New Army "Caliber Configuration Study"

[JASmith]

Hasn't someone already run ballistics to help illuminate the question of whether .338 can do as well as .50 cal?

[cory]

Hasn't someone already run ballistics to help illuminate the question of whether .338 can do as well as .50 cal?

I was referring to it's terminal performance on vehicles and light armor.

[stanc]

That post is not enough to answer the question.

Can you expand a bit?

Tony's notional GPC is -- or at least originally, was -- meant to be used in all general-issue, infantry shoulder weapons.

7.62 NATO was originally intended to be used in all general-issue, infantry shoulder weapons.

Does that help?

[JASmith]

I was referring to it's terminal performance on vehicles and light armor.

I think we both are.

Yes, given the same impact velocity, the longer, heavier, bigger diameter bullet having greater terminal performance is almost a no-brainer. What velocities do they arrive at?

If the .338 has a significantly greater impact velocity at range, then answering the question is more challenging.

Further, as with the 7.62 replacement discussion, there will be the question of value-added by going with lighter ammunition (greater round count per pound) and weapons versus improving the terminal performance of the existing cartridge.

[stanc]

The biggest question here is, can the .338 be effective enough against vehicles and light armor to replace the 50 cal.

Against soft-skinned vehicles: Probably.

Against light armored vehicles: Doubtful.

[JASmith]

Against soft-skinned vehicles: Probably.

Against light armored vehicles: Doubtful.

Do you have numbers to back up these guesses?

[cory]

Hornady's 9th Ed. reloading manual has .338 LM at an ~MV of 2800fps at max pressure with a 250gr BTHP (B.C. 0.670) out of a 24.5" barrel.

Barret lists 50 BMG at a ~MV of 2750fps with a 29" barrel and 2500fps with a 20" barrel, both with a 661gr (what looks to be a BTHP) (B.C. 0.62). So for comparison to the .338 LM we could say 2625fps MV for the 50 BMG.

http://www.barrett.net/ammunition/50bmg

I'm not sure how using a .338 Norma Magnum would change the MV.

All that being said, I think it's fair to say the .338 won't be as effective as the .50, but will it be effective enough to meet mission requirements.

[stanc]

I think that the proposed .276 Penderson and the .280 British (the 7x43mm version) could have been GPC's. They were intended for individual weapon and LMG use. I don't know if they were to be used in the MMG role, however.

IIRC, a .30-cal M1917 HMG was converted to .276 Pedersen. (The US did not have MMGs in WWII, only air-cooled LMGs and water-cooled HMGs.) However, .276 Pedersen may not have been a good GPC, as it reportedly was inferior to .30-06 in armor penetration.

Ironically, the Japanese had the 6.5mm Arisaka and the Italians had the 6.5 Carcano, but both initially used round-tipped bullets which had poor terminal ballistics. They both decided to move up to to a larger caliber. I do not know if the Japanese reevaluated the 6.5 Arisaka after switching to the pointed bullets which would yaw after impact.

The Japanese adopted spitzer bullets for 6.5 Arisaka prior to the First World War, so they would've had plenty of time and opportunity to evaluate it in combat.

[stanc]

Do you have numbers to back up these guesses?

7.62mm is the standard chambering for US tank co-ax machine guns, and M80 Ball does a good job of ventilating auto and truck bodies. What a .308" 147gr bullet can do, a .338" 300gr projectile ought to do even better.

[JASmith]

7.62mm is the standard chambering for US tank co-ax machine guns, and M80 Ball does a good job of ventilating auto and truck bodies. What a .308" 147gr bullet can do, a .338" 300gr projectile ought to do even better.

The question refers to the .338 vs .50 cal and the metric is whether "good enough" holds.

You can see that Cory is getting us close to an answer. "Doubtful" still needs to be backed up with numbers.

[Michael]

(The US did not have MMGs in WWII, only air-cooled LMGs and water-cooled HMGs.)

Incorrect. M2 Browning was in service and considerd a heavy machine gun. M1919 was considerd a medium machine gun. BAR was considered a light machine gun.

[stanc]

.338 Norma Magnum -- 300gr @ 2650 fps in GD LWMMG
.50 Browning M33 Ball - 660gr @ 2910 fps in M2HB (velocity @ 78 ft from muzzle)

[stanc]

M1919 was considerd a medium machine gun. BAR was considered a light machine gun.

Not by the US Army, they weren't. The M1919 was classified as a light machine gun, and the BAR as an automatic rifle. (The initials "BAR" are an abbreviation of Browning Automatic Rifle.)

9:30-12:00

http://www.youtube.com/watch?v=8KqemCtq3B8

5:30-6:00

http://www.youtube.com/watch?v=Oyj-ZHXFKQI

[joker31]

You said that in one fight, "My team alone expended 3200 Rounds in 8.5 hours..."

Doesn't that argue for the smallest, lightest cartridge feasible, so as to maximize the number of rounds carried?

Since the infantry squad currently has two M249 LMG's, I presume you mean add one in a larger caliber? Doesn't that contradict your statement above?

Not exactly, we could have never carried that much ammo on our backs along with all the other crap we had to carry, I had 100Lb+ of gear alone for my role in the mission. We were using vehicles up to a point where we had to leave them, then set up a cache site and set an overwatch over it then my team went into the village, the helo's were dropping it from about 40ft in body bags (Speedballs) One semi bad-guy I knew that was fighting against us later told my team mate that they thought we were dropping in robots to fight because we never stopped advancing, we advanced like robots right towards them and some guys were shot and didnt fall down.... was kinda funny. It really hurts morale when you think your fighting an indestructible enemy. My battle load was 350 rounds of 5.56 in Pmags 11 30rounders and one 20 rounder with tracers for 10.5in M4, 120 rounds of 7.62 for my M14 EBR, went in country with a Leupold, turned in with a NF on it. then was issued a KAC SR-25 and Pmags with a NF but never got to use it in Combat.

Pistol was a Sig M11.

[Michael]

Not by the US Army, they weren't. The M1919 was classified as a light machine gun, and the BAR as an automatic rifle. (The initials "BAR" are an abbreviation of Browning Automatic Rifle.)

In the context of the ongoing discussion, the BAR was employed as the SAW/IAR of its time, while the M1919 was employed the M240G of its time; hence the terms used are relevant to the discussion.

If you look at the criteria I posted earlier of Light v Medium v Heavy, they also fit the parameters. I will add some additional criteria that I think should be fairly widely accepted;

Light – Employed by single person (BAR, SAW, IAR)
Medium – Employed by a team (M1919, M60, M240G)
Heavy – Employed by a team, but due to system/ammo weight/bulk, normally fixed or vehicle mounted (M2, M1917, Mk19)