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Posted: 4/7/2014 7:38:00 PM EDT
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I just received a new upper today.
Upon inspection of the bore I notice an imperfection (burr) at the gas port. I blast some air down the barrel to see if it will blow out, no luck. Run a brush through and it takes it out. The gas port looks noticeably larger (compared to my other rifles where the port is hardly noticeable). So is there any effect of a larger gas port? Should I be pissed? Send it back? |
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Larger gas ports will allow much more gas through, it could "over charge" your action and damage your bolt/upper over time. I have read reports from credible sources stating that carbine length AR's will erode (enlarge) gas port premature vs mid-length or rifle length AR's as the port is closer to the initial blast of gas. Once they enlarge the report stated that slamming of the bolt will occur, stressing your BCG. For whatever that's worth, hope it helps!
P.s. I feel when you put hard earned $ down for ANYTHING, it should at least meet your expectations, and hopefully surpass them...I'd send it back or at least contact the company. |
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Quoted: compared to same length 16" carbine, mid-length should have bigger port size, since it has shorter dwell time and less pressure when gas reaches port +1, that is correct. Gas ports vary from different manufacturers as well. I've seen 16" Carbines from .059 - .073 I've seen 16" Mid's from .070 - .089 Think about where we are today vs 20 years ago with the AR platform. There was just Colt and a few others making AR's. There was no steel cased Russian .223 on the market back then either. Today, with so many different ammo types, AR mfgr's, various sources making all the different parts.....barrel makers don't want to have a barrel come back when someone is trying to run 'underpowered' ammo....so they oversize the ports....actually let me re-phrase 'underpowered': As some have pointed out ammo like Tula actually gets decent velocity. It really isn't 'underpowered'. The issue as determined by LuckyGunner's article here: http://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/ is that they are using a faster burning powder - most likely the same powder they are putting in the AK rounds. So the peak pressure's occurs before it gets to the gas port as pictured below.  So if it works with that lower pressure ammo then obviously it will be overgassed when running higher pressure ammo. Some articles on this here: http://www.recoilweb.com/micromoas-govnah-adjustable-gas-block-38489.html and here: http://www.recoilweb.com/micromoas-govnah-adjustable-gas-block-pt-2-of-2-38639.html Using a heavier buffer or stronger spring is only a bandaid to the problem and doesn't do anything to reduce the increased fouling into the action if your gas port is too large. Controlling the gas is the best way to handle this. You can see in the picture below that my product is based on actual port sizes vs using a screw to obstruct the gas flow. So you can have one port match the port in your barrel for your adverse / underpowered position and then another for milspec / quality ammo.  We have a LE agency that is using the adverse position to run Simunitions. Before they were swapping buffers/springs when running Simunitions. Now they just move the regulator plate with a bullet - no special tools.  However, as stated above, just shoot it and see how you like it. More info, video and pics on my site here: http://micromoa.com |
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