Requirements for Replacement of Currently Issued 5.56 M-855 and 7.62 M-80.

[JASmith]

Stan,

Your point is well taken.

The proliferation of shorter barrels suggests that we can reasonably expect that the standard barrel length for the new cartridge to be less than 0.5 metres.

The performance reputation of the 7.62X51 is in a .5+ metre (20-24 in.) barrel. Many, if not most, of the complaints about the 5.56 are partly a result of its use in the 14.5 in (0.37 metre) barrel.

So, if we hypothetically decided that we must use a .308 in bullet, the cartridge would have to be larger than the 7.62X51mm NATO in order to just match the trajectory with, e. g., the M80 bullet.

So, an alternative threshold might be "Equal or better the vertex and wind drift of the 7.62X51 M80 at 1000 metres when using a 20-inch barrel." The complementary threshold statement might then be "Equal or better the vertex and wind drift of the 7.62X51 M80 at 1000 metres when using a 14-inch barrel."

For Tony: Does this alternative fit your vision better?

Cheers!
Joe

[bwaites]

Wow! While you guys look for the magical bullet and cartridge combination that will match .308 ballistics from a 14 inch barrel the hordes have stormed the gates and overtaken you! LOL!!

Good luck with this search, because its simply impossible. You cannot launch a projectile from a shorter tube and match velocity and external ballistics unless you increase powder capacity. Increasing powder capacity increases weight, but more importantly, increases recoil, putting you back at square one!

I'm all for improving what is available to our Joes, but this is an impossible task without changing the paradigm and using some other type of cartridge. It simply won't and can't happen using traditional brass and bullets.

What you are proposing is a shift as radical as the shift from black powder to smokeless.

[Tony Williams]

The US Army seems set on the idea that weapon overall length not exceed that of the M4, so much so that the XM8 was fitted with a 12.5" tube!

Makes you wonder why they are so dead set against bullpups, considering that you get an 8 inch advantage in barrel length for the same length gun...

I am happy for a barrel length of 20 inches to be specified when making comparisons with the 7.62mm, since in reality guns being used at anything approaching 1,000 metres would probably have such a barrel. (Although having said that, the British troops seem delighted with the 7.62mm L129A1, which has a 16 inch barrel. But then, their only alternative is an SA80...)

It seems reasonable to specify a 14.5 inch barrel when making comparisons with 5.56mm. That actually makes the use of both sets of comparisons quite sensible.

[JASmith]

Wow! While you guys look...

The secret sauce is a smaller caliber than 7.62...

[JASmith]

...I am happy for a barrel length of 20 inches to be specified when making comparisons with the 7.62mm, since in reality guns being used at anything approaching 1,000 metres would probably have such a barrel...It seems reasonable to specify a 14.5 inch barrel when making comparisons with 5.56mm. That actually makes the use of both sets of comparisons quite sensible.

We might be approaching the trajectory question a bit awkwardly.

A way of looking at this might be to ask that the rifle/carbine has a point blank range (based on the average size of the torso) that is equal to or better than the 5.56 and that the GPMG application has the direct 7.62 comparison.

[Tony Williams]

We might be approaching the trajectory question a bit awkwardly.

A way of looking at this might be to ask that the rifle/carbine has a point blank range (based on the average size of the torso) that is equal to or better than the 5.56 and that the GPMG application has the direct 7.62 comparison.

Yes, but I was also thinking that the new round would replace 7.62mm in the semi-auto DMRs like the M110 and M14EBR.

Clearly, it would make sense with one general-purpose round to have the DMR simply being a longer/heavier barrel version of the standard rifle/carbine.

[JASmith]

Yes, but I was also thinking that the new round would replace 7.62mm in the semi-auto DMRs like the M110 and M14EBR.

Clearly, it would make sense with one general-purpose round to have the DMR simply being a longer/heavier barrel version of the standard rifle/carbine.

Yup!!!

[Tony Williams]

A follow-up thought - given the likely weight of the DMR and the reduced recoil of our general-purpose cartridge, it could also be given selective fire to act as an automatic rifle.

[stanc]

4. To replace the 7.62x51 a new cartridge needs to achieve the following:
- to equal the barrier penetration performance of the 7.62mm M80 in terms of overall penetration of a range of media...

How about using 6.5x55 as sort of a surrogate for your proposed round, and conduct barrier penetration tests with it versus 7.62 M80? That way you can get some hard data (at relatively low cost) to validate the theory that your intermediate round can actually equal 7.62 penetration.

Norma markets 6.5x55 ammo loaded with the 120gr FMJ, and IIRC other companies offer 139gr loadings. And on your side of the Atlantic, it might even be possible to get mil surplus AP?

[Tony Williams]

As you are probably aware, gun and ammunition purchasing is a non-trivial issue over here, with all sorts of hoops to jump through to obtain permissions. Basically, rifles can only be bought for hunting or target shooting, you have to apply for specific calibres of rifle and ammunition (and can't acquire anything else without going back to ask for permission again), and AP ammo is effectively banned.

I am in an unusual position in that have permission to own any type of ammo (except HE) in any calibre I want (I need that for my research work) but only in very small quantities for each type, and the price of that is that I don't possess any guns at all. Thanks to some military and other connections I do occasionally get to shoot all sorts of weapons, including those which are banned to civilians in the UK, but I'm not in a position to organise the kind of shooting tests you describe.

[LR1955]

The secret sauce is a smaller caliber than 7.62...

Joe:

Negative. The secret is a 130 grain 7.62 whose bullet is about 1.3 inches long.

Saves a bunch of money in terms of re-tooling, less recoil than the issued M-80, longer danger space, 1/3 higher velocity, 1/3 better penetration and 1/3 greater lethality.

I can do the same with a 80 grain 5.56. Retain the parent case for both which saves billions in re-tooling and RDTE.

LR1955

[stanc]

A 130gr 7.62mm spear @ 3800 fps!!!

What secret sauce are you using, Gene?

[stanc]

I am in an unusual position in that have permission to own any type of ammo (except HE) in any calibre I want (I need that for my research work) but only in very small quantities for each type, and the price of that is that I don't possess any guns at all. Thanks to some military and other connections I do occasionally get to shoot all sorts of weapons, including those which are banned to civilians in the UK, but I'm not in a position to organise the kind of shooting tests you describe.

Unfortunately, few of us are. All of the photos of you shooting a variety of weapons led me to think that you might be in a position to do such testing. Well, it seemed like a good idea...

[stanc]

Makes you wonder why they are so dead set against bullpups, considering that you get an 8 inch advantage in barrel length for the same length gun...

Yup. BTW, I just finished reading your "Why Bullpups?" article.

http://www.quarry.nildram.co.uk/bullpups.htm

Since it wasn't mentioned therein, you might be interested to know that the SAR-21 bullpup -- despite right-side ejection -- can be fired from the left shoulder. Some years ago, I had the chance to shoot a SAR-21, and noticed the ejection pattern was such that the empty cases appeared as though they would not hit a "lefty" in the face. Just to be certain, I fired it from the left shoulder, and had no problems with the ejection.

[JASmith]

How about using 6.5x55 as sort of a surrogate for your proposed round, and conduct barrier penetration tests with it versus 7.62 M80? That way you can get some hard data ...

Stan,

Good idea to get hard exterior and terminal ballistic data relevant to the size of cartridge being considered. We can do that by using handloads with, say, a .260 Remington, or 6.5X55, or any 6.5 mm rifle that can be loaded to the requisite velocities.

In the meantime, back to the requirements list. Are there any additional comments on the threshold and objective statements for item #1? I plan to tweak again in the next day or so.

Cheers!
Joe