Law Tactical folder & A5 buffer issues

So I’m running into an issue with my sbr. It’s a Geissele URG-I 10.3” on a KAC ambi lower. I added a KAC sandcutter bolt carrier. The URG-I 10.3 shipped with a H3 buffer and Super42 spring. I’ve ran it for over 1k rounds since August, including through a 2 day class with no stoppages. For the record I run Gen3 Pmags and Federal American Eagle .223 55grain FMJ exclusively (but carry ammo is LE223T3, also .223 pressure). I currently do not own a suppressor for it. My only complaint is the increased sight disturbance under recoil compared to my mid length 14.5” & 16” guns. I decided to add a law tactical folding adapter and at the same time a A5 buffer system to try and tame some of that recoil. Also at the same time I added a LMT enhanced bolt to try and mimic the KAC E3 that I originally wanted but was out of stock everywhere. So I bought the SR25/M110 receiver extension from Magpul, A5H2 buffer from Vltor, and a SpringCo Green Rifle spring. The castle nut, receiver end plate, and buffer retainer were all changed too, but none of that should matter. I meticulously put it together. Went to the range to do a function check, and got repeated bolt over base malfunctions, and failure to lock back after the last round. Now the receiver extension for the law folder adds 2oz to the cycling mass. I figure the buffer mass was just too much and was causing short strokes. So I replaced one of the tungsten weights with a steel one. Same story. Replaced the final tungsten weight with a steel, and while the bolt over base malfunctions stopped, it still fails to lock back on the last round. I then swapped rifle springs with a guy running a cheap LuthAR spring that was identical in length but felt slightly less stiff and it started locking back. I will admit the rifle was dry while doing my testing, but it was pretty clean, so I’m not sure the lack of lubricant should matter that much. I’ve ordered a Wolff standard power rifle spring to try since SpringCo does not make more than one rifle spring.

Should I ditch the A5 system all together? With the 2oz carrier extension and a A5H0 buffer, I still have .5oz more cycling mass than before with no extension and a H3 carbine buffer.

I’d like to think that lack of lube alone would not cause malfunctions in a clean gun. I do normally run it wet with Slip2000 EWL30.

Is the SpringoCo green not a direct replacement for a standard weight/power rifle spring?

Is there anything else that I’m missing that I should check? I don’t feel any binding when hand cycling dummy rounds. Ejection under recoil doesn’t seem as far or consistent as before.

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It seems like everything should work.

Verify proper stroke with bolt lugs ~1/4" past the bolt stop.

Perhaps swap the bolt back to the original and lube it up.

Personally, I prefer not to run any 5.56 barrel under 14.5" without the A5. It sounds like your total reciprocating mass is ok. Unless your E-bolt extractor tension is weak, it should be fine to replace a milspec bolt.

The Sprinco green is indeed stiffer than a milspec rifle spring, and I would only use it with an A5H3 or H4. Try a factory Vltor or Colt spring.

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Originally Posted by CESwartz07

So I’m running into an issue with my sbr. It’s a Geissele URG-I 10.3” on a KAC ambi lower. I added a KAC sandcutter bolt carrier. The URG-I 10.3 shipped with a H3 buffer and Super42 spring. I’ve ran it for over 1k rounds since August, including through a 2 day class with no stoppages. For the record I run Gen3 Pmags and Federal American Eagle .223 55grain FMJ exclusively (but carry ammo is LE223T3, also .223 pressure). I currently do not own a suppressor for it. My only complaint is the increased sight disturbance under recoil compared to my mid length 14.5” & 16” guns. I decided to add a law tactical folding adapter and at the same time a A5 buffer system to try and tame some of that recoil. Also at the same time I added a LMT enhanced bolt to try and mimic the KAC E3 that I originally wanted but was out of stock everywhere. So I bought the SR25/M110 receiver extension from Magpul, A5H2 buffer from Vltor, and a SpringCo Green Rifle spring. The castle nut, receiver end plate, and buffer retainer were all changed too, but none of that should matter. I meticulously put it together. Went to the range to do a function check, and got repeated bolt over base malfunctions, and failure to lock back after the last round. Now the receiver extension for the law folder adds 2oz to the cycling mass. I figure the buffer mass was just too much and was causing short strokes. So I replaced one of the tungsten weights with a steel one. Same story. Replaced the final tungsten weight with a steel, and while the bolt over base malfunctions stopped, it still fails to lock back on the last round. I then swapped rifle springs with a guy running a cheap LuthAR spring that was identical in length but felt slightly less stiff and it started locking back. I will admit the rifle was dry while doing my testing, but it was pretty clean, so I’m not sure the lack of lubricant should matter that much. I’ve ordered a Wolff standard power rifle spring to try since SpringCo does not make more than one rifle spring.

Should I ditch the A5 system all together? With the 2oz carrier extension and a A5H0 buffer, I still have .5oz more cycling mass than before with no extension and a H3 carbine buffer.

I’d like to think that lack of lube alone would not cause malfunctions in a clean gun. I do normally run it wet with Slip2000 EWL30.

Is the SpringoCo green not a direct replacement for a standard weight/power rifle spring?

Is there anything else that I’m missing that I should check? I don’t feel any binding when hand cycling dummy rounds. Ejection under recoil doesn’t seem as far or consistent as before.

Sent from my iPhone using Tapatalk

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Op, did you ever get your set up sorted out with the A5 extension?

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Originally Posted by Korgs130

Op, did you ever get your set up sorted out with the A5 extension?

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The fix was to run an A5H0 buffer and a standard spring.

I still run that identical lower setup, but now with a KAC E3 MOD 2 CQB 11.5” upper. It runs both unsuppressed and suppressed (Sandman-K) in this manner with .223 ammo. I may end up trying the green spring again though now that I primarily run suppressed.


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Good to know. Glad you got it worked out.