Due to ammo costI'm switching to a PCC. what would you keep as urban self defense long gun?.Best self defense PPC?JP GMR-15 APCSig MPX PPC

I have no experience with the JP, but my 8” MCX has been flawless. Honestly I like everything about it, except the magazines. I like to have a bunch of magazines, and at $50-$65 each, it adds up quick.
If it took Glock mags like the JP, it would be perfect imo.

I voted for the GMR-15. Here is why.

1 - I own one and love it (stock model with no major upgrades since buying five years ago).
2 - Buddy I shoot with has the GMR-15 and said he is going to shoot his until it has a FTF or FTE and the last time I talked to him (match two months ago) he was over 3000 rounds so far without cleaning the gun since its last cleaning.
3 - JP’s are built for competition (a lot of rounds and rough handling).
4 - JP has a HUGE group of upgradable parts.
5 - They run on Glock mags.

I know nothing about the MPX but several Steel Challenge club shooters have sold theirs because they had FTF or FTE issues and stated that it was related to making sure the gun was kept clean and well lubed. Again this is not from my direct experiences so these could have been excuses to sell their MPX’s to justify buying JP, not sure.

Two CON’s of the GMR-15 over the MPX -

1 - Weight - The GMR-15 is not light as compared to the MPX I handled but JP’s new JP5 is lighter than the GMR-15.
2 - Barrel length - The MPX is the winner on this topic without question.

As a PCC addict (literally I have them all), I'm going to say it doesn't matter without some guidance as to what's most important to you. I've no issues with either as far as reliability goes.
Example if you want a zillion mags for every gun, or run glocks normally, then get the JP. The price difference on mags alone will buy you a large amount of spares and an optic etc. If you want a folding stock for example (I'm assuming we are talking rifles here per your choice of words) then you really want an MPX. Etc. Etc. for lots of the differences. And then again for a self defense gun I'd want a short barreled one and depending on how the brace situation sorts out the sig is way better for that. Suppressed is another example.

JP will support your gun with parts and service. SIG’s support is far less.

One other thing to consider, the MPX is on the heavy side.

For a SD gun I'd lead towards the mpx. I have a gmr-15 and love it, but love it as a comp gun. The mpx fills more of a sub gun role. Other ones to consider are the b&t apc line, the tp9 if you want a dedicated suppressor, or the scorpion.

What size are you looking at? Super compact sub gun or a carbine size gun that shoots 9mm, or something in the middle?

Only thing I'll add with the gmr, if you go that route, get the new mlok forend. They are lighter than the mkiii one (I have the mkiii just because I wanted the weight), and I have had zero luck with trigger tech triggers in mine. Their top end one and their duty one each have burst fired on me, and has had an oob cause of it. Stick with either the factory jp trigger or the Wilson if you want a 2 stage.