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Just when you thought it wasn't going to get bigger...

Here's the skinny
- 800 cubic inches of chamber
- 120" barrel length of schedule 80 3"
- 1:1 ratio
- twin igniters
- chamber fan
- MAPP metering/regulating
- Sureshot AL bits, custom shoulder rest
- Sabots to carry 2" UHMW compound rounds
- Estimated 750 fps with 232gram UHMW compound round good for a few thousand ft/lbs. of energy

This is a prototype developed for an international defense contractor.

Videos hopefully if its not shipped to soon.

Hey JSR... sabots finally!

Wow! that looks very beastly. 750fps! thats just amazing. Could you make a video?

damn , are these going on the order form
I'm sure recoil on that will be quite...noticeable, considering it
only has like 4000 ft/lbs, nice job again i would really like to see that thing in action
ggdt only predicts 624fps with my 1500ci 3" porter @ 100 psi so that thing must be a beast i might need to make a huge combustion, just so i could have a beast like that

jagerbond wrote:Hey JSR... sabots finally!

HA! Finally I knew if I complained enough...

Brilliant job, I'm sure if that round had struck the centre of the door panel it would have happily gone clean through.

Any comments on the accuracy with sabots? From the design they look like the petals should come away quite cleanly. Also I like the fact that the sabot projectile is from the preceeding calibre, the Germans did this in the second world war where for example the sub projectile for their 88mm APDS round was the full calibre projectile from the 75mm gun.

One small thought, how about having the central projectile as a simple UHMW cup filled with say 100 0.177" lead BBs, or 10 0.38" steel bearings. The whole assembly should fly out at more than 750 feet per second, et voila, shotgun

Fantastic design and build as usual Mike
I thought something was keeping you busy!

Excellent sabot design.
Is there any means to "tether" the pieces together?
Thinking in private use not military.
It may not be worth if they don't fly to far.

jackssmirkingrevenge wrote:
Brilliant job, I'm sure if that round had struck the centre of the door panel it would have happily gone clean through.

I think its got more to offer. We got everything operational and seeing it was midnight decided only to test a few rounds. We'll get the AF dialed in and get some chrony data.

jackssmirkingrevenge wrote:
Any comments on the accuracy with sabots? From the design they look like the petals should come away quite cleanly. Also I like the fact that the sabot projectile is from the preceeding calibre, the Germans did this in the second world war where for example the sub projectile for their 88mm APDS round was the full calibre projectile from the 75mm gun.

D

Accuracy not tested yet, but if you look at the photo you can see the 3 small dents where the sabots hit the door. The petals seem to have all hit equidistant from the round. We tested some 3" compounds -- heavy hitters close range but low CD.

jackssmirkingrevenge wrote:
One small thought, how about having the central projectile as a simple UHMW cup filled with say 100 0.177" lead BBs, or 10 0.38" steel bearings. The whole assembly should fly out at more than 750 feet per second, et voila, shotgun

I'll see what we can do.

Great gun as usual and i like the shoulder rest maybe if you were to add some leather or padding to help it not to slip.

But Great design i give it 5 stars!!!

jagerbond wrote:I'll see what we can do.

I'm sure you'll come up with something providing some kind of universal "cup" sabot would allow customers to fire pretty much anything which fits into it the barrel, without having to worry about getting a good seal.

In the interest of improving penetration, reducing the diameter of the sub projectile would certainly imporove performance. Remember that reducing the diameter to 1" from 2" gives you 25% of the original surface area, with a corresponding reduction in the amount of energy required to penetrate a given target.

Taking this to the extreme, 10 inch nails (you can cut them down of course, for the sake of tradition ) with some sort of fin or conical tail attachment would make very scary penetrators...

This is a prototype developed for an international defense contractor.

I'm guessing more details of its intended use would be classified...

jackssmirkingrevenge wrote:
In the interest of improving penetration, reducing the diameter of the sub projectile would certainly imporove performance. Remember that reducing the diameter to 1" from 2" gives you 25% of the original surface area, with a corresponding reduction in the amount of energy required to penetrate a given target.

We have a preset minimum round size of 40mm, luckily the 1.5 UHMW comes a tad oversized. We will probably increase the steel nose to 1/2" for extra CD.

I'm guessing more details of its intended use would be classified...

They have not asked me to sign a NDA and, they found us... There is still a lot to be sorted out. At least there's some initial funding.

Figure I'll give you guys an update. This large build has seen quite a bit of evolution and we've seen some interesting data. Looking at the data, a coaxial configuration may get better results (10%) with a 1.5 to 1 ratio than a 1 to 1 ratio.

C/B ratio = 897CI / 633CI or 1.41 / 1 ratio
Extended Chamber / Short Barrel / Gas set to 39PSI
677fps 676fps 661fps average 671fps

C/B ratio = 671CI / 633CI or 1.06 / 1 ratio
Regular Chamber / Short Barrel / Gas set to 32PSI
610fps 609fps 599fps average 606fps

C/B ratio = 671CI / 792CI or .85 / 1 ratio
Regular Chamber / Long Barrel / Gas set to 32PSI
614fps 617fps 658fps average 629fps

C/B ratio = 897CI / 792CI or 1.13 / 1 ratio
Extended Chamber / Long Barrel / Gas set to 39PSI
703fps, 699fps, 720fps average 707fps

Also, worth noting was the ignition placement. Initially we placed to igniters near the breech end and could make only 450fps. placing the igniters at the fore (furthest from the barrel) got us the numbers above.

Our metering system needed an auxiliary tank to support the added fuel needs.

Yes, We did not see the estimated 750fps with a baseball. But we did make some 3" compound rounds and put 3" holes clean through a car door! Pics to come.

Our metering system needed an auxiliary tank to support the added fuel needs.

Ha!

jagerbond wrote:Figure I'll give you guys an update. This large build has seen quite a bit of evolution and we've seen some interesting data. Looking at the data, a coaxial configuration may get better results (10%) with a 1.5 to 1 ratio than a 1 to 1 ratio.

Also, worth noting was the ignition placement. Initially we placed to igniters near the breech end and could make only 450fps. placing the igniters at the fore (furthest from the barrel) got us the numbers above.

I was getting some results like that in larger sizes where the longer barrels performed at lower than expected performance. The focus seems to be shifting from C/B ratio (still important) but the simple dimensional relation of the barrel bore to length becomes important. If you wish to gather barrel performance data, I've had great success in clocking stuff in the barrel to find the acceleration roll off distance. More info on the procedure is in the contest wiki site. The link to the barrel trim page is here. Feel free to PM me if you need more information on implementing the test for yourself.

https://inteltrailblazerschallenge.wiki ... rim+method

auxiliary wrote:Ha!

It's not all good

patent description wrote:Auxiliary apparatus with injector of radio-opaque fluid and device for extending and immobilising the penis in the ray path for retrograde urethrography

Man that thing is big...even though I see what looks like a shoulder mount, it's probably not very practical to be handheld...could there be a ground mount of some sort in the works?

Love the sabot, love the monster energy available...

800 cubic inches isn't all that big. My 2 inch valve launcher is only 100 cubic inches smaller. It's slightly larger than 3 US gallons.