First, thanks to many folks on this forum for contributing so much information about their experiences with respect to the M&P15-22. I have learned a TON of information from the folks here. My rifle is 5 weeks old, more than a thousand rounds thru it, and I love the weapon.
I wanted to "give something back" to the forum... so here it is.
I've got an extensive machining background (mostly milling and grinding), and have included some minimal technical information for those who may want to attempt this at a local machine shop. G-code and M-code are second languages for me. For those of you with machining in your blood, I've "dumbed-down" most of the discussion, considering some folks may not know much about it.
I had my barrel threaded by a local mom-and-pop machine shop a few weeks ago, to accomodate installation of a commercially available flash suppressor. I've worked with this shop for many, many years and know the owner and the employees very well.
Disassembly:
I bought a Shoo-Wrench and made some soft pine vice jaws to remove the barrel from the Upper Assembly. I won't go into details - as there is already a thread and very good video explaining all of that. I will tell you that my pine wood vice jaws started life as a piece of 4x4, about three inches long. I drilled a 5/8" hole down the center, then cut the block in half thru the center of the hole, and then sanded down the cut faces until I got a good fit around the barrel. Took me less than ten minutes to make this "tool". If that doesn't make sense to you - I suggest you simply buy a set of commercially available vice jaws.
Barrel Threading Sketch:
I took my barrel to the local machine shop and gave them the attached sketch, depicting the dimensions of the thread form. If you attempt to do the same with a local machine shop.....do so at your own risk. I will NOT take ANY responsibility for your barrel getting messed up. I can tell you that the shop I used had no problems using my sketch, and all is well on my weapon. If the machine shop you select doesn't understand the sketch, I suggest that you take your barrel and leave. If you don't understand the sketch, I suggest you seek out a gunsmith.
Other notes:
The machine shop (should ask you) will want to know the hardness of the barrel. You can assure them that the barrel has a "Rockwell-C hardness of approximately 30", and will machine very well. They may want to check the hardness to make sure. The normal method is to simply run a ******* file against the steel and see if the file will actually remove some steel. Don't be alarmed
if you see them trying to file your barrel (on the end to be threaded, of course).
Gage:
If you use a local machine shop, I also strongly suggest you have the flash suppressor in hand, and give it to them to use as a "gage" to make sure they cut the thread correctly - and make sure the suppressor fits before removing the barrel from the lathe. It's much easier to take a spring cut across the threads while the barrel is in the machine than it is to figure out the suppressor doesn't fit when you are back at home.
The .500-28 thread isn't common (except for the firearm world), and most places aren't going to have a gage or even a hex nut to use as a gage to make sure they cut the thread correctly. Sure, they could measure over pins, etc.... but I don't want to get too technical here.
Re-Black Oxide the finish:
After machining the thread on my barrel, I asked the machine shop to "repair" the black oxide finish they removed (due to the machining). They used what I call a black-oxide touch-up kit. It's basically a cleaning fluid, and a second fluid that puts black oxide back onto the steel. When they were done, my barrel looked "factory-made".
Installation:
The design sketch I attached accomodates a standard crush washer. When installing my suppressor, I hand-filed down the thickness of the crush washer such that I have only about 1/3rd of a turn of torque (past finger tight) holding the suppressor on. I put nearly 350 rounds thru the gun since adding the suppressor, and it hasn't come loose.
Again, use this sketch and the information I have provided above at your own risk. Yes, my barrel turned out perfect, and I'm very happy.
No, I cannot and will not help anyone get thier barrel threaded using the machine shop I know about..... wait, on second thought, I'll be happy to help anyone get thier barrel threaded - but at a cost of $600/each plus shipping, cash only, prepaid.
One last thing... the sketch doesn't accurately depict the external details of the M&P15-22 barrel in the top view. That's actually a "sketch" of a 5.56 barrel - which I also had threaded using the same sketch.
Semper Ordnance !
I wanted to "give something back" to the forum... so here it is.
I've got an extensive machining background (mostly milling and grinding), and have included some minimal technical information for those who may want to attempt this at a local machine shop. G-code and M-code are second languages for me. For those of you with machining in your blood, I've "dumbed-down" most of the discussion, considering some folks may not know much about it.
I had my barrel threaded by a local mom-and-pop machine shop a few weeks ago, to accomodate installation of a commercially available flash suppressor. I've worked with this shop for many, many years and know the owner and the employees very well.
Disassembly:
I bought a Shoo-Wrench and made some soft pine vice jaws to remove the barrel from the Upper Assembly. I won't go into details - as there is already a thread and very good video explaining all of that. I will tell you that my pine wood vice jaws started life as a piece of 4x4, about three inches long. I drilled a 5/8" hole down the center, then cut the block in half thru the center of the hole, and then sanded down the cut faces until I got a good fit around the barrel. Took me less than ten minutes to make this "tool". If that doesn't make sense to you - I suggest you simply buy a set of commercially available vice jaws.
Barrel Threading Sketch:
I took my barrel to the local machine shop and gave them the attached sketch, depicting the dimensions of the thread form. If you attempt to do the same with a local machine shop.....do so at your own risk. I will NOT take ANY responsibility for your barrel getting messed up. I can tell you that the shop I used had no problems using my sketch, and all is well on my weapon. If the machine shop you select doesn't understand the sketch, I suggest that you take your barrel and leave. If you don't understand the sketch, I suggest you seek out a gunsmith.
Other notes:
The machine shop (should ask you) will want to know the hardness of the barrel. You can assure them that the barrel has a "Rockwell-C hardness of approximately 30", and will machine very well. They may want to check the hardness to make sure. The normal method is to simply run a ******* file against the steel and see if the file will actually remove some steel. Don't be alarmed
if you see them trying to file your barrel (on the end to be threaded, of course).Gage:
If you use a local machine shop, I also strongly suggest you have the flash suppressor in hand, and give it to them to use as a "gage" to make sure they cut the thread correctly - and make sure the suppressor fits before removing the barrel from the lathe. It's much easier to take a spring cut across the threads while the barrel is in the machine than it is to figure out the suppressor doesn't fit when you are back at home.
The .500-28 thread isn't common (except for the firearm world), and most places aren't going to have a gage or even a hex nut to use as a gage to make sure they cut the thread correctly. Sure, they could measure over pins, etc.... but I don't want to get too technical here.
Re-Black Oxide the finish:
After machining the thread on my barrel, I asked the machine shop to "repair" the black oxide finish they removed (due to the machining). They used what I call a black-oxide touch-up kit. It's basically a cleaning fluid, and a second fluid that puts black oxide back onto the steel. When they were done, my barrel looked "factory-made".
Installation:
The design sketch I attached accomodates a standard crush washer. When installing my suppressor, I hand-filed down the thickness of the crush washer such that I have only about 1/3rd of a turn of torque (past finger tight) holding the suppressor on. I put nearly 350 rounds thru the gun since adding the suppressor, and it hasn't come loose.
Again, use this sketch and the information I have provided above at your own risk. Yes, my barrel turned out perfect, and I'm very happy.
No, I cannot and will not help anyone get thier barrel threaded using the machine shop I know about..... wait, on second thought, I'll be happy to help anyone get thier barrel threaded - but at a cost of $600/each plus shipping, cash only, prepaid.
One last thing... the sketch doesn't accurately depict the external details of the M&P15-22 barrel in the top view. That's actually a "sketch" of a 5.56 barrel - which I also had threaded using the same sketch.
Semper Ordnance !
Last edited:
