Duplicating m72 ammo

[Morgan321]

I'm trying to duplicate(or improve) the performance of m72 ammo using imr 4895, smk 175, federal 215, and once fired m72 brass. The m72 consistently shoots 1moa for me but is $$$ and hard to find. Gun is a box stock 700 with skinny barrel in a nice stock.

I loaded up some rounds from 46.6 up to 48.0 and shot them at 500yd. All 3.28 inch long. 47.0 and below produced consistently located groups of about 5 inches, very similar to the performance I get from m72. 47.4 and above produced rapidly increasing group sizes (up to 8-9 inches) and the groups moved rapidly high-right as the loads got stronger.

I chronoed five rounds at 47.0 and the results were in the mid 2500fps range with 119 spread and sd of 45. I shot four m72 rounds and they were around 2520 with spread of 24 and sd of 10. The m72 was from 1961, seems amazing for 52 year old ammo!

My scale is a cheap digital, don't even remember where it came from. It only measures in increments of 0.2 grains but seems to be consistent. I weigh bullets and they are always within 0.2 of each other(Amax and smk).

Could a tenth or two of powder variation from my cheap scale cause such a large spread of velocities? If not then what else could I look at? A quick online calculation shows that 119fps spread could be up to 5 inch difference in drop?! I'd love to eliminate that variable!

I had a single round at 49.0 to check for pressure signs, it looked OK. Should I continue above 48.0 to look for the groups to tighten back up? I'm ok with the 2500+ velocity as it's right there with the m72 which just reaches 1000yd for me. But if I could get extra velocity I'd take it.

Suggestions?

PS: in the interest of full disclosure, the ammo was loaded with a lee loader and a hammer. Yes, I know.

 

[Greg Langelius *]

Some very old research of mine suggests a load of 50gr IMR-4895 for the original M72 cartridge. The same source also reports the exact same charge for the M2 ball and M2 Overhead Fire round. Overhead fire does not equate with AA usage, but rather to ammunition assigned for use to fire over crawling/infiltrating trainees. We veterans have all been there.

I use IMR-4064 for my Garand loads, basically 50.0r of IMR-4064 with the Hornady 150gr FMJBT. I took this load directly from the NRA's Garand reprint, and they recommend 47gr of IMR4064 for the 175gr bullet weight range, and 46gr of IMR-4895.

First, this research source gives only an estimation, as the arsenals loaded according to velocity, not charge weight.

Next, powder lots, the entirely different bullet (173gr arsenal vs 175gr SMK) spec, bore length, and the bore's land/groove diameters all exert significant variance on load pressures and actual velocities.

Lastly, the Garand loads are considered to be downloaded to avoid issues with the crucial Oprod alignments.

Bolt gun requirements are not the same, and barrel profiles, etc. will dictate significant variances in charge weight/accuracy nodes.

One or two tenths is not likely to cause large velocity differences in a casing with the larger capacity of the .30-'06.

There are so many other influences, including chrono issues, that I have ceased using a chrono, and make all my load development decisions based on the target, pressure signs on the fired casing, and repeatability.

At some point, I have often found that chrono indications can become as confusing as they can be helpful. At the end of that trail, it's the target that speaks the truth that counts the most.


Greg

 

[Morgan321]

To narrow the scope of my question - given that the m72 ammo is extremely consistent for me and the very tight velocity spread it has, I can't help but feel the large velocity spread of my ammo is the primary cause of it not grouping as well as the m72.

The brass is all once fired in my rifle. It doesn't get annealed or anything fancy like that. I haven't even been cleaning it much beyond a quick brush inside the neck and a primer pocket brush. Could thorough cleaning reduce velocity spread?

I have no experience, but the "slop" in my cheap scale seems to be around 4-5 granules of powder which is too light for it to even register. I can't imagine a few granules of powder making a difference big enough for to notice with a cheap gun?

I've ordered a proper press, next time around I am going to clean the brass and use a proper press to load the rounds and go from there.

Given that the 47.0 load performed very similar to the m72(which is the best factory ammo I have found out of 6-7 brands), should I try 3% higher, around 48.5? I only test up to 48.0, and had a single 49.0 round to check for pressure(no signs).

 

[Morgan321]

Bueller?

 

[Heman]

I have a slow lot of 4895 pulldown and run 47.5gr of 4895 with a 175SMK which matches M72 specs. With new IMR4895 I think it is around 46gr. With the M1 you don't want to push the load. I've never seen where 50gr of 4895 was the charge for the M72 ammo. I know the lots did vary due to the differences in powders but only time I've seen 50gr was in M2 ball. If 47gr shoots well then stop there and start practicing.

 

[338RUM runner]

tag for later

 

[sinister]

Here's your Army data sheet for M72 (Note: Litz' book has Sierra 173s at 1.295" and 175 Match Kings at 1.240"):

 

[Morgan321]

How come my m72 ammo is only 2520fps? The chrono was 10 feet from the muzzle. Temperature was around 50f, but that can't account for so much difference can it?

Would it be worthwhile to test in the 48.5-49 range? (About 3% above the 47.0 that performs similar to72?).

To clarify, the gun is a 700, not an m1. The m72 ammo is simply the best performing ammo I have found out of 6-7 factory rounds I have tried.

 

[sinister]

...and what year was it loaded?

There's a reason it was surplused.

The M1's barrel is 24", as is the Springfield's.

 

[Morgan321]

I was wondering about the age... 50 years seems like a lot, but it shoots great and those velocity numbers are excellent.

And being fired in a bolt gun I figured would give a bit more velocity if anything since there's no gas bled off for the action? My barrel is 24 inches.

 

[Heman]

Did some quick reading over at German's Salazar's blog and FA didn't produce match ammo from 1940-1957 and didn't start production again till 1958, when they started up this was with M72 and the charge used was 48gr of 4895. Why I'm skeptical of that army fact sheet.

The Rifleman's Journal: History: US National Match Ammunition - Ray Meketa

Then all production went to LC in 1962 So when it lists competition weapons in the above army posting it is referring to the M1 Garand or I'm guessing it would have been M70 Winchester's as the 1903's were gone by then from the military teams. With this in mind I would be hesitant to shoot the 50gr charge through a M1 Garand as the chamber pressure will be above the 50,000psi listed. I'm guessing the 4895 they had was slower burning than what we have hence why everyone says in the 46-47gr range. The surplus 4895 I have is from pulled AP ammo from Jeff Bartlet and the charge in this ammo was higher than listed in the manual due to the burn rate of the powder. However since this is a bolt gun work it up and find out what shoots the best.

 

[Greg Langelius *]

How come my m72 ammo is only 2520fps? The chrono was 10 feet from the muzzle. Temperature was around 50f, but that can't account for so much difference can it?

Would it be worthwhile to test in the 48.5-49 range? (About 3% above the 47.0 that performs similar to72?).

To clarify, the gun is a 700, not an m1. The m72 ammo is simply the best performing ammo I have found out of 6-7 factory rounds I have tried.

I repeat:

First, this research source gives only an estimation, as the arsenals loaded according to velocity, not charge weight.

Next, powder lots, the entirely different bullet (173gr arsenal vs 175gr SMK) spec, bore length, and the bore's land/groove diameters all exert significant variance on load pressures and actual velocities.

Add factors like jacket thickness/composition, core hardness, bore fouling state to the mix, as well. For example, a reduction in bore drag results in a lower velocity, as moly shooters know quite well.

The spec sheet shown here was not my source.

Greg

 

[Heman]

Greg wasn't doubting your source just I haven't heard of charges up to 50gr being used to get the velocity. I know in tearing apart M2 ball aside from the usual variance associated with ball it is interesting to note the differences in the charges from various lots due to the difference in powder. Question I would like to know is you see surplus IMR-4831 for sale. What was that loaded or used in?

 

[Greg Langelius *]

My understanding from reading the historical monologue on the IMR website is that IMR-4831 was originally formulated to propel the 20mm AA cartridge sometime around the beginning of WWII.

My research on military .30-'06 loads comes from Cartridges of the World, 8th Ed., and the NRA's reprint on the M1 Garand. My Garand load is 150gr HDY .30 cal. FMJBT, 50.0gr IMR-4064, Rem case, and the CCI-200 primer. The info I get from CotW was that the same charge was listed for both the M2 and M72 cartridge. Listed, yes, but used? Hard to tell, considering the note I previously posted regarding arsenal loads being loaded to match the specified velocity, and not to an arbitrary charge weight.

The only load I will recommend from experience is the M2 equivalent load I posted just above. I only use commercially packaged propellants, I haven't seen any surplus IMR-4831, and I use H-4831SC in its place.

Reviewing your earlier posts, I seriously doubt that a military rifle will clearly demonstrate performance differences with +/- .2gr charge variances within a load as large as the .30-'06. I also doubt that a 215 primer is needed, I get very consistent performance with the non-magnum 200 primer, which is clearly adequate to deliver consistent ignition in the .30-'06 case.

My own reloading philosophy centers around keeping the process as simple as possible, and performing those basic steps with consistency and diligence.

Excessive fouling will definitely affect performance, but it takes several hundred rounds fired to generate that level of fouling, IMHO.

That said, I still clean and oil my Garand after each range session. My reasons are that I don't shoot the Garand much more than once a year, it's a historical artifact, I was trained with the Garand in the Marines, and old habits die hard. I don't go to sleep with a dirty Garand in my possession; it's just like grating fingernails on a blackboard for folks like me.

Greg

 

[Alaska]

YEAR HEADSTAMP VELOCITY CHARGE
30-06 M72 Match Load Data

1957 FA 57 Match 2640fps 48.0gr
IMR4895
1958 FA 58 Match 2640fps 48.0gr
IMR4895
1959 FA 59 Match 2640fps 48.0gr
IMR4895
1960 FA 60 Match 2640fps 48.0gr
IMR4895
1961 FA 61 Match 2640fps 48.5gr
IMR4895
1962 LC 62 Match 2685fps 48.1gr
IMR4895
1963 LC 63 Match 2695fps 46.7gr
IMR4895
1964 LC 64 Match 2669fps 46.0gr
IMR4895
1965 LC 65 Match 2708fps 46.5gr
IMR4895
1966 LC 66 Match 2711fps 47.2gr
IMR 4895