I have on hand: 748 / H414[760] / 4064 / 4350 / 4895 / 3031 / 4198
The 7.62 cartridge was developed with IMR 4895 as the propellant. This is recorded in the American Rifleman. National Match ammunition was loaded with IMR 4895, not the exact blended lots we have, but it was IMR 4895. You can find that in the American Rifleman. You can't go wrong with IMR 4895 as long as you stay within appropriate pressures and velocities. Port pressure is the primary concern here. The gas system on the M1a is more flexible than that of the Garand, but still you will find ammunition that works fine in a bolt rifle will cause problems in a M1a. Therefore I am going to suggest that you use powder no faster than IMR 3031 and no slower than IMR 4064.
I have used IMR 3031, data is below, it shot well. Just does not throw well due to its long powder grains . IMR 4064 is an outstanding powder in its own right, does not throw well due to its long grains, but I knew many competitors who used IMR 4064.
For a time Accurate Arms AA2520 was popular, I have data below, but generally speaking, I preferred stick powders to this ball powder. I never used Win 748 because of my distaste of ball powders. I found AA2520 to be peaky and it left more residue in the gas system than the stick powders. It shot well if you hit its sweet spot.
I have data with IMR 4895, AA2495 and H4895. Accurate Arms told me the AA2495 was a copy of IMR 4895, at one time H4895 was also a copy. Now H4895 is considered an advanced powder, but over my screens, I don't see much of a difference between these powders, charge for charge. I would use any of them, have used all of them, and I would simply buy the cheapest.
You have IMR 4895, I would start with that and try a 150/155 grain bullet with 42.5 grains IMR 4895. I would start with 40.5 grains with a 168 SMK and end at 41.5 grains. With 175 grain bullets I would start at 40.5 grains and end at 41.0 grains. My self imposed limits were 2700 fps with a 150 grain bullet, 2625-2650 fps with a 168, and 2550 to 2600 fps with a 175. Faster does not necessarily produce better results and is harder on the rifle.
Some of this data was developed with the old nickle plated WLR. That primer was less sensitive than the new brass color WLR. I do not recommend sensitive primers in this mechanism for safety reasons. I do not recommend Federal primers as it is the most slamfiring primer on the market. The primer the military used was the #34 primer, which is less sensitive than any of the commercial primers on the market. This is the appropriate primer. Tula makes a mil spec primer, unfortunately only CCI offers a mil spec primer in large rifle, Winchester and Federal make mil sec primers for the military, but don't offer those product lines to the public. Of the commercial primers on the market, the CCI200 seems to have a hard cup, but the overall sensitivity is still commercial. This mechanism has its risks, always feed rounds from the magazine to slow the bolt down. When you fire single shot, press a round in the magazine, don't drop it in the chamber and drop the bolt. There are a surprising number of slamfires and out of battery slamfires have have occurred by shooters reloading their M1'a this way.
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[B]M1A 1/10" 6 groove Douglas[/B]
Primer Comparison between WLR, CCI 200 and CCI #34
150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
18 May 2008 T = 70 °F
Ave Vel = 2700
Std Dev = 30
ES = 85
High = 2736
Low = 2651
N = 10
150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC CCI 200
OAL 2.785
1 Feb 2014 T = 55 °F
Ave Vel = 2712
Std Dev = 8
ES = 22
High = 2723
Low = 2701
N = 5
150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC CCI #34
OAL 2.785"
1 Feb 2014 T = 55 °F
Ave Vel = 2675
Std Dev = 30
ES = 80
High = 2707
Low = 2627
N = 5
150 gr Hornady FMJBT 41.0 grs IMR 3031 Lot 385 Mixed LC WLR OAL 2.785
28 Sept 2008 T = 80 °F
Ave Vel = 2693
Std Dev = 40
ES = 126
High = 2747
Low = 2621
N = 14
168 Sierra 40.0 grs IMR3031 lot FEB23B LC90 CCI#34
18 May 2008 T = 71 °F OAL 2.750"
Ave Vel = 2533
Std Dev = 17
ES = 45
High = 2551
Low = 2506
N = 6
v. good group
168 gr Sierra Match 41.5 gr AA2495 wtd. LC77 WLR OAL 2.800
T = 75- 80°F
22-Apr-99
Ave Vel = 2588
Std Dev = 16
ES = 48
Low = 2564
High = 2612
N = 6
168 gr Sierra Match 41.5 gr AA2520 LC Mixed WLR OAL 2.800
T = 75- 80 °F
22-Apr-99
Ave Vel = 2601
Std Dev = 14
ES = 38
Low = 2584
High = 2622
N = 10
175 gr Sierra Match 40.5 gr AA2495 LC65 W/W OAL 2.800
29-Jun-96
Ave Vel = 2523
Std Dev = 22
ES = 65
Low = 2489
High = 2554
N = 10
175 gr Sierra Match 41.0 gr AA2495 LC82 W/W OAL 2.800
29-Jun-96
Ave Vel = 2528
Std Dev = 23
ES = 89
Low = 2481
High = 2570
N = 10
175 gr Sierra Match 41.5 gr AA2495 LC87 W/W OAL 2.800
29-Jun-96
Ave Vel = 2579
Std Dev = 13
ES = 40
Low = 2564
High = 2604
N = 10
174 FMJBT 40.5 grs H4895 wtd, lot 4501 LC mixed WLR
OAL 2.800"
18 May 2008 T = 71 °F
Ave Vel = 2524
Std Dev = 36
ES = 90
High = 2587
Low = 2497
N = 5
good group
174 FMJBT 41.0 grs H4895 wtd, lot 4501 LC mixed WLR
OAL 2.800"
18 May 2008 T = 71 °F
Ave Vel = 2594
Std Dev = 14
ES = 30
High = 2609
Low = 2579
N = 5
174 FMJBT 41.5 grs H4895 wtd, lot 4501 LC mixed WLR
OAL 2.800"
18 May 2008 T = 71 °F
Ave Vel = 2593
Std Dev = 15
ES = 42
High = 2613
Low = 2571
N = 5
Best group
174 FMJBT LC79 Match M118 White Box
18 May 2008 T = 71 °F
Ave Vel = 2550
Std Dev = 16
ES = 41
High = 2564
Low = 2523
N = 5[/SIZE]
