MPX SBR or MPX-K? - Page 1

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Posted: 12/29/2017 2:03:48 PM EDT

I am wanting to buy two, one for myself and my wife; strictly as our home defense PDW. With the air pellet versions, this also provides some good cheap training opportunities on our personal range.

However, I’m not sure which provides the best ballistic data, an 8” or 4.5” barrel with 9mm, and if that should be a determining factor. What says ARFCOM?

Posted: 12/29/2017 2:16:13 PM EDT

[#1]

9mm really sees no benefit from barrels longer than 4". In fact most quality HPs perform fine out of a 3" barrel.

It will have pistol terminal effects, and pistols suck. Practice emptying 15 rounds into target.

It will not penetrate even the cheapest $40 pawn-shop armor.

It will not benefit from the enhanced terminal effects of rifle projectiles going >2,000fps.

It will be more likely to over-penetrate and/or pass through walls than 5.56mm.

On the plus side it will be pretty quiet if you stick a can on it and shoot 147gr loads.

The MPX-K is one of the coolest guns I have ever shot though. It shoots great and offers many legal advantages over an SBR.

Posted: 12/29/2017 3:22:34 PM EDT

[#2]

I'd say kinda go in the middle.

Go with the 8 inch gun and have the barrel cut down(or swapped) and run a suppressor under the handguard. Mine was cut to 5 inches and had a 3 lug installed over the barrel(mp5 style vs an adapter screwed onto the end). It got some paint too.

Posted: 12/29/2017 3:48:20 PM EDT

[#3]

Quote History

Quoted:
I'd say kinda go in the middle.

https://imagizer.imageshack.com/v2/1024x768q90/924/ElnMLC.jpg

Go with the 8 inch gun and have the barrel cut down(or swapped) and run a suppressor under the handguard. Mine was cut to 5 inches and had a 3 lug installed over the barrel(mp5 style vs an adapter screwed onto the end). It got some paint too.

View Quote

That’s gorgeous. Great call on the 8” and having the barrel cut to allow an integrated suppressor.

Posted: 12/29/2017 3:57:40 PM EDT

[#4]

Quote History

Quoted:

That’s gorgeous. Great call on the 8” and having the barrel cut to allow an integrated suppressor.

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At this point you can buy aftermarket 4.5 inch barrels so you don't even need to have the 8 inch one cut if you don't want. When I did mine the k guns were not out(or very hard to find) and no one was doing aftermarket barrels yet. I was at TSC machine having the sbr engraving done and Mike had some mp5's he had done in the burnt bronze. He was playing with the sig as he hadn't seen one yet(he is a hk roller lock guy) and I said I wanted a shorter barrel with 3 lug. He said he would do it so we talked options and I left the gun with him for that and the refinish. It was his idea or his assistant Dale's to leave the top rail black. Only thing I changed was I didn't have them fill in all of the engraving. It really came out great.

Mine has run everything I've put through it although some ammo is more gassy than others and I'm a south paw. Might be able to adjust that some screwing with the gas but I've just been more picky with ammo. Again it runs everything though so I don't want to mess with it too much.

Posted: 12/30/2017 5:53:42 AM EDT

[#5]

I love my mpx k
I run an obsidian on it but the gas. Holy crap. It’s TOO much. Literally burns my eyes after like 5-8 rounds. I haven’t bought that gas buster ch or decided to put some silicone like some people have.

I was going to get an mp5 originally but I went with the mpx due to the design and price. Yes mp5 is mp5 but it was gonna be like twice the mpx almost.

You cant go wrong with the mpx. I run a lage folding stock on mine.

Posted: 12/30/2017 9:24:59 PM EDT

[#6]

Quote History

Quoted:
I love my mpx k
I run an obsidian on it but the gas. Holy crap. It’s TOO much. Literally burns my eyes after like 5-8 rounds. I haven’t bought that gas buster ch or decided to put some silicone like some people have.

I was going to get an mp5 originally but I went with the mpx due to the design and price. Yes mp5 is mp5 but it was gonna be like twice the mpx almost.

You can go wrong with the mpx. I run a lage folding stock on mine.

View Quote

Try different ammo. I found some ammo very gassy vs others.

Posted: 12/31/2017 5:07:36 AM EDT

[#7]

Quote History

Quoted:

Try different ammo. I found some ammo very gassy vs others.

View Quote

Yeah. I should. But with like 4 different guns that use 9mm gotta pay what I can afford. But I’ll keep that in mind as someone else told me same

Posted: 12/31/2017 5:20:35 AM EDT

[#8]

Here’s a older pic.
Although I think with an omega 9k would be better (size wise/look wise) and that was the original plan but the obsidian was getting some great reviews etc and also being that it was prior to 41f and omega along with bucmja other cans were out of stock and no idea if would come in stock in time for the deadline I went with the obsidian. If at some point I decide to get my sot ( I’m an ffl)or wait times in general come down then I’ll get an omega.

Posted: 12/31/2017 11:20:30 AM EDT

[#9]

Quote History

Quoted:
I love my mpx k
I run an obsidian on it but the gas. Holy crap. It’s TOO much. Literally burns my eyes after like 5-8 rounds. I haven’t bought that gas buster ch or decided to put some silicone like some people have.

I was going to get an mp5 originally but I went with the mpx due to the design and price. Yes mp5 is mp5 but it was gonna be like twice the mpx almost.

You cant go wrong with the mpx. I run a lage folding stock on mine.

View Quote

I have run this same setup with Obsidian in K config with 147gr speer lawman and 158gr fiocchi. Both have been great to me. Cut down factory barrel to 4.5"

OP, i prefer the K between the two. you can always pay $100ish and get a long hand guard to partially cover a suppressor on the 4.5 k barrel. Easier then buying the longer only to have to send off the barrel to cut it down or buy an aftermarket 4.5" barrel unless you specifically want that 3lug aftermarket barrel

Posted: 12/31/2017 5:08:07 PM EDT

[#10]

Suppressed MPX-K SBR is the correct answer..

Attached File

Next to Kriss Vector SBR

Attached File

Posted: 12/31/2017 10:02:02 PM EDT

[#11]

I used to have that collapsible sig stock. It sucked. It had too much wobble.

Posted: 1/1/2018 7:55:13 PM EDT

[#12]

I love the Sig Factory 4.5" barrel....its just as accurate as the 8" barrel. From the ballistic charts...velocity will be lower with the shorter barrel...but from my range time with both barrels...accuracy is about the same. Without a can...the 4.5" barrel makes for a really compact system...with the can..its still OK...but lots of can will stick out past the handguard.

Posted: 2/5/2018 12:06:16 PM EDT

[#13]

I did mine SBR wouldn't have it any other way. It started life as a 8" pistol, I like it so much better with the 4.5" barrel. It's my home defense weapon with a Trijicon MRO on the way its perfect! SBR stamp took 7 months.

Posted: 2/5/2018 1:12:17 PM EDT

[#14]

JayRock,
Which Stock is that???

I’ve got an 8” running Obsidian short with 9mm end cap and gas isn’t bad at all. Using 147’s reloads.

Posted: 2/5/2018 1:59:35 PM EDT

[#15]

looks like lage

Posted: 2/10/2018 11:13:36 AM EDT

[#16]

Finally got my pics to post so here's mine. SBR 8" cut to 4.5" with a collapsible stock.

Posted: 2/11/2018 1:29:38 AM EDT

[#17]

I ordered one from my local shop today. Went with the 4.5" and brace for a couple of reasons:

1) I travel quite a bit and don't want any hassels with crossing state lines

2) in TN a rifle can't be carried with a round chambered in a car, not a problem with the pistol.

3) A handgun falls within the handgun carry permit, not so with a SBR

4) the brace doesn't really give up anything to the stock in terms of functionality

5) Don't see the need in paying Uncle Sam and doing unnecessary paperwork.

Just my .02, but there are some damn fine looking SBRs in this thread.

The main reason I can see in a SBR are that "shouldering" it isn't an issue and that you can use a foregrip. Anything I may be missing?

Posted: 2/11/2018 2:27:40 AM EDT

[#18]

You loose the front grip ability on the gun and personally I don't think the pistol braces feel as good or are generally as sturdy as the stock. Just limits you options more. I will say some of the braces though seem to be pretty good.

Posted: 4/17/2018 10:10:04 PM EDT

[#19]

Any of you guys running the Sig combo VFG-handstop thingy on your SBRs? I just bought one but haven't installed it yet (will try it this weekend). They were hard to find in stock in black (found it at Rainier) but in pics they look just right on the MPX SBRs. Pic here

Posted: 4/18/2018 9:59:59 AM EDT

[#20]

Quote History

Quoted:
Any of you guys running the Sig combo VFG-handstop thingy on your SBRs? I just bought one but haven't installed it yet (will try it this weekend). They were hard to find in stock in black (found it at Rainier) but in pics they look just right on the MPX SBRs. Pic here

View Quote

Yep...see my pic above. Sig VFG might be a little small for large hands but it works well for me using a thumb break grip. Grip does get warm when using a can underneath the grip.

Posted: 4/22/2018 8:15:55 PM EDT

[#21]

Tried it this weekend and gotta say I was a bit disappointed. It looks good on the MPX but I just didn’t get as comfortable a hold with it as I do with a BCM vertical grip. I’ll try shooting with both back to back but so far I feel like BCM is the winner (I use a thumb-over-the-top grip).

Posted: 4/23/2018 8:03:44 PM EDT

[#22]

i been trying to find a metal/alum version of that exact or similar foregrip but i cant seem to find one. What i have now (in the pics i posted) seems to work for me but i always wanted one of the sig type ones.

Posted: 4/23/2018 10:23:46 PM EDT

[#23]

Quote History

Quoted:
i been trying to find a metal/alum version of that exact or similar foregrip but i cant seem to find one. What i have now (in the pics i posted) seems to work for me but i always wanted one of the sig type ones.

View Quote

https://a3-tactical-inc.myshopify.com/collections/firearm-accessories

Posted: 5/19/2018 2:51:53 PM EDT

[#24]

Spot on! The right call. Good luck

Quote History

Quoted:
I ordered one from my local shop today. Went with the 4.5" and brace for a couple of reasons:

1) I travel quite a bit and don't want any hassels with crossing state lines

2) in TN a rifle can't be carried with a round chambered in a car, not a problem with the pistol.

3) A handgun falls within the handgun carry permit, not so with a SBR

4) the brace doesn't really give up anything to the stock in terms of functionality

5) Don't see the need in paying Uncle Sam and doing unnecessary paperwork.

Just my .02, but there are some damn fine looking SBRs in this thread.

The main reason I can see in a SBR are that "shouldering" it isn't an issue and that you can use a foregrip. Anything I may be missing?

View Quote

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