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Posted: 12/20/2021 8:56:57 AM EST
[#1]
Quote HistoryQuoted:Except one thing, this "nipple" in the barrel extension does not align with the gas hole in the barrel. Should it? If I were to draw a line from the gas block hole to the "nipple" seen here, they are not in the same parallel. The "nipple" is your index pin, it most definitely needs to be inline with your gas port in the barrel. Looking down the barrel from chamber end, which direction (L/R) is the GP rotated in relation to the index pin? |
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Posted: 12/20/2021 9:59:54 AM EST
[#2]
It kind of is almost aligned, maybe off a bit (say 1mm) but not totally sure. You can see on the pic.
Maybe I rotated the extension when I got the bright idea to remove the fin and was removing the barrel nut. It didn't seem to be torque to some crazy figure and did not take that much effort. On the other hand, the extension seems really solid in it in the extension to barrel fit, and the barrel ring I rotated had much less tension on it than the barrel extension tension. Seems like the gas tube is the sole issue here but then it's my subjective (and often flawed) understanding 
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Posted: 12/20/2021 10:06:04 AM EST
[#3]
What Tig said... Some wrenching must have been done on the muzzle device to get the gas block and old barrel nut off and the new one on, if there was one?
The plot thickens, but at least things are narrowing down. Interested to know who made the barrel now. It's hard to tell if the gas port is not lined up with the indexing pin from the picture, but looking at the carbon around the gas port, your gas block might not have been aligned with the gas port which would cause the gas tube to not be aligned. |
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Posted: 12/20/2021 10:12:26 AM EST
[#4]
Quote HistoryQuoted: It kind of is almost aligned, maybe off a bit (say 1mm) but not totally sure. You can see on the pic. Maybe I rotated the extension when I got the bright idea to remove the fin and was removing the barrel nut. It didn't seem to be torque to some crazy figure and did not take that much effort. On the other hand, the extension seems really solid in it in the extension to barrel fit, and the barrel ring I rotated had much less tension on it than the barrel extension tension. Seems like the gas tube is the sole issue here but then it's my subjective (and often flawed) understanding https://i.imgur.com/2WcLXKt.jpg Not aligned. Your gas tube is binding, I'll put money on it. Have you recently removed /attempted to remove a MD on this barrel? Did you have any difficulty? If so, what method was used? |
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Posted: 12/20/2021 10:14:47 AM EST
[#5]
No, I never messed with the muzzle device. Neither installed it nor attempted to remove it.
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Posted: 12/20/2021 10:16:54 AM EST
[#6]
Quote HistoryQuoted: Not aligned. Your gas tube is binding, I'll put money on it. Have you recently removed /attempted to remove a MD on this barrel? Did you have any difficulty? If so, what method was used? How do I realign it? that is, rotate the barrel extension. I don't think I have the tools to do that. I am looking for a solid vise. But even if I got the extension in a vise, via the rod, how do rotate it back? I can see it's a bit off but can't connect the dots. I think I most likely knocked it out of the alignment when I did the rod thing without the fin. |
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Posted: 12/20/2021 10:20:10 AM EST
[#7]
Quote HistoryQuoted: No, I never messed with the muzzle device. Neither installed it nor attempted to remove it. That type of misalignment is typical of removing a difficult MD while holding the bbl solely by the extension, which is why I ask. Possibly damage that was preexisting and now is showing up after reconfiguring. |
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Posted: 12/20/2021 10:21:04 AM EST
[#8]
Quote HistoryQuoted: How do I realign it? that is, rotate the barrel extension. I don't think I have the tools to do that. I am looking for a solid vise. But even if I got the extension in a vise, via the rod, how do rotate it back? I can see it's a bit off but can't connect the dots. I think I most likely knocked it out of the alignment when I did the rod thing without the fin. Quote HistoryQuoted: Quoted: Not aligned. Your gas tube is binding, I'll put money on it. Have you recently removed /attempted to remove a MD on this barrel? Did you have any difficulty? If so, what method was used? How do I realign it? that is, rotate the barrel extension. I don't think I have the tools to do that. I am looking for a solid vise. But even if I got the extension in a vise, via the rod, how do rotate it back? I can see it's a bit off but can't connect the dots. I think I most likely knocked it out of the alignment when I did the rod thing without the fin. You can't effect the barrel extension when using a Reaction Rod to tighten or loosen a barrel nut, that would only be possible if you were wrenching on the muzzle device. Your gas block wasn't properly aligned with the gas port on the barrel, I think that's the culprit. |
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Posted: 12/20/2021 10:36:29 AM EST
[#9]
Quote HistoryQuoted: How do I realign it? that is, rotate the barrel extension. I don't think I have the tools to do that. I am looking for a solid vise. But even if I got the extension in a vise, via the rod, how do rotate it back? Realignment is a crap shoot honestly. In most instances this situation ends in shit canning the barrel. Welding the GP closed and redrilling is an option, but best left to a competent smith, IMO. The carbon ring is indicative of how far the GB and GP were misaligned if I'm seeing things correctly. |
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Posted: 12/20/2021 10:37:08 AM EST
[#10]
Quote HistoryQuoted: You can't effect the barrel extension when using a Reaction Rod to tighten or loosen a barrel nut, that would only be possible if you were wrenching on the muzzle device. Your gas block wasn't properly aligned with the gas port on the barrel, I think that's the culprit. Absolutely. |
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Posted: 12/20/2021 11:00:15 AM EST
[#11]
What's the size of the gas block journal on this barrel? Looks way bigger than .750.
I'm wanting to point you in the direction of an appropriate sized gas block jig to get you lined up properly. But you really need a vise to hold the thing steady to drill a dimple for a set screw. Also, try sticking a snug fitting drill bit (can't be any play) into your gas port and take a look down the barrel extension end of the barrel towards the muzzle. That may give you a better idea of alignment of the gas port in relation to the indexing pin. If possible, maybe you could take a picture from that angle as well. |
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Posted: 12/20/2021 11:05:56 AM EST
[#12]
Quote HistoryQuoted: What's the size of the gas block journal on this barrel? Looks way bigger than .750. Also, try sticking a snug fitting drill bit into your gas port and take a look down the barrel extension end of the barrel towards the muzzle. That may give you a better idea of alignment of the gas port in relation to the indexing pin. If possible, maybe you could take a picture from that angle as well. I believe that it's .936", if I'm tracking correct from the OP's previous threads. Appropriate sized drill bit or pin gauge in gas port is an excellent visual aid. |
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Posted: 12/20/2021 11:23:52 AM EST
[#13]
correct, 0.936"
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Posted: 12/20/2021 11:43:31 AM EST
[#14]
Quote HistoryQuoted: correct, 0.936" Then here you go. > https://www.kawvalleyprecision.com/KVP-AR-15-Gas-Block-Dimpling-Jig-p/kvp-dimpling-jig-.936.htm |
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Posted: 12/20/2021 11:45:02 AM EST
[#15]
The diameter of the gas block hole is 0.11"
The diameter of the gas block measured at the gas block port is 0.936" (shows a bit off but 0.936" is the correct value I got)  
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Posted: 12/20/2021 11:45:16 AM EST
[#16]
Quote HistoryQuoted: I believe that it's .936", if I'm tracking correct from the OP's previous threads. Appropriate sized drill bit or pin gauge in gas port is an excellent visual aid. Quote HistoryQuoted: Quoted: What's the size of the gas block journal on this barrel? Looks way bigger than .750. Also, try sticking a snug fitting drill bit into your gas port and take a look down the barrel extension end of the barrel towards the muzzle. That may give you a better idea of alignment of the gas port in relation to the indexing pin. If possible, maybe you could take a picture from that angle as well. I believe that it's .936", if I'm tracking correct from the OP's previous threads. Appropriate sized drill bit or pin gauge in gas port is an excellent visual aid. 
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Posted: 12/20/2021 12:15:01 PM EST
[#17]
Quote HistoryQuoted: Realignment is a crap shoot honestly. In most instances this situation ends in shit canning the barrel. Welding the GP closed and redrilling is an option, but best left to a competent smith, IMO. The carbon ring is indicative of how far the GB and GP were misaligned if I'm seeing things correctly. Re: barrel extension and the indexing pin - I think that's the way I got it, it's doubtful I made any changes to it. Re: gas block position: Thanks for pointing it out, with the carbon ring. I didn't notice the significance of it. I seem to have made a bad assumption here, that just because I got it that way it must have been correct and I double checked your theory. Re carbon ring. The gas block was not installed correctly in the previous incarnation. I will try hand-tightening the barrel nut, installing the gas block correctly this time and see if the gas block tube is in alignment with the BCG/carrier key. I installed the gas block to be perfectly centered over the gas port and then the 2 tiny screws on the other side no longer aligned with the marks left from the previous install. Meaning it was not installed correctly, as I read it. The question at this point, how do you align the gas block precisely over the gas port on the barrel, since when you install the gas block, you no longer see the actual port? And have to work blind more or less, what am I missing here. |
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Posted: 12/20/2021 12:31:35 PM EST
[#18]
Quote HistoryQuoted: Re: barrel extension and the indexing pin - I think that's the way I got it, it's doubtful I made any changes to it. Re: gas block position: Thanks for pointing it out, with the carbon ring. I didn't notice the significance of it. I seem to have made a bad assumption here, that just because I got it that way it must have been correct and I double checked your theory. Re carbon ring. The gas block was not installed correctly in the previous incarnation. I will try hand-tightening the barrel nut, installing the gas block correctly this time and see if the gas block tube is in alignment with the BCG/carrier key. I installed the gas block to be perfectly centered over the gas port and then the 2 tiny screws on the other side no longer aligned with the marks left from the previous install. Meaning it was not installed correctly, as I read it. The question at this point, how do you align the gas block precisely over the gas port on the barrel, since when you install the gas block, you no longer see the actual port? And have to work blind more or less, what am I missing here. Several methods out there, everyone has their preferences. THIS is foolproof. ETA: You will likely still experience issues with your gas tube binding with your gas key. It's liable to take a bit of dicking around before you find a sweet spot that will function acceptable. |
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Posted: 12/20/2021 1:38:51 PM EST
[#19]
Quote HistoryQuoted: The question at this point, how do you align the gas block precisely over the gas port on the barrel, since when you install the gas block, you no longer see the actual port? I feel you need both alignment and dimpling for both set screws to ensure they positively engage and not shift due to previously made screw marks. My go-to dimpling jig. Make sure and use carbide bit to get a good cut into the barrel. No need to go too deep. |
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Posted: 12/20/2021 2:19:18 PM EST
[#20]
Quote HistoryQuoted: Several methods out there, everyone has their preferences. THIS is foolproof. ETA: You will likely still experience issues with your gas tube binding with your gas key. It's liable to take a bit of dicking around before you find a sweet spot that will function acceptable. |
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Posted: 12/20/2021 2:29:41 PM EST
[#21]
Quote HistoryQuoted: A piece of spaghetti with the right diameter and length will work too. Quote HistoryQuoted: Quoted: Several methods out there, everyone has their preferences. THIS is foolproof. ETA: You will likely still experience issues with your gas tube binding with your gas key. It's liable to take a bit of dicking around before you find a sweet spot that will function acceptable. Absolutely. |
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Posted: 12/20/2021 2:33:11 PM EST
[#22]
I'd loosen the gas block, put the rifle in battery, then snug up the gas block.
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Posted: 12/20/2021 2:39:21 PM EST
[#23]
Your gas block is possibly installed backward. I did this once and had the same issues you have. Was going crazy until I figured it out and then felt like a dumbass.
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Posted: 12/20/2021 2:52:08 PM EST
[#24]
Quote HistoryQuoted: I installed a YHM rail on one of my rifles and had a similar issue. My rail is the one with removable picatinny rails. The rear most screw in the top rail was a bit too long and put pressure on the gas tube. I filed off about 0.030" off the screw and everything was fine. I've had this exact problem before |
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Posted: 12/20/2021 9:32:15 PM EST
[#25]
Quote HistoryQuoted: I've had this exact problem before Quote HistoryQuoted: Quoted: I installed a YHM rail on one of my rifles and had a similar issue. My rail is the one with removable picatinny rails. The rear most screw in the top rail was a bit too long and put pressure on the gas tube. I filed off about 0.030" off the screw and everything was fine. I've had this exact problem before I will investigate this. Thanks for the idea |
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Posted: 12/20/2021 9:40:24 PM EST
[#26]
Quote HistoryQuoted: I feel you need both alignment and dimpling for both set screws to ensure they positively engage and not shift due to previously made screw marks. My go-to dimpling jig. Make sure and use carbide bit to get a good cut into the barrel. No need to go too deep. Is there a link for a .936 one? |
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Posted: 12/20/2021 9:41:33 PM EST
[#27]
Quote HistoryQuoted: I'd loosen the gas block, put the rifle in battery, then snug up the gas block. will try this |
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Posted: 12/20/2021 9:46:42 PM EST
[#28]
Quote HistoryQuoted: Is there a link for a .936 one? Quote HistoryQuoted: Quoted: I feel you need both alignment and dimpling for both set screws to ensure they positively engage and not shift due to previously made screw marks. My go-to dimpling jig. Make sure and use carbide bit to get a good cut into the barrel. No need to go too deep. Is there a link for a .936 one? I already linked it this morning, up above. ^ |
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Posted: 12/21/2021 9:06:46 AM EST
[#29]
Quote HistoryQuoted: I already linked it this morning, up above. ^ Got it, I did not notice the "KVP .936 AR-15 GAS BLOCK DIMPLING JIG" option at the bottom. |
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Posted: 12/24/2021 6:25:43 AM EST
[#30]
Quote HistoryQuoted: I'd loosen the gas block, put the rifle in battery, then snug up the gas block. Exactly what I came here to say. I have had to do this when I couldn't get the gas key to go over the tube on a build when the gas block was perfectly aligned inside of the forend. It has since become my standard procedure when tightening a gas block to have the BCG in battery, then wiggling the gas block side to side to find the center of its movement. |
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Posted: 12/24/2021 8:43:23 PM EST
[#31]
Quote HistoryQuoted: Your gas block is possibly installed backward. I did this once and had the same issues you have. Was going crazy until I figured it out and then felt like a dumbass. |
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Posted: 12/25/2021 1:27:51 AM EST
[#32]
Quote HistoryQuoted: How would that be if the tube only goes in one side? 
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Posted: 12/26/2021 10:14:17 AM EST
[#33]
Perhaps he meant the gas tube installed upside down?
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Posted: 1/3/2022 5:39:16 PM EST
[#34]
@ad_nauseam
Any updates on getting the gas block centered over the barrel port and it fixing the centering of the gas tube in the upper? |
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Posted: 1/8/2022 11:03:48 PM EST
[#35]
Quote HistoryQuoted: @ad_nauseam Any updates on getting the gas block centered over the barrel port and it fixing the centering of the gas tube in the upper? I loosened the gas block and realigned the gas tube to be correctly aligned with the BCG. Manually, it cycled smoothly. Test-driving it, it also cycled well without any issues. I did have a hard time tightening the screws of the gas block while maintaining the proper alignment and ended up taking it to a gunsmith just to be completely certain the entire operation is done correctly. Though I am pretty certain I could have done it myself. It runs and feeds mostly everything at this point. Except strangely enough, I still get failure to go into battery with 325gr. Hornady FTX . They seem to be underpowered. I don't remember having issues with them before. But the "blue tip" 300gr TSX fed really nice and cycled nice without any issues with anything. It had a noticeably stronger kick than red tip FTX. Maybe at this point it's an issue with the buffer weight. I did use the same lower/buffer I used previously. I noticed the blue tip 300 grainers (and a few other 300gr variants) kicked more than the red tip FTX which would not consistently go into battery. Yes, it's the 50-cal master race reporting. |
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Posted: 1/9/2022 12:58:30 PM EST
[#36]
Quote HistoryQuoted: Exactly what I came here to say. I have had to do this when I couldn't get the gas key to go over the tube on a build when the gas block was perfectly aligned inside of the forend. It has since become my standard procedure when tightening a gas block to have the BCG in battery, then wiggling the gas block side to side to find the center of its movement. This actually helped. |
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Posted: 1/9/2022 2:51:35 PM EST
[#37]
Quote HistoryQuoted: This actually helped. If this doesn't work it usually means you have a bent gas tube. Most gas blocks have huge holes in them that allow for a significant amount of misalignment. It may not look pretty from the front, but it should run. |
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Posted: 1/9/2022 4:33:37 PM EST
[#38]
I had a rifle that worked perfectly well...until I changed out the gas tube. What I found was that the little "bulb" on the end of the gas tube was worn unevenly...one side had almost zero bulb left, indicating that the gas tube and gas key were a little out of alignment. It took a while to get the new gas tube aligned correctly.
I had to remove the bolt and rotate the gas block just a teeny bit to one side. Then the bolt carrier (with bolt removed) mated up very smoothly with the gas key, and reliable operation returned. |
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Posted: 1/10/2022 4:24:45 PM EST
[#39]
To reiterate, it's mostly working except still doesn't go into battery with one type of ammo.
Seems like it's ammo dependent at this point. |
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Posted: 1/10/2022 5:18:36 PM EST
[#40]
Quote HistoryQuoted:
Was this with a barrel nut that required timing? https://www.brownells.com/gunsmith-tools-supplies/rifle-tools/barrel-tools/barrel-nut-alignment-gauge-sku080216014-26480-1991.aspx 
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Posted: 1/10/2022 6:32:12 PM EST
[#41]
Quote HistoryQuoted: Added to wish list. Quote HistoryQuoted: Quoted: Was this with a barrel nut that required timing? https://www.brownells.com/gunsmith-tools-supplies/rifle-tools/barrel-tools/barrel-nut-alignment-gauge-sku080216014-26480-1991.aspx Added to wish list. I have the Brownells one and the one from Specialized Armament. They both work, but the one from Specialized Armament is nicer. |
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Posted: 2/11/2022 8:11:25 PM EST
[#42]
Is it just me or does the gas key end of the gas tube look "peened" flat'ish ?
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