View Full Version : Bad Thread Spec or Normal?
My second upper build
The barrel is an Upper tier I won't name yet 5.56
Muzzle devices are having a hard time screwing on by hand
Getting really tight in the first couple threads by hand
Mds are Larue and v7 so not junk
I don't remember if being that tight on my first build
In fact pretty sure I could thread that one most of the way by hand
That was an fn chf barrel
Check the OD of the threads with calipers or a micrometer
Sounds like muzzle threads are bad. Maybe check it with a screw pitch gage just to see if anything stands out.
I usually find them a little on the loose side till I get to the shoulder/washer.
Assuming the MDs are gtg, then you've got a thread problem. What you describe isn't normal. Can you tell if there is damage/a bad spot? You could chase the threads if you have minor damage to otherwise good threads. Or, return the barrel... Many variables here, including what you have and your ability/confidence/tools. For example, if the threads had minor damage and were then nitrided... much harder (pun intended) to fix than phosphated CMV.
My second upper build
The barrel is an Upper tier I won't name yet 5.56
Muzzle devices are having a hard time screwing on by hand
Getting really tight in the first couple threads by hand
Mds are Larue and v7 so not junk
I don't remember if being that tight on my first build
In fact pretty sure I could thread that one most of the way by hand
That was an fn chf barrel
What muzzle device? By chance is it a device for a can?
I second the recommendation to measure thread od and tpi with calipers. Make sure they match the muzzle device threads.
Are you sure the MD threads are 556 (1/2 x 28)?
Maybe take them to lowes if you dont have a theead checker, and make sure they are what you think.
I second the recommendation to measure thread od and tpi with calipers. Make sure they match the muzzle device threads.
Are you sure the MD threads are 556 (1/2 x 28)?
Maybe take them to lowes if you dont have a theead checker, and make sure they are what you think.
If only the Lowe's female thread board went to 1/2-28...be much cooler than the scale gadget :D
I think I had one guy that figured out an FAL lower and was able to assist with whatever I was cobbling together.
Here's some pics. I think it's mis-threaded. What do you all think?
4963849639
I second the recommendation to measure thread od and tpi with calipers. Make sure they match the muzzle device threads.
Are you sure the MD threads are 556 (1/2 x 28)?
Maybe take them to lowes if you dont have a theead checker, and make sure they are what you think.
I am 100% positive the MD threads are correct. One MD came off a Larue Upper 5.56/223Wylde. The other I installed and then removed from my first build which has an FN / CHF barrel in 5.56mm
Averageman
01-07-18, 17:17
Have you tried chasing the threads?
Have you tried chasing the threads?
I'm not going to modify this if it's wrong I'll ask the mfg to replace or seller for refund
Here's some pics. I think it's mis-threaded. What do you all think?
4963849639
Can you measure them? Do you have calipers?
The threads look shallow, but its difficult to tell.
Dionysusigma
01-07-18, 17:50
https://i.imgur.com/SKvGQx7.jpg
Maybe it's just me, but it looks like (circled in red) the threaded portion got bonked on something hard and deformed the threads.
https://i.imgur.com/SKvGQx7.jpg
Maybe it's just me, but it looks like (circled in red) the threaded portion got bonked on something hard and deformed the threads.
trick of the light- no issues with that section
Now strangely enough. I tried a YHM Fantom Flash hider and - voila - threads on just fine!
Weird that the Larue Tranquilo brake ( that I took OFF my 556 Larue ) and a VSeven Ti flash hider won't thread on beyond the first thread or so.
Thoughts?
Averageman
01-07-18, 18:32
Measure the thread pitch, it is always good to have this tool.
Measure, then turn the barrel 180 degrees and measure it again. If the measurement does not exactly correspond the threads were likely "dinged" along the way. You can send it back or you could simply chase the threads.
This isn't likely a manufacturing issue, it is more likely to be a shipping issue or someone fumble fingered your barrel between you and the manufacturer. There is likely little possibility that this is fixable on your workbench in five minutes.
Okay, I was typing that as you were working, good luck, it would seem you have the answer.
trick of the light- no issues with that section
Now strangely enough. I tried a YHM Fantom Flash hider and - voila - threads on just fine!
Weird that the Larue Tranquilo brake ( that I took OFF my 556 Larue ) and a VSeven Ti flash hider won't thread on beyond the first thread or so.
Thoughts?You mentioned they were used. Is there carbon build up on the threads in the muzzle devices?
Sent from my SM-S327VL using Tapatalk
You mentioned they were used. Is there carbon build up on the threads in the muzzle devices?
Sent from my SM-S327VL using Tapatalk
No carbon build up whatsoever. The Larue Tranquilo MD has seen Zero rounds as it was immediately removed from a factory fresh Larue upper.
Most likely a case of tolerance stacking.
Barrel manufacture anticipates sloppy muzzle device. Muzzle device manufacture anticipates sloppy barrel threads.
Barrel manufacture was right when you installed the YHM.
Is the barrel nitrided? If so, chasing the threads might be a bit of a chore.....
Buy some calipers.
You can likely answer your own questions after that, or at least provide data for us. Im not sure having us specuate will benefit you.
tigershilone
01-08-18, 02:08
Pics are not the best, take them from directly 90 degrees away from suspected damage, preferably with the damage at the top of the pic where the white is. As long as they aren't galled, most thread issues can be fixed.
Where the MD's you are trying to install originally installed with rock-set or another thread-locker? From what I'm hearing in this thread the used muzzle devices might still have garbage on their threads from the previous install. Check those MD's on another barrel, that will tell you if it is the MD's or barrel.
Get a thread gauge and check your threads. Put the 28 tpi gauge in the threads and hold it up to the light, it will show defects pretty quick. local hardware store should have one. https://www.amazon.com/gp/product/B0007CXJJA/ref=s9_acsd_topr_hd_bw_bHLv4t_c_x_w?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=merchandised-search-3&pf_rd_r=5G365VFFDDRWPKT5C4AF&pf_rd_t=101&pf_rd_p=c7bc0fa5-ae27-5142-bd45-fddc0c2ba5e1&pf_rd_i=256422011
A 28 tpi thread file will clean up lightly damaged areas nicely. Probably have to special order this one https://www.amazon.com/CTA-Tools-8235-Thread-Restorer/dp/B00M9FZEIM/ref=sr_1_1?s=hi&ie=UTF8&qid=1515398494&sr=1-1&keywords=thread+file+28
I'm going to take a guess that the manufacturer that made the OP's barrel is Ballistic Advantage.
This defect has been quite common from them over the last year... Four of the five barrels that I have received from them have had issues threading on certain muzzle devices. I have also had issues with these barrels not accepting my 5.56 GO gauges.
Others have had this "tight threading" issue as well and there is a thread about it over on TOS.
What's TOS?
The Other Site.
TOS = ARFCOM. This place is also known as TOS over there.
I would just give you a link but I'm not sure if I'm allowed to or not.
It's in the Industry section in the Ballistic Advantage forum under the title "barrel threads".
The Other Site.
TOS = ARFCOM. This place is also known as TOS over there.
I would just give you a link but I'm not sure if I'm allowed to or not.
It's in the Industry section in the Ballistic Advantage forum under the title "barrel threads".
You could send it to him in a PM
You could send it to him in a PM
Will do, thanks for letting me know.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.