CMP Updates Ammo Specifications for 1903s, 1903a3 and M1 Garand

JohnC · Apr 20, 2021

Got this email just now from the CMP

Dear CMP Family,

The CMP advises to not use .30/06 ammunition in M1 Garands, 1903s, and 1903A3s that is loaded beyond 50,000 CUP and has a bullet weight more than 172gr. These rifles are at least 70 years old and were not designed for max loads and super heavy bullets. Always wear hearing and eye protection when firing an M1 Garand, 1903 and/or 1903A3 rifle.

This warning is an update/addition to the Ammunition section in the Read This First manual enclosed with each rifle shipment (M1 Garand manual-page 6 and M1903 manual-page 10).

Civilian Marksmanship Program

CMP originally said up to 180gr is fine in the M1, appears they've backed off a little from that. Perhaps some damage they've seen pop up in armorer's shops? I know there are plenty of videos showing the safety for "hot loads" in M1s, but interesting that the CMP is decreasing their upper limit AND 1903 based actions are lumped in there.

ken792 · Apr 20, 2021

50k CUP is SAAMI max for .30/06. Basically, CMP is telling people it’s ok to shoot max pressure loads as long as they stay under an arbitrary bullet weight, while also saying the rifles weren’t designed for max loads.

They say the rifles were not designed for heavy bullets either, except the M1903 was designed for a 220gr round nosed bullet in the original .30/03.

M1 Ball and M72 match ammo were 173gr, so they exceed that 172gr.

What’s heavier? A ton of bricks or a ton of feathers?

N3uka · Apr 20, 2021

Sure, burst my bubble. I thought the email was a precursor to them shipping my rifles. Guess I still need to wait a few days.

dist1646 · Apr 20, 2021

Must be trying to lawyer proof!

Allen65 · Apr 20, 2021

I wonder if the email was in response to a particular incident? The age statement was odd; age doesn't matter for most steels' strength, only original metallurgy and the stresses (cyclical and momentary) and environmental conditions it has been exposed to.

135sohc · Apr 20, 2021

Allen65 said:
I wonder if the email was in response to a particular incident? The age statement was odd; age doesn't matter for most steels' strength, only original metallurgy and the stresses (cyclical and momentary) and environmental conditions it has been exposed to.

Given the age of most mil surplus guns and the unknown round count each one has cycled.. Age does not matter but it would be safe to assume any mil surplus type gun has probably had way more cycles on it than most here will ever come close to reaching on a 'new' or non mil surplus gun.

I have full trust and confidence in both of my mil surplus guns, being 104 and 84 years old now. But I also keep in mind of their age and knowing I have zero idea of how many rounds they have cycled. The head spacing checks out well in the safe zone but I don't shoot anything beyond new standard factory loads because of their age, wanting to keep all my fingers and not damage (to me) something that is irreplaceable.

Vile Shadow · Apr 20, 2021

Thankfully my Garand is .308, but I personally wouldn’t go higher than 150 gr .30-06 in a milsurp, especially a Garand

Allen65 · Apr 20, 2021

Sling Blade said:
Thankfully my Garand is .308, but I personally wouldn’t go higher than 150 gr .30-06 in a milsurp, especially a Garand

Why? When the Garand entered service, the standard round was M1 Ball, which was a 173 grain projectile. IIRC the 150 grain M2 Ball was introduced during the 1930s because M1 Ball's maximum range was well beyond the berms, and the safety buffers behind them, at several major Army and NG ranges.

Vile Shadow · Apr 21, 2021

Allen65 said:
Why? When the Garand entered service, the standard round was M1 Ball, which was a 173 grain projectile. IIRC the 150 grain M2 Ball was introduced during the 1930s because M1 Ball's maximum range was well beyond the berms, and the safety buffers behind them, at several major Army and NG ranges.

Just helps me feel a little better

Ponder_MD · Apr 21, 2021

This really does smell of some sort of legal CYA for the CMP.

I do agree that the age of the rifle and the wear and stress on the components should be taken into consideration. My M1 was re-arsenaled with a new barrel in 1949. That barrel was horribly, horribly worn from heavy use in the service of the ROK, and then also possibly from being in the hands of Korean civilians later on. Now imagine how many cycles that operating rod has taken, even if the users only fired M2 ball. Now imagine firing powerful hunting loads from it today.

Would it really be a surprise if a 72 or 78 year old operating rod gave up?

C&RTactical · Apr 21, 2021

I guess American Rifleman could be liable at some point with this old data. I have used this and it has been a great load. Though once I expend the last of my 190 grain bullets I am going to switch to 155 grains I have.

ken792 · Apr 21, 2021

Sling Blade said:
Just helps me feel a little better

What’s the difference firing a 150gr bullet at 50k CUP chamber pressure vs firing a 180gr bullet at 50k CUP chamber pressure?

Light bullets can have high chamber pressure too since they tend to use faster powders.

CMP just said max chamber pressure is fine when they picked 50k CUP.

Ponder_MD said:
This really does smell of some sort of legal CYA for the CMP.

I do agree that the age of the rifle and the wear and stress on the components should be taken into consideration. My M1 was re-arsenaled with a new barrel in 1949. That barrel was horribly, horribly worn from heavy use in the service of the ROK, and then also possibly from being in the hands of Korean civilians later on. Now imagine how many cycles that operating rod has taken, even if the users only fired M2 ball. Now imagine firing powerful hunting loads from it today.

Would it really be a surprise if a 72 or 78 year old operating rod gave up?

M1903 and M1903A3 rifles don’t have op rods or gas systems and they got lumped in there while M1917s got left out.

Heavier bullets are very easily loaded with low gas port pressures by using the appropriate powder charges.

Powerful hunting loads that are factory or handloads made within published data still don’t exceed the 50k CUP that is SAAMI max.

Ponder_MD · Apr 21, 2021

All very true, especially the part about the 1903's and 1917's.

gwchem · Apr 21, 2021

I think it's just a CYA. My guess is some people tried really hot 180/200 grain loads and blew up a rifle. It's really a pressure issue, not bullet weight.

Qbeam · Apr 21, 2021

Would the adjustable gas plugs eliminate/reduce this issue on M1 Garands? I can see someone having a Garand with the adjustable gas plug letting someone shoot heavy loads, and then that person buying a Garand and not using an adjustable gas plug having it "blow up" with heavy loads because "they worked in that other guy's Garand."

This would be CMP's CYA effort from the Legal Department. As for the 03 and 03A3, the metallurgy may be an inherent issue with the pressure.

Q

ken792 · Apr 21, 2021

Qbeam said:
Would the adjustable gas plugs eliminate/reduce this issue on M1 Garands? I can see someone having a Garand with the adjustable gas plug letting someone shoot heavy loads, and then that person buying a Garand and not using an adjustable gas plug having it "blow up" with heavy loads because "they worked in that other guy's Garand."

This would be CMP's CYA effort from the Legal Department. As for the 03 and 03A3, the metallurgy may be an inherent issue with the pressure.

Q

The gas system has nothing to do with peak chamber pressure and the gas tapped off at the gas port has nothing to do with blowing up a bolt, receiver, or barrel.

The CMP is evidently not concerned about 03 actions handling pressure, because they just told everyone it can handle max pressure. If they were concerned, they would have picked a number below 50k CUP.

All 03A3s are nickel steel and the metallurgy was never in question.

But, it is true that the M1903 (and standard Mausers for that matter) have bad case head support when compared to something like an M1. The case will fail long before the lugs shear or the receiver comes apart.

Melnic · Apr 21, 2021

Cross linking to the Master Po NRA load data on the Garand

https://www.mdshooters.com/showthread.php?t=234195

Vile Shadow · Apr 21, 2021

ken792 said:
What’s the difference firing a 150gr bullet at 50k CUP chamber pressure vs firing a 180gr bullet at 50k CUP chamber pressure?

Light bullets can have high chamber pressure too since they tend to use faster powders.

CMP just said max chamber pressure is fine when they picked 50k CUP.

Yall know more bout this than me so Im outta my element here, but it seems to me a heavier bullet is harder on the gun and would make higher pressure because the heavier bullet needs more “oomph” to move it. I have noticed that a shotty will kick harder with heavier shot

Bob A · Apr 21, 2021

Mass x Velocity = mass x velocity. (MV=mv)

Heavy x slow can equal light x fast. The heavier the bullet the more pushback, if the velocities are equal. The heavier the firearm, the more force it takes to generate recoil.

Both sides of the equation must balance each other.

Wear and tear on the guts of the gun is different from recoil forces. That has more to do with operating mechanicals. Chamber pressures, springs and things that use recoil to perform mechanical actions within the gun, and the mechanical limits of the parts involved all come into play.

ken792 · Apr 21, 2021

Sling Blade said:
Yall know more bout this than me so Im outta my element here, but it seems to me a heavier bullet is harder on the gun and would make higher pressure because the heavier bullet needs more “oomph” to move it. I have noticed that a shotty will kick harder with heavier shot

Heavier bullets either get less of the same powder that a lighter bullet gets or gets a slower powder. Less powder generates lower peak pressures. Slower powder generates a lower peak pressure, but maintains it for longer.

Heavy bullet or light bullet, it still must be below the 50k CUP or 60k PSI max pressure that SAAMI sets if it’s industry compliant ammo. The current 60k PSI max for .30/06 is the same pressure as the old 50k CUP, just different units measured by different methods.

Notice how with different amounts of the same powder, both a 150gr and a 180gr can stay in the same pressure ranges.

CMP Updates Ammo Specifications for 1903s, 1903a3 and M1 Garand

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