Need a 308 Mil Dup load

[chrisf8657]

Hi guys,

I need a 308 Dup load for a 150g FMJ in a 18 or 20 in bbl that does the mil std. of 2750-2760 and has actually ben chronoed.

Thanks!

 

[Bart B.]

You'll need to chronograph any load you make in your rifle to ensure it's leaving the speed you want it to. The reason is, different bore and groove diameters across all the barrels made for your .308 will produce a muzzle velocity spread of at least 100 fps. Tighter barrels shoot bullets faster than looser ones. Stronger firing pin springs make higher muzzle velocities than weaker ones. To say nothing about the differences your barrel and set of components in your shooting temperatures will produce for muzzle velocity.

And 30 caliber bullets vary in diameters, too. They range from .307" to a bit over .309" which can cause a 100 fps spread in muzzle velocity in the same barrel.

All of which means what ever you use for components, you may well be anywhere within 150 fps or more of what you want. You'll need to chronograph different loads at the same range the data was based on to find one with a desired velocity. Note that two people shooting the same rifle and ammo often get over 50 fps difference in muzzle velocities.

Lake City Arsenal (near Kansas City, MO) specs for military M80 ball 7.62 NATO ammo with 150-gr. bullets is 2750 +/- 30 fps at 78 feet from a 22 inch test barrel. That's about 2800 fps at the muzzle. They (and other arsenals) typically use powders and primers not sold commercially. Stuff you can buy won't be the same.

And their bullets are "glued" in case necks with asphaltum and crimped; how would you duplicate the release force needed to initally push one out of the case? To say nothing about the bullet's diameter and jacket hardness you would have to match.

Why is it important for you to shoot 'em out at only 2750-2760 fps?

 

[chrisf8657]

Not important, just trying to duplicate the load.

I have a Rem 700 and a PTR-91 FYI

 

[Slamfire]

You are not going to get 2700 fps out of an 18" PTR 91 by duplicating loads developed in longer barrels.

The only way to get 2700 fps is with over pressure loads.

I don't know the length of the typical pressure barrel used in the arsenals, but I believe it was longer than 20", 22".

I conducted 150 grain load development with estate sale IMR 3031, and some AA2520. AA2520 is a ball powder, an excellent 308 powder and filthy. Still it shoots well. It used to be very popular with M1a shooters.

IMR 3031 is the fastest burning powder I would use in a gas gun. It may be a better choice than IMR 4064 in a service rifle. Slow burning powders are undesirable in semi automatic mechanisms. Low pressure at the gas port is better on the gas system and easier on the brass.

IMR 3031 is an excellent powder, I used mine up shooting it in Highpower matches (short range 300 yard ammo) and I would be using it if was shorter grained. As it is, it does not throw worth a flip. At a bargin price, I would buy it. But all things being equal, I will use IMR 4895/AA2495/H4895.

I did not develop any 150 grain loads with IMR 4895 which is my favorite 308 service rifle powder.

IMR 4895 is about the most versatile medium case powder. I recommend you try to find loads with IMR 4895 and buy a keg.

You can compare velocites between the 22" barrel of my M1a and the 18" barrel of my PTR 91.

M1A 1:10" Douglas Barrel


150 gr Hornady FMJBT 41.0 grs IMR 3031 Lot 385 Mixed LC WLR OAL 2.785

28 Sept 2008 T = 80 °F

Ave Vel = 2693
Std Dev = 40
ES = 126
High = 2747
Low = 2621
N = 14

150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
18 May 2008 T = 70 °F

Ave Vel = 2700
Std Dev = 30
ES = 85
High = 2736
Low = 2651
N = 10




PTR91 18" barrel



148 gr IMI FMJBT 42.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL LT 2.800, set to cannelure
30 April 2008 T = 75 °F

Ave Vel = 2496
Std Dev = 33
ES = 88
High = 2537
Low = 2449
N = 10

150 gr Hornady FMJBT 42.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
30 April 2008 T = 75 °F

Ave Vel = 2499
Std Dev = 29
ES = 94
High = 2539
Low = 2445
N = 10

best accuracy,

150 gr Hornady FMJBT 43.0 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
30 April 2008 T = 75 °F

Ave Vel = 2544
Std Dev = 32
ES = 84
High = 2574
Low = 2490
N = 5

 

[Bart B.]

SlamFire 1's remarks:

I don't know the length of the typical pressure barrel used in the arsenals, but I believe it was longer than 20", 22".

I conducted 150 grain load development with estate sale IMR 3031, and some AA2520. AA2520 is a ball powder, an excellent 308 powder and filthy. Still it shoots well. It used to be very popular with M1a shooters.

IMR 3031 is the fastest burning powder I would use in a gas gun.

Arsenal accuracy test barrels for 7.62 NATO ammo are all 22 inches long; 30-06 barrels were 24 inches. Pressure test barrels for each may well have had different lengths but it didn't matter. Accuracy tests were never done with pressure test barrels.

AA2520 quickly gained acceptance with medium cartridge folks when it came out. So many claimed great accuracy with it, it was one of several used to develop loads for Sierra's 155-gr. Palma bullet in the .308 Win. case for the bullet's debut at a big match in New Mexico. Those of us back in early 1991 developing the load used Federal cases with 210M primers and were handed a plain brown box of 1000 bullets. Other powders used were RL15, IMR4895, IMR3031, and a few others I now forget. We all had to use metered charges as progressive loaders would be used to make a couple hundred thousand rounds for various international teams to use.

Tests at 1000 yards from half a dozen Palma rifles with all powder types was interesting. Some powders did very well, a few were so-so and one was a waste of time to load. After the accuracy tests were done, samples were sent to a ballistics lab for pressure testing. As predicted, loads with AA2520 had the most uniform charge weights, muzzle velocity and peak pressure. Extremely repeatable ballistics indeed. AA2520 loads also had the worst accuracy of all; by a large margin. Some of us nicknamed it "wash tub ammo."

IMR3031 was the dirtiest and had only so-so accuracy.

IMR4895 was selected as it shot the most accurate inspite of greater spreads of charge weights, muzzle velocity and peak pressure. It shot into about 8 inches at 1000 and about 3 at 600 yards; 1/4th the size of groups with AA2520.

 

[Slamfire]

Tests at 1000 yards from half a dozen Palma rifles with all powder types was interesting. Some powders did very well, a few were so-so and one was a waste of time to load. After the accuracy tests were done, samples were sent to a ballistics lab for pressure testing. As predicted, loads with AA2520 had the most uniform charge weights, muzzle velocity and peak pressure. Extremely repeatable ballistics indeed. AA2520 loads also had the worst accuracy of all; by a large margin. Some of us nicknamed it "wash tub ammo."

IMR3031 was the dirtiest and had only so-so accuracy.

IMR4895 was selected as it shot the most accurate inspite of greater spreads of charge weights, muzzle velocity and peak pressure. It shot into about 8 inches at 1000 and about 3 at 600 yards; 1/4th the size of groups with AA2520.

Bart B: Very interesting read. I have friends who made Distinguished and High Master with AA2520 in M1a's. Palma rifles are much more accurate, and you shoot at 1000 yards with the things, so maybe the things you observed would be in the noise level with an M1a.

I recall trying to find the 1000 yard target over the post of my M1a!. Shooting a post at 1000 yards is a matter of faith, because you ain’t aiming. As you know, a service rifle shooter is satisfied to shoot in the 180's at that distance, whereas some Palma shooters I know will throw hissy fits if they drop below 190.

I think my first 1000 yard outing with a service rifle, I shot a 164 or something equally bad. Horrible experience. I apologized to my target pullers. They were fast crew and I made them work hard as I was all over the target.


The gentleman asking for data, I can assure all that the accuracy of a PTR 91 is not within the realm of a Palma Rifle. If AA2520 is very consistent in pressure and velocity variations, it might be a good candidate for that rifle.

One of the problems with AA2520 and all Accurate Arms powders is the last keg can be totally different from the current keg. Accurate Arms changed vendors so often that I have often had to develop loads with a different lot. Their loading data is next to useless, and I don’t approach maximum loads with their stuff, cause I might be blowing primers with the new can. I have one 90’s vintage keg of AA2520 that is so sooty, that it clogs my .223 powder funnel.

I did find the Chinese made Accurate Arms powders to be pretty good. I shot over 27 lbs of Chinese AA2495 and got my Distinguished and a Regional Gold in a M1a using the stuff. Incidentally, AA2495 is AA copy of IMR 4895. Foolishly they call it AA2495 instead of AA4895, so hardly anyone knows it is a copy.

I am glad to read that IMR 4895 is still good stuff, with 155’s and at 1000 yards.

You have any suggestions in a 1:10 barrel out to 600 yards with these components?

 

[The91Bravo]

If you want a mil load, for the M-118LR it is:

175 Grain Sierra Boat Tail Hollow Point Match King

Federal No 210M Match Primer

43.8 Grains of Winchester 748

I am getting prox 2650 FPS in my sub 1/2 MOA M24 SRS (Rem700 LA BDL with Shilen #7Contour Heavy Barrel)

Here she is:

 

[chrisf8657]

Slamfire,

Thanks, I know 22in velocities aren't going to come out of a 18 or 20in bbl, I wasn't sure what the BBL lengths were for the military weapons.

However, anything that's still extremely deadly on game (or people) using 168 or 150g bullets is what i'm after.

Thx for the info

 

[hawmanai]

works for me

Google "m852 duplicate" and use Sierra Game King 165 boattail hollow points instead of target bullets.

Accurate and have yet to recover one from a deer as it goes clean through, you have to be careful of where you shoot as it will destroy a lot of meat.