Gas Gun Question

J

Jay Cutright

New member
I have a Colt Competition H-Bar here that stovepipes cheap ammo. The rifle shoots Remington ammo without fail but the guy has a truck load of Tul Ammo to shoot and he wants me to come up with a solution. The ammo shoots fine in a Bushmaster but not the Colt, what can I do to fix this problem.
Thanks...Jay
 
not to be a smart azz, but shoot it in the bushmaster. some gas guns just will not work with some ammo. doesnt matter that they are both AR's, they are individual rifles. advise the gentleman that you should always buy a box or 2 of ammo before buying it in bulk.
 
I've seen the gas port be partially obstructed by the holes not being perfectly lined up between the gas block and barrel. Clean the ports and gas tube too. May have to open the port a tad.--Mike
 
mwezell said:
I've seen the gas port be partially obstructed by the holes not being perfectly lined up between the gas block and barrel. Clean the ports and gas tube too. May have to open the port a tad.--Mike
Click to expand...

I built a 16" AR some years ago that gave me fits with extraction. Frequently, the bolt would not unlock, other times it would leave the expended cartridge in the chamber while the bolt would move rearward.
After playing with various buffer weights and beefing up the extractor spring, I finally determined that the gas port was too LARGE. . The bolt was beginning to extract before the cartridge case had relaxed. By reducing the size of the gas port, the problem went away. IIRC, the barrel manufacturer had drilled a 0.093" gas port in the barrel and I reduced it to 0.071" thereby reducing the gas flow to the bolt and delaying the time when the bolt began to move.
I am not saying that you may not have a problem with a blocked port, but I am saying that you need to be careful that you don't go oversize and upset the balance of the system.
 
Last edited:
There have been many upgrades since that rifle was produced including extractor upgrade kits. Brownells carries all the upgrade extractor kits and many more upgrades.

Take the bolt apart clean out all carbon, reassemble wet using something like Break Free CLP. Also clean out the gas tube.

Once again Brownells can help.
 
Herzo said:
I built a 16" AR some years ago that gave me fits with extraction. Frequently, the bolt would not unlock, other times it would leave the expended cartridge in the chamber while the bolt would move rearward.
After playing with various buffer weights and beefing up the extractor spring, I finally determined that the gas port was too LARGE. . The bolt was beginning to extract before the cartridge case had relaxed. By reducing the size of the gas port, the problem went away. IIRC, the barrel manufacturer had drilled a 0.093" gas port in the barrel and I reduced it to 0.071" thereby reducing the gas flow to the bolt and delaying the time when the bolt began to move.
I am not saying that you may not have a problem with a blocked port, but I am saying that you need to be careful that you don't go oversize and upset the balance of the system.
Click to expand...

Good points, and I agree completely. Since it cycled the "better" ammo, but not the "cheapo" stuff, and because I've seen it several times, I'll still bet the port is partially covered. Either way, you do have a very good point and way well be right in the end. I should ask, Is the bolt locking back on the last shot?--Mike
 
Last edited:
Yes, the bolt locked open on the last shot.
He says it worked fine until he ran out of Remington ammo and started using Tul, you cant get to the second shot with this stuff.
I took it apart to see if the ring gaps were all in line & I'm going to clean it up before I put it back together and try it with his Tul and what ever I have to test in it. (Black Hills)
Some body, some where, told him to put in a lighter buffer spring and thats what he brought it to me to have done.
 
Last edited:
Another thought, remove the laquer (Scotch Brite/Steel Wool) from a few cases and see if it cycles. Freind has a Colt match H-Bar HB (pre ban) and this was his issue (Wolf ammo). He sold his remaining supply.
 
I've never had any problems with my handloads in my Bushmaster with the factory carrier and buffer spring, but it absolutely refused to work with some Winchester white box. Failed to extract, stuck cases in the chamber, just generally ugly. Fired the rest of the Winchester in a bolt rifle and it worked fine there - big surprise. Since it's usually set up for heavy bullet loads with a carrier weight and heavier Cr-Si buffer spring and functions fine with them I don't mess with factory stuff anymore. The Russian iron cased stuff just offends my delicate sensitivities.

And yes I know it's steel slathered in something to keep it from rusting. Uff da!!!
 
mwezell said:
Good points, and I agree completely. Since it cycled the "better" ammo, but not the "cheapo" stuff, and because I've seen it several times, I'll still bet the port is partially covered. Either way, you do have a very good point and way well be right in the end. I should ask, Is the bolt locking back on the last shot?--Mike
Click to expand...

You are undoubtedly on the right track. I just wanted to throw out the caution in case someone decided that more was better.

I would keep the original buffer spring - again, these are a balanced system and the buffer/spring is matched to the barrel length and the buttstock (regular or collapsable).
 
Herzo said:
You are undoubtedly on the right track. I just wanted to throw out the caution in case someone decided that more was better.

I would keep the original buffer spring - again, these are a balanced system and the buffer/spring is matched to the barrel length and the buttstock (regular or collapsable).
Click to expand...

Herzo, I was just thinking the opposite. If the bolt is locking back, isn't it getting enough gas? I'm starting to think you may have been right in the first place...too much gas. I've made bushings for the gas port to restrict gas before for the same reason. Sounds like if he rules out the obvious possibilities,(use original buffer and spring) he'd be better off not using that ammo or letting someone have a look at it. I've never been very good at fixing guns with my keyboard:confused::D--Mike
 
mwezell said:
Herzo, I was just thinking the opposite. If the bolt is locking back, isn't it getting enough gas? I'm starting to think you may have been right in the first place...too much gas. I've made bushings for the gas port to restrict gas before for the same reason. Sounds like if he rules out the obvious possibilities,(use original buffer and spring) he'd be better off not using that ammo or letting someone have a look at it. I've never been very good at fixing guns with my keyboard:confused::D--Mike
Click to expand...

I read his post to say that the bolt was locking back with the Remington ammo. If it stovepipes with the Tul, I'm not certain that it will lock back (short stroking).
The symptom of too much gas that I experienced was a failure to extract the spent cartridge from the chamber. This occurs when the bolt begins to retract before the pressure drops enough for the case to relax and release it's grip on the chamber walls. We are talking mili-seconds here.
Then again, it could be a rough chamber (relatively speaking) that slows the extraction due to the lacquered case.
I would certainly start with a clean gas system and check the size of the gas port. If he has an H-bar, that would be a 20" barrel and the gas port size is different than that required by a 16" carbine. I used to know what those sizes were, but that was 15 years and 2 hard drive crashes ago..
I found this on AR-15's website:

For 5.56mm
Colt's gas port sizes are:
* 10.5" - .093
* 11.5" - .081
* 14.5" - .063
* 16" - .063
Unfortunately, I could not find a number for a 20" barrel.

Also about halfway down on the same http://www.ar15.com/archive/topic.html?b=3&f=122&t=505773 is a posting by DaJester in which he goes through his procedure for curing shortstroking. One of his points is to run some low pressure ammo through it - specifically Wolf - to see if he can make it happen. I would caution that they are talking about short barrelled AR's here, but the principles apply. Another diagnostic tool that he uses is to put a specific flash hider that effectively increases the barrel length to see if that cures the problem. Unfortunately, an H-Bar does not have a threaded barrel so that would probably not be a choice. I would be hesitant to change the gas port size based on one ammo, unless I had problems with other types also.

It would also be interesting to measure a fired Remington case from each rifle to see if there are significant differences in the chambers.
As a reloader, I might shoot a series of reduced loads using Remington brass to see if I could duplicate the stovepiping. That might tell me if the power of the ammo would be causing the problem.
I have never shot any lacquered ammo in any of my AR's so much of this would be theoretical.
 
Last edited:
I recently built a AR for myself in .223 with a 26" Lilja .224-8 3 groove barrel. I drilled the gas port to .110" and haven't had any problems with it cycling. I'm using a ammo box of Georgia Arms 55 gr ballistic tip loaded rounds and matched the chamber size to the brass that I had. My reamer had .020" freebore, but could have used zero freebore and still worked well, opened the neck to .250". It works well and shoots well.
 
Powder burn rates, gas tube length, and dwell time are all factors...as well as spring pressure and carrier weight. Proper function is a balancing act of several factors at the same time...ad to that, different bullet weights and reloading. A bigger port with an adjustable gas block makes for a tunable sytem but still doesn't ensure reliability unles the other factors are in "harmony". All that said, the system is still pretty forgiving and will work well even if things aren't "ideal"--Mike
 
lefty o said:
if the gun runs on other ammo, you do not modify the gun to run chitty ammo!
Click to expand...

You do if that's what the customer wants, and you do when light recoil and reliability are big factors...like in many 3-gun competitions. They expect nearly 100% reliability and recoil is never a good thing, especially when speed and reliability are THE name of the game. At matches where power factor is not a consideration, lighter recoil means faster split times(follow up shots). I've worked on many semi-auto rifles,shotguns, and pistols just for the sole purpose of making them run light loads..reliably or lessen perceived recoil. It's not BR. Recoil and reliability are huge in the game they play.--Mike
 
bingo!

ok ar's are chambered for brass cased ammo...NOT for laquer coated steel.......
the most common issue with lacquer steel in ar's is sticking cases...
ak/sk's are designed around the lacquer steel case and have large chambers ...they deal with krap in the chamber by having large chambers...

why degrade a competent rifle to function on krap ammo ??
i hate colt rifles but it seems pretty foolish to spend big bucks on a name( colt) and then be penny stupid on ammo selection...
buy an ak in 223 and shoot up the ammo.
sell the ammo take a loss and buy decent ammo

mike in co
(ps..this another case of fixing the symptom (case sticking) instead of the problem(wrong ammo/chamber))
 
Last edited by a moderator:
I like where you fellas are going with this.
I'm going to clean the rifle and put it back together & see what happens without all the extra oil that it came in with and see if the bolt will lock open on the junk ammo. I'll get back with you in a day or two.
Thanks...Jay
 
Jay Cutright said:
I like where you fellas are going with this.
I'm going to clean the rifle and put it back together & see what happens without all the extra oil that it came in with and see if the bolt will lock open on the junk ammo. I'll get back with you in a day or two.
Thanks...Jay
Click to expand...

Look for ejector and/or extractor marks on the brass when you try it again.--Mike
 
sorry, i didnt see any mention of this being a "game" gun. all i got was someone wanted to burn cheap ammo through it.
 
You must log in or register to reply here.
Back
Top