Mil Spec 308 load data

M

Machineguntony

New member
Gentlemen,

Does anyone have a link or resource or mil spec 308 loads?

I was hoping to replicate the military round using my own available powder. I have 150 grain FMJ mil spec projectiles. I need the pressure data, so that I can extrapolate how much powder to use in my rounds.

Thanks
 
There was a thread about this a little while over a year ago you can find here. There's a link in that thread to the military Tech Manual which is a decent starting point for load data, but it's also something that should be cross checked with other sources pretty well rather than followed verbatim. Personally, I've had good success duplicating 7.62 ball with something around 43-44 grains of BL-C(2) and a 150 FMJ.
 
Any recipie for a given military bullet weight is good enough to work up to. If you must have exact mil spec velocity, arsenal chronographs are centered 26 yards from the muzzle and their test barrels are fired in free recoil; not held by someone.

Without precision pressure measuring equipment like arsenals use to test your loads in your barrel, it's a waste of time to try to duplicate mil spec pressures.
 
Just a side note,
As far as I know, only the Marines hand load specifically for a particular rifle.

The general military ammo is mass loaded.
So if you reproduce the bullet, case, ect.
And get the chronograph to confirm your muzzle velocity,
You should be able to pretty much reproduce any given load.
 
150gr M2 bullets are flat based and for 30-06.

147gr boat tail bullets are for 7.62x51 M80 ball.

BLC-2 is the cannister grade of WC846. Load to 2,750 fps from LC brass using CCI #34 primers.

Sealing the necks with asphaltum is optional. Crimp to cannelure.

Jimro
 
.30 M2 didn't use a 150. Close enough though.
No military(or any manufacturer) uses an exact load. Every lot will be loaded to get a specific velocity for a particular bullet. Might be the same as the last one or might not.
7.62NATO uses a 147 grain bullet at 2,733 ft/s with max pressure of 60,191 psi(max loads) for Ball ammo. Not a 150. No NATO spec for a 150. There is no milspec for .308 either. Again, close enough. Not all NATO countries use BLC-2.
There are hordes of readily available commercial powders that produce that velocity with a 150. Many of 'em on Hodgdon's site.
CCI #34 primers are nothing more than magnum primers. Brilliant marketing, but you do not need magnum primers.
 
All yes and no. First, don't use TM 43-001-27 for load data. It's not meant for that, but rather as a rough reference. It has some questionable and confusing information in it. For example, for .30-06 it says the 152 -3 grain M2 Ball FMJ was loaded with 50 grains of IMR 4895, and then says the 174.5 -3 grain M72 match ammo was also loaded with 50 grains of IMR 4895. The former might have been true for one particular lot of of IMR 4895, but I have the M72 load history for 1958 through 1966, and it averaged 47 grains or IMR 4895. And, owing to the varying nature of bulk powder burn rates, that load varied from a high of 48.5 grains in 1961, to a low of 46.0 grains in 1964. Interestingly, the light 1964 load ran 29 fps faster than the heavy 1961 load. Bulk powders are only for people able to test pressure. TM 43-001-27 also reports copper crusher results as psi rather than CUP, which would be the SAAMI equivalent, and this has caused no end of confusion about how commercial and military pressures compare.

For 308, the original M80 load spec calls for a velocity of 2750 fps ±30 fps at 78 feet from the muzzle of what I presume to be a standard 24" test barrel. The gas port pressure is to be 12,500 CUP ±2000 CUP, with the chamber peak pressure not exceeding 50,000 CUP. The requried combination of velocity and gas port pressure and maximum peak chamber pressure narrows the powder burn rate and progressivity selection. The drag function of the 147 grain bullet is such that the muzzle velocity has to be 2809 fps to make that 78 foot velocity requirement. The velocity at 15 feet from the muzzle will then be 2802 fps. Again, that would most likely be for a 24" tube. Add or subtract about 25 fps for each inch of difference longer or shorter, but not too far from 24".

BL-C(2) is the narrower burn rate tolerance canister grade version of WC 846. Fired with the CCI#34 primer, it should be a good combination, as that primer and the CCI 250 are formulated specifically to ignite this type of powder well.
 
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JeepHammer, all the service competition rifle teams hand load ammo for some rifles, but rarely, if ever is a specific load used for only one rifle unless it's a 300 meter free rifle used by someone on their International Team in international competition. Even their match rifles typically all use the same load recipe. Service ammo's never handloaded; their sniper ammo is typically supplied by Black Hills or Federal; sometimes another commercial company or is standard arsenal match ammo.

T. O., there are military specs for commercially loaded sniper ammo; it has to shoot to an accuracy and velocity standard as well as others.
 
CCI #34 primers are nothing more than magnum primers. Brilliant marketing, but you do not need magnum primers.
Click to expand...
It is more than marketing. They are the only primer used in military 7.62 ammo. That means they pass a specific specification. They have a thicker cup and are less prone to slam-fire in firearms subject to that. The "magnum" is used to ignite the ball powder used in 7.62 (WC846/B-LC(2)) reliably. So you may need them if you are using a ball powder, and it does not hurt anything to use them.
I prefer to use #34 for 308, in particular for my FAL variant. When those are scarce, I buy LRM. For my bolt action 308, #34 may not be needed, but I don't want to stock more than one LR primer.
Good point about the TM not being load data. But it does identify specific components and fps, which is handy if you want to duplicate milspec, or its performance.
 
Specifically, I am reloading for my M60E6. I took a former marine shooting, and he told me that the brass was ejecting in an incorrect position. It was probably due to the bolt not going far back enough, due to either the pressure of the round being too low or the spring in the op rod being too strong/new.

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Tony,

I would definitely be looking at mil sensitivity spec primers for the MG. Board member Hummer70 described once investigating an MG OOB fire that killed the soldier to the right of the gun. You don't want any extra sensitivity. CCI #34 or Tula KVB762. I would also look at ensuring the primers are seated deeply enough. You want them a minimum of a typing paper thickness (0.003-0.004") below flush with the case head for use with that device. I can get you plans for making a gauge for checking seating depth if you PM me.

You may even find you want to crimp primers for the MG, depending on the action's timing. The whole reason primer crimping started in the 1920's was because of primers popping loose and falling into full auto actions and jamming them. If that doesn't become an issue for you, then you don't need to bother. I think Corbin or someone else had a die and ram for doing that on an arbor press.


T. O'Heir said:
CCI #34 primers are nothing more than magnum primers. Brilliant marketing, but…
Click to expand...

Marco is correct that this is not so, but doesn't have the mechanism quite right. I spoke with CCI. They told me both the cup and priming mix are identical to the CCI 250, but the anvil is different in the #34. The legs are shorter and spread at a wider angle to reduce the sensitivity to match the military H-test specification.

I also spoke with Federal about their new GMM205MAR mil sensitivity spec small rifle match primer, and they said they achieve the difference by cup thickening for that primer. So that may be what Marco was thinking of.

Military%20Primer%20Sensitivity%20Specs%20b_zpsrwtfvv5j.gif


T. O'Heir said:
…but you do not need magnum primers.
Click to expand...

It's not the magnum aspect (making more start pressure gas) of these primers that matters. In addition to the reduced sensitivity to help discourage slamfires in the #41 (same as CCI 450 with shallow anvil) and #34, in 1989 CCI reformulated all their magnum priming compound specifically to better ignite the heavily deterrent coated Western Cannon series of spherical powders from St. Marks. These are or have been sold in canister grade to handloaders as: 296 (H110), 540 (HS6), 571 (HS-7), 748, 760 (H414), H335, BL-C(2), H380, and US869, which are WC296, WC540, WC541, WC748, WC760, WC844, WC846, WC852, and WC869, respectively, in bulk grade.

Alan Jones, who worked on priming mix design (among other things) at CCI explains the above in this article. He points out that magnum primers can result in reduced velocity spread for some loads, particularly where there is low loading density, even when the cartridge is not magnum and the extra ignition effort is not required. Hartmut Broemel alludes to the unpredictability of magnum priming results in QuickLOAD's manual, pointing out they can actually reduce velocity and pressure under some circumstances. So, the bottom line is you have to knock your load down maybe 5% and work back up to a sweet spot with a magnum primer before you know whether it will improve your load performance consistency or not. There's no telling up front whether you will benefit from it or not.
 
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Unclenick,

What is a MG OOB? I can't figure the "OOB", but it sounds dangerous. Is this something that is possible because I am shooting an open bolt gun?
 
OOB = Out Of Battery
Cartridge fires but bolt is not locked in battery. I believe this is the same as slamfire.
Not specific to open bolt (fullauto) guns, where trigger releases the bolt to feed and fire each cartridge.

"In firearms and artillery where there is an automatic loading mechanism, a condition can occur in which a live round is at least partially in the firing chamber and capable of being fired, but is not properly secured by the usual mechanism of that particular weapon. The gas pressure produced at the moment of firing can rupture the not fully supported cartridge case and can result in flame and high pressure gas being vented at the breech of the weapon, potentially creating flying shrapnel possibly injuring the operator."
http://en.wikipedia.org/wiki/Out-of-battery
 
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Unlike our rifles, the M60 does not have a floating firing pin, so I would not be overly concerned with primer sensitivity. Proper seating (below flush) however is some thing to ensure.

while the design of the M60 is like that of our rifles, in the sense that the bolt must be locked before the firing pin can reach the primer, unlike the M1/M14, where the firing pin can bounce off the primer then waits for the hammer to fall, in the M60 once the bolt locks the firing pin is carried forward to strike the primer (firing the round) by the remaining forward motion of the op rod driven by the springs.

SO, an unintentional firing due to the firing pin bouncing off a too sensitive primer cannot happen in an M60.

A high primer, on the other hand, can result in a slam fire in the M60, or in any other autoloading firearm.

Cartridges of the World 3rd edition (Barnes 1972) gives the GI 7.62x51 info as follows

Cartridge, 7.62mm NATO AMMUNITION (.308 Win.)

Cartridge 7.62mm, NATO, Ball, M59
Weapon: Gun, machine, 7.62mm, M60; M73; Rifle 7.62mm, M14

BALLISTICS:
Velocity: 2750 +/- 30ft/sec at 78 feet
Pressure: 50,000psi max avg
Accuracy: Carton or clip pack - 5" mean radius at 600 yards
Link pack - 7.5" mean radius at 600 yards

CARTRIDGE: 393 -27 grs.
Case: 190 -20 grs.
Bullet: 150.5 - 6.5grs (cut cannelure) 150.5 - 5.5gr (knurled cannelure)
Core: 55 - grs - steel
Filler, point: 24 -1 grs lead antimony
Filler, base: 14.5 -1 grs lead antimony
Primer: 5.430 - 0.520 gr lead styphnate
Propellant: WC 846 double base, spheroidal, 46 grs. IMR 4475, single base, tubular, 41grs.
Point Identification: Plain Tip

take it for what it's worth.
 
44AMP,

I totally forgot about M59 ball. We haven't shot any of that in ages. All our semi auto 7.62 rifles (M14, M110) are fed M118LR or Mk316 Mod0 whenever possible, or delinked M80 if not possible.

Jimro
 
Marco Califo said:
OOB = Out Of Battery
Cartridge fires but bolt is not locked in battery. I believe this is the same as slamfire.
Click to expand...

Marco,

Actually the term OOB Fire is usually used to distinguish an out-of-battery ignition from a common slamfire, where the gun goes off as the bolt finishes closing. Fortunately, the latter is by far the most common kind, so if you just keep your muzzle pointed in a safe direction as you close the bolt, it's a rude surprise, but no harm is done. The OOB fires can pretty much destroy the weapon. In rifles it commonly blows out the magazine well and damages parts in that area, tears off the steel lip that surrounds the cartridge head off the bolt, and splinters the stock, among other things.


44 AMP,

I don't recall what kind of MG Hummer70's investigation was about. The most common cause of slamfires is high primers, and that may apply to OOB fires as well, but I don't actually know. The latter are uncommon enough that it's hard to collect enough detailed data about them to reach a solid conclusion It's also possible to have a malfunction like a firing pin getting stuck part way our of the firing pin tunnel, so some other odd thing that's not the fault of the ammunition at all. The one thing that seems pretty certain about the MB OOB he looked into, is that the primer was not high in that case, as it was military ammunition. I've also been present for a Garand slamfire with M2 Ball issued for the match where this occurred, so the primer being correctly seated and having a military sensitivity spec does not save you 100% of the time. It's just an added layer of discouragement of untoward discharges.
 
There is always a lot of confusion on military spec for 7.62 ammo particularly pressure and velocity. I believe Uncle Nick is more right in post #8, max pressure 50,000 CUP not psi which is pretty close to 60,000 psi. It is misquoted in many publications including some military documents and as quoted by 44 AMP post #15 in "Cartridges of the World" as 50,000 psi.

Velocity spec is also as in post #8 measured way out from the muzzle and thus the often specified lower velocity military spec does not clarify the muzzle velocity is higher.

This is also why so many claim 308 should not be used in 7.62 rifles (too high velocity, too high pressure). This is only partially true for the super performance very high velocity 308s. Also some powders in some 308s may not perform well in 7.62 rifles like the M1A. There are slight differences in head space of the 2 but become irrelevant in reloading if you resize your brass to your requirements for your rifle. There are no 7.62X51 dies, only 308 dies.
 
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