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View Full Version : Chopping down existing PS90 bbl?


daywalker
04-24-2006, 09:20 AM
I read a post recently by darkest2000 off handly saying that the existing barrel can be cut, crowned and threaded so a CMMG replacement P90 barrel isn't needed. Can this be done? I guess I assumed that FN changed the dimensions of the barrel so it couldn't be used as a P90 barrel. Also, is the twist rate the same between the PS90 barrel and the CMMG barrel? I bet Jayson at IGF could do this work for much cheaper than buying a brand new barrel, if it is possible.




DW

btown02
04-24-2006, 09:33 AM
I read a post recently by darkest2000 off handly saying that the existing barrel can be cut, crowned and threaded so a CMMG replacement P90 barrel isn't needed. Can this be done? I guess I assumed that FN changed the dimensions of the barrel so it couldn't be used as a P90 barrel. Also, is the twist rate the same between the PS90 barrel and the CMMG barrel? I bet Jayson at IGF could do this work for much cheaper than buying a brand new barrel, if it is possible.




DW
You can cut the barrel but you will mess up the chrome lining and need to have it refinished. The twist rate is the same. I would guess after you had to make all the corrections to the cut barrel it would be cheaper to just buy the replacement.

jmz5
04-24-2006, 09:50 AM
I agree with btown, it would be cheaper just to buy a new one

daywalker
04-24-2006, 11:20 AM
You can cut the barrel but you will mess up the chrome lining and need to have it refinished. The twist rate is the same. I would guess after you had to make all the corrections to the cut barrel it would be cheaper to just buy the replacement.

That is an Internet myth. If done correctly (ie, having a competent gunsmith cut the barrel), you will not have a problem with the chrome lining. I have had many barrels cut back that have chrome lining and not one had or has any issues with flaking lining. So with that said, I can get the barrel cut, crowned and threaded for $80 as opposed to $250 for a replacement barrel. Since there are no dimensional or twist rate differences, I don't see a reason to buy the CMMG barrel when I have a fully functional barrel that would otherwise go to waste.


DW

btown02
04-24-2006, 11:46 AM
Then jump on in there and do it. Let us know how it turns out. Just so you will know it was FN that said you could not cut the barrel without messing up the lining. The following is what FN had to say about the lining in the PS90 barrel.

Were they hard chrome plated or "soft" chrome plated like on an AR or M-16 barrel?

Very few people have the ability to even do hard chrome plating.
You will have to buy a new barrel. Cutting down the PS-90 barel will ruin it because it will crack and peel the hard chrome plating.

daywalker
04-24-2006, 12:04 PM
I think Bushmaster and H&K said the same thing, however, both my HK barrels exhibit no flaking of the chrome lining. I will be sending the barrel out later this week to IGF.

Anyone know how the barrel is measured? Is it 10.3" from end to end (length #2 in picture) or from muzzle to chamber face (length #1 in picture)?

http://img.photobucket.com/albums/v482/sysgln/ps90/bbl.jpg



DW

btown02
04-24-2006, 12:08 PM
It won't hurt to give it a try. If it fails you'll be able to by another barrel to go in it.

Rypht
04-24-2006, 12:09 PM
heeey, nice picture... finally get to see one of these things apart

Rypht
04-24-2006, 12:11 PM
From the ATF's mouth ( http://www.ttb.gov/regulations/tdatf396.htm ) :



Firearm. * * * For purposes of this definition, the length of the

barrel having an integral chamber(s) on a shotgun or rifle shall be

determined by measuring the distance between the muzzle and the face of

the bolt, breech, or breech block when closed and when the shotgun or

rifle is cocked.

gundoc
04-24-2006, 01:49 PM
before you start cutting you might want to check the diameter of the original barrel...i believe its undersize for a 1/2-28 thread...so your going to have to come up with a flash hider to fit the undersize barrel or the whole project is an exercise in futility

ruf
04-24-2006, 02:26 PM
Thanks for the pic of the disassembly. So there are only threads at the end of the barrel?

daywalker
04-24-2006, 02:43 PM
before you start cutting you might want to check the diameter of the original barrel...i believe its undersize for a 1/2-28 thread...so your going to have to come up with a flash hider to fit the undersize barrel or the whole project is an exercise in futility
If I'm not mistaken, the P90 bbl is undersized and will not directly take 1/2x28 thread without some sort of adapter. I will be using a P90 flash hider since it was designed to lock the barrel to the reciever.

At lunch, I cut the barrel/sleeve aft of the pin so it all easily came apart. I could care less in keeping the sleeve/hider combo intact since it is already SBR'd and I will not be going back to the stock config. When the flash hider gets here, I will be sending the bbl and flash hider to Jayson at IGF. I'll let everyone know how it turns out.

Oh, and that pic is from one of darkest2000's posts on this forum.




DW

btown02
04-24-2006, 02:45 PM
DW, keep us updated and when you get it back some pics please.

gundoc
04-24-2006, 08:04 PM
here is a link for the adapter you will need http://www.trosusa.com/

ruf
04-24-2006, 08:22 PM
I'm not seeing it? Is it buried somewhere on the site?

btown02
04-24-2006, 08:36 PM
All the way on the bottom on the left, ADAPTERS.

CMMG
04-24-2006, 09:45 PM
We should have our thread adaptor done this week.

Jeff

ruf
04-24-2006, 11:31 PM
I saw the adapters. It jumps from 8mm for the P22 to 1/2".

daywalker
04-25-2006, 09:07 AM
What ruf said, there isn't listed or at least now there isn't a PS90 to AR15 thread adapter.



DW

Mark McWillis
04-25-2006, 10:11 AM
I'm not seeing it? Is it buried somewhere on the site?

They haven't made it on to the web site yet as they are brand new. E-mail me and I'll send you info on them. They are in stock and ready to ship.

Mark McWillis

daywalker
04-25-2006, 11:47 PM
I thought about this again today and thought maybe it would just be easier to buy the CMMG replacement bbl so I called today to see if CMMG even has any barrels available and I was told no and the batch that will be done in a couple of weeks is already sold out. I asked when another batch will be completed and the lady said she didn't even know if they were going to do another batch. So it looks like my only alternative is a chop, crown and thread (unless someone wants to sell a spare CMMG bbl).



DW

CMMG
04-26-2006, 09:04 AM
We have plenty more barrels in the works. I don't have an ETA on them at this time.

Jeff

odontia32m
05-06-2006, 09:30 PM
My smith has cut barrels for me, recrowned them and installed flash hiders. When recrowned, the inside chrome bore is essentially polished. You will have no problems. BTW he charges me $50 and I am just a guy off the street. 50 verses 250? Seems like a no brainer.

Bob

Hoover 1
06-22-2006, 03:19 PM
Any names and telephone numbers of "smiths" who have threaded PS90 barrels?

Thanks in Advance,

Hoover 1

btown02
06-22-2006, 04:11 PM
Any names and telephone numbers of "smiths" who have threaded PS90 barrels?

Thanks in Advance,

Hoover 1
I think most made up their mind it was easier and cheaper to just buy a replacement barrel.

daywalker
06-23-2006, 10:17 AM
Just an FYI. Mark at TrosUSA said he would do the cut, crown and thread job only after he did one first and made sure there was no flaking of the chrome lining. He felt confident that it wouldn't. Don't know where he is with it anymore since I just broke down and bought a CMMG barrel.




DW

Hoover 1
06-26-2006, 03:11 PM
Mark at TrosUSA got back to me today in response to a request I made.

He said he needed to do some additional testing on cutting the barrels, but it looks like it will probably work out OK.

Hopefully, he will be ready for some work in August. :MM

Hoover