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argyle1812
August 31, 2011, 01:59 AM
im looking for a good 7.62 nato load using 308 brass and IMR-4895 powder please post your favorite recipe! btw is 7.62 nato pressure maximum 50k psi or 58k psi? i cant find a clear answer online.

steve4102
August 31, 2011, 02:54 AM
Pressure for the NATO is 50K CUP which equates to about 60K PSI. Same as the 308.

The cartridge specs for the 7.62 Ball M118, 172gr bullet-44gr IMR 4895,2640fps. That's about equal or maybe a little hotter than 308 load data. Use 308 data and as always, start low and work up.

mehavey
August 31, 2011, 06:58 AM
The cartridge specs for the 7.62 Ball M118, 172gr bullet-44gr IMR 4895,2640fps.
Huh?

http://i55.tinypic.com/2urtchg.jpg

steve4102
August 31, 2011, 07:04 AM
HMMM, got it from here.

http://www.ar15.com/media/viewFile.html?i=32231

mehavey
August 31, 2011, 08:01 AM
We both may be right

http://riflemansjournal.blogspot.com/2010/04/history-lake-city-m118-special-ball.html

The "special ball" and repackaging game kinda confused things. I also remember discussion that the earlier lots were found to be beating up the guns at Perry, and the subsequent loadings were reduced to the lower number. I do know that the case I got about 9 months ago whose box label I showed in post #3 just above and chrono'd in post #4 here:
http://thefiringline.com/forums/showthread.php?p=4722385&highlight=m118#post4722385
were right on posted velocity of 2,550.

It may be a generational thing :) and Uncle Nick/SlamFire may have to weigh in here.

Charlie_98
August 31, 2011, 08:18 AM
By '.308 brass' I assume you mean commercial brass, not military brass... there is a difference.

You also need to specify a bullet or bullet weight and purpose.

My M80 equivalent load is 43.0grn IMR4895 and a 147grn Winchester FMJ (in LC brass with #34 primer,) that's my plinker load. But I also load the 168grn Nosler BTHP for paper punching and long-range shooting.

kraigwy
August 31, 2011, 08:38 AM
43-44 grns of 4895 is fine for 150 grns bullets. But a bit hot for 168-175s.

The M118 was loaded with 42 grns of 4895 but that is a canister lot, the go to round for high power is 41.5 grns of 4895 for the 168 SMKs .

It works, not only in my gun but the 24 NM M14s I had for the Alaska NG Rifle team (when we couldn't get military Ammo). It also matched Federals 308 Match ammo.

Hornady Reloading Manual (7th addition) has an excellent section on reloading the Service Rifle.

The M1A/M14 is a great, accurate rifle, you don't need to un-duly hammer the operating rod to make it work.

Unclenick
August 31, 2011, 10:28 AM
The problem with weighing the Lake City charges is that the powder isn't canister grade, but rather is bulk purchased. It therefore has more variation lot-to-lot than in the blended canister grades handloaders buy. If you look at old load data for the .30-06 NM ammunition, you see through the years that 4895 was used the load charge weight varied several grains because the bulk powder burn rates changed. I'm sure that if you pulled M118 or M852 NM ammunition made in different years, you'd find the charges also varied with the powder lot used.

A few years .30 Cal NM (.30-06) using IMR 4895 and 173 grain 9° BT FMJ match bullet. Note variation from year to year to produce velocities that don't always reflect the change in charge weight.

Charge weight IMR 4895
FA 60; 48.0 gr. 2640 fps
FA 61: 48.5 gr. 2640 fps
LC 62: 48.1 gr. 2685 fps
LC 63: 46.7 gr. 2695 fps
LC 64: 46.0 gr. 2669 fps
LC 65: 46.5 gr. 2708 fps
LC 66: 47.2 gr. 2711 fps

I pulled a bunch of Federal GMM 168 gr. SMK ammo down at one point and found 43.5 grains of IMR4064 that was a good match to the canister grade 4064 I had, and that I could copy that load with my powder. I understand they've since gone to Reloader 15. If they used 4895 before going to 4064, I don't know, since I only pulled down samples from the one lot. You do need to keep in mind Federal commercial .308 cases have more internal capacity than Lake City, so you'd expect the load to have to be reduced a bit for LC brass.

If you look through military ammo specs from before the mid-90's, you find military copper crusher numbers reported as "psi" at the same time a commercial maker would have reported them as "CUP" (I don't know why "CUP" gets caps while "psi" gets lower case, but that's how SAAMI publishes them). The SAAMI conformal piezo spec is 62,000 psi MAP (Maximum Average Pressure). I'll have to check, but I recall SAAMI MAP allows up to 4% deviation from average, so 64,480 psi would be the allowed extreme spread in SAAMI compliant ammo.

The NATO allies use 415 MPa, which the CIP uses for both 7.62 NATO and .308 Winchester. That converts to 60,191 psi, but the CIP measuring system sets the sample point further forward in the case, so it sees a bit of the pressure drop at the bullet base that occurs when the bullet starts moving. That makes them tend to read about 2,000 psi lower than the SAAMI setup does in this pressure range. So the same ammo would measure closer to 62,000 psi in SAAMI equipment.

mehavey
August 31, 2011, 11:04 AM
My solution was to work up the charge that my particular lot of IMR4895 would push a 175SMK out at 2,550 (70 degrF) using Winchester brass. A session at the range and a Temp conversion using QuickLoad got me there in a 2-step.

But Uncle Nick and others are correct that brass manuf/volume and powder lot will make this a custom mix as opposed to a "42.5gr IMR4895-is-the-secret" recipe.

argyle1812
August 31, 2011, 12:17 PM
thanks for all the replies. btw the bullet im using is the 155 gr Hornady A-Max.