This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.
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If only u could solve the flash problem of 556 in 6 inch barrels.
Could one heavily port the barrel with holes...and have some kind of long flash hider running around the holes
Pretty simple it's already been designed look barrel on the aksu at the end
Like Wilson said, the aksu muzzle device is one possible route.
Going to an 8 inch "barrel" with a pepperpot reflex suppressor is another.
Or you could just roll yourself a round for this specific implementation that gets you most of what you want without having to go to quite the extremes this design represents.
All 3 of these approaches are viable.
A Fourth approach would be to use something akin to a cbj style sabot for a 5.56 projectile in a blackout case that'd work pretty decent.
I'm not able to do the math (especially without knowing what a cbj style sabot would weigh etc) but I think this would be one of those cases where you could come out substantially ahead even after losing the sabot's parasitic mass because of the swept volume increase so long as you could keep the cartridges effective RC high enough.
Oh man ... I realized that we already have almost the perfect loading for this already, we just need to dust it off and tweak it some.
5.56X38 FABRL !
Iirc it was getting absolutely hilarious velocity at only 38k psi or something insanely low in it's original instantiation. If we push 50k or 55k psi which should be doable with modern powders and even lightweight cases you could sling absolute monsters of a pdw round out of this thing relatively easily.
The 6x35 would definitely utilize its propellant load more effectively than the 5.56x45 in a very short barrel with its combination of higher swept volume and lower propellant volume. Of course, a sabotted round with a straight-walled case would maximize the swept-volume, with the added complexity of dealing with the sabot, its mass, accuracy issues, etc. Has anyone seen a formal analysis of the current state-of-the-art sabot round that does a decent job of quantifying the tradeoffs between it and a bottlenecked cartridge?
Theres the 223 timbs... a tokarev firing .224 bullets.
The 300blackout CBJ would be good for this gun but i doubt sabots have good accuracy in 6 inch barrels.
The .221 fireball is my first choice. No muzzle flash in short barrels and roughly 650 ft lbs from 6 inchers....thats better than 5.7x28
My ultimate fantasy GPC has always been a .224 valkyrie shooting 40grain FABRLs.
At high energies i wonder if they would stabilise well....the FABRL document mentions a twist rate of 1-in-5
6x35 is an equally valid answer, especially with a good projectile behind it.
However my preference is for something with a generously sub 1.0 FF and the .89 of FABRL sounds really nice.
IDEALLY you wrap that .89 ff bullet in a sabot similar but not identical to the cbj to push as much velocity as possible.
My reason for that preference is pretty simple, it'll give said projectile serious legs simply by it shedding velocity slower.
But yeah, I'd be down with 6x35
I have a friend whose messed around with a pdw cartridge based on a slightly altered fireball case, and that can very much get you to a "pocket carbine" performance level.
I wish cbj would just upsize their original sabots so we could throw a really nice existing 5.56 projectile on the lighter side out of it. Something like I can't remember the company's name but they do a 50 grain projectile that's already very well known for good performance.
Personally I've got a couple projects I'm finishing up and then I'm going to start gathering parts to build myself a "cheek pistol" either loosely based off the old Argentine "almara MPA" concept OR an americanski diy pp-2000 inspired... "Thing" that takes some cues from the existing fgc9 build (which is shockingly similar in the bolt and carrier area to pp2000)
Whichever one I decide to do first I'll be doing it based around printable 9x19 Glock magazines initially running single feed to get the concepts functional.
Once I get them functional, the plan is to slowly work alterations to get it to function in double stack double feed.
After I get that working, I'll be transitioning the caliber to .22 tcm, which is a much more fun and appropos caliber for something like a "cheek pistol"/pdw.
In either concept's case I'll be going with a non reciprocating charging setup.
Personally, I think that the "pp2000ski" will work best since the grip to muzzle alignment actually has a slight reverse cant to it. The issue with it though is going to be getting the fucker to feed reliably at all even in 9 single feed, getting it to double stack double feed... Well let's just say that if anyone can get me a gsh 18 magazine (or just the body and follower) that'd be very helpful LOL.
Getting one or both to running double stack double feed is the first step towards exploring more interesting pdw concepts though, so I figured I'd talk a little about it here.
Here's the pictures of the conceptual basis of version A and B.