Reduced loads for AR-10

Discussion in 'Ammunition & Reloading' started by L308, Apr 12, 2016.

  1. L308

    Albany, Oregon
    New Member

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    I am working to develop a reduced recoil load for my Armalite AR-10. The Hodgdon on-line reloading manual says that you can use H4895 powder at 60% of the maximum load listed in their manual to make reduced loads. The max load for a 150 grain bullet in 0.308 is listed as 45.5 grains. Since I would like to use 150 grain bullets I was thinking to start at 27.5 grains (45.5 grains X 0.6 = 27.3 grains) and work up to the minimum load of 43.0 grains. I imagine the action won’t cycle at the lower loads; but I am hoping that at some point the gun will start cycling.

    My question is this: Does anyone know if there are any safety concerns with this idea?

    Thanks much in advance for your help.
  2. Dyjital

    Albany, Ore
    Flavorite Member Bronze Supporter

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    Make sure the bullet leaves the barrel every time.

    Other than that.... Nope. Have fun.
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  3. OutlawHoss

    Well-Known Member

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    I wouldn't start that low at all, just at the minimum listed load. I think what should be said is they are recommending 60% reduction in power, as expressed best by pressure, not literally the amount of powder (and I would get this data from an actual reloading book; they'll have much more load development info about the pressures involved than most online loads, and less likely to be someone's pet load that got posted widely). I've never seen any load recommendation show that dropping the grains by 60% produces any kind of viable round; the pressure drops off exponentially at such low loads and 27 grains won't do much at all. In fact, at that small of a charge in a case that lists at 56 gr capacity/water, you're getting close to detonation issues. More likely is having a bullet stuck in the barrel; it would be an exercise in futility at best, and a re-arraignment of your face at worst. If you want a low and slow round, try a different cartridge, like the AAC Blackout.
    Gas guns need a minimum of pressure to operate as it is. What is your twist rate, and length of barrel? Lower end bullet weight means a faster load to get usable performance. For reference, a M80 round, 147gr at 2733 fps, is designed for a 1:12 twist; the M118LR is 175gr at 2580 fps, which is in a 1:10 barrel. I think you'll have better success at reduced power loads with heavier bullets, or at least one suited to your barrel's twist. I recently found the lowest power load that performs well (ballistically) in my DPMS LR308 is a 168gr at 2420fps. It was very accurate, but at that load it started to not fully cycle the action, and threw the brass to about 1:30 from the port, a diagnostically under-powered (under-gassed) load. 3 to 4 o'clock is 'the zone' for a properly gassed load.
    Hope this is helpful!
    Last edited: Apr 14, 2016
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  4. Roop

    La Grande
    Active Member

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    My pet load is 39grs of H4895 under a 150 gr hornady fmj. this load cycles in my bushmaster lr308, but this rifle is a bit overgassed. The listed starting load of 43grs wouldn't shoot accurately, and the full power loads were all over the place. I too have read the bit about using reduced loads with H4895, the Lee reloading manual has an extensive section on reduced loads, especially as they relate to cast bullets in cartridges like the 30-06.

    As an alternative to H4895, you can try out accurate 5744. I played around with loads in the low 20s range a few years ago and had really good luck. I only quit using it because of the powder shortages.
  5. OutlawHoss

    Well-Known Member

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    Yes, using cast is way different than copper plated, so there's that too.
    I'm not familiar with the 5744. I had no idea there was a powder for 308 in such small charges. If you can adjust your gas block than that's a huge advantage, one I haven't experimented with myself.
    Such small charges in a 308 case makes me a little nervous, but if they're listing it as such for that particular powder, it's could be a good round. I just wouldn't use a powder at a load that's so reduced beyond what's listed.
  6. AMProducts

    Maple Valley, WA
    Jerk, Ammo Manufacturer Silver Supporter

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    I've shot EH-LOT of .308 handloads over the years from various bolt-guns I owned. One of my personal favorites was a 150gr M80 over top of about 35grs of H335, it was a bit dirty, and I would be skeptical that it would cycle the AR-10, but it was an accurate fun load. I developed it for a 4-lb .308 pack rifle I had that was just brutal on the shoulder without something a bit lighter. IIRC MV was about 2100FPS from a 20".

    Another powder you might try that responds really well to these types of situations is IMR3031, which is often used as a smokeless replacement in black powder cartridges. A buddy of mine has an 11mm mouser that he loads with paper-patched bullets and 3031. I think I'm using ~41gr of 3031 in my .308 match loads (168gr SMK) but don't quote me. My normal preferred powder is Varget, but while that was in short supply I bought a few drums of 3031, which maybe some day I will finish using.

    In all, I'm not really sure exactly what you're trying to achieve here, recoil reduction or cost savings are the two obvious, at which point I would say "shoot your AR-15 more" to both. I actually barely shoot my .308 rifles any more, I can push .223 out to nearly 1000yards with my bolt gun and 75gr SMK's, and anything less than 600 I can beat up nicely with any of my AR-15's. Unless you really need something really big, really dead, really far away, shoot .223, and if you do need that, buy a .50 cal upper :)

    Another thing you may consider, if you're looking for something easier on the shoulder long term, but still want to reach out and touch... think about rebarreling to 6.5 creedmoor.
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