Suppressor Bore Diameter

[keith13b]

I'm looking into Form-1'ing and building a dedicated Grendel suppressor because the threads on my AA uppers are not standard and I want a direct thread. I see a lot of people happy with a .30 cal can with a standard industry overbore of 0.067". I assume this is for convenience. Is it worth it to keep a tight overbore? I have read mixed comments. Some people say keep a 0.05" overbore, some say 0.06" and some say as tight a 0.04". What say the Grendel community? I understand this is a risk vs reward, but some say go larger for safety as the audible difference is not noticeable, and some say tighten it up as long as you have concentric threads, but not too tight to get a baffle strike.

I just want to build the best all around suppressor specific to my Grendel's since they all share a unique thread pattern. Assuming a perfect world, what would you do for bore size. I will add in a safety factor of my own, but what would be ideal in your opinion as a baseline?

[Bigs28]

I have a tbac ultra 7 can that is 6.5 or .264. Not sure what the actual diameter is but tbac advertised it as a couple decibels less then a 30 cal can. You could probably call them and ask what the actual diameter is. Some people have claimed on a semi auto the 30cal cans are more quiet at the shooters ear then the 6.5 cans but the 6.5 are more quiet on bolt guns. Im happy with mine either way.

[Klem]

Keith,

0.5mm or .02" is about industry norm for the least clearance around an exiting bullet - certainly no less. So for a 6.5mm calibre the suppressor hole will be 7.5mm. I measured one for 6.5mm at 7.7mm/.0415".

If you want to turn it into a half suppressor by widening the hole and directing more sound forward then up to you. Depends what you want to use it for.

[mel]

this one is drilled for 30 cal i always use a 21/64th bit which is .328 , baffle design and spacing is more important then how tight the bore is around the bullet specially on a gas gun
this is on a 6mm arc 6 baffles in this can shooting full power 75g bullets at over 3k fps
[video=youtube;MtjbdrXO36c]https://www.youtube.com/watch?v=MtjbdrXO36c[/video]

[mel]

heres my other can drilled the same, on a 6.5 grendel 8 baffles in this one
[video=youtube;kxJnw-YxVls]https://www.youtube.com/watch?v=kxJnw-YxVls[/video]
also shooting a 90g full power load at over 3k fps

[LRRPF52]

If I was shooting a bolt gun, I would use the smallest bore available for the cartridge to chase decibel rating.

For gas-operated firearms, especially the AR-15’s internal expansion operating system, I use .30 cal for the 6.5mm to allow blow-by so there isn’t as much back pressure into the BCG and port noise from the ejection port/bolt carrier relief vents.

Shooter’s ear is actually quieter with a .30 cal can, but the muzzle is a bit louder.

I personally care about shooter’s ear the most.

For a direct-thread, my biggest concern is thread concentricity and shoulder squareness with the bore.

I also highly recommend the Bootleg Adjustable Gas carriers for suppressed AR-15 use, or any AR-15 where you want ease of gas adjustment without the headache of tiny set screw gas blocks.