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 30HRT chronograph and load report using AA1680
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krochus
Average Member

USA
92 Posts

Posted - Oct 20 2009 :  16:41:24  Show Profile Send krochus a Private Message  Reply with Quote
First let me preface this by saying that I have no real idea what the chamber pressures involved below are. Unlike other posters I'm not gonna claim these loads are completely safe just because the rifle hasn't blown up and brass comes out in one piece[span style='color: red;']. Use this at your OWN risk.

30 Herrett Tactical Rimless

[/span]
Rifle- 20" white oak AR15 upper chambered for 30HRT topped with a vintage 6x redfield

Cases- once fired Hornady 6.8spc reformed in RCBS 30Herrett dies, trimmed to 1.590"

Bullet- 125grn Speer TNT HP

Primers- Magtech SR and then CCI400

Powder- AA1680

COL- 2.275"

all groups were 5 shots at 100yds


First off the run using Magtech primers

25.0grs/ avg velocity 2350fps/ group, no data

26.0grs/ avg velocity 2450 fps/ group 1.5"

26.5grs/ avg velocity 2510 fps/ group 1.0"

27.0grs/ avg velocity 2563 fps/ group 2.4"

27.5grs avg velocity 2588 fps/ group 3.1"

the velocity spread with the magtech primers was HORRIBLE as was accuracy , particularly as pressure increased prompting me to go back out today and try a different primer

CCI primers

26.5grs avg velocity 2470fps/ group 1.3"

27.0grs avg velocity 2526fps/ group 1.6"

27.5grs avg velocity 2580fps/ group 1.4"

the velocity spread with the cci's was very tight, in the case of the 27.0grn load only 18fps for the 5 rds fired

[span style='font-weight: bold;']NOTES and thoughts[/span]

all charges below 27.5 for the most part produced no measurable case expansion just above the head, 27.5 produced about .0002" + or - more (my tools aren't that accurate) Given that this load more or less hits my target velocity of 2600fps and is just where case expansion starts I'm inclined to treat it as the MAX loading.

Some brass failures on the first firing after forming occurred, in the form of cracking radially round the neck shoulder junction. According to Herrett guys if you don't use new cases to form this is a common problem, I annealed the 2nd batch and thus far they've all survived.

the source for this load is the infamous 28grn 7.62x39 load found in the old Speer No12?


[span style='font-weight: bold;']CONCLUSION[/span]

No doubt about it this cartridge is fast, beating my 20" x39 by 200fps when it's fed charges that don't stretch the brass badly, I'll have to buy a sack O brass and try some 100 and 110grn bullets.

Some of my 7.62x39mm adventures and exploits
http://thehighroad.org/showthread.php?t=405210
http://thehighroad.org/showthread.php?p=2274479#post2274479
http://thehighroad.org/showthread.php?p=5111739#post5111739

BISCUT
Moderator



3497 Posts

Posted - Oct 21 2009 :  04:20:59  Show Profile Send BISCUT a Private Message  Reply with Quote
krochus,

I noticed you are using Hornady 6.8spc brass. I've found, at least in AR's that Silver State Armory brass is far superior to Hornady and Rem brass.

SOunds like an interesting cartridge you have there.
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krochus
Average Member

USA
92 Posts

Posted - Oct 21 2009 :  04:40:11  Show Profile Send krochus a Private Message  Reply with Quote
quote:
Originally posted by BISCUT

krochus,

I noticed you are using Hornady 6.8spc brass. I've found, at least in AR's that Silver State Armory brass is far superior to Hornady and Rem brass.

SOunds like an interesting cartridge you have there.



That was my next question actually, the 40pcs of HRN brass I have came with the upper. To me the rem brass with it's LR primer pocket is ruled out. In my experience with 7.62x39 trying to get accuracy while igniting less than 30grs of powder with an OVERKILL primer is a crapshoot. Ironically rem is the best brass out there for x39 because of it's SR primer pocket.

So that just leaves me the Hornady case and the Silver state cases.

In what way do you feel the silver state cases are superior? My HRN cases were surprisingly constant in weight and capacity. Please elaborate as I need to buy more brass and I'm all for getting the best stuff possible

Some of my 7.62x39mm adventures and exploits
http://thehighroad.org/showthread.php?t=405210
http://thehighroad.org/showthread.php?p=2274479#post2274479
http://thehighroad.org/showthread.php?p=5111739#post5111739
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BISCUT
Moderator



3497 Posts

Posted - Oct 21 2009 :  09:11:02  Show Profile Send BISCUT a Private Message  Reply with Quote
IMHO Silver State Armory brass is the best out there for 6.8spc. They are now the sole mil supplier of 6.8spc loaded ammo, and are pumping out tons of it. They just moved to Washington St from Nevada. Call them up and ask for Nancy.

Their brass is much stronger than Rem or H-Day. Primer pockets are good on relatively hot loads up to 12 reloads. I really pushed one of my AR hard and the primer pockets remained usable for many more reloads. I was using a mix of SSA and H-Day brass. H-Day was done after 1 over max loading. Rem was weaker than H-Day so I did not try it w. overmax loads.

SSA also makes SM R and LR primer pockets. I've never used LR. I've always used SM R and have found Wolf SM R Mag primers to be fantastic for my application.
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