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Posted: 8/17/2014 11:17:29 AM EDT
[#1]
If I had to pick a nominal configuration for 10.3-10.5" unsuppressed I would say standard spring, H2 buffer. Most Army CQBRs run that configuration (since that is standard in the M4A1 host lower). I have heard of some armorers going to H3s in order to get a gun to run right, but that is rare IME.
It is also a function of ammo and gas port size. For example, DD Mk18 barrels have larger gas ports and I run a Springco Blue/H3/M855 with good results in mine. 14.5" is as long as I go and the same applies: standard (Sprinco white) or Sprinco blue with at least an H; H2 preferred. As for extractor springs, I run whatever came in the bolt until I change them out. I am currently using BCM's SOPMOD Bolt Upgrade/Rebuild Kit for replacement parts. I plan to try Springco's 5 coil extractor springs sometime in the future (when I run out of BCM kits). |
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Posted: 8/17/2014 11:28:11 AM EDT
[#2]
10.5": H2 buffer, Crane O-ring and blue spring insert on the extractor, regular M4 spring. That's pretty much a winning combo for most 10.5" rifles.
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Posted: 8/17/2014 2:32:55 PM EDT
[#3]
My 11" setup is using a regular carbine buffer spring and H2 buffer and also using the BCM extractor upgrade kit. It usually gets shot suppressed so it has an adjustable gas block too.
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Posted: 8/17/2014 3:13:51 PM EDT
[#4]
11.5:
Unsuppressed it was great with a ST-T2 buffer using all kinds of ammo - from Tula to Mk262. When I got my can it slowed the cycling down a bit when I used weak ammo, so I switched to a carbine buffer and it runs great now. Action spring is a standard carbine spring (colt). 12: Runs great with the standard carbine buffer and spring. This isn't going to be suppressed (IDF clone). |
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Posted: 8/18/2014 6:57:12 AM EDT
[#5]
With a properly done gas port I think the H buffer is good to go for most all configs.
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Posted: 8/18/2014 3:55:00 PM EDT
[#6]
Vltor A5 is always the correct answer.
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Posted: 8/19/2014 8:22:31 AM EDT
[#7]
Quote HistoryQuoted:
11.5: Unsuppressed it was great with a ST-T2 buffer using all kinds of ammo - from Tula to Mk262. When I got my can it slowed the cycling down a bit when I used weak ammo, so I switched to a carbine buffer and it runs great now. Action spring is a standard carbine spring (colt). 12: Runs great with the standard carbine buffer and spring. This isn't going to be suppressed (IDF clone). Shouldn't that be the opposite way? A suppressor increases back pressure making the gun over-gassed. Therefore, you should have to go up on your buffer weight not down right? |
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Posted: 8/19/2014 2:00:59 PM EDT
[#8]
Quote HistoryQuoted: I would say standard spring, H2 buffer. Most Army CQBRs run that configuration (since that is standard in the M4A1 host lower). Quote HistoryQuoted: I would say standard spring, H2 buffer. Most Army CQBRs run that configuration (since that is standard in the M4A1 host lower). I use that exact configuration for all my port size testing since that is the military M4 standard configuration just as you mentioned. In fact, I use it with all my upper configurations and do all tuning in the upper with our patented gas block and leave the lowers un-modified. Quoted: Shouldn't that be the opposite way? A suppressor increases back pressure making the gun over-gassed. Therefore, you should have to go up on your buffer weight not down right? I would agree with that with the exception of when you are regulating the gas. In many cases, when you regulate the gas, the RoF will actually go down due to the increased dwell time. Below is a video of a DDMK18 commercial upper which has a .082 port but we are bringing the unsuppressed port size down to the .070 size as specified by Crane to yield a RoF of 830 RPM. Suppressed with a 556 Saker increases the RoF to 1024 RPM with the same .070 port. Then with a .049 port the RoF went slower than un-suppressed at 726 RPM. Of course, if we wanted to get closer to the unsuppressed .070 RoF of 830RPM, it would be a simple matter of increasing the suppressed port size.  http://micromoa.com https://www.facebook.com/MicroMOA |
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