AR15.Com Archives
 Shortening M4 bbl. to 11.5
Catman2  [Team Member]
5/3/2010 9:03:41 AM
I've been on the fence about having ADCO shorten an M4 14.5 to 11.5. I've seen pics of it done but it shows about half of the skinny dimension of the m203 cut before the FH. But by my measurement after sticking a cleaning rod down the bore to the bolt face which is 16.1 (ADCO shortened the RRA bbl. to 14.5 and pinned a 2" EA2 on bringing out to 16.0 -16.1) and subtracting 4.5", it hits roughly the center of the m203 cut or half an inch from the FSB shoulder. If there is an 1/2"allocated for thread then I would think that 1/2" would be covered by the FH thus snugging it up to the m203 shoulder or the step down. If there is less than 1/2" used for thread then obviously it would expose more of the actual m203 cut. Here is a pic where I airbrushed the EA2 where I hope it would go showing the shoulder but none of the m203 skinny bbl.

Please tell me if the pic is accurate.

bigbore  [Industry Partner]
5/3/2010 6:53:55 PM
the shoulder will still be there as in your picture.
Catman2  [Team Member]
5/3/2010 8:36:25 PM
Originally Posted By bigbore:
the shoulder will still be there as in your picture.


And only the shoulder? If so great as I can deal with the shoulder as long as none of the pencil bbl. section shows.

Also, I'm planning on putting an extended A2 just like the pic which leads to the next question. You perm'd the SDI EA2 on
thats in the pic. Can it be salvaged and reset at 11.5? Not trying to be tight a$$ but it's virtually brand new.

bigbore  [Industry Partner]
5/3/2010 8:53:07 PM
Originally Posted By Catman2:
Originally Posted By bigbore:
the shoulder will still be there as in your picture.


And only the shoulder? If so great as I can deal with the shoulder as long as none of the pencil bbl. section shows.

Also, I'm planning on putting an extended A2 just like the pic which leads to the next question. You perm'd the SDI EA2 on
thats in the pic. Can it be salvaged and reset at 11.5? Not trying to be tight a$$ but it's virtually brand new.



We mill the muzzle device off which destroys it. We can carefully remove it so it can be reused, but the labor cost we charge to do that is double the cost of a new flash hider
Catman2  [Team Member]
5/4/2010 7:35:46 AM
Originally Posted By bigbore:
Originally Posted By Catman2:
Originally Posted By bigbore:
the shoulder will still be there as in your picture.


And only the shoulder? If so great as I can deal with the shoulder as long as none of the pencil bbl. section shows.

Also, I'm planning on putting an extended A2 just like the pic which leads to the next question. You perm'd the SDI EA2 on
thats in the pic. Can it be salvaged and reset at 11.5? Not trying to be tight a$$ but it's virtually brand new.



We mill the muzzle device off which destroys it. We can carefully remove it so it can be reused, but the labor cost we charge to do that is double the cost of a new flash hider


So how long is the theaded area, 1/2"? I don't mean to wear this out but I'm paranoid about the m203 pencil section showing.

bigbore  [Industry Partner]
5/4/2010 7:46:59 AM
I'll post a pic this afternoon
Catman2  [Team Member]
5/4/2010 5:57:50 PM
Originally Posted By bigbore:
I'll post a pic this afternoon


cool, thanks

bigbore  [Industry Partner]
5/4/2010 9:04:50 PM
Catman2  [Team Member]
5/4/2010 10:55:17 PM


Thanks Bigbore.

Since you cut a reccess or stepdown before the shoulder did you have to lay the angle back on the shoulder
so it's less steep?
bigbore  [Industry Partner]
5/5/2010 9:52:27 AM
the step you are seeing before the taper is the collar for the ops mount, not the barrel.
Catman2  [Team Member]
5/5/2010 7:33:05 PM
Originally Posted By bigbore:
the step you are seeing before the taper is the collar for the ops mount, not the barrel.


Really, don't confuse this with questioning you but if we're talking about the collar to the left of the taper it looks absolutely seemless, as in good work.


bigbore  [Industry Partner]
5/5/2010 8:20:20 PM
here is a pic of an M4 barrel cut to 11.5 with the ops collar
Catman2  [Team Member]
5/5/2010 8:37:16 PM
Originally Posted By bigbore:
here is a pic of an M4 barrel cut to 11.5 with the ops collar
http://www.adcofirearms.com/detailpics/m4spkg.jpg


You know, that don't look bad at'tal. I think an A2 FH on an M203 cut looks goofy but the step down would actually make a longer EA2 like I plan to put on or a Phantom stand proud and on purpose.