7.62X39 cast Lee .310/1332RGC loads for an AR?

[curator]

I have an AR15 with a 7.62X39 upper with rifle length gas system, I am interested in shooting the Lee .310/155 2R/GC boolit cast from 50/50 COWW and Lino. I have several potential powders ranging from AA1680, Rx7, SR4759, IMR 4198 & 4895 & 4064 as well as WC 846 and BLc-2. I would like to keep velocities around 1600-1800 fps, but have no issue with 2000 fps+ with accuracy since I am only punching paper at this point. Loads for Sierra 125 & 150 PSP condomized bullets will also be appreciated. Boolits are water-dropped and lubed with LBT blue and test at BHN 22+. TIA! curator

[curator]

OK, no reply from the forum. The Post should have read Lee .310-150/2R GC in an AR15 platform. Nonetheless, I cast about 200 of these from WD COWW + 2% tin and sized to .311 with LBT Blue lube. I loaded them over a "ladder" load from 22.0 to 24.0 IMR 3031 at 1/2 grain intervals. Shot from sandbags off a bench, at 50 yards. The 22-23 grain loads were not all that accurate. Boosting the charge to 23.5 grains and 24.0 grains tightened up the group big time. 5-shot groups were right around .75-1.0".

My AR is a 7.62X39, 16 inch,.310 groove diameter, 1 in 10 twist, rifle length gas system, free floated handguard from Radical Arms. It is mounted with a 4X scope. Guesstimates of about 1600 fps for the more accurate loads, but I will confirm them next week. 7.62X39 seems to be a useful cast boolit round in the AR15 platform judging by my first trial.

[bruce drake]

http://castboolits.gunloads.com/show...on-the-7-62X39
http://castboolits.gunloads.com/show...llet-load-data
http://castboolits.gunloads.com/show...h-cast-bullets
http://castboolits.gunloads.com/show...th-125-gr-cast
archive has ton of data out there already.

[curator]

Bruce Drake:

Thanks for the links. I appreciate your response and helpfulness. As a consummate researcher, I had already done a thorough search on this and other sites before I posted this thread. Loads for SKS, AKs and bolt/break open rifles are different than ones that will be both accurate and function in the AR-15 platform. None of the links you offered give information about this specific use. No commercial loading data is available on the Lee boolit and using it in the direct gas impingement system of the AR15. Since my rifle has a "rifle length" gas system, I assumed fast powders like AA1680 and Rx7 might not function the action unless the velocity and pressure was fairly high. That might negate best accuracy with a cast boolit. My best guess in using IMR 3031 provided both reduced pressure, slower burning, and good action functioning as well as excellent accuracy. I suspect I could also duplicate these results using Varget or IMR4895, but there was almost no room in the cartridge case when I approached 24 grains.

I am sharing this data for those who may be interested in casting boolits for their ARs chambered in 7.62X31.

[Rcmaveric]

I reload cast for the Grendel. Its the same case fire formed with a 6.5m bullet. I also have a rifle length system and 24 inch barrel. Great results with 2400 at low and high velocity. RX7 and 4198 are both great powders and accurate high end loads that function the riffle. Due to the lack of reloading data for Grendel i use 7.62x39 data often, which there is a wealth of data. Quickloads is a great tool to see if i have the right amount of pressures to operate the system. BLC-2 and 4064 worked okay (not that accurate) but would not function the riffle and once raise to a PSI that would function the riffle the accuracy went out the window. I would imagine that the larger bore diameter would also be served well from a faster powder to fill the volume of the bore quicker and keep pressures up.

Shouldn't need bullets that hard. Plain old CWW air cooled work just fine for me. Here lately I have been using reclaimed range scraps 50/50 with COWW+ 1-2% Tin. Works great in everything pushed out to 2050 FPS.

[curator]

Thanks for the informative post! I had considered AA2400 but rejected it as too fast burning for a rifle length gas system in the 7.62 barrel. It has given erratic functioning in my .300 Blackout with 150 grain slugs. I have used Reloder 7 in the 7.62X39 with considerable success with 125 grain j-word bullets. With cast, I have found that function and accuracy are often difficult to get in one load. Good to know you are getting performance with cast in your Grendel. That has been on my ist for my next AR build as I already cast for 6.5X55 Swede and .260 Rem. What weight boolit are you using? Is your Grendel rifled with 1 in 9" or the 1 in 7.5" twist?

[Rcmaveric]

I had the BHW Polygonal 20 inch, 1 in 8 twist until an accident. That upper now hangs on the wall above my reloading bench as a shrine to remind myself to pay attention. I use the Midway special barrel 24 inches in 1-8 twist now. I use the NOE 266-125-GR mold for the Grendel pushed at 2050 fps. I also cast and reload for the .260 Rem and often use the 6.5x55 data. For that i use the RCB 6.5-140-SIL and still working up loads. I haven't t tried the RCBS bullet in the Grendel due to COL being short due to mag but it might work. i have found accurate loads with NOE bullet in the 260 over RX7.

My thinking is that cast bullets swag and have less barrel resistance than copper jacket bullets. So a faster powder is needed to generate the gasses needed to maintain good pressures to operate the riffle. The fine line is to not generate so much peak pressure as to over pressure the lead. Cast Bullet Basics For Military Surplus Rifles
By C.E. Harris Rev. 9-6-93 and Beagles article Cast Bullet Powders Making Whatever’s On Hand Workwere are how i chose my powders that worked. I was trying other powders with out success till i read them and took down notes.