Engineers & Machinists-your mission 7.5 FK BRNO dies

**unclejumbo** · February 13th, 2021, 12:41 PM

I ordered the new 7.5 FK BRNO PSD pistol. At a price of $1.50 per round, it seems to be a prime candidate for reloading. Especially given the possibility of the cartridge not catching on. With that said, there are no reloading dies yet made for it that I've found.

I'm ignorant when it comes to machining. Would it be possible to take a current set of available dies and recut them to load this cartridge? If so, what caliber would be the best host? Or add an insert into a 10mm die to size the neck? Maybe a mixed set of dies, one to size the neck and another to size the body?

I tried to find some dimensional drawings and find only very basic other than a 3D printer software link which is too small to make out.

Anyway, if any of you are bored and want to tackle this endeavor, it could be a money-maker. I can't be the only one wanting to reload for this. I know custom dies are made by several companies but I already have an extra set of carbide dies for 10mm. And I have no idea if the custom die makers can legally make dies for proprietary calibers.

**Walleye Hunter** · February 13th, 2021, 12:49 PM

I'm thinking of two guys here who might be able to help you out on that. I'll offer up use my lathe for it if they want/need.

**Delkal** · February 13th, 2021, 01:40 PM

The 7.5 FK BRNO is a proprietary cartridge covered by patents and trademarks so other companies cant produce cartridges or dies unless BRNO decides to license it (unlikely). I don't think they will publish the chamber specs either. A machinist could reverse engineer something but that takes skill and money. I may be wrong but I don't think you machine the inside of a die. You make a reamer, cut the die, then harden the die. The cost to do this for just one die is a lot more money.

You could probably get by with just neck sizing for a few reloads and can probably find some common 30 cal. die that can work for this. You might even get lucky and it will have a shoulder with a close enough angle for when you need to bump the shoulder. You will probably still need a machinist to cut the die shorter. For the body it looks like this case is close to a 30 remington so you might be able to use a separate die to size the body.

Also. You would need to be a very experienced reloader to even think about this. You will never see any reloading data on this cartridge so you will need to develop one yourself from scratch. This is doable for a reduced power target load but even a reloading expert would be foolish to try and come up with a max load even close to factory specs.

**abner13** · February 13th, 2021, 01:55 PM

To make dies you would need the original specs and have a reamer made. If ya can't get the specs on paper , a chamber casting can be made and measured. A chambering reamer could be used if it's on the tight side.

Being a limited production item , ya might not see reloading tools and supplies very soon. Case has a 10mm/.40 SW head/rim according to one of the articles.

**JenniferG** · February 13th, 2021, 06:20 PM

The 7.5 FK is a completely new proprietary cartridge caliber. The case is 27 mm long with a total length of 35 mm, and a head diameter of 10.8 mm. This caliber is not a necked-down version of any other caliber. The case is designed to withstand higher pressures than usually used in pistol calibers.

This cartridge will not fit in any other manufacturer's magazine, nor will it function in any other current production model pistol.

Muzzle velocity: 610 m/s (2000 fps)
Velocity at 100 m (110 yds): 465 m/s (1525 fps)
Muzzle energy: 1200 J (880 ft/lbs)
Energy at 100 m (110yds): 700 J (520 ft/lbs)
Bullets weights:
Monolithic HP and JHP bullets: 95gr
Monolithic flat nose bullets: 101gr

Dimensions
Case length:
27 mm

Total length:
35 mm

Head diameter:
10.8 mm

Bullet diameter 7.8 mm (0.307 in)
Neck diameter 8.5 mm (0.335 in)
Shoulder diameter 10.8 mm (0.425 in)
Base diameter 10.8 mm (0.425 in)
Case length 27 mm (1.063 in)
Overall length 35 mm (1.378 in)

https://gunsmithtalk.wordpress.com/2...4/7-5-fk-brno/

**unclejumbo** · February 13th, 2021, 07:12 PM

Thanks much Jen.

Look at that, the neck has a step down or taper.

I'll have to do some digging and see what's close.

Also, I read an American Rifleman article and the author said that if people wanted to reload it, they'd have to buy a set of custom made dies. He didn't mention if that would violate any patents. I'll give Hornady a call on Tuesday, they do custom dies. They're 4 to 5 times as much as mass produced but they said they can make them from once fired cases.

The 7.5 FK is a bottleneck design, 35 mm in overall length according to CIP (Europe*s version of SAAMI) specifications. The cartridge could be aptly described as the 7.5x27 mm, as that*s the case length. It is important to note that there is no parent cartridge to the 7.5; it is a case design all of its own. The 95-gr. solid-copper hollow-point bullets clear the muzzle at an advertised 2000 f.p.s., resulting in 844 ft.-lbs. of energy. At 100 meters, the bullet is still traveling at 1525 f.p.s. and producing 491 ft.-lbs. To accomplish this, the 7.5 FK operates at 50,570 p.s.i., which is higher than nearly any handgun cartridge on the market today with the exception of the .454 Casull. This thing is hot.

https://www.americanrifleman.org/art...-field-pistol/