Discussion in 'Handloading and Reloading' started by DMW1116, Jan 23, 2021.
ETA: no I don't have a chronograph.
By "replicate," do they chronograph the same ?
Do they shoot the same POA=POI?
This is where a crony is nice for comparison.
The following is arguable and just something I read and took note of.
Sierra 168 MK
43.5 IMR 4064
Fed 210m primer
For the 175 MK
41.8 grains of IMR 4064
Now how those stack up I really don't know. While I still have a few boxes of the Federal 168 grain MK bullets I load mostly AA2495 for my AR 10. While the above loads look reasonable I really can't swear they duplicate Federal's load and Federal's choice of cannister powder.
That would be all I was concerned with.
My most accurate load is 42.5 grains of IMR 4064, CCI #34 primers, 175 gr SMK, 2.800 to 2.805 COAL. It just locks the bolt back. One more click closed on the gas block and it will eject, but won't lock back on the last round.
ETA A fair number of my firearms have never had a factory round through them as I prefer my more accurate handloads for them. YMMV
20" barrel and 41.2gr was running right at 2400 out of the DPMS LR. Thats about as high as I like to throttle that rifle, and she was doing around an inch at 100.
I know in Garands and M14 rifles (I presume the M1A replica) the condition of a high gas port level can bend operating rods and peening some parts - over time - and just cause wear and tear more quickly. The muzzle velocity - when you have or can use a chronograph - is NOT a reliable predictor of internal pressure.
I do not know what model rifle you are using. That bit of information might or might not provide a clue.
I would suggest you, after consulting reloading manual, switch to a faster powder and therefore use less of a charge. Barring that, have a chat with someone who has the same rife as you and compare notes.
55ksi Chamber/12ksi at 15" port
At least that's reassuring. The 42.5 grain load has been more accurate than I'd ever expected out of this rifle. Load data goes all the way to 45 grains, but I never tried that. I saw some cratering and flattened primers in the 43 to 44 grain range.
FYI, in the Garand, slower burning powders create a higher port pressure that is detrimental to the life of the op rod system. Newer powders that have been developed since WWII that are suitable for a 30-06 rifle burn slower than what is acceptable for the Garand. That is the reason that a couple gas pressure reduction plugs on the market developed for the Garand are available.
The AR-10 has a completely different gas system than the Garand. I'm not familiar with the port pressure limitations on AR-10 are, but I am sure the the AR-10 has different requirements from the Garand.
I use CFE223 in my AR-15 204 Ruger loads in a 26" AR-15 prairie dog rifle and it performs well. For reliable functioning of the AR-15, I had to increase the weight of the buffer to slow the bolt down. An adjustable gas block would do the same but the rifle was built and the heavier buffer was the easier solution.
If the factory loads do not lock the bolt back and your reloads do, I would be questioning the pressure of the reloads.
If you had primer indicators at 43 and you are shooting at 42.5, you might be pushing it. Do the factory load primers look good?
Chrono would be good now to really understand the load differences.
My hand loads will cycle with the gas block closed 6 clicks, but won't lock the bolt back unless it's at 5 clicks closed. The Federal GMM needs 4 clicked closed to lock the bolt back. I originally set the gas block with Federal 150 gr soft point. This locked the bolt at 7 clicks closed, but wouldn't reliably eject at 8.
I say all this to make sure I'm not thinking about it backwards. The Federal GMM has less pressure overall, therefore needs the gas block open a bit more to get full function. The 150 gr soft points generate higher pressure overall and only need the gas available after closing the block down 7 clicks from fully open. My hand loads are in between, requiring 5 clicks closed. Does that make sense to anyone but me?
Federal/Commercial needs more (1-click more) gas port opening to lock back, than your 4064-based reloads.
- Leave things at Federal/4 clicks closed position.
- Walk away...
Ok.....ill tell you right now that quite hot for an AR10. I always use service rifle data for that DPMS, and none of the data i have go past 42gr with IMR 4064 with my 168 SMK or 168 A Max, the 2 projectiles of put thru it.
Ejection is right in that range. Some is at 3 and the stuff I tried yesterday was about 4. Yesterday was a 180 gr hunting load with 41.7 gr of IMR 4064. I need to clean it today, so I'll check everything out while its apart. I took it apart last weekend and cleaned it after shooting a few loads for testing. I didn't see any issues inside, but it has less than 100 rounds through it.
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