M1 garand handloads

[tangolima]

Originally Posted by 44 AMP

Not initially. When the op rod gets sprung (bent) the first sign is a significant degradation in accuracy. IF you keep on battering the action with unsuitable loads, the out of spec bend will eventually affect function, commonly in the feeding cycle.

Just can't wrap my head around this one. The gas port is right next to the muzzle. By the time anything starts moving, the bullet is long gone.

-TL

Sent from my SM-N960U using Tapatalk

[Jeremy2171]

Originally Posted by 44 AMP

Not initially. When the op rod gets sprung (bent) the first sign is a significant degradation in accuracy. IF you keep on battering the action with unsuitable loads, the out of spec bend will eventually affect function, commonly in the feeding cycle.

You might notice an accuracy change if your rifle was a NM and you were a pretty good shot.

Service grade rifle?? Not likely to notice anything.

Originally Posted by 44 AMP

No, I have not.

You have..see below...

Originally Posted by 44 AMP

Not to the military...
The information I gave regarding the M2 round is exactly a I found it published in 1972. PSI Max. Avg. The military standard has always been psi, and they don't list anything in CUP.

SAAMI specs are actually irrelevant, other than to illustrate that they are different than the military specs.

Up until the 80's ALL pressures were written as "PSI" as the ONLY method in use was the "copper crusher" method. So your TM with the 50,000 psi is actually "CUP".

When technology got better and we went to Piezoelectric transducers... we continued using "PSI" with the given the older numbers would be referenced as "CUP".

SAAMI max pressure:
CUP - 50,000k
PSI - 60180

Two different numbers...two different tests...but they are both "equal".


And THAT is why there is so much confusion over "pressures" in the garand. Too many "readers" and not enough "researching". Combine that with youtubers who parrot the misinformation....it doesn't help matters.

[mehavey]

Very interesting (and relevant) thread here:
https://www.m1garandforum.com/forum/...iss/43047-ammo

[44 AMP]

Just can't wrap my head around this one. The gas port is right next to the muzzle. By the time anything starts moving, the bullet is long gone.

Yes, the bullet is long gone, but the gas pressure is full pressure in the barrel and the gas cylinder until the bullet leaves the muzzle and the gas can vent. The "shove" of the gas on the parts continues briefly after the bullet clears the barrel and then drops off rapidly, but that hard push has already happened, and the moving parts are under pressure and perhaps still accelerating when the pressure drops off.

Consider this, slam a door, without riding it closed with your hand?, you've pushed the door, but once the door begins moving and moves away from your hand, the push of your hand stops. The door keeps going, until it hits the doorframe with some force.

When the pressure in the gas cylinder is too high, it shoves the piston which pushes the op rod too hard. The extra hard push also results in a harder than normal stop, due to the increased op rod velocity, and the result can be the long fairly thin in places. with several "dog leg" bends in it, op rod flexes past the point of returning to true, and stays bent where, and in a way its not supposed to be.

This changes the harmonics of the rifle and the usual result is a loss of accuracy. A 2moa gun can suddenly turn into a 5 or even an 8moa gun, with no visible to the shooter change to the gun in the field.

Up until the 80's ALL pressures were written as "PSI" as the ONLY method in use was the "copper crusher" method.

I have seen pressure values written as PSI, CUP, and LUP well before the 80s.

So your TM with the 50,000 psi is actually "CUP".

So, you're saying the Army is wrong???

[Unclenick]

Not wrong, just traditional. The Army and the CIP both use the same units for copper crushers and for piezoelectric transducer instruments. CUP is a SAAMI term of art, and nobody else seems to have adopted it fully, though, IIRC, board member FALPhil said his brother, who worked in Aberdeen's munitions lab, said the techs there used the term CUP among themselves to avoid having to say "psi by crusher" and "psi by transducer" to segregate the two. But it never made it into the tech manuals (TMs). Here's and example for a 5.56 M852 load.



Back to the topic at hand. Someone who worked with the ballistic tech who posts as PowderMonkey in the link Mahavey provided, posted here in the middle of last year. The work is interesting technical information, but the physics is flawed. As variable as the gas cylinder pressure measurement can be, and the fact there is no military standard for measuring it makes it uncomfortable to rely on, as Tangolima points out in that old thread, it is the pressure that matters. The op-rod only sees that pressure, not the gas port pressure, and the peak force on the op-rod piston is that pressure divided by the area of the piston head and is typically around 450 lbs. The peak value of that pressure varies both because of all the tolerances and the fact that the speed of the bullet changes how long the port pressure maximum is pushing gas into the cylinder, which the gas port pressure measurement does not take into consideration, while the cylinder pressure does. The peak force is present only briefly, but it is long enough to impart enough velocity to the rod to, in effect, throw it rearward with enough momentum to unlock the bolt, extract the case, and compress the op-rod spring after the force is long gone.

I will post a bit more on this tomorrow.

[tangolima]

I can see high port pressure can bend and damage thing. But I don't see how a bent op rod affects accuracy. By the time anything starts moving, the bullet has well cleared the muzzle.

-TL

Sent from my SM-N960U using Tapatalk

[44 AMP]

The harmonics of the rifle (the way it vibrates) begin with ignition, building as the bullet moves down the barrel, and by the time the bullet gets there, the muzzle is actually moving up and down as the barrel "whips". Accuracy means consistency, and changes to the harmonic pattern from what it was, before the op rod bent to what it has become can change the point in the muzzle's arc where the bullet exits the bore. That can have an effect, changing the accuracy from what it was to something else, usually with a negative net result.

[tangolima]

I see. If the rod is so bent that it applies force to the barrel, it can change the poi. It may improve it though. Thanks for the info. Didn't think of that.

-TL

Sent from my SM-N960U using Tapatalk

[Jeremy2171]

Originally Posted by 44 AMP

So, you're saying the Army is wrong???

No, just your understanding of the topic.

The Army and SAAMI agree that the max pressure for the Garand is the same.

[mehavey]

FWIW (in this argument) I don't really care at this point.

I'll shoot mid range 150-168 commercial (rare)
Greek HXP (a lot)
- and -
Master-Po's 150-175 handloaded/medium burn powders ( a lot )

I'll avoid (i.e., save for a cold day in Hades) Heavy El Screamo Grande commercial

[44 AMP]

The Army and SAAMI agree that the max pressure for the Garand is the same.

If you would be so kind, would you point me to where SAAMI lists a max pressure for the Garand??

Not the .30-06 Springfield cartridge, but the M1 Garand rifle??

I don't know (and I'm not going to try and look) if the Army has a max pressure limit for the M1 Garand rifle. It might exist, somewhere in some ordnance document, but so what??

The Army required the guns survive proof test loads (which they do have specs for) and run on service grade ammo, which they do have their own specs for, and they list the suitable ammunition for the rifle, and do not approve of anything else.

The GI ammo is called ".30-06", by civilians, and even soldiers in casual use, but while it is dimensionally identical to the civilian .30-06 Springfield, it is not the same round otherwise. It is Cartridge, Caliber .30, followed by the bullet type and an M number. Cartridge, Caliber .30, Ball, M2 for example.

We all say M1 Garand (to avoid confusion with other M1 designated items) but the official nomenclature is Rifle, Caliber .30, M1. Garand's name is not part of the official military designation. The military is very precise with its nomenclature (for good reason) and in a great many cases uses nomenclature that is not the same as the common use terms found in civilian life. And, in many cases, the terms are also service branch specific.

An Army or Air Force building has a floor, walls and a door. To the Navy and the Marines, that same building has a deck, bulkheads and a hatch. The only trucks on an army post are on the flagpoles. All those multiwheeled cargo carrying things are "vehicles". The examples are legion, and widely ignored in casual use, but sometimes the military gets very picky about using "their" terms and only their terms. Call your rifle a "gun" in training and you WILL be doing pushups, or some other generally unpleasant physical activity to remind you to use the correct terms.

Another place they get particular is ammunition. GI ammo is NOT SAAMI spec ammo. It is govt spec ammo, and SAAMI has nothing to do with it.

The assumption that all SAAMI spec ammo is suitable for the M1 rifle is false.

Note I did not say unsafe, I said unsuitable. There is a difference.

[Jeremy2171]

Originally Posted by 44 AMP

If you would be so kind, would you point me to where SAAMI lists a max pressure for the Garand??

Not the .30-06 Springfield cartridge, but the M1 Garand rifle??

I don't know (and I'm not going to try and look) if the Army has a max pressure limit for the M1 Garand rifle. It might exist, somewhere in some ordnance document, but so what??

The Army required the guns survive proof test loads (which they do have specs for) and run on service grade ammo, which they do have their own specs for, and they list the suitable ammunition for the rifle, and do not approve of anything else.

The GI ammo is called ".30-06", by civilians, and even soldiers in casual use, but while it is dimensionally identical to the civilian .30-06 Springfield, it is not the same round otherwise. It is Cartridge, Caliber .30, followed by the bullet type and an M number. Cartridge, Caliber .30, Ball, M2 for example.

We all say M1 Garand (to avoid confusion with other M1 designated items) but the official nomenclature is Rifle, Caliber .30, M1. Garand's name is not part of the official military designation. The military is very precise with its nomenclature (for good reason) and in a great many cases uses nomenclature that is not the same as the common use terms found in civilian life. And, in many cases, the terms are also service branch specific.

An Army or Air Force building has a floor, walls and a door. To the Navy and the Marines, that same building has a deck, bulkheads and a hatch. The only trucks on an army post are on the flagpoles. All those multiwheeled cargo carrying things are "vehicles". The examples are legion, and widely ignored in casual use, but sometimes the military gets very picky about using "their" terms and only their terms. Call your rifle a "gun" in training and you WILL be doing pushups, or some other generally unpleasant physical activity to remind you to use the correct terms.

Another place they get particular is ammunition. GI ammo is NOT SAAMI spec ammo. It is govt spec ammo, and SAAMI has nothing to do with it.

The assumption that all SAAMI spec ammo is suitable for the M1 rifle is false.

Note I did not say unsafe, I said unsuitable. There is a difference.

You typed a lot that was irrelevant to the topic.

SAAMI max pressure is 50k... M2 ball max pressure is 50k.

Therefore SAAMI spec ammo is safe...hell even Mark Johnson from CMP said so in his "ammo warning".

Please tell us what SAAMI spec ammo is unsuitable for the garand.

PS since official army training films of the period call it the "garand" rifle you can argue that it is an official designation.

[Marco Califo]

I can't read this thread now because it has descended into meaningless argument, with no redeeming value. There was a topic here at one time.

[rodfac]

Plus 1 on 44 AMP's #13 post. Garands are not bolt action rifles and will not tolerate heavy weight bullets and slow powders. Pay attention to bullet weights (150-180 gr) and powders (mid range burning rates like 4895 and 4064). Rod

[Unclenick]

Here's the origin of the whole bent op-rod thing, as near as I can determine. I asked Humpy (Hummer70 on this board) because his long career at Aberdeen Proving Grounds as a firearm test director and incident investigator exposed him to a lot (he testified before Congress as a firearms expert at one point), and the fact he's been a shooting accuracy nut (twice U.S. Wimbledon Match Champion) gives him a unique perspective and experience in all these kinds of matters. Regarding the Garand bent op-rod, he said:

Originally Posted by Humpy

My contact at Crane Naval Weapons Center, Crane, Indiana (who died about 2003) told me that match Garands chambered in 30-06 were issued to Navy Shooters with three op rods as they tended to warp rather quickly shooting 173 gr Match ammo.

When the Navy went to 7.62 Match ammo, they were not issued with extra rods as the 7.62 gas port pressure was perfect and did not warp them.

They had the only op rod gage I ever saw where a rod was inserted, and if it contacted any of the NO GO points, it was removed and adjusted till it would go back in gage and not contact anywhere.

So, we get several interesting tidbits from that:

First, for all who say they never saw a bent op-rod, they probably have but just couldn't tell. The offset of the last 4.64 inches of the tube from the first 2.5" back near the handle is specified as 0.185" with +0.005" tolerance.

Second, the effect of the bend was to spoil match group precision. Nothing says the gun with an out-of-spec op-rod didn't still meet combat accuracy specs or keep the gun functioning. This is not the dramatic damage some expect when a bent op-rod is mentioned.

A third bit of information is that a bent op-rod can be bent back (adjusted) if you have a way to gauge it.

A fourth, and this is really important, is that the 173-grain National Match ammo from that period was all charged with IMR 4895, a supposedly "Garand-safe" powder. It turns out there isn't such a thing except within the context of a particular bullet. More on this below.

Neither Humpy nor his Crane contact offered a mechanistic explanation of what happens. It was just an observed fact that when the op-rod went out of spec, precision deteriorated, and when it was replaced or "adjusted" back into spec, precision returned. We can speculate about mechanisms, but the proof one exists is empirical and comes to us via the military match team armorers and their work on building and maintaining match-accurate Garands.

The above bit of revelation caused me to wonder, have all the fellows out there who say the Garand is a two-moa rifle always had out-of-spec op-rods? When I first accurized my old DCM Garand, which was nearly unused when I got it, the first ten rounds I put through it from the prone position went into 0.75" CTC at 100 yards. But groups did move out toward more like two moa over time, and the fact I did run 168 and 175-grain MatchKings in it with IMR 4895 and a few slightly slower powders like IMR4064 and Brigadier 4065, leads me to think I caused it. I know IMR 4895 is fine with 150-grain bullets at M2 Ball velocity, but I don't know how much heavier you can go with it before it is battering the op-rod too much.

So, what to do? As I said in my previous post, the gas in the cylinder is what determines the force on the op-rod's piston head. That, in turn, is determined by the pressure impulse (not just the pressure peak value) at the gas port that pressurizes the cylinder. The impulse is the port pressure multiplied by the time for which the port is exposed to that pressure. The time is a combination of the time it takes for the bullet to pass from the gas port to the muzzle, plus the time it takes the pressure drop to travel back from the muzzle to the gas port at the speed of sound in the propellant gases. Because the gas starts accelerating out of the muzzle after the bullet clears, Bernoulli's principle also drops port pressure. Eventually (typically around 100 microseconds), the pressure is no longer pushing gas into the port fast enough to raise gas cylinder pressure further, plus the op-rod is picking up velocity and starting to expand the gas cylinder, so pressure in the cylinder starts to drop. The main takeaway here is that bullet's velocity affects the impulse time component, and thus the pressurization of the gas cylinder, so peak gas cylinder pressure cannot be controlled by peak port pressure values alone; the bullet velocity has to be right as well.

The military propellant acceptance test report sheets for 30-06 include a space for gas port pressure. But the military, with each lot of ammunition, is shooting just one bullet at just one nominal velocity. If you stick to just one bullet and velocity, then the gas port pressure has a direct relationship to gas cylinder pressure. The limitation is that when you try other powders, you'd better be shooting that same bullet at the same velocity. Otherwise, you have an apples-to-oranges comparison.

The non-modified cure is to lower muzzle pressure by using a faster powder with the heavier bullets. This is the opposite of normal bolt rifle practice, where the fact a bullet is slower means there is time to burn a slower powder to avoid a higher peak pressure while relying on higher pressure further down the barrel to give you maximum velocity. However, because the powders available when the military developed the 30-06 were faster and less progressive than modern powders, the velocities for military ammo were established to be modest by modern ammunition standards for the cartridge, and fast powders still meet them safely. For example, for the 175-grain Sierra MatchKing, I would start with John Clark's old 180-grain bullet Garand data in Lake City brass, which calls for 45 grains of IMR 3031. Remember to tilt the rifle up after chambering (with your finger OFF THE TRIGGER) to get the powder back over the primer, as this is how the military and SAAMI test pressure and velocity. A Garand tends to throw powder forward, so the velocity in semi-auto mode tends to be 50 to 100 fps slower.

For 150-grain bullets, you don't have an issue. They get out of the barrel quickly enough to temper the impulse from the gas port into the gas cylinder to safe levels with IMR4895 and IMR4064 and similar powders, so sticking to 150-grain bullets is one out, but not great for bucking wind at 600 yards. You can get a .308 Garand barrel. The smaller powder volume in the 308 case lowers muzzle pressure, and 308 Garand barrels have larger gas port holes because of that. You can use some form of vented gas plug. A point mentioned by Airborne Daddy in the link Mahavey provided is that John Garand recommended M1 Ball ammo for the gun, which was ballistically about the same as National Match ammo (the bullet had a crimp cannelure, which the M1 Type bullet in NM ammunition does not, and M1 Ball was crimped, which NM ammunition was not). However, in later years, J. C. Garand himself patented a design for a vented gas cylinder plug, so he must have come to recognize some issues with higher port pressures.

[mehavey]

Once again, the restorative voice of reasoned examination.





(i.e., thanks Uncle Nick)

[Jeremy2171]

Originally Posted by Unclenick

Here's the origin of the whole bent op-rod thing, as near as I can determine.

Odd the Navy team has issues with regular issue M72 match but no other teams did nor did this discovery warrant a notice to Lake City or the Ord Dept about it "bending" oprods. I wonder if it was something else...because Jim Adell stated they (USNR) team had oprod issues when they were using 200+grn handloads for the long range matches. But no mention of issues with M72.

Hell they could have been running the guns dry for all we know.

So I'm going M72 isn't the issue....otherwise it would be big news that "match" ammo was regularly bending oprods.

Jim Thompson and I agree that lack of lubrication is the bigger concern than what ammo you use.

Considering how lossy the gas system is and the fact the oprod doesn't begin to move until the bullet is several inches out of the barrel after the gas has already begun depressurizing means those few microseconds aren't that big of a deal.

JCG made a patent for an adjustable gas cylinder lock screw...for use in case of "excessive" port pressure. So far we haven't seen any commercial ammo with "excessive" port pressure.

As far as his patent goes....no one adopted it...Including the Navy team as its not needed.

[flyer898]

Now that you have read everything here and know more than what there is to know about the Garand, its ammo, and loading same, it is time to cut down some trees.
The Garand might be the finest individual tool for falling trees at a distance yet devised.
With a reasonable hold, about three clips will fall trees up to ten inches in diameter.
Remember to be farther from the tree than the tree is tall when trying this experiment.
It is a good idea to park the pickup even farther away.