16.5" rifle length gas barrel is.....undergassed

[Bryan 45]

I have a factory configuration 16.5" upper with rifle length gas system. It had some under-gassed FTF issues when I got it, using the factory lower with rifle length buffer tube, rifle buffer, and what looks like a carbine spring, but after a couple hundred rounds it started functioning properly. I've since shot a few hundred more rounds through it with a suppressor, and it of course runs fine with the can also.

I'd much rather prefer to use a carbine stock on this carbine instead of rifle length. After changing out the buffer tube to a carbine length, using a standard carbine buffer spring, it's back to short-stroking without suppressor. Is there any combination of buffer and spring change I could make to help it out? Take the weights out of the buffer? Cut the spring? Does anyone make a reduced power carbine length spring?

Thanks!

[EaZeNuTZ33]

I used the same setup last year and had good luck with the Taccom ULW buffer system and lightweight bolt carrier.

[Bryan 45]

I used the same setup last year and had good luck with the Taccom ULW buffer system and lightweight bolt carrier.

It has it's own lightened carrier already. But the ULW might be the ticket. What spring did you use with it?

[EaZeNuTZ33]

Tim @ Taccom sent me one of his springs and I also tried a polished JP Spring. Both worked great.

[caspian guy]

Or you could try taking some or all of the weights out of your buffer...If I don't take all of the weights out I usually use pieces of aluminum rod to replace the ones I removed.

Edited October 12, 2015 by caspian guy

[Cap]

I'm having the same problem I think. I've only put about 30rds through mine hand cycling every time. Lower has a Giselle SD3G trigger and standard carbine buffer and spring. Would a reduced power spring be the best place to start?

[MarkCO]

Brownells carries a reduced power buffer spring. You can take the weights out of the buffer as well.

16 and 16.5 barrels with rifle gas typically need some warmer ammo to run 100% due to the very short dwell time. A faster powder might help if you are reloading.

[Cap]

I was shooting m193, I would like to think that's plenty warm

[michael1778]

I was shooting m193, I would like to think that's plenty warm

Yes, but it is also relatively high velocity. Therefore the time in the barrel between gas port and muzzle is less than a comparably powered (but naturally slower) 69 or 77 grain load. Have you tried any heavier bullets?

Dwell time is a function of port-to-muzzle distance as well as bullet velocity. Together they make dwell time.

Edited October 24, 2015 by michael1778

[Cap]

Nope. But if it won't run m193 it's useless to me and Adams Arms will be getting it back. An AR that won't run 193 is broken. I understand not running Tula, but milspec 55s should run in any off the shelf AR

[Darqusoull13]

Cap, my Adams 16.5"s have functioned properly on RRA, Aero and Adams standard carbine lowers on diets of anything from Freedom plinkers to hand loaded 69's going ~2850. Definitely contact Cody at Adams Arms and he will get you taken care of quickly.

[Bryan 45]

For me, changing the ammo isn't a good option.

I'll try removing weights and a reduced power spring. That should do it- since it was running fine with the rifle length tube and carbine spring.

Thanks for the suggestions, guys.

[Tuflehundon]

For me, changing the ammo isn't a good option.

I'll try removing weights and a reduced power spring. That should do it- since it was running fine with the rifle length tube and carbine spring.

Thanks for the suggestions, guys.

removing buffer weights should fix your issue. Are you using the low mass carrier from AA as well? I removed all of the weights from my buffer and got mine running 100% no matter what ammo I fed it. I'm running the low mass carrier and XLP gas block. I'm lucky enough to know a lot of the guys from Adams Arms and shoot with them fairly regularly. They helped me out a lot.

I eventually switched to the JP silent capture spring with the spring pack. I'm currently using the lightest spring and have turned the gas down 2 notches (which I think is 50%), and it still runs anything I throw at it. Just ran some M855 and M193 last weekend.

[Bryan 45]

I do have the Adams Arms light carrier. Mine is not the XLP system, it's the standard gas block, so less adjustment available on it.

I have pulled the weights out of the buffer. It will probably be a few weeks before I have an opportunity to take it out and test it.

I have no doubt AA would take care of it, but if it's something simple enough I can do, I'd rather handle it than go to the trouble of shipping it to Florida.

[Tuflehundon]

I do have the Adams Arms light carrier. Mine is not the XLP system, it's the standard gas block, so less adjustment available on it.

I have pulled the weights out of the buffer. It will probably be a few weeks before I have an opportunity to take it out and test it.

I have no doubt AA would take care of it, but if it's something simple enough I can do, I'd rather handle it than go to the trouble of shipping it to Florida.

When I had a standard buffer with all the weights removed I was running full gas on my XLP gas block. Even though it was full gas, I did notice less felt recoil.

I only turned the gas down when I switched to the JP Silent Captured Spring system, which allowed a lot more tweaking and tuning.

You should be GTG with the standard non XLP block and no weights in the buffer. That was roughly the weight of the JP low mass buffer.