M1A headspace

[buckshot85]

Tim, if you headspace a new barrel for 7.62 nato could i safely fire .308 win? how about vice versa?

[Punch The Clown]

Buckshot, I've been using 7.62 ammo in my autoloaders as the brass is way stronger than the .308. Most of the FAL guys allow an extra .002 in the headspace for the NATO ammo, but I set my FAL exactly to .308 spec and it loves 7.62 anyway. Not Shuff -just my experience.

[timshufflin]

By definition;

- The chamber of a .308 is acceptable to 7.62

- The chamber of a 7.62 may not always be acceptable to .308

Even though both cartridges have the exact same outer dimensions, the 7.62 has a thicker case wall at the base thus being able to handle the more generous headspace for it.

[buckshot85]

By definition;

- The chamber of a .308 is acceptable to 7.62

- The chamber of a 7.62 may not always be acceptable to .308

Even though both cartridges have the exact same outer dimensions, the 7.62 has a thicker case wall at the base thus being able to handle the more generous headspace for it.

so, that being said, when i send my parts to you for installation, you will then set the headspace for .308 and I will still be able to shoot 7.62? am i following ya right?

[Punch The Clown]

.308 Winchester----------------------------------- 7.62x51mm NATO
GO 1.6300-------------------------------------------------- 1.6355
NO-GO 1.6340---------------------------------------------- 1.6405
FIELD REJECT 1.6380---------------------------------------- 1.6455


OK, the GO on a 7.62 is a little more generous because the assumption is that a rifle used in combat will probably be a bit on the dirty side and chambering problems wouldn't be popular. The field reject is way more generous on a 7.62 because the brass is much stronger, so a rifle with excessive headspace for a .308 cartridge is perfectly safe with a 7.62. Notice that the NATO allows almost .008 more headspace. As far as pressure goes the specs are mis-interpreted as one is given in cup and the other in psi. Basically they're about the same.

Soooo, a .308 is safe in a 7.62 rifle as long as the headspace meets .308 specs. If the headspace exceeds .308 specs but is less than the 7.62 field spec you're limited to 7.62 brass.

[buckshot85]

thanks for the info. PTC. i am using a brand new barrel. a criterion, non-chrome, 22" GI profile. so Tim will have to ream the chamber. my point here is understand what are chamber numbers and what can i shoot in it. I also do not reload and more than likely will be shooting commercial stuff unless i can get a hell of a buy on 7.62. basically, i want the ability to shoot both.

[Prince Humperdink]

Yep,You can shoot both in a .308 chambered Rifle.

[buckshot85]

thanks guys! where has the Shuffster been lately? haven't heard much from him.

[timshufflin]

so, that being said, when i send my parts to you for installation, you will then set the headspace for .308 and I will still be able to shoot 7.62? am i following ya right?

Correct.......

[buckshot85]

boy, sometimes the crumbs on the trail have to be the size of a VW for me to follow. :confused:

[mikebaker1129]

There is a headspace that is considered to be the "sweet spot" where you can shoot either one. Gus Fisher has posted this # a few times over on CSP and the M14 forum .I think it is 1.632 if memory serves me correctly .
BTW I shoot mostly surplus.Some is better than others,and some shoots in some rifles better than others,try to find what shoots best in yours for the $. SA,German,Portugese,Hirtenberger,Australian,Indone sian,Greek,Malaysian,RadwayGreen 7.62. Pretty much anything I can get my hands on cheap,that is not total junk. I bought most of this stuff when it was reasonable.
I even bought some of the Pakistan stuff to try out for $75 per can,I do not expect it to be very accurate,but it should all go bang.

[buckshot85]

i have read some his stuff over there. i do not plan to shoot competition with this rifle and i do not plan to shoot the hell out of it either. i just want one and want the convenience of nato and commercial. i was just curious how Mr.Tim chambered them because i plan on sending it to him to set-up and maybe do some park work also.

[timshufflin]

I used to try for the "sweet spot". After talking to the folks at Manson reamers, I just ream for .308 now.

[buckshot85]

are the feed ramps on a 14 pretty tough on soft points or not?

[Punch The Clown]

I was reading the parallel thread over at the CMP forum. The talk about the dangers of insufficent throat came up. Most rifles come with very generous throat, and ammo custom loaded to minimize jump are often too long to even fit in the magazine. Match chambers with custom reamed throats are another story.