Martini Receivers and such

[Delkal]

That 9.3x74mmR bullet looks interesting if it will fit. Its long! If you want to neck it down you don't have to make it straight first. Just anneal the neck and resize the neck down till it just chambers in your rifle. This crates a false shoulder for headspace and when you fire a moderate load the case will fireform and expand to fit the chamber. This can also give less of a taper to the body and increase case capacity some. Look up some before and after pics of how they go from 223 to 7TCU, and 30-30 to 7x30 Waters. I can take more pics if you want it. There are also tricks for reloading where you don't always need a custom die while developing. You just neck size with a common die for another cartridge with the same shoulder. Then occasionally body size the case with a separate die.

I looked at the Lyman mold link I posted and there are not many gaps from .320 to .375 they didn't think of 100 years ago. I believe there are one or two gaps of 0.015 but most are within 0.002 of the next size. But many of these bore sizes are obsolete and have just been chambered in old rifles. One plus to this is that someone might have a button rifler already made for the old rifles and when developing a load you can get a mold a few thousandths larger and size it down before you make a custom mold.

[Delkal]

One other thing you need to factor in is that the larger diameter the base, the lower the max pressure should be in weaker actions. Not only is there less meat in the barrel chamber area but the larger diameter of the base means more pressure on the bolt. In a contender you can safely shoot a full power .223 but no one will chamber a 454 Casull even though it runs at the same pressure. This can cause problems (including blowing up).

Pretty sure the 303 already has a large base so this might not be a problem.

[MD66948]

A S&W . 460 or . 500 would be interesting.

[knight0334]

One other thing you need to factor in is that the larger diameter the base, the lower the max pressure should be in weaker actions. Not only is there less meat in the barrel chamber area but the larger diameter of the base means more pressure on the bolt. In a contender you can safely shoot a full power .223 but no one will chamber a 454 Casull even though it runs at the same pressure. This can cause problems (including blowing up).

Pretty sure the 303 already has a large base so this might not be a problem.

So I should make my own Martini(or other design) receiver on a larger scale? Serious question there..

[Delkal]

So I should make my own Martini(or other design) receiver on a larger scale? Serious question there..

No. The 303 British and its base diameter has been shown to be safe. Just be careful if you design a cartridge with an appreciably larger base diameter and if you do you should decrease the pressure.

Just looked and the 303 has a base diameter of .460 which should be more than large enough to design a cartridge around since it is a similar diameter to the 30-06 / 8mm mauser based variants. By comparison the .500 S&W has a base diameter of .526 which is considerably larger so this is when you need to do some serious research and a reality check. Also the 500 is loaded to a higher pressure. I have no idea of what the receiver strength of a Martini Henry is but I would pass on shooting that one.

[Delkal]

Looked some more and while the 30-06 / 308 has almost the same base diameter it has a much higher pressure than the 303 (60,000 vs 48,000) so you would need to check if these higher pressure loads are safe in a Martini Henry.

Personally I would not attempt to hotrod a Marini Henry and I would would be thinking more about heavy for caliber bullets (especially with lead) at moderate velocities and pressures. Schuetzen type rifles are known for their extreme accuracy and I doubt you will find one using modern 308 type pressures and velocities. I would research the period cartridges used and shoot for those types of velocities and pressure with your wildcat.

[flygrimm]

Just for fun I thought I'd post a picture of what the 9.3X72R case looks like compared to some more familiar cartridges. My neighbor gave me this case several years ago. I think he found it at a flea market or something.

From left to right: 577-450 Martini Henry, 303 British, 9.3X72R case, 7.5X55 Swiss, 7.62X51 NATO, 30-06 Springfield and 5.56X45 NATO.

Cartridge Comparison 1.jpg

Stuart

[knight0334]

I'm not really trying to hotrod with high pressures, but rather use a bunch of slow burning powder that keeps a reasonable pressure throughout the length of a long barrel to achieve higher velocities(sorta like how blackpowder works* in a barrel). ...push more powder down the barrel to keep a sustained pressure the length of the barrel - it is tricky to perfect, but do-able. Whereas most modern rifles(and handguns) burn most powder within the case and first few inches of the barrel and pressure starts dropping about mid-length. This is where a tapered/straight wall case works better for pushing powder down the barrel further than a necked case.

Right now I'm still in the planning stage for everything, so I'm still open to everything.


*for those that don't know. Uncontained BP burns really fast and smokeless burns slow, relative to each other. When contained like in a barrel pushing a projectile, they both burn opposite of uncontained.

[Delkal]

Definitely start with slow powders and a chrony when developing your load. When you get to the estimated velocity stop.

Your project intrigues me and it is fun to think about. So many options. One problem with wildcatting is its all been done before and by now any changes are just splitting hairs. You were thinking about 303 with an Ackley shoulder and less body taper? Already been done, look up the 303 Epps. And there are many necked up versions.

https://www.303british.com/id20.html

That 9.3x74mmR case is impressive and can be used for dangerous African game as is. So how about Ackley improving it and reducing the body taper? I found this forum post where it was already done. The velocities and energy of the improved cartridges is way more than you need for anything (maybe besides elephants). These were necked up and down too. You can decide if you want a Schuetzen rifle that can take a rino (actually I would love to see that) but how about shortening the case for north American game? Can you get to the same place with a more common parent case?

about 15 years ago, I developed a line of cartridges off of the 9.3X74R case, designed specifically for the Ruger #1.

The case was necked to: 6.5mm, 270, 7mm, 30 cal., 338 and 358. That long slender case had .010 body taper and a 40 degree shoulder angle with a neck length that matched the bullet diameter....



all of the cartridges I designed, based on the 9.3X74R case showed approx. a 300 fps. to a 350 fps. velocity gain over "standard" cartridges, ie., 270 Win., 280, 30-06, etc....

I used "near max" 270 Win. loads for the 270-9.3X74R for fireforming, as well as the same for the 280-9.3X74R and similar loads for the others....

I called the rounds "WHITE EXPRESS", for the appropiate calibers, ie., 270 WHITE EXPRESS, 280 WHITE EXPRESS, 308 WHITE EXPRESS, 338 WHITE EXPRESS, etc....

I chose to call them WHITE EXPRESS because my last name is White and I put the Express on there because I thought it a fitting name, being a round for Single Shot Rifles....

https://www.shootersforum.com/thread...wildcats.4263/

[MD66948]

Are there any companies currently making barrels the Martini-Henry?