Technical question RE: Direct thread on bolt rifle.

[FlyingHunter]

I've decided to try and run my custom bolt rifle with my AAC cyclone suppressor direct thread which usually lives on my 300 Blackout AR. Question, The AAC Cyclone does not thread all the way to the barrel shoulder as it does on my other rifles. The lock up feels strong, but has about 1/3 to 1/4 of an inch to the shoulder - is it safe to shoot and forget about it or wait? I wanted to protect the integrity of the most accurate rifle I own and of course the suppressor.

In advance, thanks.

[rjacobs]

I wouldnt do it. Cans index off the shoulder and if you dont get to the shoulder, whats it indexing off of? The crown(which SHOULD be machined true), but is the part of the can that its bottom against, is that machined true? I wouldnt say yes or no because who knows what the machining tolerances of that part of the can are because IMO AAC did not intend the can to index off of that part of the can, so machining might not be quite as tight.

To many questions.

You could get a 1/4" spacer and then run it.

[Gunfixr]

Well, I just looked at the manual for the cyclone, and it specifically states that the suppressor being concentric and aligned with the bore relies on the barrel threads being concentric to the barrel bore, and a shoulder which is perpendicular to the bore.

Therefore, the suppressor was designed to be at least snug against a shoulder on the barrel.


As a person who has cut very many threads over a long period of time, I can tell you that in order to achieve alignment of a lengthy object like a suppressor, without butting it up to a shoulder, that both the barrel and suppressor threads must be very nearly perfect to the barrel bore and suppressor bore, and, that the fit of the external and internal threads must be tight enough that installation and removal would be difficult, and the presence of the least little bit of debris would bind it from moving.

Because of the nature of gunshot residue, some clearance must be present, too much for proper alignment by threads alone. Also, nothing is ever made perfect. But, due to the nature of the double angle plane of threads, when they tighten up against something like a shoulder, the suppressor will center itself on the threads, and the shoulder will assure it's perpendicularity to the bore, provided the shoulder and rear mating surfaces are perpendicular, and that both threads are pretty close to straight.

Pretty close, as above, is real close, but not necessarily perfect.
It should be noted that hand threading by die nut, while pretty close enough for a flash hider, is not pretty close enough for a suppressor the vast majority of the time.

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[Pappabear]

I'm glad I read this thread, because my guess would have been, look through the can and make sure it's lined up and go for it. I guess it could get knocked off alignment very easily even if it were go at the beginning.

I only have one direct thread can and its in prison. Good info for December ish.

PB

[13mike]

Find or have made a spacer so it will contact a shoulder?

[Gunfixr]

I'm glad I read this thread, because my guess would have been, look through the can and make sure it's lined up and go for it. I guess it could get knocked off alignment very easily even if it were go at the beginning.

I only have one direct thread can and its in prison. Good info for December ish.

PB
The only problem with that is the clearance required in the threads for easy install/removal.


This is easy to tell. Just screw the suppressor on part way, and lightly grab the muzzle end and try to move it side to side in any direction.
With it on only a couple turns, it will wobble a lot. As it goes on further, the wobble will become less, but some will remain until it tightens against the shoulder.
If you wobble it while looking down the bore, you will see it encroach over the bore, meaning a baffle strike. Imagine it's movement during firing.


Yes, a spacer sleeve will do the job, it just has to have both sides parallel with each other.

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[Rayrevolver]

Find or have made a spacer so it will contact a shoulder?

I needed a little more clearance and bought the biggest 5/8x24 Precision Armament Accuwasher (0.10" x2) for $2 each plus shipping.

OP - I am not using them anymore, PM if 0.2" is enough.

https://precisionarmament.com/product/replacement-accu-washer-shims/

[FlyingHunter]

Thanks for all the comments. I communicated with the rifle builder today. He was very informative. First, he said shooting the rifle without full contact on the barrel shoulders is an absolute no go. I'm glad to be clear on that safety issue. Second, he advised bringing the suppressor and rifle in to assess the problem. I'll keep everyone posted.

[SC-Texas]

Thread specs from the manufacturer are provided for a reason.

Good call on asking before shooting. Make sure your builder has a set of the AAC specs


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[eodinert]

.....

[FlyingHunter]

Here's the resolution: It was not the (metal) of the threads on the rifle or the suppressor. The carbon build up on the can was severe and required a tap to chase the threads out on the AAC can. In retrospect, this was a failure on my part to carefully clean the threads of the suppressor regularly. I learned two things:

1. Regularly clean the threads on the can and use anti seize oil when mounting.

2. Accurate Ordnance not only makes the most accurate rifle I've ever owned, they gave me 5 star customer support when the issue wasn't even their product and that is above and beyond expectation. Kudos to the team at Accurate Ordnance!

[Gunfixr]

Outstanding.

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