LC brass vs WIN Brass - 308 velocities

[lshel]

I had been working up a load for 308 in LC brass using IMR4895, 168g SMKBTHP, Win Large rifle primers.Brass trimmed to 2.005" and COL 2.80". Velocity results:

 

POWDER             AVG VEL.    RANGE (3 SHOTS)  Primer Appearance

41.3                        2513                5                                ok

42.3                        2576               35                               ok

43.0                        2614               63                               ok

43.3                        2682               86                               pressure signs

44.0                        2691               22                               pressure signs

 

I also shot a 41.3 load in Win brass and velocity was 2462 fps vs 2513 fps in LC 11 brass. So the Nato brass with same powder load is building more pressure and velocity. Some loads of LC 11 brass at 43.3 g gave protrosion in primers as well did loads using 44.0g. I cut back to 43.0g  with LC11 brass and primers were okay.

Edited February 16, 2014 by lshel

[spikehunter]

That makes a little since, but good to know. My understanding is that most NATO brass is thicker and doesn't expand as readily. Thus, it builds more pressure.

[Tempest455]

LC IMO also requires more prep time as well to get them consistent.

 

I've done the same thing w/ a matrix of LC, Win, Hornday, Lapua etc.. I then measure the grains of water each will hold. It really illustrates how important case volume and velocity is.

[Caster]

Military brass, being thicker means the case capacity is less. Smaller internal dimensions mean higher pressures.

It's pretty common knowledge when working up loads with military brass to back off and work up.

Thank you for posting. Data of any kind is always welcome.

[Ron Padilla]

thanks for the last post    informative.