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Suppressors Ops and TB 5/8 x 24 thread Questions

3DHUSKER

3DHUSKER

Delivering the lead
Full Member
Minuteman
May 6, 2011
589
1
DownTheRoadFromKampKumbaya
#1
Long story short

http://bisonarmory.com/barrels.htm

Site says they are cut to
"5/8" - 24 TPI muzzle threads"
for the "Ops Inc 12th Model silencer collar shelf"

I have a thunderbeast 30p-1
Its threads say this "5/8" - 24 TPI 3A muzzle threads"
http://thunderbeastarms.com/img/threads5824.jpg

Am I going to be ok with this Bison barrel to thread the TB on.

Not getting much help from Bison. They must be on Holiday...
smile.gif


Ideas?
 
#2
Re: Ops and TB 5/8 x 24 thread Questions

I'm in same situation as I have a BO thruster on my GAP. 30p-1 pending in ATF purgatory. Gonna send my barreled action back to GA and have them turn it into full spec per Zacks dimensions just to be sure. Or, wait till I have can in hand and send both to GA. Just want piece of mind on this end.

Worse case scenario is you are biting on all threads, but can has one or two with not contact, thus leading to carbon build up on those. Shouldn't be an issue. But, if you're like me, I like being correct especially since it takes forever to get a can.
 
#4
Re: Ops and TB 5/8 x 24 thread Questions

I have the same issue with my Underground Skunkworks Perseus and the Thunderbeast. I went to the local gun shop (holder of my Thunderbeast until ATF allows me to have it) with the Perseus to check the thread and it went about 1/2 turn and then stopped. Instead of turning it hard I decided to call Shane at Thunderbeast and also Mike Bush and ask questions on the thread pitch. I am not a "smith" of anything but what I gathered is it has to do with Class 2 and Class 3 threading of the 5/8 x 24 - how the ridges and valleys of the threads can vary by depth and width on the ridges and valleys. May be a real machinist can explain it to us. Before this I thought if it said 5/8 x 24 I was good - not true.

If it makes you feel any better I took the GAP M40A3 down the next week to try the Thunderbeast and it worked like a charm.
 
#5
Re: Ops and TB 5/8 x 24 thread Questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JSTARSZ</div><div class="ubbcode-body">I have the same issue with my Underground Skunkworks Perseus and the Thunderbeast. I went to the local gun shop (holder of my Thunderbeast until ATF allows me to have it) with the Perseus to check the thread and it went about 1/2 turn and then stopped. Instead of turning it hard I decided to call Shane at Thunderbeast and also Mike Bush and ask questions on the thread pitch. I am not a "smith" of anything but what I gathered is it has to do with Class 2 and Class 3 threading of the 5/8 x 24 - how the ridges and valleys of the threads can vary by depth and width on the ridges and valleys. May be a real machinist can explain it to us. Before this I thought if it said 5/8 x 24 I was good - not true.

If it makes you feel any better I took the GAP M40A3 down the next week to try the Thunderbeast and it worked like a charm. </div></div>

1/2 turn from tight, or half turn period? IF later, you had the threads re-worked?
 
#6
Re: Ops and TB 5/8 x 24 thread Questions

that would be a half turn period and then it would tighten up and I guess could go further but it would get locked onto the threads or start stripping the ridges of the thread if I twisted the suppressor on to tightly.
 
#8
Re: Ops and TB 5/8 x 24 thread Questions

At the moment I don't have the suppressor so I am going to wait until I get it to have the rifle fixed. Talking to Mike Bush, it is an easy fix that takes less than 2 minutes to re-run the threads on my rifle to the numbers that Thunderbeast use on their thread patterns.
 
#12
#14
Re: Ops and TB 5/8 x 24 thread Questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 3DHUSKER</div><div class="ubbcode-body">Long story short

http://bisonarmory.com/barrels.htm

Site says they are cut to
"5/8" - 24 TPI muzzle threads"
for the "Ops Inc 12th Model silencer collar shelf"

I have a thunderbeast 30p-1
Its threads say this "5/8" - 24 TPI 3A muzzle threads"
http://thunderbeastarms.com/img/threads5824.jpg

Am I going to be ok with this Bison barrel to thread the TB on.

Not getting much help from Bison. They must be on Holiday...
smile.gif


Ideas? </div></div>

Sorry, I should have updated this.

Bison emailed me back and said that the barrels were threaded to 2A specs. A little looser than TB recommends for their can.
It should work but will be a little loose on the threads until it hits the shoulder so they say. I don't think I want to take that chance. May try the can and not force it, if it doesn't feel right i would/will have the threads reworked.

 
#15
Re: Ops and TB 5/8 x 24 thread Questions

Class 2 is a looser fit than 3 and should work OK. 3<span style="font-weight: bold">A</span> is the outer thread spec, 3<span style="font-weight: bold">B</span> is the inner thread spec. These are defined in the unified thread standard (UTS) and your machinist should know all about it.

Where we run into problems is when external threads are cut too large, IE, their dimensions are larger than 3A specs. This causes a galling or an interference fit and can result in the suppressor getting stuck. From time to time, we get cans (with barrel attached) back that have been stuck on due to this problem and invariably when we measure the dimensions of the muzzle threads after everything has been cut apart, they were out of the 3A spec. This typically happens when a gunsmith cuts threads and uses a brake as the gauge instead of using an actual thread gauge or thread wires to determine the final thread dimensions.
 
#17
Re: Ops and TB 5/8 x 24 thread Questions

I'm glad this came to my attention. I've wanted to cut the sako
Threads off and get them to standard specs for a 30p1. Now I know
It's to be 3a specs on the threads.
Thanks!
 
#20
Re: Ops and TB 5/8 x 24 thread Questions

As a 30P-1 owner ( with a can that had to go back to them due to smith's shortcut), listen to Zak.

Mine did the same thing: half turn, then dead stop. I put a little elbow grease into it, and it cost me a can repair.

Good thread jobs are not nearly as common as they should be, lesser cans will let it slide, and that ain't a compliment to lesser cans.
 
#23
Re: Ops and TB 5/8 x 24 thread Questions

5/8-24-2A(external thread)
O.D. .6238 - .6166.
P.D. .5967 - .5927.

5/8-24-3A(external thread)
O.D. .625 - .6178.
P.D. .5979 - .5949.

Note that the diminsions overlap quite a bit.

O.D. equals outside diameter. P.D. equals pitch diameter.

RonA
 
#24
Re: Ops and TB 5/8 x 24 thread Questions

Well I assumed, and we all know what happens when we assume, that 5/8 x 24 was universal and a one size fits all if the muzzle device was 5/8 x 24. My barrel was cut by a reputable smith recommended here on the hide. He custom fit an Ops inc brake and made a custom "smooth" thread protector. I ordered a new knurled yankee hill thread protector sized 5/8 x 24 and cant even get one turn on it. Then my buddy got an AAC Cyclone. I tried that on, very gently, and it stopped halfway down the threads. Same for his Vortex muzzle brake. I'm wanting to order a Cyclone, do I wait to see what thread pitch the Cyclone can is and then have my barrel rethreaded? Will that effect the fit of my ops inc brake? Never knew this would get so damn confusing!!
 
#25
Re: Ops and TB 5/8 x 24 thread Questions

Does anyone know of a source for caliber-matched brass or aluminum rods that a guy could slip down the barrel with the can in place to verify that the rod clears the can bore without a "baffle-strike"?

I have a cleaning rod that fits a .22 bore fairly closely and I've tried rolling newspaper very tightly at an angle; you get a pretty straight "rod", but I'd love to find pre-cut rods in .17, .22, .30, .45, etc. if anyone has any ideas.
 
#26
Re: Ops and TB 5/8 x 24 thread Questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Pflyinguy</div><div class="ubbcode-body"> My barrel was cut by a reputable smith recommended here on the hide. He custom fit an Ops inc brake and made a custom "smooth" thread protector. </div></div>

There is your problem, he custom fit. He did not cut to 5/8 x 24.
 
#27
Re: Ops and TB 5/8 x 24 thread Questions

Maybe try a hobby shop, they should sell brass tubing in at least 12 inch lengths. that should get you several inches in the muzzle end of the barrel to see if it clears the baffels. 9/32 is prob as close as you will get to .30 cal. Just a thought.
 
#28
Re: Ops and TB 5/8 x 24 thread Questions

if it's had a cyclone on it already then you know that it is "almost" right, but "close" only counts in horseshoes & hand grenades. If you order a cyclone with the same threads as your buddy's, then odds are you'll have the same result. "custom fit" doesn't mean it's not 5/8x24, it just means that he may not have used the right thread class. Or perhaps the maximum or minimum diameter is out of spec.

IMHO, contact the mfg of the can and get the specs on it, then either have that smith repair his work or have someone else check & recut as needed. My guess is that the tolerances are just wrong, which is likely a simple fix.

IMHO, if you have it totally recut i'd either have it cut specifically for the can you're going to run, or i'd have it cut 2a IF you plan to use other muzzle devices (brakes, etc) too because they may not have the precision necessary to go on 3a threads. OR send you devices in with the barrel and have them tuned up to the right tolerances too, probably the best option of the three.
 
#29
Re: Ops and TB 5/8 x 24 thread Questions

Another problem that I see too often is improper thread form from Hand ground thread tools that have the wrong angles and tools that are worn on the point and cut too large a root radius. These are particularly bad because even with a tight feeling thread there is wiggle because you are not mating angles together. If you have too large of a root radius on an external thread you have to cut the pitch diameter undersized so the root diameter will clear the minor diameter of the mating internal thread.
 
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