I like to keep my stuff so technically superior, it doesn’t run at all. I’ve saved a pretty penny on ammo.
-
ODT Gun Show & Swap Meet - May 4, 2024! - Click here for info
Over Gassed
- Thread starter Jackie Graham
- Start date
Microscopic differences won't make an issue. What I normally see on improperly sized gas ports is differences of .01-.02" or so, which can cause reliability issues.
I always check port size on 5.56 barrels, because we have accepted, industry specs to fall back on. Same cannot be said on other calibers.
Not trying to start an argument but would that difference apply if it were just the barrel? There are 3 components to the gas system, barrel, gas block and gas tube. Unless the gas port in the barrel is the smallest in the system the volume of gas would be restricted at the smallest port. I can see where a small port in the barrel might cause an under gassing issue but a larger port would still have to flow through the gas block and gas tube.
Just because gas is flowing through the tube, doesn't mean that it's "full" or flowing as quickly/violently as it could. You can definitely tell the difference in a gun that is significantly over-gassed.
Don't believe that I have experience that yet.
I don't have any suppressed guns so I could not tell you if it made a difference in any of my weapons
Local PD had S&W M&P-15's. 16", carbine-length gas system, with A2 front sights. Somewhere down the road, they took them somewhere and had the barrel cut and threaded to 10.3". The "new" 10.3's proved to be less reliable than they were when they were 16". I asked if the gas ports had been opened up to match the new barrel length, and no one could answer that.
I worked on 2 of them for officers, primarily installing new handguards/barrel nuts. While I had them apart, I checked the gas ports. A 16" 5.56 with a carbine length gas system should have a gas port of .0625". S&W tends to overgas their barrels, so these were around .068" IIRC. I opened them to .073". Talking to one of those two officers later, he stated that he isn't having any of the cycling/feeding issues that he was having BEFORE I opened the gas port.
A note on 10.3" gas ports:
Crane specs .070" for the 10.3" barrel on the Mk18. This is done for the US military, and they know what ammo they're going to be using, and all of that ammo is full milspec 5.56. Hottish stuff. Not only do they know the ammo being used, folks that are being issued Mk18" in the US military tend to keep them well-maintained, clean, and well-lubed.
Companies like SOLGW will spec the ports on their 10.3" barrels to .073". Those barrels are going to civilians and LE, and SOLGW has no control over what ammo folks will be shooting out of it, or how well they maintain and clean them. That extra .003" (3 THOUSANDTHS of an inch!) is enough to significantly enhance reliability when using .223 or lower powered 5.56 ammo.
I worked on 2 of them for officers, primarily installing new handguards/barrel nuts. While I had them apart, I checked the gas ports. A 16" 5.56 with a carbine length gas system should have a gas port of .0625". S&W tends to overgas their barrels, so these were around .068" IIRC. I opened them to .073". Talking to one of those two officers later, he stated that he isn't having any of the cycling/feeding issues that he was having BEFORE I opened the gas port.
A note on 10.3" gas ports:
Crane specs .070" for the 10.3" barrel on the Mk18. This is done for the US military, and they know what ammo they're going to be using, and all of that ammo is full milspec 5.56. Hottish stuff. Not only do they know the ammo being used, folks that are being issued Mk18" in the US military tend to keep them well-maintained, clean, and well-lubed.
Companies like SOLGW will spec the ports on their 10.3" barrels to .073". Those barrels are going to civilians and LE, and SOLGW has no control over what ammo folks will be shooting out of it, or how well they maintain and clean them. That extra .003" (3 THOUSANDTHS of an inch!) is enough to significantly enhance reliability when using .223 or lower powered 5.56 ammo.
Not all M4's are overgassed. Ones spec'ed and sold to the US military are not, unless one slips through inspection, or has a port eroded to the point that it should have been replaced already.
A properly built M4 will not be overgassed.
I understand that the gas port would have to be larger for a shorter barrel. Less time for the projectile in the barrel equates to less pressure. A larger gas flow allows for more gas in a shorter time.
