The biggest thing I take away from this. Is the fact I am glad I am more interested in classic firearms. Modern firearm furniture is expensive!

Fooling around with a certain cartridge template, scaling it up and down. Figured I'd show how I measure case capacity - this and component weight is why using SolidWorks properly is important to get the best estimates:

It's a 6mm based on the SPC case with a 1.721" case length and a 2.42" OAL (not with bullet shown, which is one of my stock 6mm bullets). Internal contour was based on 7.62 NATO, but adjusted for the SPC case's wall thickness. Initial estimates put cartridge weight at almost exactly 15g with a 77gr bullet. Depending on the resultant ballistics, the cartridge when fired from 14.5" barrels could potentially meet the specific energy threshold of 7.62 NATO at 1,000m if very fine projectiles are used.

When comparing ballistic performance of cartridges, the barrel length should always be stated. The official NATO specs are currently taken from 20" barrel for 5.56mm, and 22" barrels for 7.62mm (although of course the GPMG/M240 does have a 24.5" barrel as standard). In fact, bearing in mind that MGs are always likely to have longer barrels than IWs (especially in vehicle mounts and in the tripod-mounted support role held at platoon level) it's probably a good idea to give two sets of figures for each round, reflecting different barrel lengths.

Taurevanime said...

 

So now we get to the lovely practice that is. For a given case volume do you get the lightest total package of loaded magazine and weapon. There are probably some optimal designs. And they all change when case and magazine materials change.

Isn't engineering grand?

 

Even with the models I have, I refuse to propose a "solution" for next-generation small arms, for that very reason. I think there's a whole lot of modeling and testing of individual cartridges - let alone other kinds of research and experiments - that needs to be done before a configuration can be decided upon.

stancrist said...

 

NathanielF said...

Yeah, though the biggest factor here is additional magazine weight. One of the issues I have with Jim Schatz's article on future assault rifles is that the .264 USA AR-12 featured in it appears to just be a lengthened AR-15, so of course it will be closer in weight to an AR-15 than an AR-10...

Even going with the comparison as is, the AR12 weighs a full pound more than the M4.

Then there is the matter of having a bit more than half as many .264 rounds as 5.56mm: 130 rds of .264 (assuming 26-rd mags) vs 210 rds of 5.56mm (in 30-rd mags).

If the number of .264 mags and/or mag capacity is increased to get a better ability for sustained combat, then soldier load increases again.

 

BTW, not only was that piece of propaganda verrrrry long, it was full of errors.

 

One notes they left off polycase 5.56mm in their comparison, despite the fact that 5.56mm polycase ammo has been ordered.

Jim Schatz's article on future assault rifles

 

There is a statement in there which I have not seen anywhere else: “Current U.S. statistics reveal that 21% of small arms KIA’s and WIA’s in Afghanistan are from 7.62x54R caliber weapons” does anybody know if it is true?

Assuming that most of the other 79% were 7.62x39mm it suggest that long range fire-fights are not the main problem; possibly not even a significant problem.

CWRPHILLIPS said...

Assuming that most of the other 79% were 7.62x39mm it suggest that long range fire-fights are not the main problem; possibly not even a significant problem.

Yup, been saying that for a while as well. These very long range ambushes are a non event. They don't require a new round, just the odd DMR and something like Switchblade to make them non-viable. The majority of serious firefights - and casualties - are within 300 metres, same as always. 

Squad goes into cover with 360 degree observation while the DMR and the 7.62 MG engage. As soon as support arrives the ambush breaks off. The only casualties are likely to be in the first few seconds while the squad is in the open. 

Something to keep in mind though is one of the tactics the Chechens used, which was mentioned by the US military couple years ago as seeing use in in both Iraq and Afghanistan. It places the sniper in solid cover a few hundred metres from the ambush point with another group at much longer range. The sniper takes his shot or shots, and then when the targeted unit reacts, the long range group opens up on them with whatever comes to hand to disguise the presence of the sniper. The sniper could just be a good shot with an AK, or a Tabuk 7.62x39 Dragunov, who slides away in the confusion, or stays in cover till its over. 

autogun said...

...bearing in mind that MGs are always likely to have longer barrels than IWs...

Two words that should never be used -- "never" and "always"   ;^)

NathanielF said...

stancrist said...

NathanielF said...

Yeah, though the biggest factor here is additional magazine weight. One of the issues I have with Jim Schatz's article on future assault rifles is that the .264 USA AR-12 featured in it appears to just be a lengthened AR-15, so of course it will be closer in weight to an AR-15 than an AR-10...

BTW, not only was that piece of propaganda verrrrry long, it was full of errors.

One notes they left off polycase 5.56mm in their comparison, despite the fact that 5.56mm polycase ammo has been ordered.

Yeah.  That's one of the reasons I refer to it as propaganda.

CWRPHILLIPS said...

Jim Schatz's article on future assault rifles

There is a statement in there which I have not seen anywhere else: “Current U.S. statistics reveal that 21% of small arms KIA’s and WIA’s in Afghanistan are from 7.62x54R caliber weapons” does anybody know if it is true?

It seems to correlate fairly well with the chart on Tony's site:

CWRPHILLIPS said...

Assuming that most of the other 79% were 7.62x39mm it suggest that long range fire-fights are not the main problem; possibly not even a significant problem.

From what I gather, they are mostly harassing fire that inflicts few friendly casualties.  So yes, it does not seem to be a problem that requires a change to a GPC.