Pinning a Compensator?

[matt]

Since we all have AR's on the brain...

Can someone post a pic of a pinned compensator? I just want to see how it's generally done. Roll pin vs solid? Pinned in the radial or tangential direction?

Thanks,
Matt

 

[Cuda444]

Here's a pic of one done by ar15barrels.com. They use a blind pin... drill a hole partially into the barrel, insert the pin, weld over it and touch up blue it.

http://www.ar15barrels.com/gfx/perm-vortex.jpg
http://www.ar15barrels.com/gfx/perm-attach.jpg


ETA - Is there anyone located in Central Ma that will permanently attaching a muzzle device for a reasonable fee?

 

[matt]

does the pin have to be welded?

 

[kevin9]

I believe it has to be welded or silver soldered.

 

[Jake L]

The screw in comp must be drilled, pinned and blind welded over. Most silver solders will not meet the ATF spec. The other way to do this is to just weld the comp onto the barrel after it is screwed on. Looks ugly, however meets the ATF rules.
I am doing one right now and I will try to send a photo when I finish.
I drill the comp and the barrel and use steel pin stock. After cutting the pin to the right size I harden the pin, I then drive the pin into the hole in the comp and barrel. The pin is recessed below the comp leaving an area to drop a MIG weld into. I then file the weld smooth and cold blue the area.
I charge $35.00 to do this as long as I do not have to remove an already pinned and welded or welded flash hiders or comp. The removing of a pinned and welded or welded comp or flash hider would be additional labor charge.
Once pinned and welded or welded they are not easy to remove they are not meant to be removed easily. Isn’t that the whole idea behind pinning and welding?

 

[Rob Boudrie]

Once pinned and welded or welded they are not easy to remove they are not meant to be removed easily. Isn’t that the whole idea behind pinning and welding?

That is one way to do it.

The other way is to use an alternative method of pinning that does not use threads as the underlying attachment mechanism thus rendering it a "non-threaded" attachment. And yes, this can be done very nicely if you make the design change to the barrel and comp (ie, not just trying to add "pinning" to a screw on comp).

 

[LoginName]

That is one way to do it.

The other way is to use an alternative method of pinning that does not use threads as the underlying attachment mechanism thus rendering it a "non-threaded" attachment. And yes, this can be done very nicely if you make the design change to the barrel and comp (ie, not just trying to add "pinning" to a screw on comp).

There are muzzle brakes that use several set screws so the brake can be attached to a non-threaded barrel (thereby negating any legal nuances about tack welds, melt points, etc).

I've never used one (not sure how much I'd trust it), but if installed with a bit of thought... like drilling shallow holes where the screws make contact and a good dose of red loctite, it could minimize any chance of the brake working loose.

 

[BillK]

My nephew has a set screw break on, it's not that bad, and the machine screws have never let up (knock on wood)

 

[Rob Boudrie]

There are muzzle brakes that use several set screws so the brake can be attached to a non-threaded barrel (thereby negating any legal nuances about tack welds, melt points, etc).

There are far better ways to pin a comp than set screws if you start from scratch and are able to machine the barrel and comp to high tolerances.

You need to be very careful with set screws that push into the barrel as it is possible to deform the bore and create accuracy problems before you even see the bump on the inside. I wouldn't even consider a compensator that uses such an attachment method.

 

[LoginName]

There are far better ways to pin a comp than set screws if you start from scratch and are able to machine the barrel and comp to high tolerances.

As in a press fit?

Pete in NH (Legal-Transfers), used to offer barrels with a fake flash suppressor that was press fit on (he might still be selling them for all I know). All it was was a bird cage type suppressor that was bored out to the proper dimension.

There's no way that thing would budge no matter how hard you beat on it.

You need to be very careful with set screws that push into the barrel as it is possible to deform the bore and create accuracy problems before you even see the bump on the inside. I wouldn't even consider a compensator that uses such an attachment method.

 

[Rob Boudrie]

As in a press fit?

That's one way, and is used by SVI on their IMM Open compensated 1911 handguns. IT helps to dunk the barrel in Liq N to shrink it before press fitting.

 

[Jake L]

Are you suggesting cutting off the threaded end recrowning the barrel and doing a shrink and press fit on the barrel?
I have used this method on non-threaded barrels, however pinning and welding is much easier on a threaded barrel.
As far as using any other method (set screws, cross pinning, roll pinning) other then pinning and welding or welding the comp to the threaded barrel would be against ATF rules.

 

[Rob Boudrie]

Actually, I was suggesting starting with a barrel and comp that had no threads whatsoever, not attempting to retrofit a pressfit or pressfit plus crosspin design to an existing threaded barrel or comp. It's much easier to do this sort of think if you are assembling a gun from scratch, and have the proper machinery - this is not something a parts changer or home gunsmith is likely to be able to do.

 

[Jake L]

Most of the pin and weld jobs I do is because the flash hider has to come off and a comp must go on. On new builds I find that most people want mil-spes m4 barrels with threaded ends.