Minimum barrel diameter to thread for suppressor

LDhunter

New member
I'm toying with the idea of suppressing one of my rifles and a few of my choices have somewhat thin barrels.

What is the minimum barrel diameter I can safely have threaded?

$bob$
 
I wouldn't want any less than .730 for shoulder on 5/8 threads. It all really depends on mounting type and suppressor also.. but that is the basic.
 
I don't know about others but Thunder Beast Arms Co. recommends .725 with absolute min being .700 for 5/8-24 and .662 for 9/16-24

I'd guess they'll all have close to the same minimums.

Also, before you ever have a barrel threaded for a suppressor, make sure whoever is doing the threading knows the thread specs for your suppressor because even though it may be a common thread, like 5/8-24, there is nothing common about how the threads for a suppressor should be cut.

TBAC told me, if the person cutting the threads for your suppressor tells you they cut the threads the same as they do for a muzzle brake, pick up your stuff and leave.
 
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Does this mean that all the barrels that are already cut for a muzzle brake, ie AR's, are going to be a problem? What is needed to be a correct cut?
 
Originally Posted By: 1loboDoes this mean that all the barrels that are already cut for a muzzle brake, ie AR's, are going to be a problem? What is needed to be a correct cut?

I was thinking of asking him the same thing.
 
A lot of AR manufactures cut Muzzle brake threads with no relief or undercut. That is a problem.
They also do not use thread pitch gauges. That is a problem. Flash hiders, ect... do not need precision threads therefor they don't take the time to do so.

Take your flash hider off your standard AR and compare the threads you see to these in the link and you can see the lack of relief or undercut.

https://thunderbeastarms.com/tech/thread-specifications

 
I'll add my two cents in. Lots of good info but I would add that on pencil barrels I would ABSOLUTELY use a TOMB system or something similar. The main drawback on thin barrels is not enough shoulder for a DC to lock up solid. This causes several issues. With a brake attach system like the TOMB from SAS, the suppressor actually has MORE positive lockup and surface contact than a direct thread.
Another thing is with thin barrels you will get a little more POI shift than thick barrels (harmonics). You can minimize that by purchasing ONLY a lightweight titanium can as longer heavier cans amplify barrel whip causing more POI shift. I would look for a 7" or less can in .30cal for the most versatility or caliber specific for maximum suppression. Just remember, quality, light and short..... In that order!!

Also I've seen more barrels threaded and suppressors made than I care to mention so heed peoples advice and make SURE who threads your barrel cuts to class 3 specs with guages.
 
Originally Posted By: Kino MI'll add my two cents in. Lots of good info but I would add that on pencil barrels I would ABSOLUTELY use a TOMB system or something similar. The main drawback on thin barrels is not enough shoulder for a DC to lock up solid. This causes several issues. With a brake attach system like the TOMB from SAS, the suppressor actually has MORE positive lockup and surface contact than a direct thread.
Another thing is with thin barrels you will get a little more POI shift than thick barrels (harmonics). You can minimize that by purchasing ONLY a lightweight titanium can as longer heavier cans amplify barrel whip causing more POI shift. I would look for a 7" or less can in .30cal for the most versatility or caliber specific for maximum suppression. Just remember, quality, light and short..... In that order!!

Also I've seen more barrels threaded and suppressors made than I care to mention so heed peoples advice and make SURE who threads your barrel cuts to class 3 specs with guages.

Great advice on thin barrels.

Cant stress enough about threads cut and guages used. Just talked to another PM member about bad exp with guy cutting bad threads on his weapon.
 
Originally Posted By: 3DHUSKERA lot of AR manufactures cut Muzzle brake threads with no relief or undercut. That is a problem.
They also do not use thread pitch gauges. That is a problem. Flash hiders, ect... do not need precision threads therefor they don't take the time to do so.

Take your flash hider off your standard AR and compare the threads you see to these in the link and you can see the lack of relief or undercut.

https://thunderbeastarms.com/tech/thread-specifications



According to what you say, AR owners would be having a lot of problems running suppressors on the AR platform unless they use a QD mount. I dont hear of those issues. I am sure there is a difference in the thread cuts but just how critical is it?
 
Originally Posted By: reb8600Originally Posted By: 3DHUSKERA lot of AR manufactures cut Muzzle brake threads with no relief or undercut. That is a problem.
They also do not use thread pitch gauges. That is a problem. Flash hiders, ect... do not need precision threads therefor they don't take the time to do so.

Take your flash hider off your standard AR and compare the threads you see to these in the link and you can see the lack of relief or undercut.

https://thunderbeastarms.com/tech/thread-specifications



According to what you say, AR owners would be having a lot of problems running suppressors on the AR platform unless they use a QD mount. I dont hear of those issues. I am sure there is a difference in the thread cuts but just how critical is it?

Are you serious? A suppressor that will not shoulder up is not only stupid but dangerous. Result is baffle strikes due to loosing can (cant get it properly aligned and tight if it wont shoulder), larger than normal POI, ect. Not to mention cutting threads concentric to the bore for proper alignment. A lot of the barrels bores are not in the center of the barrel. So your telling me it is not critical to have everything lined up properly when shooting a bullet basically through a long tight tunnel? Come on man...
If the fit is not right you will have problems sooner or later. When you are directly involved with the industry you have to deal with it all the time.
Here is one I bought that I just had cleaned up last week. It had no relief cut and shoulder was not square.

8da80479-413e-4b0b-8555-bb366d07c64f_zpsdssegul2.jpg



 
Originally Posted By: 3DHUSKER
Are you serious? A suppressor that will not shoulder up is not only stupid but dangerous. Result is baffle strikes due to loosing can (cant get it properly aligned and tight if it wont shoulder), larger than normal POI, ect. Not to mention cutting threads concentric to the bore for proper alignment. A lot of the barrels bores are not in the center of the barrel. So your telling me it is not critical to have everything lined up properly when shooting a bullet basically through a long tight tunnel? Come on man...
If the fit is not right you will have problems sooner or later. When you are directly involved with the industry you have to deal with it all the time.
Here is one I bought that I just had cleaned up last week. It had no relief cut and shoulder was not square.

8da80479-413e-4b0b-8555-bb366d07c64f_zpsdssegul2.jpg



Dont get so worked up, I am just asking. I have my first suppressor waiting on my stamp. I dont claim to know everything about suppressors, in fact I am trying to learn. If you dont like someone asking questions, dont post.
 
This discussion got my curiosity aroused. The statement that a lot of manufacturers make barrel threads with no undercut made me wonder if mine were made that way. After checking six barrels, I did not find any issue with lack of undercut. There was another implication that some barrels may not have bores concentric with the o.d. The bores on my rifle barrels were all concentric as well. I would think that a rifle with a non concentric bore would have harmonic problems that would not allow it to shoot well. In any case, I have not heard of anyone having a problem due those kind of issues. I've heard of folks having a baffle strike, but the culprit is usually a loose suppressor or contamination. Empirical evidence would indicate to me that the issue may not be too widespread. Not trying to argue here, just trying to help myself understand how big a problem this might be.
 
Originally Posted By: 1loboThis discussion got my curiosity aroused. The statement that a lot of manufacturers make barrel threads with no undercut made me wonder if mine were made that way. After checking six barrels, I did not find any issue with lack of undercut. There was another implication that some barrels may not have bores concentric with the o.d. The bores on my rifle barrels were all concentric as well. I would think that a rifle with a non concentric bore would have harmonic problems that would not allow it to shoot well. In any case, I have not heard of anyone having a problem due those kind of issues. I've heard of folks having a baffle strike, but the culprit is usually a loose suppressor or contamination. Empirical evidence would indicate to me that the issue may not be too widespread. Not trying to argue here, just trying to help myself understand how big a problem this might be.

Great if you have them cut right. That is a plus.
Now for the concentric issues how do you know yours are concentric with the bore? Please explain.
 
Originally Posted By: reb8600Originally Posted By: 3DHUSKER
Are you serious? A suppressor that will not shoulder up is not only stupid but dangerous. Result is baffle strikes due to loosing can (cant get it properly aligned and tight if it wont shoulder), larger than normal POI, ect. Not to mention cutting threads concentric to the bore for proper alignment. A lot of the barrels bores are not in the center of the barrel. So your telling me it is not critical to have everything lined up properly when shooting a bullet basically through a long tight tunnel? Come on man...
If the fit is not right you will have problems sooner or later. When you are directly involved with the industry you have to deal with it all the time.
Here is one I bought that I just had cleaned up last week. It had no relief cut and shoulder was not square.

8da80479-413e-4b0b-8555-bb366d07c64f_zpsdssegul2.jpg



Dont get so worked up, I am just asking. I have my first suppressor waiting on my stamp. I dont claim to know everything about suppressors, in fact I am trying to learn. If you dont like someone asking questions, dont post.

No no... Someone who seems to be so detailed about everything else can't be so lax in this area, just was shocked that it was no big deal. no problem. I should use more smiles
thumbup.gif
Sorry I seemed brash, I just don't want my brothers in arms with their first suppressor not having a wonderful experience.

I just had another PM brother that lives 30 miles away get his first can and experience a bad thread job first time out. I recommended a smith that I knew would do it right he used another and had a can stuck half on. (Would not come off).
thumbdown.gif
 
I put these 2 together for reference, see difference?

Here is one I bought that I just had cleaned up last week. It had no relief cut and shoulder was not square.

8da80479-413e-4b0b-8555-bb366d07c64f_zpsdssegul2.jpg



Here is another without undercut. Suppressor seems tight but can still get .0015 feeler gauge between suppressor and shoulder. The can is stopping where threads get shallow and a misaligned suppressor is the result.

IMG_20150523_203755086_zpshevj7ptd.jpg

 
Originally Posted By: 3DHUSKER
Now for the concentric issues how do you know yours are concentric with the bore? Please explain.

I used an angle block and mag based dial indicator. Clamped the barrel end into the angle block. Checked bore to block dimension in two quadrants. Measured against a gauge block on each move of the mag base.

Don't see why a suppressor that is bottomed out on the threads without going against the shoulder automatically means mis-aligned? It may not repeat position as well, but it doesn't seem to guarantee being cocked. A gauge rod would be a good quick check of that if you had a rifle threaded like that. I think I would want to check that before shooting anyway. Don't most (.223) suppressors about .030 larger than the bore?
 
That is a great idea kudos on that but probably not real exact. Best way is to chuck the barrel up and dial it in on the tool to the bore then run a dial indicator on out side of the barrel. Kinda a same thing just solid so you can get exact measurements down to ten thousands.

Example: Take a bolt and a nut and screw the nut on. Is there any side to side play? You bet.. cocked to one side is miss aligned. When you run the can on and it bottoms on the threads it cocks to one side. That effects the stability of the round going through the can and effects POI.
I have seen POI from can on to can off of over 8 feet at 200 yards. He had a pretty bad thread job. After being repaired it was less than couple inches at 200.

Suppressor manufactures usually tell you to look down your bore for alignment problems and that will generally keep you from having a baffle strike and that is what they are concerned about.

The whole idea of this is to make you aware that there are things to ask and look for when having a barrel threaded or using existing threads that can make your experience a pleasant one or a bad one. Its up to you to decide what you want. Do you want to spend a 1000 bucks on a suppressor and stamp and then destroy it first time out or have it throwing bullets a foot left and a foot high at 200 yards compared to suppressor off. Some people are ok with that, some are not. That is for you to decide.

Here is a video on what I am talking about. Enjoy.

 
Thanks for all the good information. POI is quite important to me and I can see why a slightly misaligned suppressor can affect POI without a baffle strike. Alignment reproduction would be critical and thread quality would be paramount. I had to measure my bore the way I did as I had another job on the lathe that I couldn't tear down. Didn't expect my bores to have a concentricity issue anyway as they are all very accurate for me. You are right in that the best way to measure accurately is to spin it and measure run out. Incidentally, I wouldn't own a barrel that had a concentricity issue very long. Neither would I want to have threads on a barrel like the one you pictured. Can't understand why any quality manufacturer would let one like that out of their plant.
 
Originally Posted By: 1loboThanks for all the good information. POI is quite important to me and I can see why a slightly misaligned suppressor can affect POI without a baffle strike. Alignment reproduction would be critical and thread quality would be paramount. I had to measure my bore the way I did as I had another job on the lathe that I couldn't tear down. Didn't expect my bores to have a concentricity issue anyway as they are all very accurate for me. You are right in that the best way to measure accurately is to spin it and measure run out. Incidentally, I wouldn't own a barrel that had a concentricity issue very long. Neither would I want to have threads on a barrel like the one you pictured. Can't understand why any quality manufacturer would let one like that out of their plant.


I hear you brother, for the life of me I don't know what they are thinking. I just hope this helps somebody on here.
 
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