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Criterion 6.5 creedmoor barrel issues

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 12:10
supertool73 View Drop Down
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So I bought a 6.5 creed AR 10 barrel.  18" model.

Got it last week, and installed it.  I noted the threaded end of the barrel was very long.  I have a 6.5 Thunderbeast ultra 7 that uses a compact brake or flash suppressor to attach to.  So I bough an new flash suppressor for it and went to screw it on.  Turns out the flash suppressor is only threaded a .65 inches deep.  The barrel is threaded .73 deep to the shoulder.  The flash suppressor came with a shim kit but it still does not give it enough length to do it fit.  So I tried a crush washer which gave it the length, but that canted the muzzle device enough that when I looked down the barrel I could see the edge of my baffles in my Ultra 7.  Initally I was not sure if this was a threading issues or the crush washer.

So I email Criterion about how long it is and worried that it might be out of spec.  They email me back saying it is highly unlikely that their barrel could be out of spec.  So I grab a bunch of my other 5/8x24 barrels and start to measure.  Not one of them measured longer than .620 inches.  I have seven other threaded barrels both factory and custom done by a gun smith. 

So I now call them and talk to the same guy that emailed me about it.  I told him I have two different thunder beast 5/8x24 muzzle devices and neither one of them will thread all the way on.  He then tells me that Thunder beast is known for making them really short.  I said well I have 7 other threaded barrels and they thread on to all of those and I had measured them and none of them measure over .62 inches.  He said yeah that is normal for ar 15 type barrels but on larger caliber the standard is .73.  I said well I think you guys are out of the norm as 4 of the barrels I measured are not ar-15 barrels but bolt action barrels.  And the other 3 are 6.8 spc and 300 blk barrels that are 5/5x24 threaded.  He just said that's weird cause ours are the normal size.  

Anyway, just seems weird to me that they would make them so much longer than anyone else.  I really don't want to put shims in it as the look like crap and will cause a big bulge where they are larger than the barrel and muzzle brake.  Looking at the muzzle device, it looks like I could thread it a little deeper and get it to the shoulder.  Going to run it to a machine shop later today and see what they think.  




Edited by supertool73 - June/07/2017 at 13:34
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 12:47
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thunderbeast is well known for exceedingly well made cans and threads, very precisely cut.

If there is a problem, I would bet money it isn't a thunderbeast issue.

A machine shop can cut it down to work, but they shouldn't have to.

Good data point, sorry for the troubles, thanks for sharing.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 12:58
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I have a pdf from Silencerco that shows 1/2x28 or 5/8x24 muzzle thread depth to be .600 +or- .010

https://s3.amazonaws.com/com.silencerco/support/thread-specs/rifle_thread_specs.PDF
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 13:08
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Thunderbeast thread specs

https://thunderbeastarms.com/tech/thread-specifications
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 13:16
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I took a bunch of pics so you can really see how far off they are making them.  I just don't understand why they are doing this. 

Even the thread protector will not fit over the threads all the way.  I think they just have a problem that they need to fix.  But they got the attitude that their barrels can't be wrong. 

My 30 cal thunder beast 30p-1 is a thread on and it will work, but not the muzzle devices. 

Criterion barrel 6.5 creedmoor




Mossberg MVP .308 barrel


Obermyer .308 m40 barrel cut by Bugholes.com


Tikka CTR 6.5 creed barrel


Ruger 300 blk barrel


Seekins precision 300 blk barrel


Rainier Arms match 300 blk barrel.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 13:28
supertool73 View Drop Down
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I do want to add that the dude at Criterion was super nice and tried to help, but all the helps were just bandaids to the problem that the threading is to long and out of the norm.  Really if I want it fixed right I am going to have to pay to the the barrel cut off and repaired or maybe get the muzzle brake threads lengthened. 

I am going to try the muzzle brake, just hope it doesn't get ruined as they cost $125. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 13:39
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Is it mounted?

Were it me, I'd send it back if possible.

Do not use a crush washer, do not do anything that increases risk of baffle strike!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 13:43
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Yes, it is installed and has fired 5 shots, for function purposes.  I got the muzzle device several days after,  I never thought it would be an issue. 

With the crush washer it would definitely get a baffle strike.  It made it very canted.   


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 14:21
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If the crush washer could get it that canted, is the thread itself out of spec, aside from the threading length?  It sounds like it is pretty loose.

ILya 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 14:49
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Unless they are butted up against the shoulder anything will wobble pretty bad.  I can partially thread my 30P-1 on all of my barrels and until it is against the shoulder you can wobble it a bit.  So I dare bet the crush washer just crushed more on one side than the other. 

The guy at Criterion told me crush washers are fine for flash suppressors, but for something that you need to be perfectly aligned the should not be used.  I kind of figured that would be the case, but I was hoping it would work.  You can tell pretty easily if a suppressor is not aligned correctly just by looking into the chamber end of the barrel with it attached. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 14:55
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If your 30P wobbles before shouldering, I'd stop everything. That is not right, not good!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 15:02
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The threads on your barrel are likely it if spec (this Ted's field, so you should probably check with him).

If you've got the suppressor threaded on by 0.6" and it is that loose, I'd be concerned.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 16:11
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Lets not jump to a bunch of conclusions about all my stuff being out of spec based upon my few words on a computer screen.  I am not talking about wobbling like crazy.  I guess I worded that bad.  All threads have a slight bit of movement until they are tight against something.  The more thread you get into the suppressor the less wobble you get.  Obviously some are better than others.  The threads cannot be completely tight or you could not thread things onto them.  That is why they put a shoulder on them so they have something to get square and tight against. 

I have been using my 30p-1 for years and works just fine on multiple hosts.  I always visually inspect before I shoot a can for the first time.  And occasionally after. 

My 30p-1 threads onto the Criterion barrel just as good as it does onto my Greg Young threaded barrel, and my Seekins, and Tikka etc. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 16:23
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Alright.  That's fair.  There is always some slight looseness and, admittedly, my experience with suppressors is zilch (thank you, California!).

My only experience with precision threads is with optical assemblies and they are pretty tight even when they are not contacting a shoulder

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 16:42
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I wonder if the optical threads feel tighter because they are not cut near as deep.  I would assume the deeper the cut the more strength is offered.  But I no very little about it myself. 

One part of all those pics I find interesting is the difference of the relief cut near the shoulder.  Some of them are huge, others almost zilch.  The Tikka has almost no relief cut, wonder if they are done on a CNC machine where the others are done on a lathe.  I have read that those relief cuts can affect accuracy and reputability. 

Guess we will wait for Ted to clarify that as well.  

After re reading my last post.  I think I wrote badly again.  I apologize, I often write quickly without a proof read. 

When I said all threads have a slight bit of movement.  I should have put all my threads, meaning the barrels I have with my suppressor.  My info about a shoulder I got direct from Thunderbeast as I called them about threading a really thin barrel for my 30p-1.  But they said it was two small and without a substantial shoulder it could not get tight and square.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 16:47
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Wobble a few threads in is bad. If it wobbles when near the shoulder, that is exceedingly not good.

I have several cans and many threaded barrels. If you get 5+ turns in and still have wobble, I'd call that either bad threads on the barrel or bad threads on the can. Or both.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 20:05
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Your Criterion barrel's thread length is too long. It's possible they intended it to be used for flash hider only and therefore intended to be used with a washer. Usually flash hiders have enough clearance between the flash hider i.d. and the bore diameter that a tiny bit of non-concentricity isn't an issue and a crush washer can be used no problem. But this also depends on the thread's class of fit. A suppressor is another story, however, since it is longer and any angular misalignment is amplified over greater length. It needs a precision locating feature.

All 60-deg UN threads have some clearance between the pin and box threads built in to the thread tolerance or they will gall and seize up. The degree of "slop" between the internal and external thread depends on the class of fit. Most likely, they cut the thread to a Class 2A/2B fit. Class 3A/3B is a slightly tighter fit and wouldn't show any visible axial movement when being mated together. In my opinion, these threads really should be class 3 for best function.

Threads are NOT precision location features; they are fastening features only and should not be relied upon to keep your muzzle device concentric to the bore. A thread cannot ensure concentricity unless it is a tapered, locking thread and even then, threads are almost never used for precision location/alignment. This is why it is essential a suppressor locates against a shoulder, a tight cylindrical mating surface, or even better, a conical shoulder.

Finally, it's not difficult at all to shorten the barrel thread. Just take it to a competent machine shop and have them set back the muzzle by .1", re-face and crown the muzzle. However, you shouldn't have to do this; Criterion should fix it for you. Do not increase the internal thread depth of your flash hider or suppressor. That's more difficult to do properly because you have to pick up the thread lead, and only increases the gap between the end of your muzzle and the i.d. shoulder of your muzzle device when used on barrels with .6" thread length. So if your only option was to increase the internal thread depth, it would be best to increase the thread relief at the rear of the thread to a shoulder rather than try to chase the thread lead.

Loose items on the end of barrels are dangerous. Don't play around with it until it's right.
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Originally posted by supertool73 supertool73 wrote:

...wonder if they are done on a CNC machine where the others are done on a lathe.  I have read that those relief cuts can affect accuracy and reputability. 


The answer is BOTH. They are cut on CNC lathes.

Thread reliefs are essential against shoulders so that the threaded component can fully mate against a shoulder. The function of a thread relief is to allow the thread on the mating component to continue past the end of the thread on the connection with the relief. A thread relief also removes the last partial imperfect thread "feather edge" so the threaded connection doesn't bind.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 21:42
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Thanks Ted. I will call criterion tomorrow and see if they will shorten it. But i dare bet based on conversation i had today i will be paying someone to do it. Just glad i bought a stainless one and not one of their nitrade finished ones.
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Criterion barrels: noted.

Never.
Ever.
Ever.
Ever.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/07/2017 at 22:21
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Out of curiosity i threaded my 30p-1 onto every 5/8x24 barrel i have. It has wobble on every one of the right up until it contacts the shoulder of the barrel. Honestly once you get about 3 or 4 threads on the wobble feels almost the same til its tight to the shoulder. I also did the same with my thunder beast brakes and flashiders. I have 5 of them in 1/2x28 and 5/8x24. All of the wobbled right up until they make contact with the shoulders

Also my ultra 7 that has their cb attachment. It threads onto the muzzle devices and has a conical shoulder to tighten up against. All 5 of my muzzle devices have the same amount of wobble right up until the ultra 7 contacts the shoulder. Both of those tolerances would be controlled by thunder beast. So i am pretty certain at this point having wobble until they are tight is the norm. I don't see how the could be threaded on and off by hand if they were crazy tight
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Originally posted by Rancid Coolaid Rancid Coolaid wrote:

Criterion barrels: noted.

Never.
Ever.
Ever.
Ever.


No doubt. I read so many good things about their barrels but this is leaving a very sour taste. Will report my phone conversation tomorrow
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/08/2017 at 07:17
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Originally posted by supertool73 supertool73 wrote:

Out of curiosity i threaded my 30p-1 onto every 5/8x24 barrel i have. It has wobble on every one of the right up until it contacts the shoulder of the barrel. Honestly once you get about 3 or 4 threads on the wobble feels almost the same til its tight to the shoulder. I also did the same with my thunder beast brakes and flashiders. I have 5 of them in 1/2x28 and 5/8x24. All of the wobbled right up until they make contact with the shoulders

Also my ultra 7 that has their cb attachment. It threads onto the muzzle devices and has a conical shoulder to tighten up against. All 5 of my muzzle devices have the same amount of wobble right up until the ultra 7 contacts the shoulder. Both of those tolerances would be controlled by thunder beast. So i am pretty certain at this point having wobble until they are tight is the norm. I don't see how the could be threaded on and off by hand if they were crazy tight


there is a fine line between wobble and out of spec. I prefer to have the item being threaded on in hand when I do the threading or at-least one like it. That way I can cut the wobble to a minimum, but if the threads are spec the first few might have some wobble but after 1/4 threaded on it shouldn't wobble but not be tight ether.
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The second video. The kind of movement he is getting with the guage. This is what i am referring to as wobble. https://thunderbeastarms.com/videos?s=thread
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/08/2017 at 13:00
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Well Criterion said they would shorten and re-crown the threads.  Overall they have been very easy to work with, their CS has been very good. 
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