Reaming .223 Chamber

[4 Liberty]

How difficult is it to ream a .223 chamber to 5.56 NATO chamber?

 

[Gunner223]

Should be real easy. I don't think you will even need a reamer. I always thought the .223 and the 5.56 were identical.

Don

 

[mike in co]

i think the neck throat are different......a little longer in 5.56

if you new the original reamer maker it would be easy....
without it, still not hard....

mike in co

 

[Stonewall]

I do believe that there is a specific reamer designed to do this.

It just cuts the neck and throat.

I read about this on a forum but don't remember which one .....



Neck and Throat 5.56 Reamer


http://www.m-guns.com/tools.php

ftp://ftp.fwpubs.com/Outbound/Direct%20Brands/GD2013_AR15.pdf




Glenn

 

[Mike Bryant]

I saw a post on Brownell's facebook page concerning the differences between the .223 and the 5.56. Not much difference between the two. It looks like the main thing is freebore diameter is a few thousandths larger on the 5.56 and leade angle is a little different. Most all the differences are minor.

 

[4 Liberty]

Found the answer......if a reamer is used the headspace must be checked as there are, according to Smith and Wesson, so many different reamers making so many different .223 chambers that you don't know what you are getting into. If the headspace is off you have to break the barrel loose and adjust and then restake it.
Midway sells the tool you need and it is adjustable. You need to find the exact leade/throat extension to ream in. The danger of 5.56 NATO in a SAAMI .223 chamber is that it is longer and pre-engages the rifling thus creating up to 20,000 extra psi.

PTG Uni Throater Hand Throating Reamer 30/22 Caliber High Speed Steel MIDWAY USA 116 EACH
http://www.midwayusa.com/product/71...-throating-reamer-30-caliber-high-speed-steel 30 CAL BACKORDER PTG/MIDWAY #: 712693
http://www.midwayusa.com/product/22...roating-reamer-22-centerfire-high-speed-steel 22 CAL IN STOCK PTG/MIDWAY #: 224529

 

[4 Liberty]

I checked the case necks on the .223 and the 5.56 NATO and I got an average of .249". So I wouldn't want anything to ream the neck, just extend the throat and thus the leade.

 

[4 Liberty]

I think it's the freebore that matters, and by extending the throat we would increase the freebore. Question is how much. I've seen .223 and 5.56 differences of .077" but that is not much. I would extend it the difference between the OALs as this determines if the bullet prematurely engages the rifling, which is the main cause of dangerous pressure build-up.

 

[mike in co]

sorry but i think if you check..the max oal for BOTH rounds is 2.260.....its where a given bullet hits the lands and the load that are going to set up the pressure....

if you check m855 and m193 i think you will find both are SHORTER....

MIKE IN CO

I think it's the freebore that matters, and by extending the throat we would increase the freebore. Question is how much. I've seen .223 and 5.56 differences of .077" but that is not much. I would extend it the difference between the OALs as this determines if the bullet prematurely engages the rifling, which is the main cause of dangerous pressure build-up.