FK BRNO 7.5MM

[Donny Brook]

Are there, or has anyone developed, GURPS stats for the FK BRNO Field pistol?

https://en.m.wikipedia.org/wiki/FK_BRNO_Field_Pistol

[Fred Brackin]

Originally Posted by Donny Brook

Are there, or has anyone developed, GURPS stats for the FK BRNO Field pistol?

https://en.m.wikipedia.org/wiki/FK_BRNO_Field_Pistol

I brought it up a couple of years ago after an American Rifleman article.

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

The main item of interest was they velocity which I believed to be in excess of the magic point where sub 8mm rounds become full P and not P- i.e. 600 meters per second. This is seen in the WWII era M1 carbine which HT rates as P.

Damage would be about 4D P.

Accuracy would be 3 probably due to being Fine(accurate). It certainly costs enough to be that good (though I see the price has come down since the earlier article). $2000 is still enough to get you Fine(Accurate) in a more conventional pistol.

Rec is tricky to determine in a weapon you've only read about. It could be 2 in the all-steel version with its' recoil attenuating cam but could climb to 3 or more in a lighter polymer frame version.

I also speculated about it being a more practical PDW than the P90 or the HKMP7 if fitted with a shoulder stock (which there were plans to do).

[Varyon]

The Wikipedia article notes one of the design goals was to have felt recoil akin to .45 ACP +P. Looking through High Tech, it looks like just about everything that uses .45 ACP but lacks a stock has Rcl 3, while those that have a stock and use .45 ACP have Rcl 2. So, I'd give it Rcl 3 normally, and Rcl 2 if you toss on a stock (or "pistol brace") and shoulder-fire it. The 12" wound depth implies damage of around 12 points - the 14 of 4d should be fine (1 point of damage being 1 inch of penetration in flesh is, at best, a rough estimate I've come across). I don't know how to interpret the 35 mm wide permanent wound channel requirement, however; the caliber indicates pi at the velocities involved, so just go with that.

[Fred Brackin]

Originally Posted by Varyon

(1 point of damage being 1 inch of penetration in flesh is, at best, a rough estimate I've come across). t.

I would abandon that idea. It'd make 9mm FMJ do only 9 inches of penetration and average penetration of such a round is far higher.

Indeed one of the goals of modern bullet design is to make sure you get the 12" the FBI wants out of a 9mm Jacketed Hollow Point and this is commonly achieved now though it would have been rarer c. 1990 when the FBI ballistic gelatin testing started.

I've never heard of the ".35 mm" thing and it sounds dubious to me.
"

[Varyon]

Originally Posted by Fred Brackin

I would abandon that idea. It'd make 9mm FMJ do only 9 inches of penetration and average penetration of such a round is far higher.

Indeed one of the goals of modern bullet design is to make sure you get the 12" the FBI wants out of a 9mm Jacketed Hollow Point and this is commonly achieved now though it would have been rarer c. 1990 when the FBI ballistic gelatin testing started.

Is that 12" in flesh or 12" in ballistics gelatin? Because the average male chest is only about 10 inches from front to back, which would mean 12" penetration would overpenetrate whenever the target was directly facing the shooter (hitting from an angle means it has to go through more flesh to get out the other side), which seems excessive to me for a hollowpoint round.

As I said, it's a rough guideline I sometimes use to eyeball things.

Originally Posted by Fred Brackin

I've never heard of the ".35 mm" thing and it sounds dubious to me.
"

It's from the linked Wikipedia article, and one of the stated objectives when they were designing the weapon - "Target's permanent wound cavity should measure a minimum of 35 mm in diameter (1.38 in) and 300 mm in length (11.8 in)[4]." As I said, I'm not sure how to really interpret that; it feels like a 35mm wide wound channel should be pi++, but that seems far too much for this round, particularly if it's meant to penetrate 12" of flesh (wider wound channel generally means less penetration, as we see with hollow points).

[Fred Brackin]

Originally Posted by Varyon

Is that 12" in flesh or 12" in ballistics gelatin? .

Differences between those two things should not be significant.

Also, (again) you're idea of points of damage equalling inches of penetration is _wrong_ and can easily be proved so.

[Donny Brook]

I've seen youtube vids show the personal defense hollowpoint will go 21 inches into ballistic gelatin; the big game penetrator will pass right through 32".

[Varyon]

Originally Posted by Fred Brackin

Also, (again) you're idea of points of damage equalling inches of penetration is _wrong_ and can easily be proved so.

Alright, I guess the overpenetration rules need some revamping then; for 2d+2(0.5) pi (9mm JHP) to penetrate 12" of flesh on average, flesh needs to provide right around DR 0.375 per inch. An average person has a chest that is around 10 inches deep and 20 inches wide, giving Cover DR between 3.75 and 7.5, averaging out to 5.625 for a character with HP 10 (the average). So, it would be more accurate to say characters give cover DR equal to HP/2 for Living characters, HP/4 for Unliving characters, and HP/8 for Homogenous characters, rather than the RAW HP, HP/2, and HP/4.

[Fred Brackin]

Originally Posted by Varyon

Alright, I guess the overpenetration rules need some revamping then; .

You're still underestimating bullet penetration. 12" is minimal for FBI standards and is a goal for modern hollow points. FMJ bullets would penetrate roughly twice that far.

I wouldn't adjust for Unliving and Homogenous either. Lost HP are relevant to function and Unliving and Homogeous targets have simpler and/or harder to disrupt functions. Indeed, Homogenous target don't really have analogues to organic functions.

[Rupert]

Originally Posted by Donny Brook

I've seen youtube vids show the personal defense hollowpoint will go 21 inches into ballistic gelatin; the big game penetrator will pass right through 32".

Expansive big game bullets are intended to penetrate things like sable antelope, elf, and buffalo shoulder blades before expanding. For really serious big game, you don't use expansive bullets (and bullets that don't significantly deform at all are popular because they give consistent performance). Ballistic penetration tests for these are pretty pointless, because how much meat they'll go through isn't the question - it's whether they'll stand up to heavy bone, and possible several layers of it.