I doubt there is 'definitive data' about the powder type and charge amount - you might find MV specs - e.g for M118LR MV at 70 feet, 2575 +/- 30 fps.
The powder type can change depending on availability, price, etc. The powder weight is determined by testing the batch of powder and loading for the desired MV.

There are 'data sheets' that give info about how a particular batch of ammo was produced, and its test results - but that doesn't mean that ALL batches are produced the same way, or give the same test results.

Jay Kosta
Endwell NY USA

 

The exact charge weight varies from lot to lot as necessary to meet the velocity requirements.

The definitive source for the type of propellant is the drawings. And, generally, the exact type of propellant/primer combination may not be the exact same commercially available, stuff you have.

For M118LR - 175 SMK, #43 primer and Reloader 15 loaded to 2650 fps, which is a pretty hot load.

 

For M118LR - 175 SMK, #43 primer and Reloader 15 loaded to 2650 fps, which is a pretty hot load.

Technically, it is supposed to be 2,575 ft/sec ± 30 ft/sec, at 78 feet (26 yards) from the muzzle, with a standard deviation of the velocities not greater than 28 ft/sec, out of a 22 inch test barrel with a unique chamber with weird lead, so what velocity and pressure you see doesn't easily correlate to any service rifle unless you have a bunch of rounds to test.

 

Current M118LR is 43 grains of RL 15 in a Lake City LR case.

Mk 316 Mod 0 is 43 grains of IMR 4064 in a Federal case, Match primer.

I believe the 118LR used more powder at one point, but was backed down to 43 because of high pressures in the desert.

They both send the 175 SMK to 2650 out of my M1A. I consider both loads to be top end for an M14 and use a Schuster ported/overbored gas plug when shooting either. The rifles I have used like the Mk 316 load better.

 

M118LR has had a few variations during it's life - the initial loadings for it in 1995 used WC750 (42.8grs) and was not intended for use in an M14. MV in an M24 ran 2660 (24" bbl)
From 1996 - 1999, 118LR used 43.8 of WC750 - and this ran 2750 out of an M24. The last lot of that ammo was LC99C173-013. Definitely do not use that in an M14.
Later in 1999, the recipe changed - the powder was switched from WC750 to REL15. That loading used 44.3grs. MV out of an M24 ran 2750. The impetus for that was improved temperature sensitivity.
In 2002-2003 the Army & the Marines began using M118LR in their M14's in the desert and as can be expected - there were reports of damaged/broken op rods and other parts from deployed units in Iraq.
In 2003 & 2004 the load was reduced again - and it varies based on, as Lysander correctly stated, they load to a velocity standard. This load varied between 42.8 - 43.1 of REL15. Velocity ran 2709 from an M24 and 2685 from an M14. Both the Army and the Marines authorized this ammo for use in the M14DMR & M110 rifles. Performance in the M110 was poor due to the loss of velocity (20" bbl).

Mk316 is another animal altogether. Developed in 2008 as a joint SOCOM/Navy effort with Federal Cartridge Co. That stuff started life with 41.7 of IMR4064 with flash reduction modifications. The brass was specialized for this requirement. It had more uniform neck concentricity and beefed up web/case head area. They use Federal 210M primers.
Out of an M24, MV runs 2640. It was not intended for use in M14's, but rather the MK11 and the MK17. It should be ok to use with an M14.
Federal really pulled out the stops for this ammo - each lot is loaded with single lots of primers, cases, bullets and powder - no mixing or blending. Consistency is amazing - (which is what we hand loaders do anyway.)
Your results may vary.

 

Thanks for the very helpful information.

The posted info covers what I was looking for. You guys are great.

 

Federal also sells the Mk316 Mod 0 cartridge direct to the public. It is not cataloged, but the code is GM762M2. It will have FC and a 2-digit year as the headstamp. Unpolished case, purple primer sealant.

Per Federal, this ammo has not gone thru the government selection process, so it cannot be boxed as Mk 316 Mod 0.

 

BTW - I loaded the 175SMK in Federal cases with 42.0 grains of H4895 and WLR primers - MV was ~2625, and they worked OK at 1000 yards in 308Win
M1 Garand.

Jay Kosta
Endwell NY USA