Army Testing Shows Piston Retrofit kits Are Not Less Accurate, And. . .

[lysander]

A few things to take away from this:

1) If you decide that a piston kit is for you, go with the next higher, or maybe two higher, buffer weight. That will calm the cyclic rate down.

2) Loctite on barrels does little, if you like to do mag dumps.

3) Accuracy with piston kits is fine.

4) Piston kits add only 3.2 ounces in some cases, 7-3/4 on the outside.

5) Carbine length gas systems are rough on bolts, standard or piston, but bolt can take a fair amount of abuse. Check them regularly with a 10X loupe if you don't have a mag-particle set-up; pay special attention to the two lugs either side of the extractor. The crack indications on the bolts were probably large enough to see under 10X.

6) Pistons do better in regards to cook-off mitigation.

7) High cyclic rates are bad, very bad.

8) Expect your cyclic rate to increase around 100 rpm after 6000 rounds.

9) If you think something is missing in the instructions/manual supplied with after market products, or it does not perform the way you expected it to, call the manufacturer and complain, they can't fix it, if they don't know its wrong.

10) The "mil-spec" M4 Carbine is not required to be all that accurate, 5.6 inches at 100 yards new and 7.0 inches after 6000 rounds.

While is was not stated in the report, I think most of the light strikes/failures to fire were due to bolt carrier bounce during automatic fire. The front face of the weapons with large numbers of LS/FF showed considerable beating. Again, a heavier buffer would have helped.

[Clint]

One curiousity is the accuracy.

Baseline with the ARS handguards ranged between 2.5-4.5"

Replacing the ARS handguards with plastic and installing the piston kits ranged between 2.5-3.5", with most around 2.5".

Perhaps the handguards rather than the piston are main the source of the accuracy improvement.

What other possible explanation is there for the accuracy improvement?

[SGTMAJ]

Thank you . This is really useful information

[Outlander Systems]

Phenomenal information.

This is the bread and butter of M4C right here.

[556BlackRifle]

lysander, Thank you for taking the time to prepare and share this very interesting information with us.

[556BlackRifle]

One curiousity is the accuracy.

Baseline with the ARS handguards ranged between 2.5-4.5"

Replacing the ARS handguards with plastic and installing the piston kits ranged between 2.5-3.5", with most around 2.5".

Perhaps the handguards rather than the piston are main the source of the accuracy improvement.

What other possible explanation is there for the accuracy improvement?

One might argue that the added weight of the piston system changed the barrel harmonics such that it became more accurate. This could be proven or disproven by removing handguards from the equation during accuracy testing.

[marktwoa]

Thanks for putting this together and sharing.

I'm taking two things from this:

1. I don't see enough of an argument to switch from DI to piston. In fact it's almost the opposite.

2. Hopefully the team that did this test will not allow that suppressor they used to be bought en masse and deployed.


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[lysander]

One curiousity is the accuracy.

Baseline with the ARS handguards ranged between 2.5-4.5"

Replacing the ARS handguards with plastic and installing the piston kits ranged between 2.5-3.5", with most around 2.5".

Perhaps the handguards rather than the piston are main the source of the accuracy improvement.

What other possible explanation is there for the accuracy improvement?

Possible.

But, the argument against is the ARS attaches the rifle in the same manner as the plastic handguards.



And, the Govt profile barrel, with the added weigh at the muzzle showed a slight improvement in extreme spread over the original pencil profile. Indicating there may be a harmonics influence.

The other possible explanation could be the modifications necessary to the firing stand required to hold the plastic handguards, made it more rigid.

In any case, a piston kit probably will not degrade your accuracy.

[lysander]

Thanks for putting this together and sharing.

I'm taking two things from this:

1. I don't see enough of an argument to switch from DI to piston. In fact it's almost the opposite.

2. Hopefully the team that did this test will not allow that suppressor they used to be bought en masse and deployed.


Sent from my iPhone using Tapatalk

1. Well, to be honest, this report will not end the debate, perhaps just be more fuel on the fire. All of the problems seem to stem from the higher cyclic rate, and a high cyclic rate can be controlled by heavier buffers smaller gas ports and sometimes choice of springs. Although, from the Army's point of view, they agree with you.

2. The manufacturer of those suppressors does have a contract to supply suppressors, whether or not the type used in the test is the same model bought by the Army or Navy, I don't know. But, that's why the Army spreads money to test and develop stuff, rather than just buy off the shelf on the whole.

[caporider]

A few things to take away from this:

2) Loctite on barrels does little, if you like to do mag dumps.

Loctite is the wrong answer for securing suppressor mounts. Rocksett is much preferred, and I'd like to know if Rocksett was supplied by the suppressor manufacturer...