Hello everyone. I purchased a M&P T quad rail and barrel nut from my friend. I installed rail on my M&P sport. In doing so the delta ring/barrel nut was eliminated and the M&P T barrel nut was installed with the rail. However, after installation the gas tube seems to rattle around in the new barrel nut when the bolt is locked back. When the bolt is forward, the noise is gone. It seems kinda loose in the upper as well. The gas tube is correctly pinned/aligned, and they are the original parts. Some people say it's normal because it's aligned dead nuts, however it didn't move with delta ring installed. I have fired 200+ rounds without a hiccup, any suggestions? Thanks!
Gas tube rattle after FF quad rail install
- Thread starter Ski360ca
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scooter123
Member
A gas tube that rattles is an indicator that the gas tube is PERFECTLY aligned. This is a GOOD thing.
It's when they don't rattle you have a potential for problems. First potential issue is that the bolt engaging on the gas tube may drag on one side due to the misalignment. Over time that will cause uneven wear to the gas tube and gas key on the bolt carrier leading to leakage severe enough to cause the bolt to Short Cycle. It can also put a small amount of pressure on the barrel which could, in theory, effect accuracy. To be honest as heavy as a barrel is compared to the gas tube I think that accuracy concern is really WAY WAY OUT THERE. However, uneven wear on the gas tube and gas key is a reasonable concern.
It's when they don't rattle you have a potential for problems. First potential issue is that the bolt engaging on the gas tube may drag on one side due to the misalignment. Over time that will cause uneven wear to the gas tube and gas key on the bolt carrier leading to leakage severe enough to cause the bolt to Short Cycle. It can also put a small amount of pressure on the barrel which could, in theory, effect accuracy. To be honest as heavy as a barrel is compared to the gas tube I think that accuracy concern is really WAY WAY OUT THERE. However, uneven wear on the gas tube and gas key is a reasonable concern.
it's a radial movement at nut/upper, not lateral back/forth movement
crracer_712
Member
You removed the FSB from the barrel, leaving the gas tube attached to the FSB? What exactly does the Barrel nut that you installed with the new hand guard look like? Did it have notches or holes that you had to align during the torqueing of the barrel nut in order to allow gas tube to insert in to upper receiver?
Just looking at my standard barrel nut, the gas tube rest in the grove and with the delta ring installed, it doesn't really rattle or move enough to make a noise.
Since you replaced the barrel nut, just wondering what style of barrel nut was utilized. a photo might be beneficial.
Just looking at my standard barrel nut, the gas tube rest in the grove and with the delta ring installed, it doesn't really rattle or move enough to make a noise.
Since you replaced the barrel nut, just wondering what style of barrel nut was utilized. a photo might be beneficial.
crracer_712
Member
strange, that's the exact rail and barrel nut that is on my M&P 15 300 upper, I checked it last night with the bolt open, no movement unless I poke around on it.
shawnfergie
Member
Maybe the hole in the barrel nut for the gas tube is slightly over sized and is causing a rattle. I would say if you are getting the noise then it is aligned, better yet, if the gun functions great, you are good to go.
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