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1/16/2020 9:48:49 PM
Posted: 1/17/2015 5:19:42 PM EST
I am building an SPR. I would like an 18'' barrel, but the barrel I want has a rifle length gas tube. My lower is set up for a carbine with a carbine buffer and buffer tube. Are these compatible? Will it function correctly? School me up
Link Posted: 1/17/2015 5:20:43 PM EST
It should work just fine.
Link Posted: 1/17/2015 5:27:38 PM EST
I am about to pull the trigger on this, but I am hesitant
Link Posted: 1/17/2015 5:29:57 PM EST
Yes Gas system and Stock have nothing to do with each other.

There are tons of rifle gas system and carbine stock tubes and rifle buffer and shorter gas system guns out there
Link Posted: 1/17/2015 5:30:59 PM EST
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Originally Posted By TeeRex:
Yes Gas system and Stock have nothing to do with each other.

There are tons of rifle gas system and carbine stock tubes and rifle buffer and shorter gas system guns out there
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Thanks TeeRex.
Link Posted: 1/17/2015 5:32:05 PM EST
This should answer your questions. As noted in the diagram below, the action spring compression distances only differ by 1/10th of an inch between a rifle receiver extension and carbine receiver extension. Using a carbine receiver extension with a barrel with a rifle length gas system, I would use a H6 buffer (5.2 oz) being it matches the weight of a rifle buffer.

Link Posted: 1/17/2015 5:35:23 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By AR-4C:
This should answer your questions. As noted in the diagram below, the action spring compression distances only differ by 1/10th of an inch between a rifle receiver extension and carbine receiver extension. Using a carbine receiver extension with a barrel with a rifle length gas system, I would use a H6 buffer (5.2 oz) being it matches the weight of a rifle buffer.

http://i1286.photobucket.com/albums/a601/AVIDavid1982/Mobile%20Uploads/photo_zpsd2200e15.jpg
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I am running the Spikes S2 buffer
Link Posted: 1/17/2015 10:24:24 PM EST
[Last Edit: 1/17/2015 10:25:26 PM EST by DoctorLove]
Would an H3 buffer work?
Link Posted: 1/17/2015 11:17:56 PM EST
the original Crane Mk12 SPR has a rifle length gas system and end-users would frequently drop the SPR uppers on their M4A1 or Mk18 lowers. check out the Mk12 SPR clone thread for tech info, original rifles in use and board members' SPR clones
Link Posted: 1/17/2015 11:44:27 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By DoctorLove:
Would an H3 buffer work?
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Depends on how close to undergassed that particular rifle is. Some might need a lighter buffer. Worst case that is all you need to change.
Link Posted: 1/18/2015 8:55:29 AM EST
Should be fine,

18" rifle gas with carbine buffer and tube
Link Posted: 1/18/2015 10:06:16 AM EST
Don't the Canadian military take rifle length uppers and put them on carbine buffer lowers? They have a 20" rifle length barrel and a H2 buffer spring lower. It works for them for years and adds reliability.

For me, I have a rifle length with ST-T3 buffer though I do have a T2 buffer as well in standby. It works.
Link Posted: 1/18/2015 10:38:47 AM EST
Link Posted: 1/18/2015 11:23:24 AM EST
[Last Edit: 1/18/2015 11:23:54 AM EST by ZekeMenuar]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By DoctorLove:
Would an H3 buffer work?
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Buffers are cheap. Get an H3 and try it.

I use 9mm buffers in my carbine lowers. I believe they're heavier than H3 buffers.
I mix and match my lowers with my uppers.
The carbine lowers work with carbine, midlength and rifle uppers. No issues.
My rifle lower worked with the aforementioned uppers. No issues,
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