I did not need a lecture on the balance and handling of bullpups, thanks.  I am just as aware of those charcteristics as you.

However, I did grossly misread your post, and thought you were talking about locating the pistol grip in front of the "tumor"

A bullpup with pistol grip near the center of balance seems possible, but the gun would be rather tall.  Something like this:

"A bullpup with pistol grip near the center of balance seems possible, but the gun would be rather tall.  Something like this"

I actually got to handle the Tavor12 at SHOT show last year. It looks weird but actually handled surprisingly well. 

The 'tallness' could be an advantage as well, in that it would likely make a longer, 30rd magazine more palatable. 

gatnerd said...

With a very front heavy weapon, most of the weight is supported by the shooters left arm, held away from the body, which exerts more mechanical leverage against the shoulder and makes it more fatiguing. 

I experienced a painful example of that a couple of years ago, when trying out a SCAR H fitted with a heavy TI night sight + scope combination. I had great difficulty in getting a clear view through the sight (as described HERE) and spent so long trying to get a sight picture that my left arm just gave up. I had to lie down to shoot the gun. I'm an old guy now, but I'm not in bad shape for my age. I went on to shoot some Tavors from the standing position, and they were no problem at all - I could have carried on all day with those.

PS My left shoulder gave me trouble for months afterwards, I must have seriously overstrained it.

"I experienced a painful example of that a couple of years ago, when trying out a SCAR H fitted with a heavy TI night sight + scope combination. I had great difficulty in getting a clear view through the sight (as described HERE) and spent so long trying to get a sight picture that my left arm just gave up. I had to lie down to shoot the gun. I'm an old guy now, but I'm not in bad shape for my age. I went on to shoot some Tavors from the standing position, and they were no problem at all - I could have carried on all day with those.

PS My left shoulder gave me trouble for months afterwards, I must have seriously overstrained it."

Yes, the effect of weapon balance on fatigue is quite profound. 

I first noticed it a few years ago, playing with a LMT MARS AR15, with its rather heavy monolithic handguard + suppressor. I was quite taken aback by how much front heavy this combination was, and how quickly fatiguing it was to hold steady. The suppressors weight, and even worse, that weight extended to the furthest end of the rifle where it exerts maximum leverage, really has an effect disproportionate to the weight increase.

In my personal collection, the difference between my AUG and my AR is really pronounced.

The AR is a modern, mlok handguard model with medium contour barrel, and currently only iron sights. Weight is 6.5lbs. 

My AUG, by comparison, is fully accessorized with an ACOG, Surefire Light + mount, sling, and loaded 42rd mag, and weighs in at 10.25lbs. 

Yet just standing in my living room, holding aim at the lightswitch on the wall 10yd across the room, the unloaded 6.5lb AR becomes more tiring to hold on target then the 10.25lb loaded AUG, despite the AUG being nearly 4lbs heavier. 

So when I look at the 6.8 Textron, with its tumor + likely 8lb weight + a suppressor...I shudder at the balance. 

The TFB article seem to imply that they also may have built a battery into that tumor section, further adding weight forward of the pistol grip... 

As good as LSAT is as a technology, its hard to see it winning with this current carbine configuration. On the other hand, given SIG's case design, I'm extremely skeptical that SIG is achieving much in the way of cartridge weight savings. 

The real wildcard is GD/True Velocity/Beretta submission. If they can produce a decent rifle and LMG with more conventional ergonomics, I suspect they will win out over Textron. 

Pardon my ignorance, but how is it possible to use a suppressor with a cased telescopic cartridge? Doesn’t that type of cartridge use some kind of polymer wad at the front?

gatnerd said...

Several different articles over the last few months have mentioned a steel base / brass body. It's possible they are all wrong in their reporting; that said the bases sure look shiny like machined steel. 

Right, but steel base + 20% weight reduction are not a good match, and according to this picture I'm not 100% confident that the base is steel, could be light alloy also...

"Right, but steel base + 20% weight reduction are not a good match, and according to this picture I'm not 100% confident that the base is steel, could be light alloy also..."

Im certainly rooting to be wrong, and to have it actually be some sort of alloy / 20% lighter.

That said, my gut is that SIG is likely lawyering the solicitation.

From what I recall, the solicitation calls for the 6.8 to be "20%+ lighter then it's equivalent brass cartridge."

That could be interpreted as we hope: 6.8x51 hybrid is 20% lighter then 6.8x51 brass.

But it could also be interpreted as 6.8x51 hybrid  at 80kpsi is equivalent  in velocity to, say, 270 WSM brass at 62kpsi. Therefore, because the hybrid case allows for a smaller cartridge to hit the target velocity, it is in effect saving 20% weight vs its larger brass ballistic equivalent.

i.e.

270 WSM (29g)= 130gr @ 3000fps from 16"

6.8x51 (24g) = 130gr @ 3000fps from 16"

-->6.8 is 20% lighter for same performance 

Hopefully I'm wrong.

gatnerd said...

270 WSM (29g)= 130gr @ 3000fps from 16"

6.8x51 (24g) = 130gr @ 3000fps from 16"

-->6.8 is 20% lighter for same performance 

This is my best guess also.  I think that an important detail is that at least one report states that the Sig entries could be easily converted to 7.62x51 with barrel swaps.  My cynical self thinks that Sig is betting that this project will mostly fail and that the weapons will spend most of their lives shooting standard or reduced weight 7.62x51 or 6.5 Creedmoor cartridges.   They will provide the OPTION  to shoot the 6.8 Wondercartridge when needed, though.   Sig also touts major felt-recoil reduction.  Now the military would have 7.62x51 (or 6.5mm) weapons as controllable as their 5.56x45 predecessors.  They might believe that this will be enough of an improvement over the existing weapons to tilt the scales their direction.  Let someone else provide reduced weight ammo for the existing cartridges.

gatnerd said...

So when I look at the 6.8 Textron, with its tumor + likely 8lb weight + a suppressor...I shudder at the balance. 

The TFB article seem to imply that they also may have built a battery into that tumor section, further adding weight forward of the pistol grip...

The comment that "the carbine appears to have a deep receiver with what may be a battery pack" is uninformed speculation by the author.

The "tumor" covers part of the rifle's operating mechanism.

Is there a publicly available drawing of the workings of the Textron CT system?