I had a good customer bring in a early 20" M16 1-14 soda straw barrel that was butchered. He had wanted it chopped down to 16" and re-threaded.

Someone had attempted it... Basement hammer, hacksaw and chisel method. Now he brings it to me. First thing I noted is that the threads are all buggered up, looks like they tried to used a die with no oil. Further inspection reveals that the threads are not concentric or square to the Bore.

Then I pull out my Idiot Stick. This is a 16.125" length of #7 drill rod. (.201") you know where this is going. . . After inserting a stripped bolt, I used the Idiot stick and well it was plain as sunrise that this BBL was a good 1/2" short. - I pointed this out and boy did he turn red. (didn't mean any insult, but he was a LE H&K certified armouror...)

After stripping it of all parts I gave him $30 for the barrel and figured I could use it to make a XM177 lookalike.  I have cut & crowned the barrel @12" and threaded it about 1" so that with the XM type flashhider installed it will be 16.1".

This appears to be a Colt Chrome lined barrel so being the paranoid quality obsessed freak that I can be I have decided not to drill the barrel, but have the gas port EDM'd.

What I need is the proper location and diameter for the hole for best function.

BTW - This is a keeper, I don't intend to sell this as it is "non-Standard". It will be a replacement for my existing XM177 lookalike which has a incorrect size flash hider. I want it to be right.

Lastly, once this is done I'm going to need to send it out to be refinished, any recommendations?

Thanks for reading and your replies. - GAB

Not to insult,, you state: "It will be a replacement for my existing XM177 lookalike which has a incorrect size flash hider".


The sight base/gas port go in the same place as a 16", 10.5" or 11.5". So use your old as a "demonstrator" for your measurements. Colt port size on the 11.5" is around .067"? I have Bushmaster that is .083". Start with .065" and work from there till you get it to fire single round in mag and lock bolt open.

Something like this?

I had to open up the gas port on  my 10.5" barreled upper to .095 a couple years back. It has been steadly reliable since then. The gas port on the new M4 barrels is .062" per the latest drawings from Rock Island.

The XM177 lookalike was a PWA (SA) receiver with car stock. Barrel has a permanently attached flash hider that was smaller (edit, Diameter) than the "real" XM177 "suppressor" and also the slots were not near authentic in size & placement. There were no visible markings on this barrel, so I have no clue who made it. I will say that I got it in 90'.

A friend of mine had a "Real" "2 stamp" XM177 and after comparing several flash hiders, I found one by (I think) Bushmaster that had the proper external features.

I had no intention of tearing down the old barrel, its only fault was that it was visually incorrect. - I can do that way, I was just hoping some one had the numbers down on paper.

www.kurtskustomfirearms.citymax.com/board/board_topic/11341/5710.htm

Kurt likes .105, CT likes .086

shrug

The Colt 609 (XM177E1) used a .081 port. The 629 (XM177E2) used one in the .1 range...

Numbers retrieved from a sketchy memory of a conversation held about a decade ago in your shop.

I believe the source was Dave. (YMMV)

If the barrel is heavy, constant spiral from original machining, and a dark black/clear shine effect, it is most likely a Bushmaster. I bought similar barrel in '90 from them. Oly had a "dry" green/grey finish, had one also.

OK I guess I'll try .095".

I still have nightmares about some of the things Dangerous Dave #2 did, I don't think I ever relied on any info from him without confirming from a second and maybe third source.

SBR7_11 : It has a very dark "dry" green/grey finish...