I've caught the itch after learning about the 5.7x28 mm's performance in home defense (performance vs. armor, weight, size, capacity, and not over penetration).

Ignore ammo cost, larger cartridges (if I was working for a security company, especially in a more hostile environment, then I'd be interested 9mm, 10mm, .40 cal, 45 cal or 5.56 mm.

In my research I've found that there are basically two families, the FN P90/Kel Tec 50 variants and the more traditional magazines for H&Ks, SIGs, AR57, Diamondback and CMMG.

So I think that I'd prefer the latter with:
- Foldable "brace"
- Suppressor
- Red dot
- Under mounted light as this would be for HD
- Forward grip/rest (living abroad, so I need to check current regulations for my state)

I am a bit of a Sig fan, but all the videos and reviews of the Banshee and  DBX are enticing... Just never owned those brands, so I don't know about reliability and aftermarket parts. I wouldn't be looking to FA, but would be interested in a custom build, but on what system?

So, who has issues with the 5.7 for HD, especially in urban areas, and what are your thoughts and suggestions.

Thanks from Erbil, Iraq (not in security, gov or mil).

(Mod please move if this should be in a subforum.)

Suppressed PS90 SBR.  All day long.

Old picture.  It has an Aimpoint T-1 now and side rails.  And there are shorter cans than my OG Gemtech.

First choice P90, second choice PS90.

I enjoy my CMMG 8” 5.7 upper on one of my SBR AR lowers, but CMMG dropping the mag capacity down from 40 to 32 makes me enjoy it a lot less.  It’s definitely a cheaper option than buying and SBRing a PS90, though.

Thanks. I am not sure I could get used to the ergenomics and cheek or chest wield.

A foldable brace is also important. I hate them on rifles like AKs but like having the option on pistol length firearms.

Who is the resident 5.7 expert, or which forum would be best for comparing different brands or builds?

Not many realistic cases you'd need to reload 50 rounds, but do you find carrying and reloading a PS90 significantly more time consuming? I've also wondered about their cycling reliability, but I guess they made the mag and firearm basically proprietary.

Have you seen anything interesting with Sig or HK mods?

Sourcing good anti-personal ammo in any quantity is a problem for most even if you are willing to pay for it.  Inventories are very volatile, at least for the civilian/consumer market.

I like my suppressed SBR ps90. I would love it if it was more reliable though. Seems to fail to eject, feed every once in awhile.

No, I find the CMMG conversion more appealing than the PS90 for a number of reasons that outweigh mag capacity, but it’s still disappointing for them to have dropped the mag capacity from 80% of the PS90 mag capacity to 64%.  One of the appealing things about the 5.7 guns is increased ammo capacity, which somewhat makes up for a small, light round.  If you’re stuck with 30-ish round mags, why not stick with 5.56 or 300BO?

I don’t think anyone will ever do a mod for HKs as there’s no appeal there, plus the 5.7 round competes with HKs own 4.6 PDW round.  Besides, what HK would you use it in?

For Sigs, I don’t see any interest there either.  5.7 is still a niche, expensive round.

Yeah im not big on the ergonomics and wield of the PS90/bullpup style.

I'd much prefer a folding brace and 40 round vertical mag if that combo can be built.

Thoughts on modding a Sig or HK (pistol length)? Where do those or the AR57 get you with ballistics? Still supersonic?

Is there a resident 5.7mm expert on the board?

Keltec p50 + Stamp + Stock adapter

You know that the defunct* AR57 used P90 magazines?  Mounted on the top of the receiver and ejecting out of the magazine well.

* No longer manufactured - for several years now.

That thing is a bitch to reload as in change magazines (esp. compared to a P90/PS90).

Yes, I hope that 50 rounds would be enough, but what about misfeeds...

I'd feel more comfortable with a 40 round "traditional" vertical magazine. I saw DemoRanch's video on the P50. He made reloading look not too bad, but he did have some issues with a red dot (not sure what brand) being too high for eye relief leading to parallax issues...

i see they have upgraded to allen screws instead of phillips.

talk you out of it?  Well go look at 5.7 prices...

I love the caliber but damn the ammo prices...   In late 2019 at local gun show, my buddy and I were going to split a 2k round pack, think it was $800.  It got late and we were tired and said, we will do it at next show...

Speaking of which are the AP black tip rounds illegal? And is there a hollow point?

SS197SR is a 40 grain Hornady V-Max.

SS195LF is a 29 grain open tip lead free bullet.

I don’t believe that the black tip SS190 is illegal to own, but it’s hard to find and very expensive when you do.  But if you use it in a handgun like the FN or Ruger pistols, you could get in trouble because it’s classified as AP ammo.  Both the SS192 and SS195LF rounds are HP (same bullet, the latter round essentially replaced the former).

OP, might wait until after the upcoming ATF brace rule drops before you plan this further.  There is a folding bbl AR (Fold AR), but converting it to 5.7x28mm is gonna cost.

If you can get your hands on an old AR57 upper (rumor is someone's about to reintroduce it), then you can build a carbine out of nothing more than the AR57 upper, a thumbhole stock, & a trigger jig...

Brace talk aside, I am new to pistol length carbines... Now I think I have the bug.

I definitely want to shoot and watch more testing of the 5.7 x 28mm and 5.45 x 39mm. Yes, I know that I should stop being thick headed and just go 5.56, but that's boring. Diamondback DBX vs CMMG Banshee. I don't have range time with either. I've seen some issues reported, but I'm interested to hear first-hand accounts -- again ignoring ammo scarcity?

Should this thread actually be in the AOW Forum?

You going to add a VFG or a smoothbore bbl?

5.45x39mm 7n6 is a great round, better than M855.  Don't think it's better than M855A1, but you can stockpile 7n6, or pull the bullets and load in new cases w/ non-corrosive primers and fresh powder.  It completely overpowers 5.7x28mm, they're not in the same class.

Regarding 5.45x39, the Soviet 7n6 load is a wicked little pill. I saw a wild hog that was taken with it and the wound channel looked like it was made with one of these;


Unfortunately, importation of 7n6 was banned a few years ago so what is here is becoming more expensive and harder to find.