Which .308 Ammo Is Safe?
Just got my hands on a minty .308 Ishapore Enfield MKIII No.1 mfg in 1967. Intended uses are target shooting and deer shooting.
Went to buy some more .308 ammo at the local gun shop but the owner warned me against shooting anything but the NATO .308 ammo out of the Ishapore Enfield. He said that the pressure from the commercial sporting Winchester .308 round is much higher than the NATO .308 round and will cause the rifle to "blow" when fired.
So my question for the Experts is which .308 ammo is safe for shooting in the MKIII No.1 .308 Ishapore Enfield?
Thanks.
Pack slow, fall stable, pull high, hit dead center.
Went to buy some more .308 ammo at the local gun shop but the owner warned me against shooting anything but the NATO .308 ammo out of the Ishapore Enfield. He said that the pressure from the commercial sporting Winchester .308 round is much higher than the NATO .308 round and will cause the rifle to "blow" when fired.
So my question for the Experts is which .308 ammo is safe for shooting in the MKIII No.1 .308 Ishapore Enfield?
Thanks.
Pack slow, fall stable, pull high, hit dead center.
0
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There are differences between .308 and 7.62X51MM Nato rounds. One of which is headspace and the other is pressure. If the gun is marked .308 use .308. If it is marked 7.61X51MM Nato then use the military rounds. Here are the specs:
Chamber Headspace Gauges
.308 Winchester
GO: 1.630"
NOGO: 1.634"
FIELD REJECT: 1.638"
7.62 x 51mm NATO
GO: 1.635"
FIELD REJECT: 1.6455"
Chamber Pressures
.308 Winchester
MAP: 62,000 psi
MPSM: 66,000 psi
Minimum Proof Pressure: 83,000 psi
Maximum Proof Pressure: 89,000 psi
7.62 x 51mm NATO
Maximum: 50,000 psi
Proof pressure: 67,500 psi
Sources: .308 Winchester data from ANSI/SAAMI document Z299.4-1992, Pressure and Velocity, Centerfire Rifle Sporting Ammunition
7.62 x 51mm NATO headspace data from Jerry Kuhnhausen's M1/M1A shop manual.
Pressure data from TM 43-001-27: Army Ammunition Data Sheets Small Caliber Ammunition
Jim Kammerer0 -
Hi,
Great question. There is too much debate on this issue and most of it is uninformed and misunderstood.
IMHO, I think the 7.62 Nato and the 308 Winchester are largely interchangeable since you will be using an older military rifle. A match chamber in either caliber might be a different story.
I think the real difference between the two cartridges is headspace and cartridge case construction, not pressure or cartridge dimension.
The 308 commercial and 308 military (7.62x51mm) are technically different because the 308 commercial was released by Winchester several years before the Army standarized the T64E3 as the 7.62mm. Chamber pressure measurements are irrelevant to settle the difference, because SAAMI standards and the government design specifications measured pressure by differnet methods that were not comparable. Therefore, pressure cannot be equally compared. Also as previously pointed out, chamber blueprints for the two cartridges are different, although they are only minimally different.
The issue of dimensions is largely acedemic because nobody makes 7.62mm ammo that won't chamber to the .308 chamber dimensions. Therefore, 7.62mm military will chamber adequately into .308 commerical chambers and vice versa.
That being said the headspace on military 7.62mm arms can and does run long for functional purposes. To compensate for the longer headspace Nato brass is necessary since it is stronger than commercial brass. The heavier brass prevents blowouts in a rifle with long headspace while the commercial brass is not as thick. This is the reason Lake City brass is so popular - It is strong enough to withstand the pressures generated from the longer headspace without rupture and it is reloadable.
In some 7.62mm rifles the chambers are dimensionally longer. Thus, using commercial ammo in such a rifle may increase chamber pressure due to different headspacing.
The only real way to determine is to headspace the Ishapore and see what it measures, but to be absolutely safe, use Nato marked cartridges. I would not be surprised to find that tolerances on an Indian made Enfield will be neither SAAMI nor Nato spec and would vary from rifle to rifle.
All the above information is a summary of information from the following links:
http://www.fulton-armory.com/308.htm
http://www3.sympatico.ca/shooters/7_62vs308Pt2.htm
You may read it yourself and don't feel bad if you end up confused because some of the information here is misinterpreted, especially pressure. After reading all the above, you may arrive at a completely different decision than I have.
Regards,
Heavyiron
"If I don't see you nomore on this world, I'll meet you on the next one, and don't be late!" - Jimi Hendrix0 -
I shot all manner of us made factory ammo out of my ishy 2a1 when I had it. No problems, the headspace never grew. I would not and did not shoot any "light magnum" or heavy handloads out of it though.
.0 -
If I may interject here there are two very different needs to be met with the two different types of ammo. The reason for the long headspace in the military rifles is so that you can run anything through them that resembles 7.62 Nato. The reason you will nearly always find tight tolerances on military ammo is because if it is long there may be that chance that there may be a tight chamber and it will not function. That being paramount in the military case. In the .308 case that was meant for sporting uses it is not generally necessary to ensure it functions as reliably, the emphasis is more on performance from a tighter chamber. And with a tighter chamber you can use a less thick case. If you weigh military cases you will generally find they run around 185 gr. .308 generally runs around 175 gr. This also accounts for the relative measurements that the military used overall in case pressure. Military used 49,500 C.U.P and civilian .308 was 52,000 C.U.P. The measurements that I understood to be not relative were the gas pressures at the port to make the operating system of the semi-auto/auto functions of the rifle work. Those were around 17,000 psi at the port.
In most cases .308 and 7.62 nato will completely interchange. Where you will run into trouble is if you take a civilian .308 and stick it into a loose and weak 7.62 based action and it either blows up or blows gas back at you.
If you take what you have read here seriously, take this rifle into a gunsmith and have it headspaced. After all there may some disagreement as to what the dimensions are or why, but by and large we've all said or alluded to the same thing. It's a good way to ensure what you can do with your rifle. -good luck
We have the second amendment so that all the rest are secure....UNK>0
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