Loose barrel threads affect accuracy?

204 AR

Well-known member
I've been struggling getting better than moa accuracy out of a dpms 243 barrel. It came threaded 5/8", but the fit is so loose that I got in the habit of checking to make sure the suppressor didn't come loose after each group. To be more specific, I get good groups occasionally, but when I try to verify, it always falls apart.

And to make matters worse, I swapped out the barrel as I have a couple extras, with the same results. It seems unlikely 2 barrels in a row would be so mediocre and inconsistent. I've squared the upper, tried different scopes, etc to rule that out.

So it just dawned on me that the terrible threads might be the source if they're allowing movement, or causing inconsistent vibes upon firing. Anyone experience this before?
 
Try wrapping the threads with teflon tape ( the white tape that you use for sealing pipe threads ) one of the local PO that is on the sniper team told me they do that to keep their suppressors from coming loose. And when you do take it off the teflon tape just comes off the threads very easily.
Tarey
 
Teflon on the threads is a good suggestion. I would also suggest using an o-ring between the suppressor and the barrel. This will push the suppressor towards one side of the loose cut threads and create a more constant engagement. It will also help keep the suppressor from loosening as easily when shooting.
 
using an o-ring on a suppressor not engineered for it as part of the thread engagement is a bad idea...like possibly REAAAAAAAAAALLY bad.

you're more likely to get an off-center/off-axis alignment from your bore and therefore a much higher risk of a baffle/endcap strike on firing.

this is the same reason that crush washers are NOT used on QD mount systems... the risk of causing the suppressor to be off-axis from the center of the bore.

you should ALWAYS on a direct thread mount come down to the shoulder on the barrel and secure solidly against that so that your flat/flat surface engagement helps with concentric alignment to the bore stay true.




if your can is loosening up after firing... a bit of copper or nickle anti-seize on the threads can help. its amazing what a small dab of that stuff will do to keeping your threads from backing out under fire.

i would still check and re-tighten after a few rounds warms things up, but once i did that follow up snug-down i never had a problem of the can coming loose on me again once i started adding it to my direct thread barrels.

HTH
 
Every properly threaded barrel has a relief cut next to the shoulder at the end of the threads. This is a space that works very well as a pocket to hold a properly sized O-ring. If you put an O-ring in this position and tighten the suppressor down properly, it will seat on the barrel shoulder and locate as it is supposed to. It will also be held more securely due to the presence of the properly sized O-ring. I run this setup on several suppressed weapons. I have shot hundreds of rounds through them and have never had a baffle strike. To say that a suppressor would have to be designed for this is misleading. It is a matter of having the proper relief groove on the barrel threads. It's worth noting that some guns that are made with barrels already threaded come with an O-ring installed. One example would be a Smith and Wesson .22 Victory. It would seem to me that the problem that was posted by 204 AR is related to a suppressor with threads that are too loose, since two barrels showed the same relationship. I would be looking at that threads in that suppressor and perhaps contacting the manufacturer. In the meantime, all of the solutions proposed have merit as they tend to tighten up the relationship of the barrel threads to the suppressor threads, making up for a set of out of spec threads somewhere.
 
Thanks for the suggestions. The thing with 5/8" threads seems to be that everyone has slightly different dimensions. My local smith cuts them on the large side and they fit my suppressor snugly. And it seems like these barrels happen to shoot the best.

I think I will test accuracy without the can and see if there's any difference, or if I can work up a useable load that way, then go from there. Worst scenario is $40 to have the barrel cut and re-threaded, which in the long run I'd prefer to using tape or o-rings.

I was mostly curious if anyone had seen a co-relation of thread fit to accuracy/consistency. After thinking about it, it only makes sense to me that it would be fairly important and probably often overlooked in the quest for accuracy.
 
I had thought about the teflon tape before, and after reading the suggestions here I experimented with it. I found 3 wraps gets me a much nicer feel and should keep the suppressor tight. No chance to shoot it but I will test it out the next time the wind goes below gale force. I still don't think it's a permanent resolution as I don't want to have to mess with it each time I install the suppressor, but it might help me test the theory. Right now I have a 260 barrel installed, which showed possibly better results yesterday than the 243 barrels, despite having a un-perfect chamber. (Right now I'm not impressed with DPMS barrels). If nothing else, I'll salvage the barrel extension off of one of them and have a good barrel made.
 
Originally Posted By: 1loboEvery properly threaded barrel has a relief cut next to the shoulder at the end of the threads. This is a space that works very well as a pocket to hold a properly sized O-ring. If you put an O-ring in this position and tighten the suppressor down properly, it will seat on the barrel shoulder and locate as it is supposed to. It will also be held more securely due to the presence of the properly sized O-ring. I run this setup on several suppressed weapons. I have shot hundreds of rounds through them and have never had a baffle strike. To say that a suppressor would have to be designed for this is misleading. It is a matter of having the proper relief groove on the barrel threads.

and therein lies the rub... not all barrel manufacturer's cut that thread relief in there.

which is exactly why i cautioned against using one, especailly if one isnt aware of the potential consequences of using one improperly.
 
I've never had any issues with any of my suppressors coming loose on my DPMS LR-260H. I have 2 Thunder Beast and a Mack Bros. Varminter 3.0 and they all stay tight on the factory barrel threads.
 
Originally Posted By: TxhillbillyI've never had any issues with any of my suppressors coming loose on my DPMS LR-260H. I have 2 Thunder Beast and a Mack Bros. Varminter 3.0 and they all stay tight on the factory barrel threads.

Cool.
 
For now the teflon tape seems to be working well, with 3 wraps it holds up for a couple of remove/replace cycles so it isn't too much trouble. It definitely gives a better feel while threading on and keeps it from coming loose, and I seem to have found a load that gives me the accuracy I'm after using this method. Thanks for all the suggestions.
 
More testing with the teflon tape wrap reveals some very interesting stuff. First, testing with the tape off vs on, at 200 yards without it I get 2" groups, with it under an inch every time. But the problem with the tape, poi moves slightly to significantly when I remove/replace the supressor. It is very sensitive to how much tape and how it is applied. Groups remain great but might be 1/2" to several inches away.

So, each time the can is removed for cleaning, the best method might be removing all the old tape, re-applying it exactly the same way, then checking zero and making adjustments before going hunting. This is not an ideal situation at all.

But I definitely proved to myself that good fitting threads make a big difference in accuracy.
 
I have a barrel that I use teflon tape on. I put 1 full wrap on the threads before putting can on and have not noticed a shift in POI @ 200 yds. This is on a 222 with 1/2-28 threads and Elite Iron Delta can. I clean the barrel and replace the tape each time. Works for me.
 


I joined this group to find a suppressor. The members were very helpful.
I was pointed to a Specwar 7,62. That uses an ASR mount.
I have used my suppressor on different rifles with no problems.
I worked in the machine-tool industry for 40 years, with many types of steel.
Barrels are made from steels that are easy to drill, thread, and rifle.
I have stayed away from having my rifles threaded.
Mainly, I have not found a gunsmith I would trust doing the work that lives close to me.
Each time you tighten treads the surface of the threads is deformed.
So I torque three times and release. Then torque one last time.
I mainly shoot AR-type rifles. Those are cut with CNC lathes.
The Specwar uses an ASR mount that is about $90 each. So once it goes on it stays.
I do own a DPMS in 243 and have had no problems.
You guys were right telling me to buy Specwar and thank you.
 
Originally Posted By: 204 ARMore testing with the teflon tape wrap reveals some very interesting stuff. First, testing with the tape off vs on, at 200 yards without it I get 2" groups, with it under an inch every time. But the problem with the tape, poi moves slightly to significantly when I remove/replace the supressor. It is very sensitive to how much tape and how it is applied. Groups remain great but might be 1/2" to several inches away.

So, each time the can is removed for cleaning, the best method might be removing all the old tape, re-applying it exactly the same way, then checking zero and making adjustments before going hunting. This is not an ideal situation at all.

But I definitely proved to myself that good fitting threads make a big difference in accuracy.

might be worth sending the tube in then to have the threads corrected - at least now that you know you've got a potential shooter on your hands. make the poorly manufactured threads go bye bye.

if you got enough length, i would probably just have the barrel cut at the shoulder where the current threading is and just re-threaded.

ADCO does nice work and generally turns stuff around quick. $75 + shipping. includes a Target crown too as part of the work, no charge.

they've done several barrels for me - including my 223 WOA varmint and will continue to get my work in the future when needed. very happy customer.

https://adcofirearms.com/shop/gunsmithing/arstandard-barrel-threading/
 
Originally Posted By: Plant.OneOriginally Posted By: 204 ARMore testing with the teflon tape wrap reveals some very interesting stuff. First, testing with the tape off vs on, at 200 yards without it I get 2" groups, with it under an inch every time. But the problem with the tape, poi moves slightly to significantly when I remove/replace the supressor. It is very sensitive to how much tape and how it is applied. Groups remain great but might be 1/2" to several inches away.

So, each time the can is removed for cleaning, the best method might be removing all the old tape, re-applying it exactly the same way, then checking zero and making adjustments before going hunting. This is not an ideal situation at all.

But I definitely proved to myself that good fitting threads make a big difference in accuracy.

might be worth sending the tube in then to have the threads corrected - at least now that you know you've got a potential shooter on your hands. make the poorly manufactured threads go bye bye.

if you got enough length, i would probably just have the barrel cut at the shoulder where the current threading is and just re-threaded.

ADCO does nice work and generally turns stuff around quick. $75 + shipping. includes a Target crown too as part of the work, no charge.

they've done several barrels for me - including my 223 WOA varmint and will continue to get my work in the future when needed. very happy customer.

https://adcofirearms.com/shop/gunsmithing/arstandard-barrel-threading/

And that's probably the best way. The nice thing is I can get it done locally, and take my suppressor in and have the threads matched perfectly. I have little doubt that the suppressor threads are worn a little as well, and a replacement end cap from Sico is an option also.
 
Originally Posted By: 204 AROriginally Posted By: Plant.OneOriginally Posted By: 204 ARMore testing with the teflon tape wrap reveals some very interesting stuff. First, testing with the tape off vs on, at 200 yards without it I get 2" groups, with it under an inch every time. But the problem with the tape, poi moves slightly to significantly when I remove/replace the supressor. It is very sensitive to how much tape and how it is applied. Groups remain great but might be 1/2" to several inches away.

So, each time the can is removed for cleaning, the best method might be removing all the old tape, re-applying it exactly the same way, then checking zero and making adjustments before going hunting. This is not an ideal situation at all.

But I definitely proved to myself that good fitting threads make a big difference in accuracy.

might be worth sending the tube in then to have the threads corrected - at least now that you know you've got a potential shooter on your hands. make the poorly manufactured threads go bye bye.

if you got enough length, i would probably just have the barrel cut at the shoulder where the current threading is and just re-threaded.

ADCO does nice work and generally turns stuff around quick. $75 + shipping. includes a Target crown too as part of the work, no charge.

they've done several barrels for me - including my 223 WOA varmint and will continue to get my work in the future when needed. very happy customer.

https://adcofirearms.com/shop/gunsmithing/arstandard-barrel-threading/

And that's probably the best way. The nice thing is I can get it done locally, and take my suppressor in and have the threads matched perfectly. I have little doubt that the suppressor threads are worn a little as well, and a replacement end cap from Sico is an option also.

Does the fellow use thread micrometers or wires to measure the threads?
What type of go & no-go gauges does he use to check the treads in you can.
Does he use a preformed threading tool and plunge straight in or use a hand ground tool and set at 29 degrees?
Does the maker of your suppressor tell you what class of thread they are?
I store my Specwar in the pouch when not in use not on the end of my barrel.
I was told right by this group when I bought my Specwar.
 
Originally Posted By: willy1947Originally Posted By: 204 AROriginally Posted By: Plant.OneOriginally Posted By: 204 ARMore testing with the teflon tape wrap reveals some very interesting stuff. First, testing with the tape off vs on, at 200 yards without it I get 2" groups, with it under an inch every time. But the problem with the tape, poi moves slightly to significantly when I remove/replace the supressor. It is very sensitive to how much tape and how it is applied. Groups remain great but might be 1/2" to several inches away.

So, each time the can is removed for cleaning, the best method might be removing all the old tape, re-applying it exactly the same way, then checking zero and making adjustments before going hunting. This is not an ideal situation at all.

But I definitely proved to myself that good fitting threads make a big difference in accuracy.

might be worth sending the tube in then to have the threads corrected - at least now that you know you've got a potential shooter on your hands. make the poorly manufactured threads go bye bye.

if you got enough length, i would probably just have the barrel cut at the shoulder where the current threading is and just re-threaded.

ADCO does nice work and generally turns stuff around quick. $75 + shipping. includes a Target crown too as part of the work, no charge.

they've done several barrels for me - including my 223 WOA varmint and will continue to get my work in the future when needed. very happy customer.

https://adcofirearms.com/shop/gunsmithing/arstandard-barrel-threading/

And that's probably the best way. The nice thing is I can get it done locally, and take my suppressor in and have the threads matched perfectly. I have little doubt that the suppressor threads are worn a little as well, and a replacement end cap from Sico is an option also.

Does the fellow use thread micrometers or wires to measure the threads?
What type of go & no-go gauges does he use to check the treads in you can.
Does he use a preformed threading tool and plunge straight in or use a hand ground tool and set at 29 degrees?
Does the maker of your suppressor tell you what class of thread they are?
I store my Specwar in the pouch when not in use not on the end of my barrel.
I was told right by this group when I bought my Specwar.






Holy crap Willy, I have no answers to any of that. I just know his threads run tight and that's good enuf for this idiot.
 
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