Reduced loads in AR???

[NSP64]

Anyone try using reduced cast or jacketed loads in an AR?
If you put a weaker recoil spring in it would it be possible?

You can adjust/ change springs in 1911's to achieve operation with different loads.

[Larry Gibson]

Some have had minimal success playing with the springs. However, the m1911 is recoil operated and the AR is gas operated. There still has to be enough psi up through the gas tube into the gas cylinder (that part of the bolt carrier the bolt seats in) to make the bolt carrier move to the rear unlocking the bolt, withdrawing it, cocking the hammer (probably have to reduce that spring too) overcome the recoil spring and drive back far enough to eject the spent case and pick up another round from the magazine. Quite frankly I've been shooting ARs since '65 and haven't found a reduced load using a fast burning powder that will function the action. Best results with cast bullets functioning the action reliably start with powders in the RL7 - 4895 burning range in the 1700 - 1900 fps range.

Larry Gibson

[NSP64]

But........
Have you ever owned a hybrid AR?
With a gas piston, adjustable gas block, and 2 seperate recoil springs?

[Larry Gibson]

No, but I've shot enough "reduced loads" in many other gas guns with similar gas systems as the piston driven ARs of recent. You'll still need sufficient psi to make the gas system operate. The adjustable gas block does not open up the gas port from the barrel, that is fixed. It still has to overcome not only the 2 separate recoil springs which is one more than with the DI AR but you also still have to overcome the inertia of the bolt. the force it needs to cam open the bolt and thrust the carrier and bolt to the rear to cock the hammer, extract/eject the case and pick up the next round to chamber.

Like I said; some have had minimal success cutting the springs but most of us understand that a certain residual and sustained psi is need when the bullet transverses the gas port to function the action. That generally, in a .223/5.56 AR, requires at least a medium burning powder with the bullet, cast or jacketed, in the 1700 - 1900 fps range. For example; many years a go I developed (based on Whelen's experiences with cast bullet reduced loads in his M1903 in Panama) what I called my 5.56 "Panama Load". The powder from a 45 ACP ball round was put into a 5.56 case (M193 after pulling the bullet and dumping the powder) and the 55 gr FMJBT was reseated BT forward and crimped in. Or with 5.5 gr of Bullseye loaded under the same 55 gr FMJBT. Velocity ran 1500 - 1625 fps depending on the lot of 45 ACP ammo one had to work with. Out of my M16A1 they were deadly on small game in the jungles of Panama and other parts of central America and the world. Those loads had insufficient psi to even move the bolt carrier at all and with such my M16A1 was essentially then a bolt action rifle. They also weren't much louder than M16 blanks and not quite as loud as 7.62 blanks. With an improvised suppressor there was only an annoying "snap" made by the sonic bullet that was not discernible much past 30 - 50 meters in the jungle.

However, a 55 - 60 gr cast bullet under 17 - 19 gr of 4895 with a Dacron filler (sometimes as little as 16 gr in short tubed M4s) will many times function most any AR quite reliably and most other 5.56 gas guns also such as Mini 14s, FNCs, etc.

Larry Gibson

[Nickle]

I'm 100% with Larry on this one. I've also got a bunch of experience on the AR platform, but strictly with j-word bullets, not cast boolits. However, I do know the system well enough to know his answers are right.

[NSP64]

I loaded some Midway 55gr JSP Dogtown bullets over 10-14 gr of Alliant 2400.
None moved the bolt in normal setup(factory equivalent).
I opened the gas screw and got some movement of the bolt.
I pulled one recoil spring out and 12.5-14 gr ejected, but would not lock open.
Tomorrow I will pull the spring off/ replace with a lighter one on the op rod.

[NSP64]

SUCCESS!!!
I changed the op rod recoil spring to a lighter one and 14 gr of 2400 would lock open and strip another round out of the mag.
Anything below 14 will not work.