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Posted: 5/11/2018 5:57:21 PM EDT
I just got a sandman S and was installing the comp that came with it on a 300blk upper. I used three of the med shims and one small one to get the timing right. I gave it about an 1/8 turn with my wrench. Everything seemed fine tell I took it out of the vice. What would cause the shims to crumple like this? I just put a 556 device on my BCM and it does not look like this.
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Posted: 5/11/2018 6:00:28 PM EDT
[#1]
It appears there's not much shoulder for them to back against to, can you take a few more pics, and what is the OD at that point on the barrel?
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Posted: 5/11/2018 6:01:13 PM EDT
[#2]
It looks like the barrel diameter is too thin, not enough shoulder.
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Posted: 5/11/2018 6:11:19 PM EDT
[#3]
Quote HistoryQuoted:
It looks like the barrel diameter is too thin, not enough shoulder. |
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Posted: 5/11/2018 6:17:51 PM EDT
[#4]
I wouldn't risk it.
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Posted: 5/11/2018 6:19:25 PM EDT
[#5]
Quote HistoryQuoted:
I wouldn't risk it.  Attached File |
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Posted: 5/11/2018 6:33:23 PM EDT
[#6]
Quote HistoryQuoted:
What's the fix? Use the big thick shim plus all the others to do another turn? https://www.AR15.Com/media/mediaFiles/296004/IMG_7508-541138.JPG |
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Posted: 5/11/2018 6:40:09 PM EDT
[#7]
Quote HistoryQuoted:
may have to get a different barrel unfortunately, I'm sure someone else will chime in with other options if there are some, which I'm interested to know about as well Quote HistoryQuoted:
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What's the fix? Use the big thick shim plus all the others to do another turn? https://www.AR15.Com/media/mediaFiles/296004/IMG_7508-541138.JPG |
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Posted: 5/11/2018 6:59:51 PM EDT
[#8]
Might be able to use a SCAR flash hider since it indexes on the muzzle versus the shoulder.
@Mageever |
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Posted: 5/11/2018 7:00:56 PM EDT
[#9]
Didn't someone JUST go through this with a PSA barrel?
Returned it for a Faxon barrel IIRC |
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Posted: 5/11/2018 7:22:56 PM EDT
[#10]
Quote HistoryQuoted:
I don't get what the problem would be from shooting it? Besides it coming loose? What about just using the crush washer I took off the old device? On top of having very little shoulder height I suspect the barrel has a large radius in the corner where the threads meet the shoulder which causes the the flash hider to pinch the shims unevenly. The area labeled detail e in this image. https://thunderbeastarms.com/tech/thread-specifications |
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Posted: 5/11/2018 7:28:08 PM EDT
[#11]
Could you do something like a lock-nut or thin nut to create a larger face to crank against?
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Posted: 5/11/2018 7:29:34 PM EDT
[#12]
Why would the shoulder matter it threads on The threads just fine
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Posted: 5/11/2018 7:33:45 PM EDT
[#13]
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Posted: 5/11/2018 7:36:26 PM EDT
[#14]
I bet I could use the really large shim and a smaller one to time it still. Wonder if the thick one would bent too
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Posted: 5/11/2018 7:36:53 PM EDT
[#15]
The problem is very likely an improper radius at the bottom of the threads.
There should be a clearance down to the minor threaded diameter, then a square shoulder, but often, in it's place, there is no reduction from the thread major diameter, and then a radius to the shoulder -larger than major diameter. This radius causes the shims to wrinkle, and can cause a crooked muzzle device. I have seen more than one of these barrels that would not pass a rod test as received, then fixed with a proper relief and shoulder cut behind the threads. |
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Posted: 5/11/2018 7:44:58 PM EDT
[#16]
Quote HistoryQuoted:
Why would the shoulder matter it threads on The threads just fine https://www.AR15.Com/media/mediaFiles/296004/IMG_7510-541228.JPG My dealer put my ASR brake on. The shims look like you describe. I assume they did it right, but now I'll need to check. My can is still in jail, I was going to check when I got. |
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Posted: 5/11/2018 7:47:09 PM EDT
[#17]
The shoulder is what keeps it square.
The threads alone are not enough to make sure it tightens down and is square. A crush washer isn't recommended because it too can cause a misalignment. |
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Posted: 5/11/2018 7:56:04 PM EDT
[#18]
Should I try the larger shim like in my picture above or do you all think my shoulder is off?
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Posted: 5/11/2018 8:03:20 PM EDT
[#19]
Quote HistoryQuoted:
Why would the shoulder matter it threads on The threads just fine https://www.AR15.Com/media/mediaFiles/296004/IMG_7510-541228.JPG Try holding the barrel strait up vertical. Place a shim onto the shoulder and check for visible space between the shim and the shoulder. |
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Posted: 5/11/2018 8:12:18 PM EDT
[#20]
Quote HistoryQuoted:
It may just be the picture and angle, but the shiny markings on the shoulder look uneven. Probably an indication the shims aren't seating flat on the shoulder. Try holding the barrel strait up vertical. Place a shim onto the shoulder and check for visible space between the shim and the shoulder. Quote HistoryQuoted:
Quoted:
Why would the shoulder matter it threads on The threads just fine https://www.AR15.Com/media/mediaFiles/296004/IMG_7510-541228.JPG Try holding the barrel strait up vertical. Place a shim onto the shoulder and check for visible space between the shim and the shoulder. |
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Posted: 5/11/2018 8:45:17 PM EDT
[#21]
Quote HistoryQuoted:
I jus tried that. I had the light of a window in my background and turned the gun a few times to look at the shoulder and it looked even all the way around on the big shim. Quote HistoryQuoted:
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Why would the shoulder matter it threads on The threads just fine https://www.AR15.Com/media/mediaFiles/296004/IMG_7510-541228.JPG Try holding the barrel strait up vertical. Place a shim onto the shoulder and check for visible space between the shim and the shoulder. Try re torquing the brake down but this time hold the barrel vertical while you hand tighten the brake down to keep the shims from drooping down while the barrel is horizontal. |
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Posted: 5/11/2018 8:54:01 PM EDT
[#22]
Quote HistoryQuoted:
This big shim came with the muzzle device? Try re torquing the brake down but this time hold the barrel vertical while you hand tighten the brake down to keep the shims from drooping down while the barrel is horizontal. Quote HistoryQuoted:
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Quoted:
Why would the shoulder matter it threads on The threads just fine https://www.AR15.Com/media/mediaFiles/296004/IMG_7510-541228.JPG Try holding the barrel strait up vertical. Place a shim onto the shoulder and check for visible space between the shim and the shoulder. Try re torquing the brake down but this time hold the barrel vertical while you hand tighten the brake down to keep the shims from drooping down while the barrel is horizontal.  Attached File |
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Posted: 5/11/2018 8:58:19 PM EDT
[#23]
How much turn should you get out of shims? I am are used to crush washers where you keep crushing tell its where you want. Stays the same tightness the whole time you turn
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Posted: 5/11/2018 9:01:10 PM EDT
[#24]
You could try accuwashers or get a flashider and you don't need to index it at all. But if it were me I would go with another barrel.
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Posted: 5/11/2018 9:01:47 PM EDT
[#25]
Quote HistoryQuoted:
Should I try the larger shim like in my picture above or do you all think my shoulder is off? What is the OD of your barrel? I don't know if Dead Air publishes a thread spec guide, but you can take the TBAC one posted above as well as look up AAC's and SilencerCo's. Does it meet those minimums? |
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Posted: 5/11/2018 9:13:38 PM EDT
[#26]
Quote HistoryQuoted:
You could try a larger ID shim to overcome the radius, but since your barrel OD appears to also be lacking, it's not going to be a winning situation. What is the OD of your barrel? I don't know if Dead Air publishes a thread spec guide, but you can take the TBAC one posted above as well as look up AAC's and SilencerCo's. Does it meet those minimums? Quote HistoryQuoted:
Quoted:
Should I try the larger shim like in my picture above or do you all think my shoulder is off? What is the OD of your barrel? I don't know if Dead Air publishes a thread spec guide, but you can take the TBAC one posted above as well as look up AAC's and SilencerCo's. Does it meet those minimums?  Attached File Attached File |
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Posted: 5/11/2018 9:24:22 PM EDT
[#27]
There does not appear to be anywhere near enough shoulder there to properly torque down a suppressor mount and be positive that everything is aligned correctly and will remain that way.
A new barrel is going to cost you $150-$200, minus whatever you get back for either returning that barrel or selling it in the EE. How much is a new suppressor going to cost you after you put a round through a few baffles or worse? ETA: Here's a thread discussing a topic like this. TBAC recommends no less than a .750 OD on the barrel for a 5/8x24 thread pattern (which I'm assuming is what your barrel is threaded) and I could take a pretty educated guess and say that most other suppressor manufacturers would agree. http://forum.snipershide.com/threads/smallest-barrel-diameter-to-thread-a-barrel-5-8-24.201509/ |
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Posted: 5/11/2018 9:38:48 PM EDT
[#28]
Quote HistoryQuoted:
ETA: Here's a thread discussing a topic like this. TBAC recommends no less than a .750 OD on the barrel for a 5/8x24 thread pattern (which I'm assuming is what your barrel is threaded) and I could take a pretty educated guess and say that most other suppressor manufacturers would agree. |
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Posted: 5/11/2018 9:43:21 PM EDT
[#29]
Quote HistoryQuoted:
There does not appear to be anywhere near enough shoulder there to properly torque down a suppressor mount and be positive that everything is aligned correctly and will remain that way. A new barrel is going to cost you $150-$200, minus whatever you get back for either returning that barrel or selling it in the EE. How much is a new suppressor going to cost you after you put a round through a few baffles or worse? ETA: Here's a thread discussing a topic like this. TBAC recommends no less than a .750 OD on the barrel for a 5/8x24 thread pattern (which I'm assuming is what your barrel is threaded) and I could take a pretty educated guess and say that most other suppressor manufacturers would agree. http://forum.snipershide.com/threads/smallest-barrel-diameter-to-thread-a-barrel-5-8-24.201509/ |
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Posted: 5/11/2018 9:45:30 PM EDT
[#30]
My Ballistic Advantage .300bo barrel did shims the same way. Said it is normal.
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Posted: 5/11/2018 9:46:58 PM EDT
[#31]
Quote HistoryQuoted:
My Ballistic Advantage .300bo barrel did shims the same way. Said it is normal. |
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Posted: 5/11/2018 9:49:55 PM EDT
[#32]
Quote HistoryQuoted:
Yup, TBAC recommends a min of .750" OD (it's in the PDF linked above). SilencerCo recommends 0.720" min. OP I’d get a new barrel or risk having a pretty high likelihood of a baffle strike at some point in the future. |
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Posted: 5/11/2018 9:50:01 PM EDT
[#33]
Quote HistoryQuoted:
Like this? I am not sure how accurate it is because my digital caliper seems to be acting up and the battery is halfway corroded. https://www.AR15.Com/media/mediaFiles/296004/IMG_7519-541349.JPG https://www.AR15.Com/media/mediaFiles/296004/IMG_7518-541351.JPG |
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Posted: 5/11/2018 9:50:46 PM EDT
[#34]
Quote HistoryQuoted:
My Ballistic Advantage .300bo barrel did shims the same way. Said it is normal. |
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Posted: 5/11/2018 9:52:43 PM EDT
[#35]
Measure your shim thickness, buy a washer that thickness. Buy some rocksett and use it on your muzzle device. Have fun and forget about it. Hell, I wouldn't even worry about the shims. rocksett will hold that bad boy on until you wrench it off..
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Posted: 5/11/2018 10:06:44 PM EDT
[#36]
Quote HistoryQuoted:
My can is like $1200 after tax stamp. This PSA barrel groups really good too. Quote HistoryQuoted:
Quoted:
There does not appear to be anywhere near enough shoulder there to properly torque down a suppressor mount and be positive that everything is aligned correctly and will remain that way. A new barrel is going to cost you $150-$200, minus whatever you get back for either returning that barrel or selling it in the EE. How much is a new suppressor going to cost you after you put a round through a few baffles or worse? ETA: Here's a thread discussing a topic like this. TBAC recommends no less than a .750 OD on the barrel for a 5/8x24 thread pattern (which I'm assuming is what your barrel is threaded) and I could take a pretty educated guess and say that most other suppressor manufacturers would agree. http://forum.snipershide.com/threads/smallest-barrel-diameter-to-thread-a-barrel-5-8-24.201509/ When using shims you shouldn't turn too far past hand tight ~1/4 turn is proper tight. |
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Posted: 5/11/2018 10:20:06 PM EDT
[#37]
Quote HistoryQuoted:
You might be able to find a suppressor spacer that could help transition between the thin should and the shims. Otherwise I would suggest new barrel. When using shims you shouldn't turn too far past hand tight ~1/4 turn is proper tight. Quote HistoryQuoted:
Quoted:
Quoted:
There does not appear to be anywhere near enough shoulder there to properly torque down a suppressor mount and be positive that everything is aligned correctly and will remain that way. A new barrel is going to cost you $150-$200, minus whatever you get back for either returning that barrel or selling it in the EE. How much is a new suppressor going to cost you after you put a round through a few baffles or worse? ETA: Here's a thread discussing a topic like this. TBAC recommends no less than a .750 OD on the barrel for a 5/8x24 thread pattern (which I'm assuming is what your barrel is threaded) and I could take a pretty educated guess and say that most other suppressor manufacturers would agree. http://forum.snipershide.com/threads/smallest-barrel-diameter-to-thread-a-barrel-5-8-24.201509/ When using shims you shouldn't turn too far past hand tight ~1/4 turn is proper tight. |
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Posted: 5/11/2018 10:55:22 PM EDT
[#38]
Quote HistoryQuoted:
1/4 turn is a full 90 degrees. That's a lot of turn force. When I put my 556 muzzle device on today with shims I could only get maybe 1/8th turn before I felt like I was going to break something in my vice on the gun Quote HistoryQuoted:
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Quoted:
There does not appear to be anywhere near enough shoulder there to properly torque down a suppressor mount and be positive that everything is aligned correctly and will remain that way. A new barrel is going to cost you $150-$200, minus whatever you get back for either returning that barrel or selling it in the EE. How much is a new suppressor going to cost you after you put a round through a few baffles or worse? ETA: Here's a thread discussing a topic like this. TBAC recommends no less than a .750 OD on the barrel for a 5/8x24 thread pattern (which I'm assuming is what your barrel is threaded) and I could take a pretty educated guess and say that most other suppressor manufacturers would agree. http://forum.snipershide.com/threads/smallest-barrel-diameter-to-thread-a-barrel-5-8-24.201509/ When using shims you shouldn't turn too far past hand tight ~1/4 turn is proper tight. |
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Posted: 5/11/2018 10:57:30 PM EDT
[#39]
Quote HistoryQuoted:
Sounds about right, you're not going to get a full turn like with crush washers. With shims you should only be able to turn a fraction of what crush washers can. Quote HistoryQuoted:
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Quoted:
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There does not appear to be anywhere near enough shoulder there to properly torque down a suppressor mount and be positive that everything is aligned correctly and will remain that way. A new barrel is going to cost you $150-$200, minus whatever you get back for either returning that barrel or selling it in the EE. How much is a new suppressor going to cost you after you put a round through a few baffles or worse? ETA: Here's a thread discussing a topic like this. TBAC recommends no less than a .750 OD on the barrel for a 5/8x24 thread pattern (which I'm assuming is what your barrel is threaded) and I could take a pretty educated guess and say that most other suppressor manufacturers would agree. http://forum.snipershide.com/threads/smallest-barrel-diameter-to-thread-a-barrel-5-8-24.201509/ When using shims you shouldn't turn too far past hand tight ~1/4 turn is proper tight. |
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Posted: 5/12/2018 12:33:15 AM EDT
[#40]
What you're looking for is a KBA Custom SCAR 17S Muzzle Shoulder Ring . I used one on a barrel with a similar profile, and it worked beautifully!
Here's another recent thread on the topic: https://www.ar15.com/forums/Armory/Shoulders-on-7-62x39-barrels-or-the-lack-thereof-/20-488394/ *Edit* Forgot to add that you might also want to try some different shims. The OD is rather large on the supplied shims, and seems to contribute to the warping if the shims aren't perfectly centered. Mine looked like cupcake wrappers when I first tried it without the shoulder ring. I've been using PRI and Gemtech shims for most of my newer projects, and they seem to work a little better for me. I've also ran into trouble using the supplied shims with the Dead Air flash hider, as the OD is so large that it interferes with the wrench flats. It's not a problem if using an AAC Blackout installation tool, but I think the smaller OD shims fit better and look better too. |
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Posted: 5/12/2018 12:53:25 AM EDT
[#41]
Quote HistoryQuoted:
What you're looking for is a KBA Custom SCAR 17S Muzzle Shoulder Ring . I used one on a barrel with a similar profile, and it worked beautifully! Here's another recent thread on the topic: https://www.ar15.com/forums/Armory/Shoulders-on-7-62x39-barrels-or-the-lack-thereof-/20-488394/ *Edit* Forgot to add that you might also want to try some different shims. The OD is rather large on the supplied shims, and seems to contribute to the warping if the shims aren't perfectly centered. Mine looked like cupcake wrappers when I first tried it without the shoulder ring. I've been using PRI and Gemtech shims for most of my newer projects, and they seem to work a little better for me. I've also ran into trouble using the supplied shims with the Dead Air flash hider, as the OD is so large that it interferes with the wrench flats. It's not a problem if using an AAC Blackout installation tool, but I think the smaller OD shims fit better and look better too. |
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Posted: 5/12/2018 1:25:27 AM EDT
[#42]
PSA is not the only company using this barrel profile. My guess is that muzzle devices & suppressors were not really taken into account when it was designed (besides a standard flash hider & crush washer), and it's become a legacy issue now that suppressors are much more prevalent.
Considering the SCAR 17S shares a similar problem, it seems we're in good company. I'm just glad someone (KBA Custom) came up with a simple solution for us. |
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Posted: 5/12/2018 8:35:47 AM EDT
[#43]
Quote HistoryQuoted:
PSA is not the only company using this barrel profile. My guess is that muzzle devices & suppressors were not really taken into account when it was designed (besides a standard flash hider & crush washer), and it's become a legacy issue now that suppressors are much more prevalent. Considering the SCAR 17S shares a similar problem, it seems we're in good company. I'm just glad someone (KBA Custom) came up with a simple solution for us. |
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Posted: 5/12/2018 10:01:34 AM EDT
[#44]
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Posted: 5/12/2018 10:05:26 AM EDT
[#45]
Quote HistoryQuoted:
Will that washed work for me? It's not a scar 17 |
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Posted: 5/12/2018 10:08:51 AM EDT
[#46]
Quote HistoryI agree that this is probably the safest bet. It even has me considering redoing the barrel I used the SCAR shoulder ring on.
Don't sell the existing brake, though! Just find or build something else to put it on, like a 6.5 Grendel! 
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Posted: 5/12/2018 10:14:14 AM EDT
[#47]
Quote HistoryThere is some built up carbon on the front of the crown. That would have to been compleatly cleaned up perfect to use that yes?
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Posted: 5/12/2018 11:00:55 AM EDT
[#48]
Quote HistoryQuoted:
There is some built up carbon on the front of the crown. That would have to been compleatly cleaned up perfect to use that yes? |
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Posted: 5/12/2018 4:37:19 PM EDT
[#49]
Quote HistoryQuoted:
What do you mean? 
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Posted: 5/12/2018 5:00:12 PM EDT
[#50]
Quote HistoryQuoted:
I don't get what the problem would be from shooting it? Besides it coming loose? What about just using the crush washer I took off the old device? |
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