The idea is I want as low a profile red dot as I can get. I ruled out the Aimpoint Micro because it's just to small for me I don't care for the small tube effect so that's out.

I really like the Trijicon MRO and SRO so its down to them. I'm a huge fan of LaRue mounts and they have one specifically for the MRO and It sounds like the SRO fits an RMR mount.

Next is the type of mount. My understanding is B&T makes some great mounts, but I'm not sure which to get, or which height. There is an RMR mount that replaces the rear sight and I think that's pretty cool, just not sure I want to abandon the rear sight.

What I don't like about super low profile red dots on MP5s is they're just too busy. I don't like to see irons through my red dot window, so I'd like to clear the front sight, but then I worry the sight will sit too high and it will feel awkward to shoot. Although I suppose having the round Hk front sight would blend well with the round red dot window if I go with the rear sight replacement, or without it and just mounting a rail the rear iron may not be in the way. When all is said and done I'll have an A2 stock but will also look into a collapsible one in the future

Have you cheeked an MP5 with an A2 stock on it? Before you make any decisions you may want to in order to get a feel for where you would want the optic to set in line  of sight. I find that I have to bare down on the stock to get good LOS with open sights where as with a rail and an optic, its more a natural LOS position.

Not yet but I have one on the way. Right now I'm leaning heavily towards an SRO with a LaRue QD RMR mount and trying to figure out which B&T rail mount would be best. I want to get the short one they sell just not sure on it's height yet

If you’re going to use an A2 stock and you don’t want to see the front sight, you’ll have a very heads up shooting position.

Not sure if this will help, but see pics here (I’m the OP, tlrgsxr)... https://www.hkpro.com/forum/hk-long-gun-talk/513556-pictorial-examples-various-red-dots-b-t-sp5-mounts.html

That is very helpful and thats the mount I've been looking at. Appreciate you

I can't belive what a pain in the ass it is to find anything MP5 related right now... I can find a B&T 21222 anywhere, or anything else for that matter. I think I found one B&T but its huge and takes up most of the receiver

Of your choices, I'd go with the MRO... but I'd still recommend you consider an Eotech. Love it on my PTR clone. Clears the irons for an awesome sight picture and very easy to pick up and track under recoil.

I have an exps2 on my AR pistol. It's too big on the SP5 for me. I've got an Umarex MP5 .22 with some cheap claw mount on it so I already popped it on to see what I thought and I didn't like it.

I'm still a bit torn between the MRO and SRO but I think its going to be the SRO because of the low profile and large window. I know the durability is an issue and it's definitely not a duty sight, but this gun will be my baby andy safe queen so if it got dropped there would be a whole other set of problems

@BabaYaga777

https://bt-parts.com/bt-21222-b-t-mounting-rail-nar-low-profile-mount/

They’re a month out but just order and forget about it.  They also have factory HK MP5 mags in stock.

I wonder how accurate that is.  It has been saying 4-6 weeks eta on the B&T stocks since I started looking about a month ago.

They were accurate when I ordered MP5 mags before they were in stock, and ordered again in stock. Shipped fast once in stock. If they’re unavailable everywhere, what’s it hurt to drop the order?  From what I understand they’re B&T’s US parts distributor, so they’ll get new imported stuff before everyone else.

I guess you're right but man, I have a serious aversion to ordering and paying for things that aren't in stock.

I've never done business with these guys, so maybe it will go through ok.  In the past, however, with several different vendors and retailers in every single instance of doing so I regretted it later.

Sweet thanks for the heads up I'll do that. It's not like one is likely to come in stock amywhere anytime between now and then anyways

You could always just keep an eye on their site or call once a week too if that’s a concern.