M1 NM 30-06 "Go To Load"

[Plain Old Dave]

OK, new update: Most recent published data I have found states the 46gr of IMR 4895 is with civilian brass; the NRA M1 data says reduce by 2gr for milsurp brass. So, 44gr of IMR4895 behind M118 bullets in USGI M72 brass with Winchester LR primers looks like the way to go; checked with Sierra (going to 175SMKs when the 118s run out) and 46 is a near-max load for the M1 data they have. I'd also think that the lower handload might make finding brass somewhat easier. Questions:



1) Will setting my reloading dies with a loaded FA 1960 M72 round get me where I need to be for OAL/cartridge headspace, or do I need a cartridge headspace gauge?



2) Has anybody used a load with what I will be using at 600? That's what these are for; to start with for zero, I intend to use the standard comeup from my 300 zero.

[Maury Krupp]

"OK, new update: Most recent published data I have found states the 46gr of IMR 4895 is with civilian brass; the NRA M1 data says reduce by 2gr for milsurp brass."
All my brass is USGI or HXP and I've never had a problem with 46.0 IMR4895.

"So, 44gr of IMR4895 behind M118 bullets in USGI M72 brass with Winchester LR primers looks like the way to go;"
If you can get the desired velocity (~2640-2700fps). It takes 46.0gr for me.

"...checked with Sierra (going to 175SMKs when the 118s run out) and 46 is a near-max load for the M1 data they have."
Sierra is known for listing the lowest load data out there. Cross-check against a couple other sources, test for pressure signs and desired velocity, then decide.

"1)...do I need a cartridge headspace gauge?"
Yes.

"2) Has anybody used a load with what I will be using at 600? That's what these are for; to start with for zero, I intend to use the standard comeup from my 300 zero."
If you load it to a velocity of 2640fps at 78ft from the muzzle, thousands of people have shot millions of rounds of it; it's a clone of M72 Match. The standard comeup will get you in the black; refine for your conditions and hold.

Maury

[Plain Old Dave]

Interesting... IMR says 46gr is a starting load with 175s, NRA says 46gr is with civilian brass and to reduce by 2gr with military brass. This is confusing; I really wish M72 was not nearly $1/round...

Moving on, though, I do see a number of people talk about the cartridge headspace gage. What will it do that setting up my dies using a loaded round of M72 won't do? If the rounds are full-length sized, won't they fit *any* .30-06 chamber?

[Maury Krupp]

The "conventional wisdom" of reducing the powder charge is based on the idea that GI brass is heavier/has thicker walls and therefore less internal volume.

After weighing random commercial and GI cases empty and full of water, I haven't found that to be true. Both types of cases held comparable amounts of water.

The "conventional wisdom" may have been true at one time but as near as I can tell it doesn't seem to be today.

Still, it's always prudent to start a couple grains below the intended charge and work up just for safety's sake.

I'm not clear on how you intend to set up your sizing die with an already loaded round?

Full-length resizing isn't really the issue anyway; it's cartridge headspace (ie, where is the shoulder?).

A case re-sized (ie, shoulder pushed back) to SAAMI minimum should fit into the chamber of any rifle with a headspace between the SAAMI min and max spec for that chambering.

If the rifle headspace is at min and the case shoulder is at max it may not fit. That's a recipie for stoppages (failure to feed, failure to fire, failure to extract) and even worse, a possible slamfire.

There are two types of case headspace gauges: One type of case gauge measures the actual shoulder position; the other is a simple drop-in min-max "GO-NO GO"

Some reloaders resize to just under the headspace of a specific rifle to reduce stretching and prolong case life. You need a gauge that measures to do this.

Others resize to min to make the ammo usable in any rifle. The drop-in will work for that.

Either way you must ensure the case will fully enter the chamber and the bolt can go fully into battery.

Maury

[Plain Old Dave]

Makes sense about headspace gages; in 10+ years of reloading I have had one Krag round that would not chamber; while annoying in a boltgun, could be disasterous in a gasgun. Thanks for the info, Maury. I figure IMR is the data to go with and they have 46 of IMR-4895 as a starting load with 175 SMKs. If that works well enough (i.e. works the bolt and is good for 150+ at 600 which is about what I scored last time I shot M72 [had gun trouble]), I am done with load development (for now). At this point in my shooting career, I will be better served by getting out and shooting the Course rather than spending who knows how long tweaking handloads.

Other question: Is there any reason to go with one brand of gage over another?

[Maury Krupp]

One brand over another? None that I know of; they'll all do the job.

Maury

[da gimp]

Wilson gages are pretty dern good, & fairly in-expensive. Have them in .308Win, .30-06, .243Win, .223 Rem. Figure they'll out last me by far. Remember to clean ALL case lube off the brass each time before inserting them into a headspace gage.

[PhillipM]

Makes sense about headspace gages; in 10+ years of reloading I have had one Krag round that would not chamber; while annoying in a boltgun, could be disasterous in a gasgun. Thanks for the info, Maury. I figure IMR is the data to go with and they have 46 of IMR-4895 as a starting load with 175 SMKs. If that works well enough (i.e. works the bolt and is good for 150+ at 600 which is about what I scored last time I shot M72 [had gun trouble]), I am done with load development (for now). At this point in my shooting career, I will be better served by getting out and shooting the Course rather than spending who knows how long tweaking handloads.

Other question: Is there any reason to go with one brand of gage over another?

I like my rcbs. If you are serious about resizing to the minimum spec, remove the gas lock screw for your reference cases else the violent extraction stretches them. This phenomenon led me to believe I had too much headspace when I first got the rcbs case mic.