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Tuning gas block - Carbine spring/ buffer/ 18 " rifle length / low


five six

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I'm having trouble tuning my gas block, can get it to lock open, but not load another round without having a failure to feed. I put locktite on, cranked it all the way down, and then half turns all the way till it locked back. Wouldn't feed the next round so i kept going till the set screw was completely out. Still no luck! Here is my setup:

-Keis adjustable gas block, similar to the PRI and JP models with a set screw that adjusts the gas (its a .750 clamp on)

-18" barrel with rifle length gas system

-carbine tube, carbine buffer, carbine spring

-Loki Super Light carrier (similar to the young super light, which is slightly heavier than the jp lmos carrier)

I bought a jp low mass rifle buffer and enhanced rate spring for a rifle tube, but would prefer to keep a carbine adjustable stock. Any thoughts on this ? Will this magically solve my problems? I can get a regular weight carrier to work with the adjustable gas system.

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Edited by five six
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If you want to run a rifle lenth spring with a cola sable stock look into the Vltor A5 system. I like it a lot. I have not tried a low mass buffer in it yet. I will require using their buffer and changing the weights.

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If you want to run a rifle lenth spring with a cola sable stock look into the Vltor A5 system. I like it a lot. I have not tried a low mass buffer in it yet. I will require using their buffer and changing the weights.

Cola Sable stock?

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Gas block and gas port may not be lined up.

whats the best way to check alignment? I was pretty careful when installing it.

Should this work or do you think perhaps a rifle buffer tube/ low mass buffer / and increased rate rifle buffer spring will fix it?

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your carbine buffer should weight as much as the JP light rifle buffer, the gun should run as is, have you checked the alignment of the gas block with the gas port on the barrel? Do you have any leaks in the BCG? is the rifle new, are you shooting it well lubed and what type of ammo?

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Gas block and gas port may not be lined up.

whats the best way to check alignment? I was pretty careful when installing it.

Should this work or do you think perhaps a rifle buffer tube/ low mass buffer / and increased rate rifle buffer spring will fix it?

I am sure there are alot of ways other than mine, but I use a little air from one side of the barrel and plug the other, manipulate the block to get the most air flow............backyard mechanic .

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your carbine buffer should weight as much as the JP light rifle buffer, the gun should run as is, have you checked the alignment of the gas block with the gas port on the barrel? Do you have any leaks in the BCG? is the rifle new, are you shooting it well lubed and what type of ammo?

Well lubed, but not dripping.

Not sure about leaks in the bcg?!?!?

Rifle is new, I was careful when installing the gas block, but perhaps i should go back and check it.

I'm using .55 grain , privi partizan, pmc, drs reloads.

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If you already have a rifle length stock and spring lying around maybe worth a try.

If you pull the gas block off after you have fired it you should be able to see where the hot gas has etched a mark if it is not aligned. Maybe worth a check.

It should run with stock parts and an adjustable gas block. I run one with stock parts(carrier and buffer) and have one with the low mass buffer and the JP low mass carrier.

A stock spring will work fine.

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Did you say you were using a lmos buffer in your carbine tube?

carbine buff, carbine tube, carbine spring( was having issues with this)

jp lmos buffer, increased rate spring, and rifle tube(is what i just installed)

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How tightly does the LMOS carrier fit in the upper compared to the standard weight? I have on occasion had uppers that were tight with a LMOS and it caused to much friction.

smooth as heck. its actually more slick, its got that special coating on it.

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If its not binding, something else is hanging up. You stated the bolt will lock back ( on an empty mag i presume) which indicates at that point the gas system is fine. Opening it up further does nothing for the forward movement of the b/c to strip a round. The heavier bolt must have just enough extra inertia to get past the resistance but is probably not working as it should. How close to the groove in the b/c is the buffer retainer. If it drags on it it can cause issues.

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If its not binding, something else is hanging up. You stated the bolt will lock back ( on an empty mag i presume) which indicates at that point the gas system is fine. Opening it up further does nothing for the forward movement of the b/c to strip a round. The heavier bolt must have just enough extra inertia to get past the resistance but is probably not working as it should. How close to the groove in the b/c is the buffer retainer. If it drags on it it can cause issues.

Hmm i'll have to check.

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FWIW, I went out this weekend to tune my JP adjustable block for the first time with a roughly similar setup (18", carbine buffer/spring/tube) it wouldn't lock 3 turns out from bottom, locked fine at 4 turns out. The set screw had a ton more adjustment left in it though I don't know where the adjustments stop having a real effect.

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