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Jp Adustable Gas Block On A Shorty Ar?


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Hello all,

I am running a 16" carbine with a short gas system. I am going to remove the normal front sight and put a (railed) gas block in its place. I was wondering if purchasing a JP adustable gas block would make any sense. Will I be able to realistically smooth out recoil on a short gas system using this part? How much could this part affect reliability?

Before I get the 5+ recommendations to upgrade to a longer gas system/longer barrel... I am buying a new 20" rifle built specifically for 3 gun in the next couple months. The 16" gun is a short-term 3-gun tool and will become backup/tactabilly-toy as soon as I get the new one.


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Mike (my cousin of the carbine) beat me to the punch. My 16" carbine runs like a champ but probably due to Benny's tweakin'. :wub:

That said, there's nothing wrong with a 16" if it runs. As for the gas block, I'd say go with a comp/carrier/buffer (or some combo thereof) change first before messing with the gas system. FSB's are cheap and a Dremel can lop the excess of that bad boy off in about 5 minutes.


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If you don't have a muzzle brake on that AR, get one.

The JP gas block will allow you to turn down the gas and soften the cycling pulse some, but it will NOT cure the 16" (short gas system) tendency to unlock a tad early and rip the brass outa' the chamber too soon. Only a pigtail gas tube that actually delays the gas pulse to the bolt carrier, or a longer gas system will fix this issue on a shorty.

That said, a 16er has a tremendous gas pulse and softening it down a bit will be fine as long as you set it right.

Turn the gas down until it won't reliably lock back on an empty mag, then open it up until it does lock back every time, then add 3/4 to one full turn more. Do this with the wimpiest ammo you will use.

Do the lock back testing using mags with a single round inserted.

In my experience, you can get a quite noticeable reduction in bolt cycling dance this way and still maintain plenty of operating range. A lower mass bot is not really a good idea in a shorty because it will now accelerate quicker and even more than it should. Excess bolt speed is a bad thing.

You will need to have a good muzzle brake on the rifle to be able to really see the effect . Without taming the recoil, it's hard to discern the bolt carriercycling dance reduction you will get.

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Thanks for the info, guys. I do have a miculek comp/break on the carbine and it certainly helped a lot to reduce recoil. I had considered a lightened bolt/buffer combo, but as this carbine is not going to be my primary 3-gun rifle soon, I had planned to leave those parts alone for the moment.

I am going to replace the existing front sight gas block with a block which features a rail. Currently I have an Eotech on this gun, but I am putting a Weaver V3 1-3x in its place. While I don't mind having a dot co-witnessed with the iron sights, I don't think I will like the same effect with a traditional optic. So, the theory was to spend a couple extra $$ and get a JP block, if it would actually further improve the recoil impulse on this carbine.

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