7.92x107mm DS

[unertl]

This is a idea that has bean on my mind for over half a decade now.

First the history and what ive bean able to find. This was designed as an antitank cartridge prior to WWII.
Cartridge specs.
107.67mm

187 grains of nitro cellulose powder

245 grain lead core steel jacketed bullet

4,180 fps velosity (1200mm barrel)

The barrel life was origanily 30 rounds but improvements got it to 300 rounds. My question is, with current barrel technology, powders and bullets, (possibabily chrome maloy barrel and maloy bullets) could it extend the barrel life even further?

 

[CJ6]

How are the cases primed ? Are primers available ? Will the bullets need to be hand made ? case availability ? strength ? Cool prodject though.

 

[Kenny474]

300 rounds after improvements! And you thought your 6.5-284 was rough on barrels!

It actually used bullets the same diameter as the 8mm Mauser, but were steel jacketed with a lead core. I would imagine it would require some type of brass or maybe copper or gilding metal solid to hold up to the extreme velocity. And I would think a softer bullet would also help barrel life a bit as well. Lathe turned solids would likely be a very viable way to produce bullets of the size and weight needed, and a custom barrel would obviously be needed.

Where you would find brass for such a round is something I have no knowledge of. I have seen a few sites where people have possessed loaded rounds, so I would imagine ammo collectors and such to have a few. But I am at a loss as to where to buy any amount of them. From what I have seen, they are quite rare.

Though if the OP has had this idea for 50 years, he may possess some amount himself.

But as far as could it be done with improved barrel life, I would think beyond 300 rounds, but not significantly more. Maybe to 500-600 rounds, and possibly even a few hundred more. But that is a LOT of powder in a small bore. Nearly .50 BMG powder charges with the same bore diameter as an 8mm Mauser. I just can't fathom it to have a very significant barrel life.

At 107mm, the cases are longer than a .50BMG and use nearly as much powder. I think this would be an interesting project to say the least. If you have had the idea for 50 years, then it is time to just build it and see what happens. You only live once, so go for what you dream of and worry about barrel life later.

Kenny

 

[jr600yd]

WOW!
Let me get thie right. An 8mm 245gr bullet pushed by 187grs of powder going approx 4,200 fps...... NO muzzel break........
Wonder what's worst, being infront of it or behind? Sure you don't want to put wheel on the thing and fire it using a lanyard?

Hey if the bug bit go for it.

Good shooting, Jim

 

[unertl]

jr600yd if you click on the pictur you can see the breack they used. It was reported to have reduced recoil 60%, and was said to be similar to that of the standard infantry rifle.

This build would take some serious finance that i don't have right now.

It would first need to be reversed engineered then improved. The reciever would be switched to a HEAVY 1 port.(prefefably left port with a right bolt) A barrel would have be located so i could find out twist rate. The new barrel would also have to be fully custom. A intact unfired round compleetly mesured and blueprints made.($120 a round) Find someone that could make the brass, its just so much longer than your standard rounds. The bullets are also a problem as 8mm(7.92) is so uncomen.(dose anyone make maloy 8mm match bullets?)

To make matters worse break in and round development would use up quite a bit of barrel life.

 

[nfhjr62]

My father worked at the Frankford Arsenal during ww2 told me he worked on some very interesting weapons and brought home one that was being worked on 60 cal. ammo (just a case and projectile) still have it.

 

[jonbearman]

You might as well buy a boyes anti tank rifle,the rounds are available from time to time and would cost about 10 to 35 dollars a round.I dont think your project is worth the money or end result.

 

[Kenny474]

One issue with even a moly coated match bullet, it's doubtful that anything jacketed in that caliber and weight is going to hold up to 4200fps, and velocity may be even higher with improved powder available today.

A cheaper alternative that would likely have a similar end result would be to neck down a .50BMG to a caliber that has a capable bullet available, say .338? You may still need to use solids, as getting a bullet to sustain the RPM's and velocity involved might prove difficult. If not, plenty of very good .338 bullets are available. You could use a common action, as many .50BMG actions are available. Brass is common, a barrel would be easy, just call Krieger, Shilen, or any other barrel maker and order a big, fat .338 caliber barrel in an appropriate twist and say 36" long. Then you are left with a few odds and ends, dies, reamer, etc. It's very possible and won't require near as many full custom pieces.

Or just buy one of these: http://www.anzioironworks.com/Anzio-20-50.html
Anzio Ironworks 20/50. Basically a 20mm Vulcan necked down to .50cal. Pushes a 750 or 800gr bullet from 3200 to 3600fps.

http://www.anzioironworks.com/20MM-TAKE-DOWN-RIFLE.htm
Or just buy the 20mm Vulcan take-down rifle. Plenty of power there! 1600gr bullet at 3300fps.

 

[Travelor]

http://en.wikipedia.org/wiki/Wz._35_anti-tank_rifle

 

[CJ6]

The 338 x 50 BMG has been done (338 Talbot). 300 rds and the barrel was toast.

 

[2644ever]

Kenny, I absolutely agree with your comment, some compromise has to be reached in order to come close to the goal. A .416 Barrett case necked down to .338, with about 165 grains of AA8700, and a monolithic .338 250 grain molycoated bullet should reach 3700 fps in a 48" barrel.
This is only (!?) 350 fps faster than what you could sensibly expect from a .338 Lapua in the same barrel length and 500 fps short of the required velocity, and with the laws of diminishing returns, it will take a lot more than the .50BMG case capacity to have any significant improvement (forget about that 4200 fps Holy Grail).

And this makes me wonder where that magical 4200fps figure comes from... I think there's just no way to reach that velocity with the components described in post#1 without an insane amount of pressure. Even with super duper steel cases, and a howitzer like receiver, you wouldn't prevent the primer to miserably fail. Chronograph technology was at its beginning and I suspect the results were wildly optimistic to say the least.

 

[Kenny474]

2644ever, I too agree the velocity of 4200fps is a bit exagarated. But nonetheless, the rifle and cartridge are still very impressive both for their time and accomplishments. If you read about the way it pierced armor, that is rather impressive even by today's standards and exceptional back nearly 80 years ago.

I have been fascinated by ultra fast rounds for some time, and built a 6-284 to have something fast for myself. Now it has worn out, I am getting pieces together for a 22-6mmAI to further satisfy my need for speed.

This project would take heavy bullets and push them to velocity beyond the reach of many small bore rounds that we consider very fast today. Would it be practical, not at all. But it would be a novelty with power and speed that would be very difficult to match.

We think a 50gr bullet at 3800fps is impressive on varmints. Imagine the impact of a 225gr Interbond or 250gr BTHP at 3800fps would be like on a woodchuck or other fat little varmint! It would be even more incredible if you could develop a bullet with explosive fragmentation that could withstand the velocity and acceleration.
Or the incredible ballistics at 1000yds with high BC bullets.

While it would be expensive and short lived, the performance would be incredible. I only imagine it could be quite fun with almost anything you used it for.

If one were willing to make sacrifices, this would be achievable with many off the shelf pieces and would still produce incredible results that would be comparable to the original idea.

Even with the obstacles that would need to be overcome and the short barrel life, I still think could be a very fun and rewarding project. Especially after wanting to achieve these results for 50+ years. It may not end up being a replica of the original rifle, but it would be an incredible rifle, and possibly worth the 5 decade wait.

Kenny

 

[2644ever]

Right on Kenny! I like that project too... With a more realistic and practical barrel length, let's say 36", it is still possible to reach 3500fps and remain supersonic slightly beyond 2300 yds with the 250 Lapua bullet. I would opt for a bit slower (1") twist rate than with the Lapua magnum round in order not to stress the jacket. Herr Unertl would just have to order a special chambering at Barrett's and he would be done for a small fraction of the envisioned costs with his initial project. And, who knows, with boron nitride coating of the bullets, titanium nitride coating of the throat, and polygonal rifling, the barrel may last noticeably more than 300 rounds. This .338 Unertl HyperMag would be the hammer of Thor on talibans!

 

[RallyFan]

Unertl,

Perhaps to achieve the performance levels, and barrel life you desire, it may be necessary to move away from rifled barrels, to smooth bores...

Starting back in the mid-80s, Steyr developed a new anti-material rifle, the IWS 2000.
The IWS 2000 is a long recoil, self loading smoothbore, that shoots a 15.2mm projectile, with a 308gr APFSDS (Arnour percing, fin stabilised, discarding sabot) projectile at 4750fps. At 1000 meters the projectile is said to penetrate up to 40 mm of RHA (rollded homogenous steel armour), with maximum chamber pressure at 4,800 bar (69,618 psi).

Oh yes, weight is 18kg (39.7lb)

 

[unertl]

I'm familure with both anzio iron works, and the steyr IWS. To me the anzio products always looked uncomfortable and the IWS would require custom injection molding for the sabot, and a flechet of any real size would be a real pain in the a$$ to make.

The speed was a plus but the realy apeal was in the chaleng of first putting it together and then finding a load that would work well in it.

One of my biggest faults is i love to tinker excesively and this seemed to be the near perfect project for that.

If i were to do a necked down case what would you think of starting with a .50-140-3.25" or a .45-120-3.25"?
It would still be a single shot bolt action, and its a shorter case than the BMG. So a BMG action would work, though it might need a diffrent bolt face diameter.

 

[CJ6]

The above cases are all low pressure, would they withstand 65,000 + psi loads ? the Chey Tac case may be a better option.

 

[Kenny474]

I would think the brass for the relatively low pressure 45-120 and .50-140 would create a lot of issues if they were loaded beyond 35,000 to 40,000psi. To get to modern big-bore centerfire pressures (60,000 to 65,000psi) a much stronger case would be needed, or significant rework of custom made brass would be necessary.

I am no wildcat expert and have no experience with very large rounds, but I would think the .50BMG, .408 Chey Tac, .416 Barrett, and possibly .338 Lapua or other such large round would be a far better starting point brass wise. They are all much thicker and would handle far higher pressure than any blackpowder derived round. Even many of the larger rounds used in Africa operate at lower pressures, though some do reach 50,000 to 60,000PSI.

But in trying to reach outrageous velocity with a large round, modern brass would almost certainly be a necessity, or pressure would be a severe limiting factor. And if one is going to invest such a large amount of time, money and effort in a project to push the limits of velocity, than it would only make sense to use the absolute strongest brass available.

I can understand the desire to use such brass, but it is best left for other things than a high velocity round. If one were building a Sharps rifle, than it would be top choice, but not for a .50BMG bolt action.

As far as a replica rifle is concerned, it is still very possible even with modern components. I am sure you could have a large Mauser type stock made, though it will be costly. Or you could have it styled differently so that it is not modern, but more easily accomplished to keep cost at bay.

When building custom, possibilities are endless, and only limited by imagination and finance. You can still build an old styled anti-tank rifle with modern components, you just need to find a way to make it work. New coatings can be had in a variety of colors, accent pieces such as muzzle brakes and covers for other small pieces can be made for low cost, there are many ways to make the rifle appear as an old anti-tank rifle while still using modern components. Just use your imagination!

Kenny

 

[unertl]

As i said before before speed was not the primary objective though it was admitedly apeeling. The novelity and the history were the primary, with a dash of potential. Im a big fan of history especialy bolt actions. The old cartridges are were our cartridges now came from and i hold them and there rifles with high respect and as such i would like to do a little something with and older cartridge.

If i were to want a superhigh power rifle i'd go for something like this:
http://www.gunsinternational.com/338-408-Custom-Rifle.cfm?gun_id=100139933

 

[John miller.22xx]

I don't know the pressure limits of the 45-120/45 basic brass but it is not made for the kind of high pressure that adapting it to a tank rifle would entail. You want some thing like that you may want to go with the .378 Weatherby cartridge necked to whatever.