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Posted: 3/14/2017 3:19:54 PM EDT
It's a Sig SRD762Ti in 7.62. My friend tried to attach it and said that the mount goes over the threads and only catches about 2-3 of them. He said it needed to be "downturned" but I don't know what that means. I don't think there is another mount specifically for .300 Blackout since it's .30 cal which is the same as 7.62, correct?
Anyone have a problem with a Sig QD mount not attaching to a Ruger American Ranch Rifle in .300 BO? 
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Posted: 3/14/2017 2:38:54 PM EDT
[#1]
You need to continue the threading on the barrel (downturn) so that the threading is longer. Send it to ADCO. If you are going to do that, it is best if they can taper profile the shoulder so it fits even better.
Also, you should remove the break portion of the attachment when attaching to a rifle. If you have used that mount before, you may need a new proprietary SIG crush washer to get it timed (aligned). |
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Posted: 3/14/2017 2:49:08 PM EDT
[#2]
Quote HistoryQuoted:
You need to continue the threading on the barrel (downturn) so that the threading is longer. Send it to ADCO. If you are going to do that, it is best if they can taper profile the shoulder so it fits even better. Also, you should remove the break portion of the attachment when attaching to a rifle. If you have used that mount before, you may need a new proprietary SIG crush washer to get it timed (aligned). What is the break portion? It's a new crush washer. So I have to send it in to get more of the barrel threaded, is that normal? I thought I've seen people with the Sig suppressor QD mount on their RARR and no one said anything about having to downturn the barrel. How much will it cost? Any idea on turn around times? |
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Posted: 3/14/2017 2:50:19 PM EDT
[#3]
Actually, if you taper that shoulder on the barrel, it may allow enough thread engagement without having to cut more threads. The inside of the adapter/ device has a taper to it.
See the image and the barrel is tapered. 
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Posted: 3/14/2017 3:24:48 PM EDT
[#4]
Quote HistoryQuoted:
What is the break portion? It's a new crush washer. So I have to send it in to get more of the barrel threaded, is that normal? I thought I've seen people with the Sig suppressor QD mount on their RARR and no one said anything about having to downturn the barrel. How much will it cost? Any idea on turn around times? The brake portion (I misspelled it). Always keep the brake off the threaded barrel adapter until it is installed on the barrel. Be sure to use Rocksett (ideally) on the barrel threads. Once the adapter is installed, screw on the muzzle brake. I don't know the cost of cutting a taper on the barrel. Someone much smarter that I am will be long to advise, I am sure. ETA: here is where the taper would go... 
ETA:#2 the design above is for 1/2-28 threads ( i was using it for conversation only), you will need to use the one for 5/8 here: 
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Posted: 3/14/2017 3:55:56 PM EDT
[#5]
Just counting the threads, the Ruger doesn't appear to be too long. What happens when you unscrew the brake portion and mount the rear half of the muzzle device (as suggested above)? That's how I've seen those being mounted. Rear half first and then the brake portion is timed with the crush washer.
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Posted: 3/14/2017 5:23:59 PM EDT
[#6]
Quote HistoryQuoted:
Just counting the threads, the Ruger doesn't appear to be too long. What happens when you unscrew the brake portion and mount the rear half of the muzzle device (as suggested above)? That's how I've seen those being mounted. Rear half first and then the brake portion is timed with the crush washer. Tried this. Didn't change it. He said it is less then 2 full turns til tight and he'd like to see 4-6 full turns. He said he'd like to see 1/2" of threads used and it's about 1/8" right now. Could I have the wrong mount? |
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Posted: 3/14/2017 8:46:17 PM EDT
[#7]
Doesn't SIG make a mount for the standard 5/8-24 x .600" threads?
If they only make them for their own tapered barrels, I'm glad I found out now. |
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Posted: 3/14/2017 8:46:49 PM EDT
[#8]
Quote HistoryQuoted:
Tried this. Didn't change it. He said it is less then 2 full turns til tight and he'd like to see 4-6 full turns. He said he'd like to see 1/2" of threads used and it's about 1/8" right now. Could I have the wrong mount? I suppose it's possible. Idk if a 1/2x28 will screw on a 5/8 that far... |
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Posted: 3/15/2017 12:24:56 AM EDT
[#9]
It's made to fit the barrel of sig rifles with their proprietary taper. It indexes on the taper so you can't simply make you muzzle threads longer.
There are a couple companies who make adapters to fit the sig qd adapters on standard 1/2-28 and 5/8-24 threaded barrels. |
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Posted: 3/15/2017 1:06:29 AM EDT
[#10]
Quote HistoryQuoted:
It's made to fit the barrel of sig rifles with their proprietary taper. It indexes on the taper so you can't simply make you muzzle threads longer. There are a couple companies who make adapters to fit the sig qd adapters on standard 1/2-28 and 5/8-24 threaded barrels. Thanks. Could you name a few? Because I looked and couldn't find any. |
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Posted: 3/15/2017 8:39:45 AM EDT
[#11]
Quote HistoryQuoted:
It's made to fit the barrel of sig rifles with their proprietary taper. It indexes on the taper so you can't simply make you muzzle threads longer. There are a couple companies who make adapters to fit the sig qd adapters on standard 1/2-28 and 5/8-24 threaded barrels. I just screwed mine on and it seems to work. Who makes the above adapters to fit the SIG QD adapters? Mark |
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Posted: 3/15/2017 9:09:57 AM EDT
[#12]
Quote HistoryQuoted:
I just screwed mine on and it seems to work. Who makes the above adapters to fit the SIG QD adapters? Mark How many full turns do you get? The adapter doesn't go over the non- threaded part of the barrel does it? |
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Posted: 3/15/2017 9:24:19 AM EDT
[#13]
Quote HistoryQuoted:
Doesn't SIG make a mount for the standard 5/8-24x.600" threads? If they only make them for their own tapered barrels, I'm glad I found out now. I agree. This doesn't help the OP but I'll be very put off of Sig cans if they don't offer muzzle devices for "normal" factory threaded barrels. I have the Ranch in 300 BLK and 5.56 and haven't had a single issue with multiple different suppressors being installed on them. I wouldn't consider spending the extra time and money to get a non-standard profile added to them. |
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Posted: 3/15/2017 11:35:58 AM EDT
[#14]
I saw the adapters in a couple YouTube reviews when I was considering one. I ended up not going with the sig because it took too long for them to show up on shelves so I never had to follow up on the adapters.
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Posted: 3/15/2017 11:54:04 AM EDT
[#15]
The Sig bases have an un-threaded portion for their taper, and then threads. Call Sig, per thier CS and Silencer guys, if you properly torque the base on with the applied Rocksett (it's in the manual) then you will not have a problem. The QD's do work fine on non-Sig tapered barrels.
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Posted: 3/15/2017 11:56:50 AM EDT
[#16]
https://youtu.be/-KRq2SHeoj0
Now I think the adapters were the other way around, to give a square shoulder on a sig tapered barrel? It's been so long that I can't remember and I'm doubting myself! The Rugers do have shorter than average threads as I recall, perhaps that is the issue? How long are the threads on your ruger? Edit: found it, I was thinking of adaptor to put square shoulder on sig barrel. 
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Posted: 3/15/2017 12:02:08 PM EDT
[#17]
I have a standard CMMG 300BO barrel with 5/8 threads and the SIG adapter snugs up nice and tight with plenty of thread engagement. It is not tapered. Like said above, maybe Ruger just has short threads. If you taper the non tapered portion on your barrel, it should allow the adapter to go on tighter.
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Posted: 3/15/2017 8:47:14 PM EDT
[#18]
Quote HistoryQuoted:
I have a standard CMMG 300BO barrel with 5/8 threads and the SIG adapter snugs up nice and tight with plenty of thread engagement. It is not tapered. Like said above, maybe Ruger just has short threads. If you taper the non tapered portion on your barrel, it should allow the adapter to go on tighter. Maybe, but the threads seem to be plenty, it's just that the mount's threads don't start until well into the mount. |
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Posted: 3/15/2017 8:48:00 PM EDT
[#19]
Quote HistoryQuoted:
https://youtu.be/-KRq2SHeoj0 Now I think the adapters were the other way around, to give a square shoulder on a sig tapered barrel? It's been so long that I can't remember and I'm doubting myself! The Rugers do have shorter than average threads as I recall, perhaps that is the issue? How long are the threads on your ruger? Edit: found it, I was thinking of adaptor to put square shoulder on sig barrel. http://imagizer.imageshack.us/v2/800x600q90/633/mHyUxh.jpg The RARR seems to have at least this many threads as the barrel pictured. |
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Posted: 3/15/2017 9:24:44 PM EDT
[#20]
Can anyone out there post a cross section diagram/dimensions of the SIG mount?
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Posted: 3/16/2017 1:03:02 PM EDT
[#21]
Quote HistoryQuoted:
Can anyone out there post a cross section diagram/dimensions of the SIG mount? My friend said the adapter is hitting the shoulder, so basically not enough threads for that particular adapter. I hate how the threads in the adapter start so deep, not right on the outside of the adapter. I haven't seen any other adapter that would work, hopefully there is one out there. I'd rather get a different adapter or modify the adapter than permanently alter the rifle barrel. |
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Posted: 3/16/2017 4:40:49 PM EDT
[#22]
Quoted:
Can anyone out there post a cross section diagram/dimensions of the SIG mount? 
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Posted: 3/16/2017 9:43:12 PM EDT
[#23]
Quote HistoryThanks again for your constant attention to questions on this board.
If I didn't state it properly, what I am hoping for are the dimensions of the muzzle device itself, in particular the internal threads and space from the rear of the device to the start of the threads. |
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Posted: 3/16/2017 10:03:42 PM EDT
[#24]
Quote HistoryQuoted:
Thanks again for your constant attention to questions on this board. If I didn't state it properly, what I am hoping for are the dimensions of the muzzle device itself, in particular the internal threads and space from the rear of the device to the start of the threads. |
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Posted: 3/16/2017 10:13:01 PM EDT
[#25]
Just got mine home.
I was floored. This is BS and there is nothing in the description when buying the suppressor that says you'll need special barrel contour and threading. |
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Posted: 3/16/2017 10:33:34 PM EDT
[#26]
Hollister says that it works with barrels with traditional shoulders:
 Failed To Load Title Did you guys somehow get a bad batch of 5.8x24 threads? |
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Posted: 3/16/2017 10:40:20 PM EDT
[#27]
So there truly isn't a Sig rep on arf, huh?
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Posted: 3/16/2017 11:04:03 PM EDT
[#28]
Quote HistoryQuoted:
Hollister says that it works with barrels with traditional shoulders:  https://www.youtube.com/watch?v=-KRq2SHeoj0
Did you guys somehow get a bad batch of 5.8x24 threads? I don't. Maybe if it was silver soldered....but not just tension or even rocksett |
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Posted: 3/16/2017 11:29:06 PM EDT
[#29]
Quote HistoryQuoted:
You trust a mount that only engages 2-3 threads? I don't. Maybe if it was silver soldered....but not just tension or even rocksett Quote HistoryQuoted:
Quoted:
Hollister says that it works with barrels with traditional shoulders: https://www.youtube.com/watch?v=-KRq2SHeoj0
Did you guys somehow get a bad batch of 5.8x24 threads? I don't. Maybe if it was silver soldered....but not just tension or even rocksett |
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Posted: 3/16/2017 11:43:06 PM EDT
[#30]
Quote HistoryQuoted:
You trust a mount that only engages 2-3 threads? I don't. Maybe if it was silver soldered....but not just tension or even rocksett I'm not a Mechanical Engineer but the only rule of thumb I've heard of is the amount of thread engagement should be at least equal to the diameter of the bolt/hole. That's nothing I have any empirical evidence for though. |
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Posted: 3/16/2017 11:55:57 PM EDT
[#31]
The adapter is tapered inside too. Thus if the barrel is either tapered or simply has standard length threaded portion, then it will fit. The barrel does NOT need to be tapered but in the OP's case, it looks like the factory has a shorter run of threads. Regular AR throws down with a flat / squared shoulder is fine.
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Posted: 3/17/2017 11:50:47 AM EDT
[#32]
Those of you with issues, are you taking off the muzzle brake or flash hider end BEFORE installing the mount? You have to take that part off, install the main body of the mount, then install the muzzle brake or flash hider front piece using the included crush washer.
The Sig mounts will work with a Sig barrel taper or a standard square shoulder. I haven't seen any issues with Sig mounts until this thread, and the other one posted yesterday, so I would lean towards improper installation before saying the mounts or barrel threads are bad. |
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Posted: 3/17/2017 1:17:19 PM EDT
[#33]
Quote HistoryQuoted:
Those of you with issues, are you taking off the muzzle brake or flash hider end BEFORE installing the mount? You have to take that part off, install the main body of the mount, then install the muzzle brake or flash hider front piece using the included crush washer. The Sig mounts will work with a Sig barrel taper or a standard square shoulder. I haven't seen any issues with Sig mounts until this thread, and the other one posted yesterday, so I would lean towards improper installation before saying the mounts or barrel threads are bad. |
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Posted: 3/17/2017 1:27:11 PM EDT
[#34]
Quote HistoryQuoted:
The adapter is tapered inside too. Thus if the barrel is either tapered or simply has standard length threaded portion, then it will fit. The barrel does NOT need to be tapered but in the OP's case, it looks like the factory has a shorter run of threads. Regular AR throws down with a flat / squared shoulder is fine. |
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Posted: 3/17/2017 2:32:29 PM EDT
[#35]
I believe the issue may be a bad batch of adapters.
The threads did not run deep enough to engage traditional threaded barrels. SS is sending out a new one. I'll update. EDIT: after watching that video Engineer posted in almost convinced it's a bad mount. The ones in the video appeared to engage the threads right away and and screw down for several rotations. |
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Posted: 3/17/2017 6:06:52 PM EDT
[#36]
First time around, I made the mistake of using a crush washer with the QD mount. Rocksett did not have enough to grab and the QD mount came off with the silencer. As the video shows, just install and tighten flat against your barrel. No issues so far after a couple range trips with my AR.
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Posted: 3/17/2017 6:56:40 PM EDT
[#37]
Quote HistoryQuoted:
I believe the issue may be a bad batch of adapters. The threads did not run deep enough to engage traditional threaded barrels. SS is sending out a new one. I'll update. EDIT: after watching that video Engineer posted in almost convinced it's a bad mount. The ones in the video appeared to engage the threads right away and and screw down for several rotations. |
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Posted: 3/17/2017 8:00:16 PM EDT
[#38]
Didn't say "bad batch" but they did send me a label to send it back for a replacement. Looking that the one they have listed on the site and the one in the video leads me to believe there probably was a few that made it out the door that were bad.
I'll update. |
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Posted: 3/17/2017 8:20:58 PM EDT
[#39]
Quote HistoryQuoted:
I believe the issue may be a bad batch of adapters. The ones in the video appeared to engage the threads right away and and screw down for several rotations. It doesn't seem possible for it to engage the threads right away, given the unthreaded taper area. Hope to get my hands on a mount this weekend and take some measurements. Otherwise, will definitely be checking it out at the SIG booth during the NRA Convention in Atlanta next month. |
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Posted: 3/17/2017 10:22:49 PM EDT
[#40]
Just broke out the calipers.
Threads begin at .40 inch from the shoulder. The first actual thread measures at .415 depth from the shoulder. Of the several different thread spec drawings I've seen for 5/8" thread pattern every single one is .62 inches from the muzzle to the shoulder. That leaves .2 inches of engaged threads. LESS than a 1/4inch. So, yeah....something is either wrong with these mounts or Sig messed up by not telling people that the barrels need some funky thread pattern. |
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Posted: 3/18/2017 3:02:10 AM EDT
[#41]
Quote HistoryQuoted:
Just broke out the calipers. Threads begin at .40 inch from the shoulder. The first actual thread measures at .415 depth from the shoulder. Of the several different thread spec drawings I've seen for 5/8" thread pattern every single one is .62 inches from the muzzle to the shoulder. That leaves .2 inches of engaged threads. LESS than a 1/4inch. So, yeah....something is either wrong with these mounts or Sig messed up by not telling people that the barrels need some funky thread pattern. |
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Posted: 3/18/2017 10:11:14 AM EDT
[#42]
How far the sig QD threads on also depends on the OD of a square shoulder. If it is small it could fit partway inside the tapered portion of the sig qd, if it's too big then maybe not at all.
It's a good design and no big deal to make your own propietary threads, but I thought it was ridiculous when they released it without an adaptor for square shouldered barrels. |
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Posted: 3/18/2017 10:16:14 AM EDT
[#43]
Quote HistoryQuoted:
Just broke out the calipers. Threads begin at .40 inch from the shoulder. The first actual thread measures at .415 depth from the shoulder. Of the several different thread spec drawings I've seen for 5/8" thread pattern every single one is .62 inches from the muzzle to the shoulder. That leaves .2 inches of engaged threads. LESS than a 1/4inch. So, yeah....something is either wrong with these mounts or Sig messed up by not telling people that the barrels need some funky thread pattern. |
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Posted: 3/18/2017 5:12:47 PM EDT
[#44]
Quote HistoryQuoted:
I believe the issue may be a bad batch of adapters. The threads did not run deep enough to engage traditional threaded barrels. SS is sending out a new one. I'll update. EDIT: after watching that video Engineer posted in almost convinced it's a bad mount. The ones in the video appeared to engage the threads right away and and screw down for several rotations. Is that the one you measured or did you measure the original bad adapter? |
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Posted: 3/25/2017 2:19:49 AM EDT
[#45]
Update: Resolved
Apparently there are different adapters for different rifles. The suppressor comes with the adapter that fits the Sig line of weapons, no surprise there. I wish they would have put this on their website, that different rifles require different adapters. The new adapter I received definitely has a lot more threads in it and they start far earlier making the threads start far closer to the end of the adapter. I'm happy that I didn't have to do anything drastic like downturn the barrel or buy a custom adapter. I know that Sig has been knocked in the past for having some horrible customer service but I've got to say that I was treated great. Their employee went out of his way to take care of me. |
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Posted: 3/30/2017 11:15:01 PM EDT
[#46]
Got a replacement adapter from SS. It definitely engages more threads but....and this is a big 'but'....it still only engages about half the threads on the muzzle.
So I suppose I have three options.... 1) Use 'as is' and put on rocksett on it and hope half the threads is enough. 2) Have the barrel turned to the SIG tapered shoulder 3) Have the square shoulder moved back a little further allowing more threads to engage. #3 is probably the easiest for a local machinist to accomplish. I don't feel like paying the expense of shipping this boat anchor of a barrel to have the work done. Shipping will most likely be around $35-40 there plus return shipping...plus machine work. Setting the shoulder back shouldn't be too hard. I just don't feel comfortable with only .35" of threads engaged even if there is rocksett involved. SIG (and Silencer Shop) really need to put in big bold letters that this adapter requires special barrel threading/contouring. 
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Posted: 3/31/2017 11:07:37 PM EDT
[#47]
Quote HistoryQuoted:
Got a replacement adapter from SS. It definitely engages more threads but....and this is a big 'but'....it still only engages about half the threads on the muzzle. So I suppose I have three options.... 1) Use 'as is' and put on rocksett on it and hope half the threads is enough. 2) Have the barrel turned to the SIG tapered shoulder 3) Have the square shoulder moved back a little further allowing more threads to engage. #3 is probably the easiest for a local machinist to accomplish. I don't feel like paying the expense of shipping this boat anchor of a barrel to have the work done. Shipping will most likely be around $35-40 there plus return shipping...plus machine work. Setting the shoulder back shouldn't be too hard. I just don't feel comfortable with only .35" of threads engaged even if there is rocksett involved. SIG (and Silencer Shop) really need to put in big bold letters that this adapter requires special barrel threading/contouring. |
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