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Posted: 11/8/2024 11:45:36 PM EDT
| Has anyone run into muzzle threads being non concentric? I finally received my suppressor I wanted to run on my 300bo upper and using an alignment rod it rubs the suppressor. I tried 3 different muzzle devices and the same every time. I tried the same set up on an 300bo AR barrel and it was centered. |
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Originally Posted By d16man: No issues with mine. https://www.ar15.com/media/mediaFiles/337946/20231126_214832-3042189.jpg I'm less than impressed with the quality of mine.   
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Originally Posted By motoguzzi: I am looking at the ones with a ASR mount already installed, I hope this will mean these are GTG. I have a 14.5 5.56 upper and did a pin and weld for that flash hider. that one had threads concentric to the bore I guess it's hit or miss. |
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Originally Posted By chuck1: I have a 14.5 5.56 upper and did a pin and weld for that flash hider. that one had threads concentric to the bore I guess it's hit or miss. Please PM me your order number. I will get you taken care of. Thanks, Josiah |
Palmetto State Armory
3760 Fernandina Rd
Columbia, SC 29210
Web Sales: 1-803-724-6950
3760 Fernandina Rd
Columbia, SC 29210
Web Sales: 1-803-724-6950
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Originally Posted By chuck1: I'm less than impressed with the quality of mine. http://i.imgur.com/pQmYwPmm.jpg http://i.imgur.com/Um1Oku4m.jpg http://i.imgur.com/whekrhFm.jpg Apparently this is an ongoing issue. I just sent in a warranty request for mine. |
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Originally Posted By chuck1: That sucks. I have a theory on the real issue but I'll keep it to myself until I hear back from PSA. Originally Posted By chuck1: Originally Posted By Muzap: Apparently this is an ongoing issue. I just sent in a warranty request for mine. That sucks. I have a theory on the real issue but I'll keep it to myself until I hear back from PSA. |
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Got the upper back from PSA. They checked the alignment and sent it back with photos of a Dead Air can mounted with an alignment rod inserted, and it looks good in the photo. I have no reason to doubt that the threads are concentric. I have Surefire cans, though, and when I install a Surefire brake per instructions, the can is still misaligned. This is an 8.5" 300 BLK upper, and the shoulder on this thing is tiny - I mean, really narrow. I'm pretty sure this is the issue - I don't think the spacer and shims are playing nice with the barrel shoulder. I tried installing the spacer backwards like it was a SCAR, and that helped some, but it's still misaligned. Has anybody here successfully installed a Surefire brake and suppressor on an 8.5" 300 BLK JAKL? If so, did you run into any issues? |
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Originally Posted By Muzap: Got the upper back from PSA. They checked the alignment and sent it back with photos of a Dead Air can mounted with an alignment rod inserted, and it looks good in the photo. I have no reason to doubt that the threads are concentric. I have Surefire cans, though, and when I install a Surefire brake per instructions, the can is still misaligned. This is an 8.5" 300 BLK upper, and the shoulder on this thing is tiny - I mean, really narrow. I'm pretty sure this is the issue - I don't think the spacer and shims are playing nice with the barrel shoulder. I tried installing the spacer backwards like it was a SCAR, and that helped some, but it's still misaligned. Has anybody here successfully installed a Surefire brake and suppressor on an 8.5" 300 BLK JAKL? If so, did you run into any issues? I got mine back several weeks ago. They said it was fine per their specs. Sent a picture but it won't open. Still out of alignment with my parts. I haven't had a chance to get all the numbers due to the lathe I need to use being busy which is why I haven't given my opinion on what the issue is yet. |
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Cannot say for sure but there have been a number of muzzle devices recently that have had issues and have had to be sent back. I would remove all the spacers and washers and thread the muzzle device on to the shoulder and check the alignment with that. I know you said it was fine on another rifle but there have been quite a few posts on the Suppressor forum where certain devices have been out of specs. Also see if the washers are not mating flush to the shoulder. If they are on the edge it may be throwing it out of alignment. Happens a lot of some muzzle devices or spacers on barrel profiles that are thin. I had to run a muzzle indexing device on my Zastava and I have one hunting rifle that I had to use a washer that is designed for guns that do not have enough shoulder to index off of. You may have already checked this though, but thought I would throw that out there. I have quite a few palmetto premium bbls (Before the sabre line) and a jakl 10.5 and they have been solid so far. |
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Originally Posted By stanprophet09: Cannot say for sure but there have been a number of muzzle devices recently that have had issues and have had to be sent back. I would remove all the spacers and washers and thread the muzzle device on to the shoulder and check the alignment with that. I know you said it was fine on another rifle but there have been quite a few posts on the Suppressor forum where certain devices have been out of specs. Also see if the washers are not mating flush to the shoulder. If they are on the edge it may be throwing it out of alignment. Happens a lot of some muzzle devices or spacers on barrel profiles that are thin. I had to run a muzzle indexing device on my Zastava and I have one hunting rifle that I had to use a washer that is designed for guns that do not have enough shoulder to index off of. You may have already checked this though, but thought I would throw that out there. I have quite a few palmetto premium bbls (Before the sabre line) and a jakl 10.5 and they have been solid so far. Shims or no shims mine is still misaligned. The same parts worked perfectly on a 300bo ar barrel so the issue is with the PSA barrel and the griffin flash hider/brake. I know I can fix the issue but I shouldn't have to due to their barrel design. Why they turned the shoulder behind the treads down is a mystery to me. It serves no real purpose, saves no weight and added more machining time to the barrel. Is it a defect? Not really but that small shoulder makes it sensitive to who's suppressor set up you want to use. Apparently they use dead air to check the barrel with and have no issues and others have successfully run other companies cans with no issues. |
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Originally Posted By chuck1: ... so the issue is with the PSA barrel and the griffin flash hider/brake. ... I've got a JAKL upper in 300 that's waiting for an SBR lower... and I am also putting a Griffin hider or brake on mine. It looks like I'll be figuring how to get the factory hider off sooner than later so I can check this. |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
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Update - I spun on a GA Tac-Comp and my Explorr 300 seems fairly well centered. That's good news. Bad news side - that brake needs to be timed, and like someone else mentioned, there's almost no shoulder for a shim to sit on. It looks like the shoulder is only about .04" from the OD of the threads. Leave a little clearance for a shim to slide over, and you only have what, about .03" of mating surface? That little landing cut from the last .75" or so of the full barrel diameter would only give another .03" ... but that's an effective doubling of the area a shim has to mate with. I'm legitimately afraid the bottom shim or two might fold or tear when being torqued down with that little overlap. (additional train of consciousness) OK - for the giggles, I pulled out this .300 JAKL short upper and a set of SureFire 7.62 shims. The shoulder area of the barrel measures 0.68". The shims are marked as ID 0.510" In a perfect world, that would mean .68-.51=.17, /2 = .085" mating surface on each side... possibly passable, but the threading has a relief cut with an OD of only 0.56"... thats enough that when a shim slides sideways, I can see light between it and that side of the barrel shoulder. I'm pretty certain that's a NoGo. PSA - I thought you were our friend. Who decided that the muzzle end of a short 300blk barrel should be too thin to properly take shims? Of all things, a short 300blk barrel is one of the most likely to be purchased with the intent of suppression. Making it incompatible with a suppressor mount muzzle device that needs to be timed with shims is... well... I can't say Evil or Premeditated, but I am leaning towards Incompetent. After thought, I'll settle on Unfortunate, as that leaves the door open to an honest design mistake. Is there any remediation for this that doesn't include a new barrel? But again, WHY? Because of this, I'm left with 3 options, each worse than the last: - Buy a hider/brake I don't want that doesn't require timing - Commission a custom shim/adapter that will somehow not slide off the edge of the barrel shoulder - Sell this upper to someone who doesn't intend to suppress it... Hey @Green0 - as the resident SME on all things Griffin, do the numbers above look suitable / safe for any of your untimed Taper / DL brakes or hiders in 5/8x24" |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
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If you are concerned about the minimal amount of thread shoulder, use a .01” thick shim as your first shim before shimming the muzzle device. That way you have at least some resistance to punching the shoulder through the shim. If you even have .03” a side, that should be enough to mount a muzzle device so long as the barrel thread doesn’t have a grooved thread relief also allowing the shims to be eccentric to the surface. |
Austin, Managing Partner - www.GriffinArmament.com
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Originally Posted By Green0: .... If you even have .03" a side, that should be enough to mount a muzzle device so long as the barrel thread doesn't have a grooved thread relief also allowing the shims to be eccentric to the surface. I'm suspecting the only 'easy' answer is a custom shoulder - a spacer with a recessed area in the bottom to slide over the barrel's OD, and just thick enough to cover the thread relief cut. I can see at least three ways that's a bad idea, but it might be better than not suppressing it. Or, there's always the option of using an untimed device or a direct thread ultralight can. Oh, wait... you have a gate lock 30, don't you. I don't own that one yet. :-) Got any oddballs on the back shelf? |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
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Thank you for weighing in, @Green0 . Disclaimer: This post contains VERY UNPROFESSIONAL amateur photos, measurements and math. Any professionals or semi-professionals, please weigh in with corrections or notes. Here are a couple of photos of the area in question: Attached File Attached File As you'll see, there really isn't much flat surface on that shoulder. I took some measurements with a caliper, as that's the only decent M&TE I have at home. It's a good caliper (Mitutoyo), but bear in mind that it's not calibrated and a caliper isn't really accurate enough for precision measurements in this application. Thread diameter @ 0.625" (of course, 5/8") OD of barrel at shoulder 0.690" Relief cut diameter 0.566" Thread diameter minus shoulder diameter is 0.065 or (divided by 2) 0.0325 along the edge, just above the number Green0 mentions. However, that relief cut is deep and the shoulder is not flat, meaning that any shims can shift around. Which they apparently did when I torqued the brake down at installation, as I was unable to get suppressor alignment. Now, here's the mating end of a Surefire flash hider. It has an inner chamfer, and the outer edge of the chamfer diameter, where the flat outer portion starts, measures 0.671": Attached File That means the engagement surface of the flat portion of the muzzle device against the shoulder is 0.0095" along the diameter edge (0.690 - 0.671 = 0.019, divided by 2). So I measured a second SF muzzle device, this time a muzzle brake. They apparently vary, as this one one was 0.655" chamfer edge to edge. This would have given me 0.0175" engagement, still way too little to be comfortable with. No wonder I can't get alignment. I was going to try using a flash hider with no shims, but with only 0.0095" engagement, I don't think I'll risk it. |
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Originally Posted By Amish_Bill: That's exactly my concern. There is a relief cut at the base of the threads with a somewhat small diameter. When I slid a shim into it and pushed it to the edge, I can see light between the OD of the barrel and the ID of the shim. I'm suspecting the only 'easy' answer is a custom shoulder - a spacer with a recessed area in the bottom to slide over the barrel's OD, and just thick enough to cover the thread relief cut. I can see at least three ways that's a bad idea, but it might be better than not suppressing it. Or, there's always the option of using an untimed device or a direct thread ultralight can. Oh, wait... you have a gate lock 30, don't you. I don't own that one yet. :-) Got any oddballs on the back shelf? My plan is to continue the threads back into the shoulder about .125. I will then make a threaded washer and face that square to the threads. I tried the .100 shim and didn't like the results. The reason I want to thread mine onto the barrel is it will make it part of the barrel and shouldn't shift any. Its a bit of work but it's the only fix I will be comfortable with. |
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Thats like a ~.0625 for both the relief and the shoulder, so that allows the shims to be so eccentric that they can leave open space like that, unshouldered. Thats really unfortunate and not ideal. Barrels should have no thread relief and get finished with a .016” or smaller tool nose radius for ideal interfacing so the shims don’t have places to rotate off to. |
Austin, Managing Partner - www.GriffinArmament.com
| Yeah, I think I just need to accept that this is a shit design with zero planning for popular muzzle devices, sell it and move on with an upper from a manufacturer who designs their product intelligently with the probable end users in mind. |
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