Originally posted by u/shadowhunter55 at 2024-12-08T22:42:45Z
*DISCLAIMER: 07/02 FFL SOT *
Introducing the mostly printed P90BLK (P90 blackout) chambered in 300 blackout powered by an upside down BRN-180 firing mechanism. The barrel assembly bolt and guide rods were stripped from a gen 2 BRN-180 upper and flipped upside down to load rounds in from the top and eject out the left side. The trigger assembly is a standard AR fcg albeit rotated slightly to get the upside down bolt to work.
FN Herstal themselves sold licensing to an airsoft company to replicate the p90 in airsoft using the actual dimensions, I bought one to rip the cad from for the starting point of this project a couple months ago.
The integral suppressor system I had already developed for the original BRN-180 upper adapting it to the existing handguard. Basically there is a port hole in the side of the barrel that dumps pressure into a metal chamber behind the muzzle that then feeds that pressure into the can ahead of it. The metal chamber is made using a piece of the same fence post used for 37mm launchers and is retained inside the receiver.
The magazine was the trickiest part of this project by far getting the transition mechanism to cooperate properly and do what I wanted it to do. For those who don’t know the p90 magazine stores the rounds laterally down the body of the magazine and then rotates the bullet to point down the barrel as the round comes up to the feed lips. An absolutely genius design that I was able to replicate for the 300blk. It’s not perfect but it functions and today (thanks to A LOT of lube) it ran like a sewing machine.
I will be offering parts kits for the hardware needed once the files are dropped. It’s really not much a few bolts springs and pins but a few of the parts you have to buy 10 of when you only need one.
I will be posting the files to my odysee 1/1/25 as a late Christmas present to you all, suppressor files included.
Live fire video: https://imgur.com/a/CNvLBen
u/Thee_Sinner · 2024-12-08 23:01:55 UTC · score 47
Holy shit its beautiful.
How many rounds are you able to put in that mag?
u/shadowhunter55 · 2024-12-08 23:10:18 UTC · score 75
20 reliably. 26 max with the current design. Physically can fit 35 but would need a different spring. Currently uses a standard AR 30rnd mag spring
u/battlecryarms · 2024-12-09 06:14:27 UTC · score 1
Without having seen it, your issue could be the taper of the cases. 20rd AR mags are straight, but anything with greater capacity than that has to account for the curvature of the stack of cartridges. The 5.7x28 has a very straight case, allowing it to be stacked in 50rd stick mags, but it requires an exotic coating to enable reliable extraction as a result.
I find 20rd mags to be totally fine for my needs as a civilian, and would welcome a shortened design that’s mechanically simple and reliable over a larger capacity one that’s finicky. An added benefit of 20rd mags is that they feel much lighter to me than 30s when running 300 BLK. That might be even more noticeable in this format, where the added weight sits further forward.
I may be able to help come up with some ideas that could make loading easier. Shoot me a PM if you’d like me to try and contribute. Also happy to think through ideas to enable downward ejection.
u/shadowhunter55 · 2024-12-09 06:19:19 UTC · score 2
The taper of the cases is part of the problem yes. Friction seems to be the biggest limiting factor so far. That and the weight. Lots of lube is helping though it ran like a sewing machine today no mag issues at all
u/battlecryarms · 2024-12-09 07:19:09 UTC · score 1
But it ran well down-loaded to 20rd, right? I’m just saying I’d rather a reliable 20 than a tricky 20+
u/shadowhunter55 · 2024-12-09 07:19:45 UTC · score 2
Yes. Yeah same here
u/No_Painting7828 · 2024-12-09 04:15:22 UTC · score 1
Is the mag the same length as the p90? Cause it looks shorter. Also are you gonna make it eject downward like p90 or is it not possible?
u/shadowhunter55 · 2024-12-09 04:16:02 UTC · score 1
It is almost exactly the same length. See other comments on downward ejection
u/No_Painting7828 · 2024-12-09 04:20:57 UTC · score 1
What's the barrel length?
u/shadowhunter55 · 2024-12-09 04:24:33 UTC · score 1
10.5”
u/cobalt999 · 2024-12-08 23:29:16 UTC · score 22
Oh interesting. I guess I just assumed helical because P-90. So it's a double stack? I would adore admiring some section views of this if you are willing to post some screenshots that show how it works in more detail :)
u/shadowhunter55 · 2024-12-08 23:32:19 UTC · score 13
Pm me
u/Dry-Neighborhood2916 · 2024-12-09 00:03:00 UTC · score 43
The P-90 is not helical. It's a box that just rotates the round right before feeding. This seems to do the same but the they are saying that the spring itself is from an AR-15 mag.
u/cobalt999 · 2024-12-09 00:12:31 UTC · score 24
Huh, yeah you are right. Now I am questioning why I thought it was helical in the first place.
https://i.imgur.com/LMEGaoY.jpeg
Still though. Getting that to feed reliably looks pretty difficult. It's hard enough to get a double stack to single feed. I have some experience designing industrial hoppers and indexing mechanisms. If you look at them wrong, they jam lol. Still though, an impressive achievement of design to get that to work well enough.
Source: https://i.imgur.com/LMEGaoY.jpeg
u/shadowhunter55 · 2024-12-09 00:36:33 UTC · score 17
Yes. This magazine took 26 iterations of that transition mechanism to function how I wanted it to. It’s not perfect and tricky to load but it’s come a long way. Yes standard 30rnd AR mag spring
u/Str0ngTr33 · 2024-12-09 03:25:24 UTC · score 2
its not papashiev
u/Fredninja22 · 2024-12-10 01:08:36 UTC · score 1
Maybe thinking of the PP-19 Bizon?
u/Suggins_ · 2024-12-09 00:09:57 UTC · score 17
Helical= bizon. I'd call p90 offset feed or horizontal feed. Yours truly, anal nerd.
u/FunkadelicRocket · 2025-03-11 19:35:47 UTC · score 1
Have you looked at using a flat spring like what MagGuts uses
u/shadowhunter55 · 2025-03-11 21:47:54 UTC · score 2
I have not. I want to stick to off the shelf components as much as possible. And I started with an AR mag spring because they are some of the most robust and reliable mag springs in existence. Lots to consider with this mag design for sure