autogun

Military Guns and Ammunition

Hosted by autogun

This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons, particularly in larger calibres (12.7+mm).

  • 3173
    MEMBERS
  • 180183
    MESSAGES
  • 0
    POSTS TODAY

Discussions

Exploring The Design Space   Ammunition <20mm

Started 25/7/15 by NathanielF; 99557 views.
NathanielF

From: NathanielF

25/7/15

Oh, very neat. I haven't seen a high res image of the .264 USA before, much less of the composite case variant.
renatohm

From: renatohm

25/7/15

Awesome job.

In short, there are diminishing returns in everything. What do you think would be the optimal weight x volume point with these parameters (rim diameter, taper, etc)? And what volume would that be?

NathanielF

From: NathanielF

25/7/15

renatohm said...

 

Awesome job.

In short, there are diminishing returns in everything. What do you think would be the optimal weight x volume point with these parameters (rim diameter, taper, etc)? And what volume would that be?

 

If you are just measuring the volume-to-weight ratio within one case head diameter, then you end up with a surprisingly long cartridge. This is because the case base itself is the heaviest part of the case. However, that additional volume isn't necessarily greatly improving your performance either.

Taurevanime

From: Taurevanime

25/7/15

I imagine there is also a diminishing return towards having much longer cases, as the action of the gun needs to be longer, and the working components of the gun are among it's heaviest too. So you really never should design a cartridge entirely separate from a gun.

NathanielF

From: NathanielF

25/7/15

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 (there are other reasons to think the comparison in that article isn't exactly representative, either, such as the handguards). I don't think in the long run that configuration will work out very well, due to bolt strength concerns among other things. 

The point of me mentioning this is that, at least with the AR platform, increasing the OAL of the round doesn't have such dramatic effects on weapon weight, but it does increase the weight of your magazines quite a bit.

In reply toRe: msg 7
NathanielF

From: NathanielF

25/7/15

Here's what I mean about the handguards, BTW:

http://www.superiorweaponssystems.com/ar10_rifle_sniper_fftube_rev3.htm

http://geissele.com/mk4-keymod.html

If we compare the two, the SWS handguard with an AR-10 barrel nut and locking ring is about three-quarters of a pound heavier than the Geissele MK4 rail and nut.

stancrist

From: stancrist

26/7/15

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.

Taurevanime

From: Taurevanime

26/7/15

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?

Taurevanime

From: Taurevanime

26/7/15

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!

In reply toRe: msg 8
NathanielF

From: NathanielF

26/7/15

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.

TOP