Which would be the superior self defence cartridge? >31gr

>But OP, where are you pulling those numbers from? Your ass?

The 31 gr .22 is just a standard 5.7x28 loading (SS190), as is the 95 grain 9mm (Winchester Ranger .380 ACP).
Some research gave that the practical bolt/slide weight on a blowback pistol is about 1.1lbs give or take (see source below).
A Liberty 78gr and Federal 165 gr .45 bullet would have a maximum velocity of 1166 and 551 fps, respectively.
By the same formula, a standard 230gr .45 bullet could only go about 395fps (80 FPE!) out of a blowback gun.

http://www.orions-hammer.com/blowback/

Whichever of them that manages 14-16 inches in the FBI gel test that you shoot the best. Otherwise whichever gets the closest to that kind of penetration.

>>34881260

Well if I made a super slick lifer looking gun I'd want it in 5.7 before any of the rest. 380 would be neat but the larger calibers you posted you can't really buy factory and might make the barrel look disproportionately big

>>34881274
The .380 manages 20 inches. You could probably find a defence load that matches, or transfers some more energy into the target.
http://www.luckygunner.com/labs/self-defense-ammo-ballistic-tests/#380ACP

SS198 should easily penetrate 20'', and SS190 will usually stay within 14-15''.
https://www.zombiehunters.org/forum/viewtopic.php?t=82043

Given this, I would assume the light .45 (78gr) bullet would have enough velocity to meet the FBI standards. Depends on exact bullet design, I guess. The 550fps .45 is right out though, I don't ever see that penetration happening with such a low velocity.

>>34881380

>luger looking gun

By the way I realize it's operating very differently than a luger, I'm referring to the classic look

>>34881380
Don't worry about availability, saint Browning will magic the calibre you choose into being in a month's time. It'll be a beautiful blowback operated gun (think 1903/PPK/1934), available in both single and double stack, and ammo will be stocked as high as any currently available load.

>>34881387

You can get a rough idea of the penetration difference if you use pf (momentum] mass*velocity/1000) instead of energy. This won't account for expansion or initial bullet diameter though. Find an equation for fmj same weight&velocity between 9mm (.355) and 38 special and how it relates to ballistic gel if you want to get more scientific between different diameters.

>>34881407

Slick guns need thin high-speed calibers imo. Also, thank you lord Browning for your contributions to my life

>>34881458
>You can get a rough idea of the penetration difference if you use pf (momentum] mass*velocity/1000) instead of energy.
What. This is the most clumsily noted formula I've seen so far, please explain.

>>34881476

Sorry, at work speed typing. Pf or power factor is mainly used by competition handguners to describe momentum. I don't shoot competition but I noticed how closely momentum is related penetration a while back and saw other nerds that have been doing the same longer. You can fairly accurately predict penetration into gel with it at handgun caliber mass and velocities. If you move to extreme ends like a golf ball with the mass of earth moving 1 fps it doesn't work so accurately but handgun calibers are all closely enough related for it to work very well from what I've seen. Try it.

Mass*velocity gives the value you're looking for. Divide that value by 1000 for the easier to say "power factor" and those people will know what you're talking about

>>34881644

Remember though, it doesn't take into account diameter or expansion rate if using hollowpoint. A 45 with the same pf as a 380 will not penetrate nearly as deep because it's fatter. You can take two of the same pf calibers with different diameters and thus different penetration into gel, find the constant, and quickly use it to get your penetration at any diameter you'd like. I haven't done this part since I only work with known calibers but it should work fine, you can test it yourself

>>34881644
If you follow the link in >>34881260
>http://www.orions-hammer.com/blowback/
You'll see that I specifically calculated all these calibres to function in a blowback gun.
The formula to calculate that depends on slide weight, caliber-to-bolt ratio, and bullet momentum (mass*velocity). So, assuming 1.1 lbs slide weight (like the guy calculated for .380 ACP), a .95 caliber-to-bolt ratio (pretty common for straightwalled handgun cartridges), I found that mass*velocity should be in the neighborhood of 112000 - it's completely momentum-based. So, all of these cartridges should have very similar penetration according to your postulates.

Honestly, I'd assume that velocity (and thus energy) would be more important than outright momentum, but I can understand the thinking.

>>34881698
So in this case
>The .380 would penetrate ~20''
>The .22 would penetrate way more
>The 165gr .45 would penetrate way less
But how would the 78gr .45 do? It should penetrate less due to the higher surface area, but according to my own head logic speed = penetration, so given the higher muzzle energy I believe it might actually be pretty damn similar to the .380. Your opinion on this?

>>34881746

Damn, I wish I had you to speak numbers with in real life, no one likes ballistics like me. Energy is helpful but I've found it less reliable. I don't have a computer in front of me and I'm about to get off work and have an hour long drive so I'm pulling this out of my head right now.

I checked the 22, 9mm, and 78grain 45 and they all come out between 73-86pf (pretty short of your 112pf); 95 grain 380 moves at about 900 fps so that's close enough to yours and scores about ~18". Knowing what I've seen in the past between tests, not doing any formulas just guessing on past numbers, I'd say you'd get 7-11" out of the 45 and 22-27" out of the 22. I'm less certain of the 22 but Id bet the 45 isn't going to cut it.

Your head logic on speed isn't wrong generally because you normally see that speed on smaller diameter rounds.

When I get home and have a computer, if you keep thread alive, I'll see if I can help further. Ive never done this but if you want to get autistic on bullets with me Ill totally email speak with you, it's my favorite subject and I'd do it for fun.

>>34882111
Thread won't 404 for about an hour or six, so no worries.

The 112 isn't PF, it's some sort of number that guy came up with in his calculations. Simply divide 112000 by mass, and you end up with the maximum velocity you can achieve in a blowbackgun, assuming a .95 bolt/caliber ratio, a 1.1lbs slide, and about a 4m/s slide velocity - all sort of the practical limits you'd expect in a blowback pistol that's not Hi-Point huge. This means blowback guns would be practically limited to 80-85PF.

Could you compensate those penetration numbers by bullet design?
Could you get more out of the 78gr. .45? It's already twice the mass and diameter of the .22, just adding a more penetrating design (like an FMJ) would be plenty methinks.
What kind of penetration would you guesstimate a 165gr .45 with an 80-85PF do? How about a 230gr?

It's wierd how you're expecting the .22 to do anywhere from 22 to 27 inches of penetration, but SS190 usually tests at around 14-16 inches in gel, from the data I've found. I could be wrong there though.

I'm looking to design a round that does the following:
>Works in a blowback gun
>Made by shortening .45 ACP brass
>14-16 inches of penetration
>Has a bullet anywhere in the 75-125gr range
I'm just trying to wrap my head around the maths, it's just proving counterintuitive at several steps (like the velocity-penetration thing).

Any idea on how to post an email adress here without getting doxxed/somebody signing me up for gay porn?

>>34882338
Bamp to keep it alive for the night.

>>34882338
Just set up a burner email.
Or you could have the discussion here, I'm sure a few of us are lurking just in case we learn something.
How are you guys going to take sectional density into account? Your 75gr .45 seems like it might not behave as expected using fomulas made for more standard bullet weights.

~bumpu

>>34882111
Send some mails to [email protected] if you're still interested.

>>34884184
>Sectional density
Haven't thought of that, and it'd probably require physical testing to prove penetration standard.

My head logic says that a faster .45 should penetrate deeper than a slower .380, despite the sectional density difference (0.055 vs. .108).

>>34888562

I'm back at work again. Sorry about last night, had to pick up a new gun and had surprise company. Got the email though.

>>34884184

After we're done, him or I can make a thread with it laid out. I've thought about making a guide to it a while back, maybe we can help a lot of canons if we clearly laid it out.

I'm emailing with a g mail account with the name "shady" in it. I made it when I was young for kind of a burner account, sorry for the unprofessionalism I might be slow to respond but I can talk in more detail. I'll try to avoid sending links and just do screenshots, I don't normally trust internet people either