Armory Sponsor
Posted: 12/23/2009 7:02:46 PM EDT
|
Working on getting a 2A1 Enfield, and will be loading for it. Now several years ago, before I was told there's a difference I shot several boxes of .308 through one with no problems. But after getting into reloading I found out there's a pressure difference. Problem is, my manual lists .308 and nothing for 7.62 NATO.
First question, how much do I reduce from .308 listings for 7.62? Second question, How much is the pressure difference between the two? I'm aware of the "back off 10% and work up from there" wisdom, and tend to keep my loads on the conservative side anyway, but is 10% off .308 enough when talking about a technically different caliber? |
|
Quoted:
Working on getting a 2A1 Enfield, and will be loading for it. Now several years ago, before I was told there's a difference I shot several boxes of .308 through one with no problems. But after getting into reloading I found out there's a pressure difference. Problem is, my manual lists .308 and nothing for 7.62 NATO. First question, how much do I reduce from .308 listings for 7.62? Second question, How much is the pressure difference between the two? I'm aware of the "back off 10% and work up from there" wisdom, and tend to keep my loads on the conservative side anyway, but is 10% off .308 enough when talking about a technically different caliber? Some commercial SAAMI 308 ammo can be loaded hotter than NATO speced ammo. This being said, just load at the lower end of the scale with whatever components you plan on using, keeping an eye on pressure. Unless you have a copper crusher system, or a piezo-electric transducer pressure dohickey, you'll not know what's what, anyhow. You should be fine running in the middle of the pack, at least concerning maximum .308 pressures, which I believe are in the mid 70,000s. Chris |
|
7.62 Nato is loaded to 50,000 CUP .308 Win is loaded to 62,000 PSI Note the different measurement units. In Theory CUP=PSI but it really does not. Sometimes it's more, sometimes less, and the only way to know how they compare in a given cartridge is to have some very expensive equipment. For the 7.62 50,000 CUP ~ 58,000 PSI. For the Ishipore I personally would stay 5% below the .308 max loads if I did not have separate 7.62 data. YMMV. |
| Load with 7.62 specs as your target. If your shooting 150gr. bullets stick to loads that give mil spec velocity of around 2750fps and stay off the ones listed for 2900fps. Some manuals do list loads for semi-auto rifles like the M1A, these should be at 7.62 spec but look carefully. Factory 168gr match works well in my jungle Ishy so I load to the equivalent muzzle velocity of 2450fps. This process has worked well for me in my Ishi Enfield. |
|
Quoted:
Working on getting a 2A1 Enfield, and will be loading for it. Now several years ago, before I was told there's a difference I shot several boxes of .308 through one with no problems. But after getting into reloading I found out there's a pressure difference. Problem is, my manual lists .308 and nothing for 7.62 NATO. First question, how much do I reduce from .308 listings for 7.62? Second question, How much is the pressure difference between the two? I'm aware of the "back off 10% and work up from there" wisdom, and tend to keep my loads on the conservative side anyway, but is 10% off .308 enough when talking about a technically different caliber? If you can get your hands on a Hornady reloading manual, it lists loads for Service Rifle in 7.62x51; these are the NATO spec loads you're looking for. |
|
If you can chronograph your ammo, then see what 7.62 NATO ammo gives you for velocity in your Ishy, and then chronograph your workups and stop in the same velocity area. This is your best and most accurate bet for duplicating 7.62 pressure (as long as you are using powders of the correct burn rate that are popular in 7.62/.308 loads). Basically velocity is a function of pressure.
A chronograph is like a speedometer in a car, you can guess or extrapolate your speed, but knowing makes all the difference. |
|
Say it this way................
For all practicle purposes................... YOU will NOT (usually) find reloading dies in 7.62 Nato........you will find them marked/made in .308 Win. As it was pointed out............7.62 Nato and .308 Winchester ammo are NOT exactly the same thing. And, 7.62 Nato and .308 Win chambers differ. See the specs for the headspace gauges and note the differences............if you don't believe me. BUT, for reloading................just use the dies marked .308 Win. and use the load data in your manual for .308 Win. Paying attention to the brass that you use (yes, it matters) and staying within the parameters set in your manual. In other words............follow your reloading manual's rules/warnings and data. AND............ USE a case gauge to check your ammo. Usually, the ammo gauge (headspace/sizing gauge) that you'll find will be marked .308 Win. Don't worry about it...........just load your ammo "correctly." Aloha, Mark |
|
I recently experienced the following:
Win 7.62x51 brass 178gr AMAX CCI BR2 primers 43.5gr RL15 2.800 COAL 2625 FPS (chrono was 15 feet from the muzzle) Win .308 brass 178 AMAX CCI BR2 primers 43.5gr RL15 2.800 COAL 2515 FPS (again, chrono was 15 feet from the muzzle) pay attention to your brass, pay attention to your head stamps, and pay attention to the max charges listed. I had to bump my .308 loads up to 45.0gr to bring the velocity up to my 7.62 load. |
|
Colt45guy listed where the real concern should be. The difference in case weight between G.I. (178 grains w/o primer) versus commercial Winchester (155 grains w/o primer) is the result of thicker walled brass in the military case. You must reduce charges when reloading military brass or risk damage to your rifle, your self and your pride.
I second the recommendation that you consult Hornady's latest manual #7 and use their service rifle loading data. Reduce by at least 1.0 full grain or more if using military surplus brass. Colt45guy's data reflects a 2.0 full grain difference between his identical charges and the difference in velocity. .308 usually sees a 50 fps change per grain of powder on average. He got 110 fps more velocity using an identical charge in military surplus brass. |
Armory Sponsor