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Posted: 9/14/2025 8:41:28 PM EDT
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Is anyone running one with a VLTOR A5 receiver extension? I googled it and found threads on HK Pro but a lot of them were old and opinions were all over the place. I am looking for someone on here that has run one and can talk about their setup. |
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I do not have an A4 upper, but I have used my MR556A1 uppers exclusively with the VLTOR A5 system. I've used buffers from Clint at HeavyBuffers.com and had no issues with his products. I have a 12.5" MR556 upper that I've run with his H2 and H3, as well as two 10.4" uppers using either of those buffer weights. I like either the VLTOR tube or the BCM tube for my builds with a Wolff XP rifle length buffer spring. I've also got a couple Springco springs as well that have been fine. I think an H3 would be a good starting point, especially given the adjustable gas block and its different vent screws that you can swap out. |
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I am currently running the Magpul receiver extensions as they have 10 adjustment positions. I shot the rifle yesterday for the first time. It was the first time I fired a piston gun. I used an H3 buffer. I tried a Geissele Super 42 spring and Sprinco Green spring. Everything functioned fine. I am looking to soften the recoil of the gun. I was shooting off the bench to zero the optic. The gun jumped around too much. Way more than any of my gas guns. I have looked around and see some people running an H4 buffer. I have also seen people swapping out the gas vents. My question is do I try the H4 buffer or keep the H3 and try larger gas vents? |
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Originally Posted By CJofFL: Consider using the HK buffer & spring and adjusting the vents, it's literally what they were made for. Originally Posted By CJofFL: Originally Posted By EzGoingKev: I am looking to soften the recoil of the gun. I’d roll with the gas vents first, Maybe a Griffin rifle length spring, if a legacy suppressor is going to be used. More leeway to tune the cyclic rate. HK’s spring/buffer are as stiff and heavy as you can go in a carbine length tube, their motto is “overgassed, oversprung, and over buffered!” I think there’s only one heavier spring for that, and it’s a machinegun action spring. |
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I tried H2/H3/H4 buffers with the Sprinco Green and Geissele Super 42 springs. After seeing a post on the HK forum I tried a Tubbs and the H2. I like it. It is soft shooting and has been 100% reliable with: - Wolf Gold - Scorpion - Tula - PMC Bronze - PMC 55g 5.56 NATO The caveat is I only have (220) rounds through it with no adverse conditions. |
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Botach has the Kynshot RB5007 on sale for $90. I picked one up and Tubbs 5.56 spring. I also picked up the extra weight/spacer Kynshot recommends with the A5 system. I shot the gun with the Tubbs 308 spring and H2 buffer I had been running to get a baseline feel. I swapped out the buffer and spring to the Kynshot with the Tubb 556 spring. It functioned 100% on non-suppressed setting and recoil was softer. Not OMG I cannot believe the difference this makes but softer. |
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I know this is an older thread but I thought I'd add my experiences so far. Just received my 11" MR556 upper today and got to work. Running an LMT lower with an A5 tube with a Geissele H42 rifle spring and A5-H2 buffer. Suppressors used were Ridgeback Defense Rhino-x, CAT WB, and Knights MCQ-2. All functioned fine, the Rhino-x and CAT WB were more punchy than the MCQ-2. I have 1.7mm, 1.9mm, 2.0mm, 2.1mm, 2.2mm and 2.3mm vent screws on the way. Ammo used was Winchester .223 and PMC X-TAC 55gr. Tomorrow I'll try and A5-H3 buffer and update. It was wild when I first fired it unsuppressed with the Apparition Instruments Nano on both settings. It literally didn't move when I fired it, it was like shooting a 22lr. Locked back on both settings on last round. But the fire ball was massive! |
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I sighted it in today and it's plenty accurate with Bone Frog 77gr TMK ammo. I switched out the H2 to an H3 and everything still functioned the same with the exception of when I switched back to the Apparition Instruments Nano unsuppressed on the -S- setting it didn't lock back with .223 pressure ammo. On an odd note, I read that someone took the vent screw completely out and he said it functioned perfect. Thought I'd give it a try and it worked fine with the KAC three prong and MCQ-2 with 5.56 ammo, weird... For now I'm leaving the AI nano muzzle brake on until my vent screws all show up to test further. |
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Originally Posted By Nobody69s:On an odd note, I read that someone took the vent screw completely out and he said it functioned perfect. |
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Originally Posted By EzGoingKev: What size groups were you getting? Only using a 6x scope though so I'll do some accuracy testing in the future with a higher power scope. Mainly just focusing on getting the functionality testing done first. |
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I did some accuracy testing but only used a red dot and 3x magnifier. Only had 43 yards available so not too great of a distance. I think I could benefit from putting a 2-12x scope on just for accuracy testing if I decided to in the future for a finer aiming point. I think I did the app correctly but I've only used it a few times. Any, here's my crappy groups. 75gr Sabre black tip Attached File IMI 77gr Attached File Bonefrog 77gr barnes match burner Attached File |
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