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Posted: 8/5/2026 10:19:06 AM EDT
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Lets keep this to actual SMG (Pistol) cartridges Of course 9mm comes to mind and it may well be the best choice; but are there other better options? I break SMGs into a few "sub" categories of SMGs. There are the Mini/Micro guns (VZ61, M11/10, Mini Uzi, Colt DOE?) and the GoToWAR SMGs (MP5, Uzi, etc) The folks at Kriss gave us the Vector initially in 45acp but eventually in 9mm, 40SW, and 10mm. There are small(er) SMGs in 32acp, 380, 9MAK and full size guns in 762x25. I had high hope for something in 357SIG but that round faded, much like the MP5/10; which seems ashamed as a 10mm sorta brings the SMG into the Magnum or Intermediate category Pick your SMG and Cartridge |
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From a performance perspective the 7.62x25 has done well since WW II but not widely supported or used by the west. Honestly I think the actual firearm ergonomics and operating system are maybe more important than the specific cartridge. For close quarters use within specific parameters used to select the weapon is important. Is the weapon for dignitary protection where conceal ability is desirable without fratricide. Is the weapon used by military for cqb house to house or in trenches? Is there a robust support network with abundant quantities of ammunition. Is the weapon a range toy with SHTF a secondary role where cartridge commonality is preferable. I personally shoot 9 mm, 45 ACP, 380 and 40. Of those options I’d choose 9 mm. Good capacity, decent ballistic performance against unarmored targets, readily a available affordable ammunition. For me, I like the MP5 and the old Colt 9 mm sub guns my department used. |
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Specific mission requirements does have an effect on choices. I carried a MP5 with the fixed stock and the sliding stock on a Personal Security Detail in the Gulf. Yep the sliding version was easier to cover but that wasnt our concern. Had there been a need for concealment something else might have been better. I did see a pilot with the HK PDW version which looked cool. I think youre right about 9mm for all the reasons that have been said over the years. That being said I do have some interest in a full power 10mm gun. Sadly 10mm seems to be limited to Kriss at this time. |
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Originally Posted By NN300BLK: Or a 5.7x28 sub gun (capacity). What 5.7 gun would you pic? The P(s)90 seems the easy button. The only other Id consider might be the Masterpiece Arms (M10 clone) because it uses FN 57 pistol mags. Its not my first choice but it sorta gives you the MP7 feel at a price you can afford |
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Originally Posted By PieterCoetzee: What 5.7 gun would you pic? The P(s)90 seems the easy button. The only other Id consider might be the Masterpiece Arms (M10 clone) because it uses FN 57 pistol mags. Its not my first choice but it sorta gives you the MP7 feel at a price you can afford Originally Posted By PieterCoetzee: Originally Posted By NN300BLK: Or a 5.7x28 sub gun (capacity). What 5.7 gun would you pic? The P(s)90 seems the easy button. The only other Id consider might be the Masterpiece Arms (M10 clone) because it uses FN 57 pistol mags. Its not my first choice but it sorta gives you the MP7 feel at a price you can afford Yeah, the PS90 comes to mind or the CMMG I might consider the KP-50 as well if they prove to be reliable and I can get over the Florida beach plastic. 
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Originally Posted By NN300BLK: Yeah, the PS90 comes to mind or the CMMG I might consider the KP-50 as well if they prove to be reliable and I can get over the Florida beach plastic. Keltec 5.7 guns are designed to pretty much operate only with the watered down 40gr ammo. Both the Sub 2000 and the P50 designs showed pressure signs on the SS198LF ammo, that other designs have not. Adding the heavy bolt to the Sub2000 helped, and on my P50 switching to the STINC lower with an AR15 hammer helped keep the system locked up a touch longer. Ideally 8-10" is a sweet spot for 5.7. My MK57 (CMMG) gets very close to the velocities that my P90 does. |
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Originally Posted By Buffman_LT1: Keltec 5.7 guns are designed to pretty much operate only with the watered down 40gr ammo. Both the Sub 2000 and the P50 designs showed pressure signs on the SS198LF ammo, that other designs have not. Adding the heavy bolt to the Sub2000 helped, and on my P50 switching to the STINC lower with an AR15 hammer helped keep the system locked up a touch longer. Ideally 8-10" is a sweet spot for 5.7. My MK57 (CMMG) gets very close to the velocities that my P90 does. Yeah, the Keltecs seem to be well engineered, but affordability and manufacturability seem to be the principal design parameters. So, I’m not exactly surprised they function best with the lower pressure ammo. I’ll keep the MK57 in mind over the Dissent. |
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Originally Posted By NN300BLK: Yeah, the PS90 comes to mind or the CMMG I might consider the KP-50 as well if they prove to be reliable and I can get over the Florida beach plastic. Ironically, I just ordered a KP50 the other day. This is the first Kel-Tech with a non-plastic frame structure, and the select-fire version (the MP50) is the very first select fire weapon they've ever manufactured. I'm intrigued by the 5.7 as it offers something a little different than conventional handgun/SMG cartridges. I'm hedging my bets that an FRT will get developed for the KP50 and my nightly prayers are that when I get hands on it, it runs reliably Having 100 rounds "on-board" is pretty signficant for even a small, fast 5.7x28mm bullet. ROCK6 |
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Originally Posted By zoe17: What about the 7.5 FK Bruno? Don't own one, but ballistics look good. Other wise 9mm for max ammo availability or 10mm for more energy. Its an interesting cartridge, but I dont know if it has any staying power in the industry... I wish they would build a PCC in 7.5 though, the cartridge seems kinda wasted in pistol form |
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I reload and do have a Glock 20.5 so I actually shoot a good bit of 10 MM. I didn’t mention the 10 mm as there aren’t many 10 mm SMG’s on the market. Ammunition in the full power 10 mm is kind of limited as most FMJ factory loads are down loaded to warm 40 S&W velocities. Typical SMG barrels tend to run from 5” to about 11.5” so longer barrel length does increase velocities. Velocity is a two edge sword with pistol caliber cartridges where the specific bullet has an impact on overall penetration. Using a JHP intended for short pistol barrels might under penetrate out of a longer barrel. My Agency tactical teams used 10.5” Colt SMG’s with W-W 115 grain +P+ JHP. This combo was very effective on the street and the cartridge/bullet didn’t produce failures to stop due to under penetration. My Agency moved to 5.56 AR-15 select fire carbines instead of the Colt SMG’s. With common use of Peltor electronic hearing protection along with two way radio interface the blast and noise associated with short barrel rifles is mitigated. More Agencies are using suppressors which mitigate weapon signature and helps to reduce hearing loss. I personally think you have to identify the task along with tactical considerations of the opposition before selecting the specific firearm and ammunition. The requirements are significantly different between responses to various incidents in LE. In a military context there are different priorities and objectives. Without knowing a given task it is difficult to know the best load out. Not knowing anything a response might entail and given a choice I would pick a 5.56 AR-15 with 16” barrel or a 14.5 if not an SBR. To me this trumps the pistol caliber SMG’s for the greatest number of scenarios. |
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Originally Posted By ROCK6: Ironically, I just ordered a KP50 the other day. This is the first Kel-Tech with a non-plastic frame structure, and the select-fire version (the MP50) is the very first select fire weapon they've ever manufactured. I'm intrigued by the 5.7 as it offers something a little different than conventional handgun/SMG cartridges. I'm hedging my bets that an FRT will get developed for the KP50 and my nightly prayers are that when I get hands on it, it runs reliably Having 100 rounds "on-board" is pretty signficant for even a small, fast 5.7x28mm bullet. ROCK6 Originally Posted By ROCK6: Originally Posted By NN300BLK: Yeah, the PS90 comes to mind or the CMMG I might consider the KP-50 as well if they prove to be reliable and I can get over the Florida beach plastic. Ironically, I just ordered a KP50 the other day. This is the first Kel-Tech with a non-plastic frame structure, and the select-fire version (the MP50) is the very first select fire weapon they've ever manufactured. I'm intrigued by the 5.7 as it offers something a little different than conventional handgun/SMG cartridges. I'm hedging my bets that an FRT will get developed for the KP50 and my nightly prayers are that when I get hands on it, it runs reliably Having 100 rounds "on-board" is pretty signficant for even a small, fast 5.7x28mm bullet. ROCK6 Yeah, the material choice and design choices make me hopeful that this is designed to be a more serious duty use sub gun rather than maximizing affordability. But I noticed that they couldn't help themselves used what looks like their classic plastic for the jungle clip. But that 100 round "on-board" capacity is a serious advantage (or even the 50 round capacity in a single magazine) and that's what caught my attention as well. I typically prefer more traditional pistol calibers (hence the mention of the Kuna in .40 SW in my original reply to the OP), but 5.7 seems to be developing a decent track record despite the slow adoption. |
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I recently picked up a Zenith MP5 clone. I really like how it shoots. I think 357 Sig or 762x25 would be great in this platform. Flat shooting rounds that feed well, should be great at distance also. The 30 SC has fallen on its face, but that would also be a great round in a sub-gun. |
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As much as I love 5.7, Im undecided if Id really class it as a SMG. Im not opposed to that but I question if "fits" the category. I am NOT a KelTec fan. I wish I could like them; but its kinda like a Ferrari built by Hyundai (good idea poor execution). IF we're gonna go the 5.7 route then Id like to add 30 Carbine to the list. 40SW is pretty much a dead cartridge. It started strong but never quite had the staying power (more recoil than 9mm and a smaller mag capacity. 357SIG could have been the answer; but sadly too that faded. I do like 10mm as a magnum SMG cartridge. 10mm has lasted, which is a big plus. The question now is what platform. I had really high hopes for the MP5/10. I wish a semi clone (and mags were available). Currently, the only 10mm option seems to be the Kriss Vector. Glock mags are great but I wish there were other options for other guns, Im not a fan of Glock mags for SMGs, because of the angled insertion required. Perhaps something like a upscaled UZI mag for Colt SMG style guns |
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Originally Posted By PieterCoetzee: As much as I love 5.7, Im undecided if Id really class it as a SMG. Im not opposed to that but I question if "fits" the category. I am NOT a KelTec fan. I wish I could like them; but its kinda like a Ferrari built by Hyundai (good idea poor execution). IF we're gonna go the 5.7 route then Id like to add 30 Carbine to the list. 40SW is pretty much a dead cartridge. It started strong but never quite had the staying power (more recoil than 9mm and a smaller mag capacity. 357SIG could have been the answer; but sadly too that faded. I do like 10mm as a magnum SMG cartridge. 10mm has lasted, which is a big plus. The question now is what platform. I had really high hopes for the MP5/10. I wish a semi clone (and mags were available). Currently, the only 10mm option seems to be the Kriss Vector. Glock mags are great but I wish there were other options for other guns, Im not a fan of Glock mags for SMGs, because of the angled insertion required. Perhaps something like a upscaled UZI mag for Colt SMG style guns The 5.7 is somewhat borderline because it was developed for a PDW (FN P90). While they did make a Thompsom in 30 Carbine, I'm not sure it would be considered a success. They still make quite a bit of .40SW ammo even if new handguns are going to be few and far between (such the Springfield/HS Produkt Kuna that was designed in .40SW). |
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Thinking about it, I had already picked my preferred SMG cartridge. I have an Uzi SMG that I can set up in 6 different cartridges. I have bolt/barrel/magazine combos such that I can shoot this gun in 9mm, .40, .45, 10mm, .357 Sig, and .22LR. Reality is that I shoot it 80-90% in 9mm, with the remainder in .22LR. The rest are interesting novelties. And it’s not a capacity thing, as I have a grease gun mag grip housing, so I can run 30-round GG mags in .45. Or if I tweak the feed lips a bit I can fit 35 rounds of .40/10/.357 in a GG mag. They’re fun, but I can’t recall the last time I shot one of those cartridges in the Uzi. And if you’re shooting suppressed, subsonic 9mm is noticeably quieter than subsonic .40/10mm or .45. If you want more energy on target, just hold the trigger down a little longer and give it a 5 or 6 round burst instead of 2 or 3. 
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Originally Posted By NN300BLK: Yeah, the material choice and design choices make me hopeful that this is designed to be a more serious duty use sub gun rather than maximizing affordability. But I noticed that they couldn't help themselves used what looks like their classic plastic for the jungle clip. But that 100 round "on-board" capacity is a serious advantage (or even the 50 round capacity in a single magazine) and that's what caught my attention as well. I typically prefer more traditional pistol calibers (hence the mention of the Kuna in .40 SW in my original reply to the OP), but 5.7 seems to be developing a decent track record despite the slow adoption. Well...we'll see. I should pick it up in a week or so. ROCK6 |
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Originally Posted By NN300BLK: Yeah, the material choice and design choices make me hopeful that this is designed to be a more serious duty use sub gun rather than maximizing affordability. But I noticed that they couldn't help themselves used what looks like their classic plastic for the jungle clip. But that 100 round "on-board" capacity is a serious advantage (or even the 50 round capacity in a single magazine) and that's what caught my attention as well. I typically prefer more traditional pistol calibers (hence the mention of the Kuna in .40 SW in my original reply to the OP), but 5.7 seems to be developing a decent track record despite the slow adoption. Someone should develop a big-ass helical mag for it and it'll be the PP19 that Russian kids will wish they had at the dacha. |