Looking at this section of the Hornady 10th . These loads were developed for the M1A-M14 correct? Are they at all useful for AR10 or bolt gun? The charge weights are pretty low in comparison to the .308 Win. Would assume it has to do with the M1-M14, heard parts bend at higher pressures. Would they make enough gas to run a 16” AR10? Shoot ok in a 24” heavy barrel bolt gun? I know I can use 308 win data but can I use service rifle data in the other? Would it be the same as shooting 762x51 through a 308 Win?
.308 Winchester “service rifle”
- Thread starter 308Loader
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The Garand's operating rod can be bent by loads that have high muzzle pressure relative to the bullet's velocity, but the M14/M1A op-rod is short and stiff and the gas piston that drives it lets gas into the cylinder via a hole in its side that cuts off the gas port as soon as it starts to move and vents the gas when it is far enough rearward. This creates a self-regulating gas system that is relatively immune to quite a range of loads, assuming the gun is in good shape.
I've measured pressure on M118 and other Lake City loads and found it to be a good deal stiffer than any of the Hornady loads, and stiffer than a lot of commercial loads. But the M1A handles them just fine. I would guess the downloading in the Hornady manual either assumes guns not in good shape or assumes the loads are to be fired in .308 Garands. Military spec M14 ammunition actually has a gas port pressure upper and lower limits that some of those Hornady loads don't meet, though mine seems to work with about anything.
I've attached the apropos pages of the military M80 specification. Just keep in mind they report pressure in "psi" universally, even with the copper crusher, rather than using CUP. You just have to read which system of measurement they use and be aware that has changed since this version of the spec was written.
The gas impingement systems are different. Because they vent as soon as the bolt carrier starts to back up, they have a lower gas port pressure limit in military specs but no upper limit. That suggests any .308 load up to fairly warm ones will get the gas system to work alright in the AR's using gas impingement (and not adapted to use a gas piston system).
I've measured pressure on M118 and other Lake City loads and found it to be a good deal stiffer than any of the Hornady loads, and stiffer than a lot of commercial loads. But the M1A handles them just fine. I would guess the downloading in the Hornady manual either assumes guns not in good shape or assumes the loads are to be fired in .308 Garands. Military spec M14 ammunition actually has a gas port pressure upper and lower limits that some of those Hornady loads don't meet, though mine seems to work with about anything.
I've attached the apropos pages of the military M80 specification. Just keep in mind they report pressure in "psi" universally, even with the copper crusher, rather than using CUP. You just have to read which system of measurement they use and be aware that has changed since this version of the spec was written.
The gas impingement systems are different. Because they vent as soon as the bolt carrier starts to back up, they have a lower gas port pressure limit in military specs but no upper limit. That suggests any .308 load up to fairly warm ones will get the gas system to work alright in the AR's using gas impingement (and not adapted to use a gas piston system).
Haha , IMR-4064 is one of the only powders I have but don’t use in my PA-10 . Only because it’s my go to match grade loading powder which my PA 10 does not need and I want better metering powders so I can throw charges . I load both IMR & H-4895 , H-335 , CFE 223 , W-748 & IMR 4320 in my PA-10 and worked up loads for each using that rifle .
All of those regardless of bullet weight with the exception of IMR 4895 I have running .5gr below cratered primers which is pretty hot all-n-all for that rifle . The AR platform seems to handle hot loads pretty well though .
Some of my loads I've worked up in the PA-10 and settled on are
All loaded in LC-brass
44.5gr W748 & 163gr AP
46gr IMR-4320 & 147gr FMJ
42gr H-4895 & 150gr FMJ
46gr W-748 and 147gr FMJ
42.5gr H-335 and 150gr FMJ
Loads I already had for bolt guns that seem to work just fine in the PA-10
42gr IMR 4064 & 150gr soft point ( one of the first loads I ever worked up and stayed conservative , Likely could go much hotter )
41gr IMR-4895 and 168gr BTHP ( This is my match plinking load I use and seems to shoot OK with most of my 308's )
I've also shot some Fed GMM ammo through it and it seems fine with those as well .
I have multiple other loads using IMR-4064 , AR-comp , IMR 8208xbr , Varget etc in 308 . However my PA-10 has a long chamber and is hard on brass . All of those other powders are using either Lapua brass or brass I have prepped for a specific firearm and don't want to stress the brass more then needed . That said with out saying what those loads are , I'd shoot them in my PA-10 if I had to but I don't
When using Hornady data I often find there minimum to be way below anything I'll likely be using . I however still start at there minimum but only load 1 or 2 rounds at each of the lower charges and jump up in 1gr increments for the first few loads . I then add more rounds per charge while reducing the charge weight as the charges increase to the point that the last few charges are 5 shots each at .4 or .5gr increments . This allows me to start safe but not waste time and components on charges I know I will likely never use .
It looks something like this
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I have never been able to get my Springfield Saint much below 1 MOA so I just slapped a reflex red dot on it and used a pound of BL-C(2) at 44.5 gns in LC cases topped with Match Burner 168's from Mid South. Cycles fine, not too hard on the brass and I can keep them in a 8 inch circle at 50 yards shooting off hand rapid fire so I figure it is good for minute of zombie in case of the apocalypse. Off a bipod and taking my time with a scope it's about a minute and a quarter load. Change the bullets to something more appropriate for hunting and it would be a nice deer load. Not exactly bench rest quality accuracy but with that muzzle brake it sure has a nice bark
I would expect them to be. Something to be remembered is that GI service ammo is NOT commercial ammo, even though using the same size cases.
The M14 was designed to replace the M1 Garand. Its ammunition was designed to replicate GI M2 ball. Same bullet at the same speed. Which is a 150gr at approx 2750fps (+/-).
"Service Rifle" loads are intended to reproduce service rifle ammo performance, for use in service rifles. This means matching the service ammo's performance in terms of velocity and general pressures.
The M14/M1A's self regulating gas system will allow it to handle ammo with a port pressure that can damage a GI issue Garand. That does not mean its a good idea. The rifles are built to run on a certain specific NARROW range of ammunition. They do pretty well doing that. Run them on something else and often, they don't do so well.
All the military velocity data for 7.62 NATO ammo show`they are about 90 to 100 fps slower than the same bullets in 30-06 ammo. Both with 50,000 CUP average chamber pressures.
SAAMI average chamber pressures for the 308 are 52,000 CUP, 62,000 PSI but their systems are slightly different.
Many thousands of rounds of 308 commercial match ammunition has been shot in military 7.62 NATO rifles with no pressure problems.
SAAMI average chamber pressures for the 308 are 52,000 CUP, 62,000 PSI but their systems are slightly different.
Many thousands of rounds of 308 commercial match ammunition has been shot in military 7.62 NATO rifles with no pressure problems.
Specifically, my surmise was they are Garand .308 loads. But their test gun was an M1A. So I'm thinking the low end of the range is just about what worked for them.
If you look at pressure curve simulation in QuickLOAD or even at real pressure curves off the Pressure Trace, one thing that becomes apparent is it takes a good bit of change in peak pressure to swing through the M80 gas port pressure range at the pressure port's 14" distance from the breech. With a 147-grain FMJ I have to go from 36.8 grains to 46.0 grains of IMR 4895 to cover the whole range. 45.8 grains would produce the upper velocity limit, though, so we'd stop 0.2 grains short of that.
As to the M80 velocity of 2750 fps. The old portable vacuum tube circuit chronograph used by the military since before WWII was based on detecting the bullet with oscillator coils resembling a metal detector. They could not locate the bullet position any more precisely than a few inches, so they put the start and stop coils 50 yards apart, with the start coil 3 feet in front of the muzzle and the stop coil 51 feet from the muzzle. This meant they measured bullet velocity with a coil pair midpoint position of 26 yards or 78 feet. Based on the BRL drag function for M80, the bullet loses about 61 fps in that distance, so the muzzle velocity would be about 2811 fps, as measured with a Magnetospeed. At 15 feet from the muzzle (SAAMI measuring distance) it would be 2799 fps. Using Hodgdon's data for a 150-grain Nosler BT as being close enough, in the Winchester brass they use, that's a 47.3-grain load of BL-(C2), which is the powder Lake City knows as WC846 and that is used in M80. The military has a specification of ±30 fps from their 24" test barrel, and that expands the range from 46.8-grains to 47.8 grains, and moves peak pressure from 45,910 CUP to 49410 CUP. To do that with IMR4895, the load goes from 44.8 to 45.8 grains. BUT, this is in Hodgdon's Winchester brass with Federal 210M primers. In military brass with the magnum #34 primers, these charge weights will come down a little.
There is no military spec for the 155-grain bullets that Hornady has used as the low charge weight in their manual with their cases and the Winchester WLR primer, so they are hard to compare.
If you look at pressure curve simulation in QuickLOAD or even at real pressure curves off the Pressure Trace, one thing that becomes apparent is it takes a good bit of change in peak pressure to swing through the M80 gas port pressure range at the pressure port's 14" distance from the breech. With a 147-grain FMJ I have to go from 36.8 grains to 46.0 grains of IMR 4895 to cover the whole range. 45.8 grains would produce the upper velocity limit, though, so we'd stop 0.2 grains short of that.
As to the M80 velocity of 2750 fps. The old portable vacuum tube circuit chronograph used by the military since before WWII was based on detecting the bullet with oscillator coils resembling a metal detector. They could not locate the bullet position any more precisely than a few inches, so they put the start and stop coils 50 yards apart, with the start coil 3 feet in front of the muzzle and the stop coil 51 feet from the muzzle. This meant they measured bullet velocity with a coil pair midpoint position of 26 yards or 78 feet. Based on the BRL drag function for M80, the bullet loses about 61 fps in that distance, so the muzzle velocity would be about 2811 fps, as measured with a Magnetospeed. At 15 feet from the muzzle (SAAMI measuring distance) it would be 2799 fps. Using Hodgdon's data for a 150-grain Nosler BT as being close enough, in the Winchester brass they use, that's a 47.3-grain load of BL-(C2), which is the powder Lake City knows as WC846 and that is used in M80. The military has a specification of ±30 fps from their 24" test barrel, and that expands the range from 46.8-grains to 47.8 grains, and moves peak pressure from 45,910 CUP to 49410 CUP. To do that with IMR4895, the load goes from 44.8 to 45.8 grains. BUT, this is in Hodgdon's Winchester brass with Federal 210M primers. In military brass with the magnum #34 primers, these charge weights will come down a little.
There is no military spec for the 155-grain bullets that Hornady has used as the low charge weight in their manual with their cases and the Winchester WLR primer, so they are hard to compare.
bacardisteve
New member
One of my favorite 308 loads is lake city brass 42gr rl15 and a 168 amax/eldm. That load has shot excellent in every 308 I've ever run it through. It's also taken many deer over the years from an m1a and ar10. It's quite mild avg 2560fps in a 20" gas gun but it gets the job done.
Lake City arsenal loaded 41 grains of IMR4475 in 7.62 NATO M80 ball packaged in 8-round clips for US Navy 7.62 Garands. That extruded stick powder's burn rate is a bit slower than IMR3031, Most accurate M80 I've shot.
The US Air Force rifle team developed the most accurate long range target load for 7.62 Garand's 1:12 twist barrels. New M118 primed cases with 44 grains of IMR4320 under .3082" 190 grain Sierra HPMK bullets. Sometimes the USN team used the Lapua 185 grain FMJ rebated base .3092" diameter match bullets that was equally accurate.
The US Air Force rifle team developed the most accurate long range target load for 7.62 Garand's 1:12 twist barrels. New M118 primed cases with 44 grains of IMR4320 under .3082" 190 grain Sierra HPMK bullets. Sometimes the USN team used the Lapua 185 grain FMJ rebated base .3092" diameter match bullets that was equally accurate.
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