I'm trying to get an M231 barrel collar machined, but as i have no dimensions to go off i'm probably going to have to run off guesswork and comparing it to other parts i have.

The part in question looks like this, for anyone who doesn't know:
http://dl.dropbox.com/u/9988278/m231gasblock/DSC00857.jpg
(Picture from Augee's M231 review thread from ages ago)

From looking at pictures of the collar next to the handguards, i've managed to use the handguards i've got to establish the folllowing.
http://dl.dropbox.com/u/9988278/m231gasblock/collar.jpg
(forgive my amazingly poor artistic skills)

It's not much, which is why i'm hoping someone out there with an M231 or someone with access to one could be kind enough to take a few measurements, so i can make sure it's as accurate as can be.

Better yet, has anyone seen any legit ones or even repros floating around? If people are managing to find bolt carriers, selector plates, and even uppers, then i'm guessing at least a couple have been broken up or the army has been selling off their spare parts, so where have all the barrel collars gone?

Member texassquirrel is the only person I've seen with a full kit.
He could probably point you in a direction .
Are thinking of making a few extra to sell?

E-mail sent.
Dustin

I've always wanted to try machining one of those, but have never been able to find dimensions or a sample to take them off of...

Another e-mail sent.
Dustin

don't know where this came from, but check the math...32mm + 6mm + 32mm  = 70mm, not 80mm

Beat me to it.

Seriously, good luck OP, I'm interested to see how this goes.

ETA: can anyone tell me what are the huge threads for? I know this is a port firing weapon, did it screw into some sort of mount or something? Forgive my noobish tendencies.

It screwed into a ball mount on an M2 Bradley.  Two in each side and two in the ramp.  The side ports were deleted in the M2A1 version when it got more armor.

actually less than 70mm since that 6mm is on the hypotenuse.

I drew that very, very late at night so something like that was bound to happen. Cheers for pointing it out, though. Knowing me i'd have tried machining it like that then wondered why it looked so funny

I'm INCREDIBLY doubtful of my machining skills, as i've not done anything too complex before this, so i won't be mass producing them.

If someone with a real one could get a mold made, then that'd likely please a lot of people.

Get a mold made, dang this guy has a great sense of humor or irony....

He must have missed the prototype FSB thread and what all it took to get that to the point it's at.

I hope he was being sarcastic. If we start making the M231 mold now we may have castings done by May of 2014!
Dustin

I've got a 231 clone, which took years to gather all the parts for.  I'll try to remember to pull the block and measure it up for you tonight.

What about the ball mount?

That would make this part useful.

Alright, fair warning, my machining experience comes from a single intro course maybe 3 or 4 years ago.

All measurements were made with my General Dial Calipers, but some might be off here or there.

Still, should give you a decent idea anyway.

If i can get one machined, i'm considering finding a museum with a Bradley in their collection and asking if they'll let me fit it into the mount.

Would be a good test of how accurate to the original it is.


And Tumerboy, thanks very much for the drawings! They look like they'll be incredibly useful, but after comparing the measurements of the hole and the thickness of my barrel, i realize i may have to modify the one i've got slightly.

Shouldn't be an issue as long as i can refinish the bits i modify to a decent standard.

I'm going to try to machine one in my spare time at the shop.  Is it aluminum or steel?

Kali, not sure what you mean?  Comparing what hole?  The hole that the barrel fits through?  The barrel is .75 under the front of the block, but something like 1.25" under the back end of the block.  I forgot to measure the barrel, and I didn't remove the block, but there is a straight step down between the two, which butts up against the inside of the collar.  If memory serves, there's a milled counterbore for the hex screw to hold the collar on, and there is a similar one on the top side where the gas tube group is held to the barrel.  There's a small steel gas seal between the barrel and the gas tube.  And the gas tube has a very small block pinned to the end, in that half round shape you can see in the front view.  You should look up the old 231 thread for specifics on those.  Someone measured and had manufactured some of those gas seals, that's where I got mine.

As for Bradleys, they're still in active service in the Military, so you won't find them in Civilian hands, or at Civilian museums until they get retired.  You may be able to find them at military run museums like Ft Knox. . . but I'm not sure.  Even then, most of the ball mounts were covered over, so any in museums may not have the mounts.  Still, I'm with you, I'd LOVE to see my clone hanging in the back ramp of a Bradley.  Or get to see what it was like to fire out the side while looking through a periscope.

VAAR, it's definitely steel.  Those threads would sheer off in the ball mount if it were aluminum.  Still, for our civvy use. . . I don't think there's any reason you COULDN'T make it in aluminum.

Yeah, the hole the barrel fits though.

The 16" HBAR barrel i've got is really strange, it's .75 up to where the front end of the FSB would be, but steps up to about .8 for the rest of the way. It's almost like it's designed for a mid length handguard setup.

I suppose i'll need a new barrel, then.