sealing off the pressure anymore? I have some lapua that has varying degree of pressure felt during primer seating on my Forster.

 

[MtnCreek]

Little resistance when seating. If it slips right in it should be discarded then. If it seats with little resistance, I'll color the head with a sharpie and throw away after that firing. I won't use loose pocket brass for anything that must function; a loose primer can lock up a mag or gun.