This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.
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My buddy who has worked through more bullet designs than anyone else I've ever met has illustrated before the danger of going that route.
If your projectile doesn't have enough mass to integrate both a sufficiently large penetrator AND enough fragmentation mass to reasonably assure fatal wounds in a human it winds up either Being a glass hammer that will zip straight through things and people leaving minimal damage. Or, it will fragment messily and be utterly turned by even light intermediate barriers. In many cases it will be the worst of both of these.
Near as he and others can tell, 37 grains is just too small. In 5.56 projectiles the optimum seems to be between 50 and 65 grains.
I was thinking a 43grainer with a 30mm long 'rod' running all the way through
Surely a sabot wouldnt work with fabrl bullets because the bearing surface is too short
Could a fabrl bullet work in a CT case if the long bullet was seated right to the bottom...i cant see how it would stay concentric as it rises up through the case.
6.8 is easier because the bearing surface is much higher up
On the sabot situation, short bearing surfaces may preclude some kinds of sabots but the original 6.5x25 cbj sabot design could match well with something like that.
When it comes to CT and very high L:D bullets I'm not really sure how it would work but I think if you poured enough money in it you could make it work. The question is, would it be worth it.
I also have no idea what you're talking about in reference to 6.8 because that's just a bullet diameter and could refer to any one of a hundred projectiles a good 5 or six chamberings.
I'm definitely not necessarily against using a 6.8 spc case as a starting point though. It's a tad girthy but who knows man?
Maybe you could make it work?
I'm basing all my comments and commentary in this particular thread on the purpose we're going for being let's make something like an mp7 except it doesn't suck.
To me that means what we're going for here is a small machine pistol with an optic and possibly a can that a trained user can use to dominate the 0-150 meters range bracket with. Bonus points if it's dangerous enough to poke 3a at 200 meters with a lethal behind armor wound and dangerous enough to generate reliable potentially lethal wounds on unarmored AK wielding adversaries at the full "AK 300 meters"
Bonus points if there's also a subsonic loading you can run with a can for specialist use.
If you just want to be pretty dominant in the 0-150 block, we already know that you can do that with essentially a Colt SCAMP 2.0 with a red dot or prism sight on top, modern projectile design and construction, and lightweight high pressure cases.
The whole thing that makes the Caleb Crye patent interesting is the potential for what's essentially a true pocket assault rifle.
That's the part that interests me and makes this something that really gets my gears turning.
Frankly the 300blk would have only average penetration at 150m...not even remotely close to something like 6.5cbj
If the goal is a improved MP7, i was thinking a variation on 4.6x30 which doesnt suck.
In other words use reverse feeding to cram in a 10 inch barrel and send a 5mm bullet with 850ft lbs.
My concern with a FABRL in CT was that if its a 32mm bullet the bearing surface will literally be at the bottom of the case.
Normal CT has little walls which hold the bearing surface but you cant do that here. I noticed that lockless are also CT and they have a different style of walls....look at the cutaway pics.
EDIT: i just noticed that the original P90 ammo (ss90) used a fabrl bullet.
It was 2.7mm longer than current P90 ammo
Well since I'm not talking about 300 blk except very tangentially that's not really an issue. (As far as the sabot round I'm speaking of, it's performance is going to have zero to do with how existing blk performs)
As far as variations of 4.6 that don't suck, we already have them, it's called 5.7x28 221 fireball and several others.
As far as your concern with FABRL in CT... Yeah it's a dumb idea I said that in my last post. The lockless stuff also doesn't really matter, and yeah you probably could make something akin to FABRL projectiles work it'd just look different.
You kinda didn't address what I was actually talking about so I'm altogether unsure of what you're trying to say here.
If you want the size of a SCAMP or MP9 then reverse feeding would be essential...this would rule out sabot rounds because they cant be crimped tightly enough.
The original MP7 was much smaller like an MP9. With reverse feeding you could bring it down to MK23 size.
As for th crye gun im very skeptical about reliability and even feasibility of that magazine
I disagree that 5.7 is better than 4.6. Its always been shown that 4.6 penetrates better. 5.7 often wont even defeat helmets at close range.
It would be useless against lvl3
1. Funny the original scamp was already smaller than an mp7 and didn't reverse feed, you're getting caught up on gimmicks.
2. The original mp7 wasn't much smaller I don't even know where you're getting this and am beginning to question whether you've ever held a gun at all. "Getting it down to mk23 size" isn't one of the goals because having something mk23 size is going to make it iffy to distance shoot.
3. Considering that the Russians have actually done magazines similar in concept and nature and in general your lack of education on the subject, I'm not super concerned about you being skeptical.
4. I don't care about penetrating shit unless I can generate a lethal wound behind the armor, which 4.6 can't. Your subjective opinion about "better" doesn't match reality or what we're trying to do with something like this so it can be safely discarded.
5. "Useless against Level 3": See this one is a fun one since the things I specifically suggested COULD actually get you something that would pop level 3 nij with even a tool steel penetrator inside 50 meters (which is infinitely more Level 3 penetration than anything you are advocating for). At the same time, I'm pretty certain by cues you have given in this conversation and others that you don't know the difference between Level 3 nij and level 3a nij, and that's a problem.
Basically everything either of us have suggested and several things not covered here will pop nij3a which is what helmets and soft armor is rated for. There's civilian 5.7 rounds that won't pop some hard nij3a like helmets but that's down to the projectile not the cartridge.
As far as "not penetrating level 3" and therefore being useless, precisely nothing you've suggested has even the barest hope of penetrating NIJ 3 plates. I have a set of NIJ 3 plates upstairs in my spare carrier that weigh a whole 3.4 pounds each and they're nothing special.
The SAPI and ESAPI plates as well as their equivalents that most militaries use are pretty much fully beyond the capability of anything in this class to punch through even at point blank. Reason being is that the SAPI plate was actually a bit beyond nij 3 in protection level offered, and the ESAPI is SOLIDLY beyond nij level 4 performance.
Truthfully penetrating NIJ level 3 like a couple of my suggestions would at closer ranges is a nice to have but only debatably necessary. There's a reason why the solutions I proposed and the direction I wanted to take this have the potential capability to do so, but I explicitly understand why I even wanted that and what it takes to do it while you don't.
You're allowing your opinions and desired feature set (which is grounded in your misunderstandings and lack of knowledge if it can be said to be grounded in anything) get In the way of actually having a decent discussion. At this point I'm just going to stop because there's nothing productive In talking to someone who refused to learn enough to discuss things.
You did say one thing that was accidentally interesting though.
Combine the Caleb Crye patent with reverse feed and you might accidentally end up with something strangely workable because then what was your round presentation spring can become a stabilizer to keep the cartridge stack properly ass up for presentation to be snagged.
Where you run into trouble is in the need to either go single feed or design something particularly clever so that it can pull cartridges from either stack...
This gets us into some weird zb-47 / erma mgd pm9 territory (the zb47 used what appeared to be triple stack single feed mags)
There's definitely some meat on this bone, even if it's very weird exotic and potentially not super practical meat.
And this is why I loved this patent in the first place. It is an alternative architecture that opens up possibilities. It shows that small arms really isn't the mature technology where only incremental and ever more costly improvements are possible.
It illustrates that there's potentially different ways to do things that may not have been practical before but could be now
I doubt reverse would work. The crye gun needs the grip at an extreme angle. Making the rounds face ass up.....what kind of grip angle would you need for that?
Frankly the best compromise is a 7.5FK with very lengthened bullets....taking the OAL to 44mm
That's not a good compromise at all.
And since we've established that you and understanding cartridge design just isn't happening that's all I'm going to say.
It's been explained to you why the 7.5 fk isn't a good starting point, repeatedly.