Suppressor thread question

Hi all.
I have just had a new barrel fitted to a rifle and the muzzle is threaded 1/2x20 for an over barrel DPT suppressor.

When I try to screw on the suppressor it is difficult to get the thread started and then it feels like it will gall up after about 3-4 turns.
I have tried a few rimfire suppressors for fit too, one feels like galling up, the other which must have a courser thread goes on.
The thread protector that came with the new barrel screws onto a couple of other 1/2x20 threaded barrels without any issues.


I plan to contact the outfit who did the work on Monday but thought I might be able to see what my options are in the mean time in order to help inform Mondays discussion.
Ultimately this is not at all about who is at fault or naming or shaming, it is about achieving an end result of being able to fit a suppressor to the rifle, hopefully without having to send it back again as the outfit is not local.

The simple option of chop and re-thread doesn't exist either as the barrel is just long enough for the over barrel DPT to not contact the forend.
My preferred approach would be just to get a new DPT suppressor that hasn't had a muzzle thread cut and have it tapped out to the same thread as the rifle barrel.

My question to the Forum is;
Is this practical from a perspective of would the thread protector have been threaded with a tapping bit in which case the same bit could be used to tap out the DPT to the same thread, or would the thread protector thread have been cut on a lathe (in which case could the same thread be duplicated inside an overbarrel DPT?)

Or am I over thinking it and is there a much easier way? Open to suggestions on that one....
thanks in advance for the input.

Well if it was me making them they would all be done with a tap, but maybe the suppressor was cut with a tool rather than a tap. Coubbee a QC issue?
Do you know anyone else with a similar suppressor to try?

suppressors in 1/2 x 20 and 1/2x 28 will nearly fit each other so maybe the thread is 1/2 x 28 a common AR15 thread

3 out of 4 1/2x20 suppressors won’t screw on more than 5 turns without getting tight, tried a 12x28 partly out of optimism, it goes about 1 turn then feels like lockup is inevitable.

The three suppressors that won’t fit on the new barrel can all fit on any of the other three barrels that are threaded 1/2x20.
The one that does fit the new barrel also fits on any of the existing three barrels. Only problem is it is a rimfire suppressor. (Cheap one that works and is probably cut to have plenty of tolerance like a.303 chamber)
The thread protector that fits on the new barrel fits on the three existing barrels too.

Judging by all of the above, the threads on the new barrel are just a touch too wide to go into a DPT

I wouldn't have thought that 1/2 x 28 would go further than 1-2 turns without picking up, it's quite a lot finer.
I had a jw15 shortened and threaded a few months back, and found that when I tried to fit the suppressor off my marlin 980 (both 1/2 x20) it bound up after about 4 turns.
It turned out the thread length of the jw15 was longer than that of the 980, and was screwing deeper into the suppressor body. That deeper section of thread that wasn't ever used by the 980 had accumulated a lot of crud which was causing the issue. A bit of a clean up and all was good.

I came across the same problem yesterday.
Rifle is threaded 1/2x20 and the suppressor is also 1/2x20 but after 3 turns it binds. Thread protector goes on fine.
I should have included the suppressor with the barrel when I sent it to the gunsmith and his tolerances must also be out.
I'm packing mine up again and sending it back to him on Monday with the suppressor so he does it right this time....let him sort it out at his cost.
I'm not going to start playing with the suppressor threads...I suggest you do the same.

Quote:

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Originally Posted by Hermitage

I came across the same problem yesterday.
Rifle is threaded 1/2x20 and the suppressor is also 1/2x20 but after 3 turns it binds. Thread protector goes on fine.
I should have included the suppressor with the barrel when I sent it to the gunsmith and his tolerances must also be out.
I'm packing mine up again and sending it back to him on Monday with the suppressor so he does it right this time....let him sort it out at his cost.
I'm not going to start playing with the suppressor threads...I suggest you do the same.

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good advice that

Quote:

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Originally Posted by Hermitage

I came across the same problem yesterday.
Rifle is threaded 1/2x20 and the suppressor is also 1/2x20 but after 3 turns it binds. Thread protector goes on fine.
I should have included the suppressor with the barrel when I sent it to the gunsmith and his tolerances must also be out.
I'm packing mine up again and sending it back to him on Monday with the suppressor so he does it right this time....let him sort it out at his cost.
I'm not going to start playing with the suppressor threads...I suggest you do the same.

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Your situation reads exactly as mine is, and in hindsight I should have included the suppressor too, it also pains me to admit you are probably right about sending it back, I just had some hope that I might be able to avoid the palaver and cost of doing so. Especially as there may be some possibility that to sort out the rifle thread may involve a new barrel if the current thread can’t be adjusted to fit.

The only sensible option is to have the muzzle thread tidied up. If you think it’s hard to cut a thread, try cutting an out of spec thread to suit another.


Sent from my iPhone using Tapatalk

Quote:

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Originally Posted by MSL

The only sensible option is to have the muzzle thread tidied up. If you think it’s hard to cut a thread, try cutting an out of spec thread to suit another.


Sent from my iPhone using Tapatalk

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It’s looking more and more like that is the situation.
I take it you understand the finer points of cutting threads, my own personal experience starts and ends with using tapping dies, what I am interested to know is whether it is a fairly straight forward process to tidy up a thread or is there some significant risk the thread could end up wrecked in the process and need to be cut off and started again.

Quote:

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Originally Posted by longshot

It’s looking more and more like that is the situation.
I take it you understand the finer points of cutting threads, my own personal experience starts and ends with using tapping dies, what I am interested to know is whether it is a fairly straight forward process to tidy up a thread or is there some significant risk the thread could end up wrecked in the process and need to be cut off and started again.

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If the tidying up of the thread doesn't work and the barrel needs to be shortened due to a rethread, then would you be willing to cut the stock forend back and then remold with something like Selleys Knead It? (cheaper than a new barrel and can look alright with a paint).

Quote:

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Originally Posted by Hermitage

If the tidying up of the thread doesn't work and the barrel needs to be shortened due to a rethread, then would you be willing to cut the stock forend back and then remold with something like Selleys Knead It? (cheaper than a new barrel and can look alright with a paint).

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I did think about that scenario, if it was wood or plastic I probably would have just gone down that path and never worried about even starting this thread, it’s a cf stock that was a right place at the right time with the right amount of money sort of purchase and I don’t know what cf is like to cut or re finish.
If there is a risk of new barrel required I will send it back to the people who originally did the work as they can fit a new barrel if the re-thread goes awry, but if there is little to know risk in getting it re-threaded locally I may take a punt.

a too big of a thread is workable. Too small is bad. At least there is something to work with.
TBH if I had access to a die set I would be inclined to chase the thread up myself but that has been part of my game in the past

Yep that was my first thought too, but being a brand new barrel and not being very experienced in threading, I fear I might wreck it and void any warranty in the process.
Thanks everyone for your input, looks like tidying up the thread is what needs to happen and given it is the male thread that is too big it should be achievable. It has been good to rule out the suppressor thread adjustment as a scenario, it will make mondays conversation much more straightforward and in the long run it will keep all of my suppressor threads compatible which has been handy so far.

Best case scenario is that the major and/or minor thread diameter are oversize. Though I suspect the thread pitch to be your trouble, which is not so good.


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Unfortunately, you've already voided the warranty when it was threaded.

On the few rifles I have had threaded the smiths insisted I also provided them the suppressor that I intended using, in order to achieve optimum fit.
Chances of variation from suppressor manufacturer to manufacturer even though they probably threaded to correct + - tolerances.

Did your smith not have the suppressor? And if he didn't how was he to confirm the fit of the barrel bush?

Trying thread caps between barrels will only roughly confirm pitch not the quality of the cut.

The collar on my mincer wouldn't screw on the mincer body properly and bound up and started to cross thread. It turned out the thread on the body was too wide to fit inside the collar thread, a bit of sanding (taking the peak off the threads on the body) fixed the problem. I'm not suggesting you try this, just giving some hope that it could be simple fix!

Quote:

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Originally Posted by Cigar

The collar on my mincer wouldn't screw on the mincer body properly and bound up and started to cross thread. It turned out the thread on the body was too wide to fit inside the collar thread, a bit of sanding (taking the peak off the threads on the body) fixed the problem. I'm not suggesting you try this, just giving some hope that it could be simple fix!

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Worst thing for a man in my situation to read just before bedtime….
but thanks I do live in hope that this is the situation, given the cap fits on the other guns it would seem the pitch is correct, bloody tempted to find out now.

At any rate I will run the callipers over it in the morning and come back with the results, with the measurements from a couple of other rifles to compare.
The other thing I can now ponder in lieu of sleeping is why I didn’t check it with callipers this morning before first posting. Honorary genius in action it would seem.

Put a DPT can on your rifle. Take it to DPT and get the experts to do it. Dpt has all the best equipment. Darren is a whizz and his crew are bloody good at their job and helpful b'stards.

Take it back to the guy who cut the thread, along with suppressor you intend to use. It is a simple job to repair, 15 minutes tops!

Saw Friwi today and picked up a new Magnum can for the WSSM. Friwi did the threading previously and had advised to get the magnum for the Sako 75 243. So another magnum. Mounted. Swing,feel balance. Perfect. Bushing done. Check again . Perfect. We both had a chuckle about getting an expert to do the job. The can is too important to not have it done right. Why. Your face is about 20 inches from the end. Well worth the travel from Hawkes Bay. Quality product. Quality advice and service. Happy hunter.