2500 fps from 12" barrel?

General Firearms Reloading & Ammunition
1

I’ve got a 12" LMT piston AR. I would like to get my 75gr Hornady hpbt loads into the 2500fps range.

I’m using
PRVI Brass once fired
CCI sm rifle primers
75gr hornady
Ramshot TAC powder.

At 22.5 grains of TAC (2250 fps) I started getting cracked necks on the PRVI brass. No other overpressure signs. Max load per TAC is 23.7 gr of powder. I don’t want to ruin the 2000 rounds of Prvi brass, so I backed off to 22 gr of powder.

I’m going to try to work up using Lake City Brass next, but even at the listed max powder (2790 fps from 24" barrel) I don’t think I’ll get past 2400 fps.

My gun has a 5.56 chamber. I don’t want to buy factory 5.56 75gr (2713 fps 16" barrel per Molon info., so should hit 2500 fps in mine) loads when I have my own reloading equipment just to get the extra velocity! How do I get there safely?

2

I’ve gotten up to ~2450 from my 10.5" using 75gr HDY HPBT, 22.5gr IMR3031, CCI450s, and a medium lee factory neck crimp. There were some slight pressure signs so I backed off a bit and I haven’t gotten a chance to chrono it since then. Sorry, I have no experience with TAC.

Edit: this was PMC brass.

3

That is odd about the Prvi brass cracking at such low pressure. TAC’s max load is 23.7 for .223 pressures, and I believe around 24.0-24.3 for 5.56 pressures. I have heard of some folks pushing 25.0 grains of TAC for a 75-grain bullet, but I’m not going to do it.

You may want to try Varget.

4

I just tried a new case lube (lanolin & alcohol- home made Dillon) and it is sooooo much smoother than before. I think I may have been overworking the prvi brass using one shot lube. My experience with it is that it is garbage. Can lasted about 450 rounds and lnl was always very hard to size. Loaded 250 tonight with new lube and it was so smooth. Didn’t feel like it was working the brass at all. I may try another workup with the prvi brass now.