BAR 2.0 - how light might it went? (1 Viewer)

[tomo pauk]

Produced in (for the FG 42 lovers, in the eye-watering) 350 thousands of copies historically.
Seeing the Johnson LMG going at under 6 kg, the MG 81 at 6.5 (but without the buttstock and bipod)and the FG 42 at 5 kg - is there any merit in the BAR going the very light path? But not only for the Americans, but also the others, including the countries that were not historical users?

(granted, seems like the recoil mass of the Johnson was allowed to make an abrupt stop before moving forward, making the weapon to have a nasty kick; there was also no muzzle brake, despite it's utility on a light weapon firing a powerful cartridge)

 

[Shortround6]

You can almost always trade durability for light weight.
Should you?
Also check out Forgotten Weapons episode on the Colt Monitor.
They got the thing down to 16lbs (without bipod) and video looks like good controllability.
However look at the slow motion sections. This thing had a fair amount of muzzle whip.
The Compensator appears to work but the cost in concussion to the shooter according Ian is very substantial.

 

[tomo pauk]

Some experimentation with the muzzle brake and/or compensator might've perhaps improved the ... experience for the shooter and his comrades sticking around.
BAR would've probably been the best with a less powerful cartridge. Unfortunately for the US or the British, this would've required that the .276 Pedersen cartridge is adopted, or perhaps that a version that uses the Savage .250-3000 is manufactured.
Other countries, like Sweden, Norway, Italy or Japan have the less powerful cartridges in use, however a light BAR in their cartridges but it would've required that the respective militaries adopt the 'automatic rifle' idea.
(I'm aware of the historical Swedish BARs that were more in the LMG category).
Less powerful cartridges would've also made the lighter BAR to have easier time to materialize.

 

[Shortround6]

The Bar receiver was very large and very heavy.

About 80% complete. One reason the BAR was reliable.
But unless you change the receiver considerably you have a problem making it light. Putting a light skinny barrel on it just leads to other problems.
You could shorten it and use a shorter cartridges but that adds to development time.
Obviously they did make it in shorter cartridges but they often left the receiver and bolt alone so no weight reduction.

The .250 Savage is nice round for hunting and a number of experimenters used it.
However it had a large amount of taper to it and while not as bad a 8mm Lebel or even the .303 (barely) and stacking large quantities of ammo (15 or more?) rounds in a magazine is going to call for curved magazine. Can be done but one more complication.
250 Savage was over about 20-22mm shorter than a 30-06 (depending on bullet), which certainly leaves room for a shorter/lighter receiver. But at that point you are not gaining much by trying to shrink the BAR down to the desired size.

 

[tomo pauk]

About 80% complete. One reason the BAR was reliable.
But unless you change the receiver considerably you have a problem making it light. Putting a light skinny barrel on it just leads to other problems.
You could shorten it and use a shorter cartridges but that adds to development time.
Obviously they did make it in shorter cartridges but they often left the receiver and bolt alone so no weight reduction.

Light skinny barrel will go well with a less powerful cartridge, but obviously not with a full-powered one, like the .30-06 or the 7.92x57. The less powerful cartridges can also use shorter barrels. Lighter, shorter and skinny barrel will be lighter barrel, no surprises there. A lighter butstock can also be used, be it perhaps skeletonized wood stock, or the sheet metal. The front hand guard can also be lighter.

The .250 Savage is nice round for hunting and a number of experimenters used it.
However it had a large amount of taper to it and while not as bad a 8mm Lebel or even the .303 (barely) and stacking large quantities of ammo (15 or more?) rounds in a magazine is going to call for curved magazine. Can be done but one more complication.
250 Savage was over about 20-22mm shorter than a 30-06 (depending on bullet), which certainly leaves room for a shorter/lighter receiver. But at that point you are not gaining much by trying to shrink the BAR down to the desired size.

The .250 Savage will kill a deer, so it should be also able to be a severe threat to an enemy soldier, too.
At any rate, the new/different cartridge will require a new magazine. I'm okay with leaving the receiver with as little change as possible.
The lower powered cartridge will also be requiring a lighter muzzle brake (= another weight saving).

 

[Shortround6]

A lot depends on what you want the new gun to do.
Like anti-personnel only or anti-vehicle (at least trucks) and tracer capability and if so, out to what range.
The 250 Savage was designed to use full length barrels, around 20-24in ( 508-610mm?) It had also be designed to use an 87grain (5.64 grams) bullet to get the 'advertised' 3000fps velocity. Using a 100 grain (6.48g) bullet cost several hundred fps. Now this was with 1915 powder and mid/late 30s powder had an advantage.
But there was no reason to use the 250 Savage as is. A case with less taper could hold a bit more powder, stack better, and restore some of the lost velocity of the shorter barrel.
But more powder also means more barrel wear and more muzzle blast.

But if the US would not switch to the .276 Peterson there is little chance they would adopt and even lower powered round. neither would be compatible with the the millions of 30-05 in storage and neither would do the long range job of the machine gun.

If you get around that there may have been a number of other guns that offered more than the BAR.

 

[tomo pauk]

A lot depends on what you want the new gun to do.
Like anti-personnel only or anti-vehicle (at least trucks) and tracer capability and if so, out to what range.

Soft skinned vehicles should've been an easy prey, that by default means the same for the enemy infantry. Tracers - about the same as then-current 6.5mm ammo.

The 250 Savage was designed to use full length barrels, around 20-24in ( 508-610mm?) It had also be designed to use an 87grain (5.64 grams) bullet to get the 'advertised' 3000fps velocity. Using a 100 grain (6.48g) bullet cost several hundred fps. Now this was with 1915 powder and mid/late 30s powder had an advantage.
But there was no reason to use the 250 Savage as is. A case with less taper could hold a bit more powder, stack better, and restore some of the lost velocity of the shorter barrel.
But more powder also means more barrel wear and more muzzle blast.

I like the 250 Savage exactly because it was mild, so there is no intention on my part to make it more powerful. I'm okay with 2800+ fps with 90-100 gr ammo, the barrel no longer than 20 in, and again I'm not interested in the 3000 fps value.
The suggestion for the .250 was just one of the several I've made.

But if the US would not switch to the .276 Peterson there is little chance they would adopt and even lower powered round. neither would be compatible with the the millions of 30-05 in storage and neither would do the long range job of the machine gun.

If you get around that there may have been a number of other guns that offered more than the BAR.

Yes, US military will not go with the .250 Savage. Especially if they've picked the .276 Pedersen in the 1930s.

 

[Shortround6]

Tracers - about the same as then-current 6.5mm ammo.

Most of the Military 6.5 ammo was using 130-160 grain bullets and had a lot more room for tracer inside the bullets.
Now the Swedes came up with an 8mm round for their big machineguns because the 6.5 Swedish was not powerful enough.
Italians also came up with an 8mm machine gun round.
Japanese came up with a 7.7mm machine gun round.
6.5s don't make good AP (or metal piercing) bullets.

If you want a medium powered rifle and cartridge and you are willing to put up with a 2 cartridge supply system then there is no reason you can't do it.
Question is where is the break in the supply chain. No real bad answer. Soviets keep the 7.62 rimmed even at company level. Platoons in the 1950s got the 7.62X39s.
Kind of depends on where the heavy machine guns are located, parceled out to the companies or held at battalion level?

 

[tomo pauk]

Most of the Military 6.5 ammo was using 130-160 grain bullets and had a lot more room for tracer inside the bullets.
Now the Swedes came up with an 8mm round for their big machineguns because the 6.5 Swedish was not powerful enough.
Italians also came up with an 8mm machine gun round.
Japanese came up with a 7.7mm machine gun round.
6.5s don't make good AP (or metal piercing) bullets.

There is no intention on my part to suggest that the 6.35-6.5mm weapon will replace all and every automatic weapon in the countries of interest. These countries can have the 7.7-8mm 'heavy' MGs as they intend to do.

If you want a medium powered rifle and cartridge and you are willing to put up with a 2 cartridge supply system then there is no reason you can't do it.
Question is where is the break in the supply chain. No real bad answer. Soviets keep the 7.62 rimmed even at company level. Platoons in the 1950s got the 7.62X39s.
Kind of depends on where the heavy machine guns are located, parceled out to the companies or held at battalion level?

Having two lightweight BARs per section/squad (ie. per 10-12 men), the heavier and often tripod-mounted automatic weapons can remain where they were. Granted, not many of the militaries will have two LW BARs available, especailly considering the huge manpower of some armies.

 

[Shortround6]

There is no intention on my part to suggest that the 6.35-6.5mm weapon will replace all and every automatic weapon in the countries of interest. These countries can have the 7.7-8mm 'heavy' MGs as they intend to do.



Having two lightweight BARs per section/squad (ie. per 10-12 men), the heavier and often tripod-mounted automatic weapons can remain where they were. Granted, not many of the militaries will have two LW BARs available, especailly considering the huge manpower of some armies.

US Marines got 3 BARs per 13 man squad in 1944/45. The Army did not.
But without having easily changed barrels having a single squad automatic was a real problem.
US doctrine (at the start of the war) was there was a 3 man BAR team, A gunner, an assistant gunner and an ammo carrier. This was in 1940.
Actual practice in 1942 in North Africa??????
30-06 BAR was supposed to be good for around 75rpm to keep from cooking the barrel, The light rounds will help. but only for so long.
Bren was good for 120rpm (changing barrels every 2 1/2 minutes) by doctrine. MG 34 as about the same.
Now the squads with the same ammo bolt guns (or the US M-1) could refill the mags/belts if they were in a position where the MG was doing most of the shooting.
If your squad automatic is using different ammo?
Or if you have several squad automatics and use them in rotation to keep them cool and restrict ammo use?

I don't know which was worse.
Lack of quick change barrel.
Not having enough ammo in the squad.

 

[marathag]

The .250 Savage is nice round for hunting and a number of experimenters used it.
However it had a large amount of taper to it and while not as bad a 8mm Lebel or even the .303 (barely) and stacking large quantities of ammo (15 or more?) rounds in a magazine is going to call for curved magazine. Can be done but one more complication.

The Ackley improved 250 Savage blew out much of the taper for more powder capacity

 

[tomo pauk]

Now the squads with the same ammo bolt guns (or the US M-1) could refill the mags/belts if they were in a position where the MG was doing most of the shooting.
If your squad automatic is using different ammo?
Or if you have several squad automatics and use them in rotation to keep them cool and restrict ammo use?

I don't know which was worse.
Lack of quick change barrel.
Not having enough ammo in the squad.

Ammo consumption of the BAR was much greater than that of the other .30-06 weapons, so trying to scour the bullets aloted for these for the BAR will quickly see the non-automatic weapons running out of ammo.
Going with the lower powered cartridge allows for carriage of more bullets for the automatic weapon, even more so when the much lower weight of the weapon is taken into consideration, since now the gunner can also carry much more ammo. The lower powered ammo will be heating the barrel less, and the, perhaps, 1st third of the barrel can have the ribs like the ZB 26 spin-offs had. Or, instead of the ribs, the corrugated sheet metal sleeve can be attached to increase the cooling area on the barrel closer to the chamber.

Several automatics per squad indeed allows for the greater flexibility.

 

[tomo pauk]

FWIW, looking at the American data found here, the 6.5mm Arisaka lost only 100 ft/s when fired from a shorter carbine barrel (19.2 in) when compared with the full-length rifle barrel (31 in). We can probably expect similar result for the other 6.5mm with the spitzer bullet?