The Firing Line Forums

Go Back   The Firing Line Forums > The Skunkworks > Handloading, Reloading, and Bullet Casting

Reply
 
Thread Tools
Old April 2, 2012, 09:03 PM   #26
Gunplummer
Senior Member
 
Join Date: March 11, 2010
Location: South East Pa.
Posts: 1,455
Again, I do not care what your position is on chamber specs as it came from bad information. SAAMI did not draw the specs for the military. I think Frankford arsenal knew what it was talking about. Putting up a smoke screen of information that does not pertain to the topic has no affect on a guy that has made chamber reamers from prints, from castings, fired brass, and the occasional wildcat. Some body explain to me how you can have thicker brass but not affect the neck diameter in the chamber? Military 30.06 and .308 brass has been known to be tight in civilian guns at the neck area. A lot of reloaders used to shave or ream the necks to thin it out. It is possible to use thicker brass and just have less case volume and basicly the same O.D. It is not possible to do that at the neck. It does not take much before you have a bad seal, especially with heavier brass, so the military chamber neck size is not overly large for the case that was intended for it.
Gunplummer is offline  
Old April 12, 2012, 10:27 AM   #27
Unclenick
Staff
 
Join Date: March 4, 2005
Location: Ohio
Posts: 10,280
Gunplummer,

I think I've solved the neck turning issue you mentioned. I'm assuming you were referring to .308/7.62 when you mentioned you remembered fellows having to turn military necks thinner. I got hold of a copy of the declassified STANAG 2340, edition 3, Annex sheets 1-4 and Annex B (chamber) drawings of the 7.62 NATO cartridge. The maximum case dimensions are identical to the SAAMI spec, exactly as Sellier & Bellot said. The NATO drawings also use the modern 0.400 inch shoulder datum (see below) for headspace, rather than the old method of breech face to body/shoulder intersect. This change was made because it gives a common diameter to case and chamber shoulders, where the old method, because the case is narrower than the chamber, has a longer number for the case than for the chamber. Also, it eliminates having to guess where the intersect lies inside the chamber metal when that corner has its allowed radius, and where it is in the air outside the case when the case body/shoulder corner has its allowed radius.

There is one significant and two minor differences in the NATO and SAAMI specs. The important one (to my mind) is the NATO design specifies brass hardness test numbers at specific locations on a sectioned case head and along locations on the case, while SAAMI leaves that to the manufacturer's discretion. That accounts for why NATO spec brass holds up better in self-loaders; its hardness is controlled. The two minor ones are that the SAAMI tolerance for finished cartridge COL allows for shorter cartridges than NATO does, and the SAAMI case length to the headspace datum diameter on the shoulder is 1.634" -0.007", while NATO uses 1.634" -0.006". So the NATO minimum case is 0.001" longer than the SAAMI minimum length case.

Of particular interest to the neck turning issue that the NATO maximum finished cartridge neck diameter over the bullet in a finished cartridge is the exact same 0.3435" that SAAMI specifies. That means the NATO case will fit any standard SAAMI minimum diameter chamber with 0.0007" clearance to spare at the neck, because the SAAMI neck mouth is 0.3442" minimum.

The problem comes with match chambers. Match chambers are smaller in neck diameter than the SAAMI standard chamber. The Clymer reamer specs show the M14/M1A match reamer for Lake City M852 match ammo has a case mouth diameter of 0.3430", half a thousandth too small for either a NATO or SAAMI maximum case necks. Palma Match chambers are even smaller at 0.3400". But Lake City never made M852 necks that thick. The spec allows necks as thick as 0.0175", but Lake City, like commercial manufacturers, made M852 brass necks about 0.0155" thick on average (their extra thickness is all near the head). Over the Sierra .308" diameter 168 grain MatchKing, that's an outside neck diameter of 0.339". So M852 not only fit the special M852 match chambers, but they'd fit the Palma match chamber, too. But bring in some foreign made NATO ammo, or possibly even some non-Lake City domestic NATO ammo with 0.016" to 0.0175" necks, and suddenly the match chambers won't let them in.

Bottom line: It's the chamber specs and not the cartridge specs, unless the cartridges were out of spec. That's also possible. Read through this document until you get to 7.62 information.

__________________
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member
Unclenick is offline  
Old April 15, 2012, 09:47 AM   #28
JRLSH
Member
 
Join Date: October 26, 2011
Posts: 30
Question?

OK, forgive my ignorance then. According to another post you should not shoot 5.56 ammo in a .223 barrel. What will happen if you inadvertantly do? Will it ruin the barrel? Or is it a matter of case size? Sorry if this question seems stupid...
__________________
JRL____________

If you heard the bang,
You weren't the target.
JRLSH is offline  
Old April 15, 2012, 02:49 PM   #29
Unclenick
Staff
 
Join Date: March 4, 2005
Location: Ohio
Posts: 10,280
What will happen is it will shoot. The peak pressure spec is higher for 5.56 NATO than for U.S. commercial ammo, but not as high as the proof load spec for commercial firearms chambered in .223 Rem. Also, the Europeans load their 5.56 and .223 to the exact same 62,366 psi MAP and commercial guns handle their .223 Rem just fine and you can buy that ammo here; Sellier & Bellot, Norma, and Lapua ammo are examples. No special warnings exist against using those come from any gun makers. US commercial .223 Rem ammo is loaded to the lower SAAMI 55,000 psi MAP spec, which will make throats last longer, but I've never seen a warning to use only domestic ammo in an American made .223 firearm, either.

Bottom line, no problem with shooting 5.56 in .223 has ever come to my attention, except where it turns up in some folk's imaginations.
__________________
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member

Last edited by Unclenick; April 17, 2012 at 08:52 AM. Reason: typo fix
Unclenick is offline  
Old April 15, 2012, 09:52 PM   #30
riggins_83
Senior Member
 
Join Date: January 19, 2009
Location: Wherever I may roam
Posts: 1,483
Generally 5.56 runs at a higher pressure and headspacing spec for 5.56 is a bit longer than 223 rem.
__________________
l've heard police work is dangerous. Yes, that's why l carry a big gun. Couldn't it go off accidentally? l used to have that problem. What did you do about it?
l just think about baseball. -Leslie Nielsen
riggins_83 is offline  
Old April 15, 2012, 11:50 PM   #31
Mike-Mat
Senior Member
 
Join Date: June 1, 2010
Location: Phoenix area
Posts: 361
Here's the dimensions for both cartridges. They are exactly the same.

223
http://en.wikipedia.org/wiki/File:.223_Remington.jpg

5.56
http://en.wikipedia.org/wiki/File:5.56x45mm_NATO.jpg

If you toggle between those 2 drawings, You'll see they are exactly the same.

Mike
__________________
Mike Mattera - Tips For Mfg
Video Training For CadCam Systems
http://www.tipsforcadcam.com
Mike-Mat is offline  
Old April 16, 2012, 01:15 AM   #32
Gunplummer
Senior Member
 
Join Date: March 11, 2010
Location: South East Pa.
Posts: 1,455
This change was made, that change was made, Yada-Yada-Yada. There was a change. Yes, NOW everybody claims to be in sync. I don't really care as I do not shoot surplus ammo any way.
Gunplummer is offline  
Old April 16, 2012, 12:51 PM   #33
wncchester
Senior Member
 
Join Date: December 1, 2002
Posts: 2,832
For reloaders the effective difference between '5.56' and '.223' is the pressure when the bullet passes the gas port on autoloaders.
wncchester is offline  
Old April 17, 2012, 08:57 AM   #34
Unclenick
Staff
 
Join Date: March 4, 2005
Location: Ohio
Posts: 10,280
Mike,

Those Wiki drawings appear to show different radius specs for the corners of the shoulder with the neck and body. Neither is an official drawing, though, and they lack the tolerance specs. After getting hold of the STANAG drawings for the 7.62, I've not yet got them for the 5.56, as it appears they may still be classified (the government site I used for the 7.62 drawings doesn't let me at the 5.56 drawings). I'll have to verify if that's the case or not (no pun intended). But I don't see a reason they'd be different any more than the 7.62 turned out to be.
__________________
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member
Unclenick is offline  
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 02:35 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2014 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Contact Us
Page generated in 0.07997 seconds with 7 queries