An adventure into reducing muzzle climb and felt recoil

[MistWolf]

0.076 mid gas port with an H
0.080 mid gas port with an H2
anything over 0.080 mid gas needs to be thrown in the trash.

This doesn't answer my question. Was an upper that was properly gassed for an H or H2 tested for function with an H3 buffer?

I recently tested an adjustable gas block equipped 11.5" upper with a carbine (3.0 oz), H (3.8 oz), H2 (4.6 oz) and A5H2 (5.3 oz) buffers. Lock back check was used to set gas block. Gas block was closed until the AR would eject but not lock back. Then, the gas block was opened one click and tested to verify it would reliably eject and lock back. With all three buffers, the gas setting was the same. Upper was tested with a suppressor.

[markm]

With all three buffers, the gas setting was the same. Upper was tested with a suppressor.

That's pretty interesting. However, adjustable gas block lack any sort of precision tuning ability. For example... the first half dozen clicks or so typically do nothing... then the next one mellows it out... then it won't lock back or eject.

In my experience with a whopping 2 different blocks, they have one good setting with a can off... then one more click with the can on. I never tried buffer swaps however, since I want to MAKE the gun run right with the standard A5 system.

[Kenneth]

One question on tuning a gun with a AGB. If your running the A5 system what buffer should you try and get it to work with? The lightest, A5H2, or another?

What are the effects of having a heavier buffer of you have a way to limit the gas?


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[vicious_cb]

This doesn't answer my question. Was an upper that was properly gassed for an H or H2 tested for function with an H3 buffer?

I recently tested an adjustable gas block equipped 11.5" upper with a carbine (3.0 oz), H (3.8 oz), H2 (4.6 oz) and A5H2 (5.3 oz) buffers. Lock back check was used to set gas block. Gas block was closed until the AR would eject but not lock back. Then, the gas block was opened one click and tested to verify it would reliably eject and lock back. With all three buffers, the gas setting was the same. Upper was tested with a suppressor.

To answer your first question yes. I would get failure to lock back when doing the equivalent of the limp wristing test on an H3 buffer with .223 pressured ammo. Thats my litmus test, if it wont function limp wristed under ideal conditions then Ive accounted for weird ass shooting positions where the stock might come off your shoulder, dirty gun, cold conditions, out of spec ammo ect.

Sorry you lost me at adjustable gas block. I dont believe in increasing mechanical complexity to fix what should be just a properly sized drilled hole on a work gun. On a race gun fine, controlled environment with specific ammo ect. But on a high round count work gun, an adjustable gas block will eventually either:
A. Adjust itself
or
B. Become non-adjustable

Same goes with adjustable bolt carriers.

[MistWolf]

That's pretty interesting. However, adjustable gas block lack any sort of precision tuning ability. For example... the first half dozen clicks or so typically do nothing...

That's because the gas block is less restrictive than the gas port, even an overly large gas port. The gas block has to be adjusted until it becomes more restrictive than the gas port before it's affects can be seen. We don't know if an AGB allows for finer tuning than simply trying the next gas port size or not, because we have no data showing how much difference changing the adjustment by one click makes compared to changing the gas port by one size.

then the next one mellows it out...then it won't lock back or eject.

Actually, I find it's very easy to find a setting where the AR ejects but does not lock back. In every case where I could not find a setting that ejected but did not lock back, there was a gas leak, or a problem with the ejector.

I think the adjustments are perfect. They are fine enough that one setting allows ejection and lock back, the next ejection without locking back. But they are not so fine that it's difficult to find the spot that separates the two.

In my experience with a whopping 2 different blocks, they have one good setting with a can off... then one more click with the can on.

This mirrors my experience as well. But that's all that's needed, plus a couple of more clicks to compensate for environmental conditions and fouling, if needed. The advantage of the AGB is that it has the flexibility to adjust gas flow to each individual rifle in any configuration.

I never tried buffer swaps however, since I want to MAKE the gun run right with the standard A5 system.

Experimenting with various buffer weights is a way to verify your choices. I discovered that swapping from an H buffer to an H2 buffer resulted in a softer, flatter recoil impulse and that the A5 recoil impulse was better still. I think carbine weight buffers are just too light (not counting ARs tuned strictly for competition).

This does not mean I think a heavier buffer is the answer to an over gassed AR. While the heavier buffer lessens the symptoms of over gassing, it doesn't fix the problem.

One question on tuning a gun with a AGB. If your running the A5 system what buffer should you try and get it to work with? The lightest, A5H2, or another?

I think the A5H2 (5.3 oz) is a good buffer. Heavy enough to keep things smooth, but not so heavy as to start pushing the AR around as it cycles.

[MistWolf]

To answer your first question yes. I would get failure to lock back when doing the equivalent of the limp wristing test on an H3 buffer with .223 pressured ammo. Thats my litmus test, if it wont function limp wristed under ideal conditions then Ive accounted for weird ass shooting positions where the stock might come off your shoulder, dirty gun, cold conditions, out of spec ammo ect.

Thank you for this information. I used 5.56 ammo, without limp-wristing and from the offhand position. The ARs tested were fouled but lubed.

Sorry you lost me at adjustable gas block. I dont believe in increasing mechanical complexity to fix what should be just a properly sized drilled hole on a work gun.

The AGB is only important to this discussion in that it was used to control and optimize gas flow during my tests.

[BufordTJustice]

Sorry you lost me at adjustable gas block. I dont believe in increasing mechanical complexity to fix what should be just a properly sized drilled hole on a work gun. On a race gun fine, controlled environment with specific ammo ect. But on a high round count work gun, an adjustable gas block will eventually either:
A. Adjust itself
or
B. Become non-adjustable

Same goes with adjustable bolt carriers.

I have not yet seen "A" occur on the gas blocks I use.

I don't understand "B" because it is the opposite of "A" and seems to directly address that concern. A std low pro gas block starts this way, as does the MicroTune from BRT.

I haven't had an AGB fail to function yet after several drops of a good lube on the adjustment screw and a few minutes to soak.

My patrol uppers (personally owned, agency certified) have worn SLR adjustable gas blocks for the last 5 or 6 years without a single issue. Lots of training rounds through each, as an understatement.

My experience has been that the gas seal and adjustment trend toward higher reliability and better gas seal as rounds counts rise.

I certainly don't begrudge you or anybody else for desiring simplicity. But these modern AGBs are developing quite a decent reputation for reliability.

I, like you, look forward to the day that most barrel manufacturers use proper gas port sizing on their barrels. But that day is not soon to come for most barrels, unfortunately.



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[Biggy]

Check out the Ballistic Advantage CHF Hanson profile 14.5. Yes, BA CHF. They are DD blanks which BA turns to their excellent (I think) Hanson profile.
You get DD CHF quality, a great profile, plus a pinned GB.

They are nice .

http://ballisticadvantage.com/14-5-i...hf-barrel.html
http://ballisticadvantage.com/16-inc...hf-barrel.html

[Fluke]

I, like you, look forward to the day that most barrel manufacturers use proper gas port sizing on their barrels. But that day is not soon to come for most barrels, unfortunately.

And I look forward to the day when barrel providers clearly state the gas port size of their barrels and hold to that number so the customer knows what they are ordering and receiving. The barrel provider who uses the proper port sizes and clearly states that size in their specs for all to see will win the customer's business.

[1168]

Check out the Ballistic Advantage CHF Hanson profile 14.5. Yes, BA CHF. They are DD blanks which BA turns to their excellent (I think) Hanson profile.
You get DD CHF quality, a great profile, plus a pinned GB.

Thanks; that barrel is also on my radar.

To answer your first question yes. I would get failure to lock back when doing the equivalent of the limp wristing test on an H3 buffer with .223 pressured ammo. Thats my litmus test, if it wont function limp wristed under ideal conditions then Ive accounted for weird ass shooting positions where the stock might come off your shoulder, dirty gun, cold conditions, out of spec ammo ect. ....snip
.

Because we want to be able to limp-wrist .223 with an H3 buffer and filthy BCG, barrel manufacturers sell us giant gas ports.

BTW, the Noveske barreled gun that brought on this gas port measuring contest is actually using an H2, not an H3 as I posted earlier. So it would have started life with an H1. Turns out my memory sucks, and I no longer keep a log for this gun. I’ll edit my earlier posts to reflect this.