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99% of your Budget AR problems, explained in one article.
- Thread starter mtdawg169
- Start date
I have seen reports of varying tolerances, with some being too tight in a carrier. Other than that, they seem to work very well.
I've run them in 4-5 carbines, all 16", with either carbine- or mid-length gas systems. I've never had an issue with them, but that ain't quite a conclusive test.
If they're out of spec, you know it right away. They just won't fit into the carrier. Other than that, they really do seem to be good to go and last quite a while. And it's been a little while since I've heard about anyone having tolerance issues with them, so it could be something that they worked out and is no longer a problem.
Here's another example of an aluminum gas block failure. This one left so much molten aluminum on the barrel, that a new block would not fit on the barrel. It had to be scraped and sanded off.
I can't find the article. I have only had two problems that popped up in all my builds. I built two 6.8 at the same time. Both were bolt issues. One was the ejector was to long not letting the round slide across the bolt face and seat in the carrier. The other the o-ring was too stiff and wouldn't let the rim of the cartridge slide over the extractor and chamber. Fixed both of the problems in about five minutes. Never had another issue with my builds other than those two. Both bolts were Daniel Defense.
I watched a Pat Rogers lecture on youtube awhile back and he said the staggered gas ring myth was total BS.
Seems like he said a properly setup AR with quality parts would run fine with 2 of the gas rings completely removed. Or maybe he said it would run with all 3 rings removed? I can't remember now.
Seems like he said a properly setup AR with quality parts would run fine with 2 of the gas rings completely removed. Or maybe he said it would run with all 3 rings removed? I can't remember now.
That gas ring deal was probably taken from building an automotive engine where the compression, oil and wiper ring should be staggard.
I've seen video of a gun running with one gas ring in place. I wouldn't advise that, but it proves that gas ring staggering isn't necessary. Three rings provides redundancy.
I thought those bolts were from ARP? It's been a long while, so maybe I'm misremembering. Anywho, back to the topic at hand. If you want to see the article, click the link in post #1.
Another subject the article touched on is the misaligned gas tube. I have witnessed misaligned gas tubes is a few factory guns (one of the worst was a Colt M4) and just about every home built AR I have ever seen. A misalignment in a gas tube can be so slight it's almost imperceptible, or so far out of spec it makes charging the rifle a real feat of strength (like the aforementioned Colt M4). Whether slight or far, gas tube misalignment will lead to accelerated gas tube wear at the gas tube/carrier key interface.
Way out of spec gas tube:
Aligned gas tube:
While poor gas block alignment can contribute to gas tub misalignment, more common (at least from my perspective) the culprit is an improperly indexed barrel nut. Installing the barrel nut requires two distinct steps, proper torqueing AND indexing of the nut. The barrel nut torque range on a standard AR runs from a minimum of 30 ft/lbs to a max of 80 ft/lbs. So once the barrel nut is properly torqued within that range, the nut is aligned by tightening the nut as required to align it with the opening in the upper receiver for the gas tube to pass through. There is a tool used, a "Gas Tube Alignment Gauge Pin", to check alignment. In a pinch I have used a drill bit to do the same check.
Checking tube alignment during barrel nut install/torqueing using a Alignment Gauge Pin:
Once your are satisfied you have the barrel nut aligned properly, there is on final check to insure you are good to go. Install the gas tube, then take your bolt carrier only (no bolt/cam pin/firing pin/ firing pin retaining pin installed) and insert it into the upper receiver. Make sure the charging handle is not installed while you conduct this final check. Slowly push the bolt carrier forward until it seats firmly against the barrel extension, just like it does when the bolt carrier group is in battery. As you do this the gas tube will insert into the carrier key. If the barrel nut is indexed properly, resulting in proper gas tube alignment....you will feel little to no resistance as you push the bolt carrier into the in battery position. If you feel resistance? Then time to remove the gas tube and realign the barrel nut. I have seen some recommend using a big flat head screwdriver to bend the portion of the gas tube that is visible in the upper receiver into alignment as an easy fix. While that may turn a badly misaligned gas tube into a slightly misaligned gas tube, I prefer an in-spec rifle.
One last note. No matter how perfectly aligned the gas tube, like many other parts in an AR (I have witnessed Bolts, Firing Pins, Extractors, Disconnectors, Springs, and on and on go south) it eventually wears out. This is a picture of a gas tube I recently replaced in a Colt M4....the type with a giggle switch. The carbine had somewhere between 15,000 to 20,000 rounds through it. The end user brought to me to diagnose an intermittent feeding issue. His story was "sometimes, but not always I will pull the trigger and the weapon will not fire. I will conduct a failure to fire drill and it runs fine. I have noticed that when it happens the gun is hot and the chamber is empty when I rack the charging handle." The first thing I did is ask....."ARE YOUR GAS RINGS STAGGERED!" I kid, I kid
. The first thing I actually did was check the carrier key. Here is the business end of the gas tube:
Completely smooth all the way around! 10 minutes and a new gas tube later.....100% reliable again.
The moral of the story? I guess it's there is a lot more that goes into to building a reliable AR than putting parts together. And even more importantly, a slightly out of spec AR can run reliably for a long time.... when reliability is measured by shooting a few hundred rounds a year. But without a doubt a well built in-spec AR will outperform and outlast a slightly out of spec AR every time, and run farther - harder - faster while it's doing it. As always, YMMV.
Way out of spec gas tube:
Aligned gas tube:
While poor gas block alignment can contribute to gas tub misalignment, more common (at least from my perspective) the culprit is an improperly indexed barrel nut. Installing the barrel nut requires two distinct steps, proper torqueing AND indexing of the nut. The barrel nut torque range on a standard AR runs from a minimum of 30 ft/lbs to a max of 80 ft/lbs. So once the barrel nut is properly torqued within that range, the nut is aligned by tightening the nut as required to align it with the opening in the upper receiver for the gas tube to pass through. There is a tool used, a "Gas Tube Alignment Gauge Pin", to check alignment. In a pinch I have used a drill bit to do the same check.
Checking tube alignment during barrel nut install/torqueing using a Alignment Gauge Pin:
Once your are satisfied you have the barrel nut aligned properly, there is on final check to insure you are good to go. Install the gas tube, then take your bolt carrier only (no bolt/cam pin/firing pin/ firing pin retaining pin installed) and insert it into the upper receiver. Make sure the charging handle is not installed while you conduct this final check. Slowly push the bolt carrier forward until it seats firmly against the barrel extension, just like it does when the bolt carrier group is in battery. As you do this the gas tube will insert into the carrier key. If the barrel nut is indexed properly, resulting in proper gas tube alignment....you will feel little to no resistance as you push the bolt carrier into the in battery position. If you feel resistance? Then time to remove the gas tube and realign the barrel nut. I have seen some recommend using a big flat head screwdriver to bend the portion of the gas tube that is visible in the upper receiver into alignment as an easy fix. While that may turn a badly misaligned gas tube into a slightly misaligned gas tube, I prefer an in-spec rifle.
One last note. No matter how perfectly aligned the gas tube, like many other parts in an AR (I have witnessed Bolts, Firing Pins, Extractors, Disconnectors, Springs, and on and on go south) it eventually wears out. This is a picture of a gas tube I recently replaced in a Colt M4....the type with a giggle switch. The carbine had somewhere between 15,000 to 20,000 rounds through it. The end user brought to me to diagnose an intermittent feeding issue. His story was "sometimes, but not always I will pull the trigger and the weapon will not fire. I will conduct a failure to fire drill and it runs fine. I have noticed that when it happens the gun is hot and the chamber is empty when I rack the charging handle." The first thing I did is ask....."ARE YOUR GAS RINGS STAGGERED!" I kid, I kid
![](https://www.theoutdoorstrader.com/javascript:editorInsertAtCursor( '<img src="/images/smilies/anim_bannana.gif" class="sm">', '[banana]' );)
. The first thing I actually did was check the carrier key. Here is the business end of the gas tube:Completely smooth all the way around! 10 minutes and a new gas tube later.....100% reliable again.
The moral of the story? I guess it's there is a lot more that goes into to building a reliable AR than putting parts together. And even more importantly, a slightly out of spec AR can run reliably for a long time.... when reliability is measured by shooting a few hundred rounds a year. But without a doubt a well built in-spec AR will outperform and outlast a slightly out of spec AR every time, and run farther - harder - faster while it's doing it. As always, YMMV.
