IN the process of building an SBR using a 10.5 inch barrel with a carbine gas system and a gas port in the .070 to .073 range. Would like to also use an A5 set up on this but unsure which Sprinco spring to use and buffer weight. On my middy I used the green spring and a VLTOR 5.3 oz buffer but not sure which one to use with this set up. I’m guessing the green will be fine for this application as well but wondering about buffer weight too. TIA!
The Green is the only choice for a Sprinco rifle spring.
The VLTOR supplied spring also works great for most people.
The A5H1 would be a good choice for this.
Thanks for that. Other than someone saying don’t use the A5 with that set up, the buffer weight was my next ??
Which buffer really depends on the gas supply / efficiency of the overall rifle.
My DD MK18 has a VLTOR on back with an H3 buffer, VLTOR spring and it works just dandy.
I use the A5 in all my built rifles, so doubt you’ll hear don’t use it here.
Which makes sense since my recollection is that gas port on the DD barrels is opened up a bit more. I have one of their barrels on another build. The BCG is good to go on this current build. OCKS, good rings etc etc so that part of the equation should be ok. Block is dimpled but not pinned. What I don’t know for certain, and I don’t have the pins to measure, is the exact gas port size. I do know the range as stated but not the exact one on this barrel. But as long as I get in the general vicinity on the buffer weight Ill be fine. After all, the worst thing that happens is I build up my collection of A5 buffers lol.
I have only done the A5 on one other build but I like it. Nest up will be retrofitting it to my 7.62 x 39 build. That is a CLGS with something like a .098 port size so I am thinking that one will require some weight behind it.
I run green with a 0.070 ported 10.3 (DD barrel) and A5H2. Works suppressed and unsuppressed.
I sold my MK18 but had the same setup as dan and it ran fantastic.
Green
As others have said, your only Sprinco option is the Green spring (the other colors won’t be long enough for safe use in an A5 tube)
I believe Vltor, Colt, and BCM also have rifle length springs, but I don’t know how they stack up in spring power. I think the Sprinco Green is the stiffest
Thanks Gents. My original question was poorly worded but you guys got me what I needed despite my ysdexlia. 
I’ve had good luck with the VLTOR spring that comes with the kits and found that spring and the A5H2 to be the ticket for most setups. The only gun I run a lighter A5 buffer in is the one with a Law folder, that little BCG extension weighs like 2oz.
Absolutely this. 2.3 oz to be exact.
I found with a 0.070" port 10.3" bbl and LAW adapter I had to switch to a 3.0 oz carbine buffer, and when I changed to an A5 I used the 3.8 oz A5H0 buffer. My dad’s BCM 12.5 runs a LAW adapter with an A5H3 and Sprinco Green (total of like 8.3 oz). We’ve never measured the port, but it must have some serious gas to cycle all that weight (it runs like a sewing machine FWIW).
I don’t have anything useful to add. I just found this post to be a reminder that after having the A5 system on my “to do” list since it’s unveiling, I still haven’t gotten around to it.
10.3" with the Crane spec .07" gas port, LAW folder, and A5H0 is the exact combo I’m running on that particular gun. I’m not shocked to hear your Dad’s BCM is gassy.
I wouldn’t bother.
I wouldn’t either unless it’s going in a new build.
If its on a SBR or pistol it would be one of the first things I do.