Home Forums Hunting & Shooting AR and Tactical Rifles AR-15 overgassed or not??

I have an AR-15 (Armalite 14.5 inch upper) that is throwing the cases at 2:00 to 2:30 about 5 feet away. The rifle is clean and oiled and the ammo is Federal 55 grain American Eagle. The butt stock is a full rifle style with a rifle buffer and spring (new and the proper length).

According to the experts a properly gassed rifle should throw the cases between 3 and 4 o'clock for optimum operation. My set up seems to be very reliable as is and fires and ejects the way it's supposed to. I'm not away of any harsh increased recoil.

My question is - Are most carbine length short barreled rifles slightly over gassed from the factory and is this an issue that I should be worried about as far as accelerate parts wear is concerned?

I have an AR that was a midlength gas system it threw the cases at 2 o'clock I swapped barrels went with rifle length gas tub guess what still throws them at 2 o'clock. I have another AR rifle length gas tub it throws them to the 4 o'clock. So who knows I think some of it has to do with your bolt carrier and extractor

Personally, as long as it isn't bending rims I don't care where it ejects. Ejection patterns are very load dependent anyway.

If you want it to keep your brass closer, either trim the ejector spring or shorten the ejector itself.

I think you're rig is fine. If you have aggressive extractor marks on the inner rim of the case, you might be getting close.

You know when they are really over-gassed, the extractor starts jumping the rim of the case, and you see failure to eject and double feed. I went through that with one carbine, but I solved it with o-ring under the extractor, and an H3 buffer.


Left is fairly normal extractor marks. Right is too much, and getting some rim jumping.

Great post MM.
I like my brass to pile up close by so I usually trim back the ejector spring one or two coils,

Sorry but that comment deserves a facepalm.

The point of tuning the gas system is not to put the brass closer or in a certain spot; you've got it backwards. Brass ejection with STANDARD bolt parts is an indication of how well the gas system is tuned, and 2:00 ejection indicates higher bolt carrier speed than necessary, which in turn indicates earlier unlocking than is ideal. Ejection patterns are "load dependent" because some loads are hotter than others, which obviously affects gas system tuning.

To the OP - yes, most mainstream off the shelf AR15 5.56 barrels are overgassed from the factory. They do this so people won't have malfunctions with cheap underpowered or inconsistent ammo. If yours is ejecting at 2:00 with American Eagle (IIRC that stuff is low end 223 power, not hotter 5.56), it's definitely overgassed. No, it won't damage the gun, ARs are pretty durable, but you can make it function smoother and better by tuning the gas system right. You can also completely screw it up if you do it wrong.

And eventually as the extractor and buffer springs wear you will have malfunctions.

Thanks Montana for the pics and others for commenting.

I just checked my case rims and they appear quite normal so I going to say I'm fine and carry on - There's not a whole lot I can do anyway as I have a fixed rifle buffer and butt stock. I also have the O ring under the extractor so that's good.

There's plenty you can do about it, lots of options with these guns, but it's up to you if you have the expertise or desire to mess with it. If you don't, just shoot it and acknowledge that it's overgassed even with weak 223 ammo.

An adjustable gas block or heavier buffer are the common ways to tune it, but if you have an A2 style front sight there are some options for reducing gas with that as well.

Yondering, I would be interested to hear more about that solution.

What the forum is for!!!
Learning from others 1st hand experience.
Can never stop learning!!!

Facepalm? The guy mentioned the distance the brass was thrown indicating some concern about it. That is a totally separate issue from over/under gas. That's why I addressed it separately.

Actually, it has little to do with how hot a load is. The pressure curve of the powder used has a lot more effect. For instance, with a standard .094" gas port in a 20" heavy barrel NM rifle, powders like WC844 are on the edge of functioning. Oftentimes, you can't load WC844 hot enough to get consistent functioning. While powders like Varget & Re15 give vigorous functioning, even with light loads.

That's about the only thing you got right.

Brass ejection direction (not distance) is not a "totally separate issue" from gas system tuning. It's a direct indicator of how well the system is tuned. Why is that hard for you to understand? The point of adjusting it is not to get the brass to land in a certain spot, the point is to get the action tuned right. You've completely missed that and are talking about adjusting the symptom instead of the cause.

I don't know why my words were so hard for you to understand, they seem pretty plain to me.
I hope you are having a good day.

There are a couple options, but one that I like is to remove the sight and tap the gas port hole (in the sight) for a set screw, IIRC a #8-32 but I'd have to check my notes. The screw can then be drilled out in incrementally larger sizes until desired function is achieved. The set screw ends up being a gas restriction bushing, and when everything is assembled it's captured in the sight between the barrel and gas tube. You can also use an unthreaded bushing but it's not as convenient.

You can do this on just about any gas block, including an A2 front sight.

The downside to that method is the development time; i.e. it takes several installs and removals to work up to the right size hole, but the upside is that once it's done, it's invisible and never loses adjustment. It's the next best thing to having the barrel port sized right to start with, and is functionally the same.

I understood your words.
Nobody, including the OP, was pointing at the ejection distance being a problem, it's the direction that matters. You advised to adjust the ejector spring until it goes where you want, which is completely missing the reason for looking at the ejection pattern.

I wondered what was the best way to do that.

Thanks.

It may be over gassed but a rifle length buffer should be able to handle it. I don't consider throwing brass 5 feet as over gassed enough to be a search for a solution. I have an Armalite 16" with a carbine gas system that needed an H2 carbine buffer to slow the bolt down. I have a feeling that the Armalites were slightly over gassed to be reliable. They were selling thousands of them over seas when Mark Westrum owned the company. A person can only guess what ammo they were fed. I fixed mine by putting a rifle buttstock and buffer system under it just like you did. I have found that powder plays a part in the direction your brass goes.

kwg

Thanks. I'll save that idea for future reference.