don't mean to bump, but is there a stock adapter from UMP to ACR without needing USC upper?
No sir, like the man said, no one makes one like that.
Not sure where you're getting an original UMP upper (they were all de-milled before sale) but they don't have a slot to put anything into. The hinge is part of the actual receiver on an original UMP receiver, so there'd be no way to insert a stock block of any kind.
If you mean something else by your question, let me know, happy to help.
I was playing with one of these last night, put it all together with my USC upper and UMP lower and the ACR stock. It's already impressing me BUT I had a few questions for you guys who have been using this stock block for a while:
1. There's a little bit of play between the components -- not a lot and it probably doesn't effect function but I don't like the stress it might impart to the polymer under recoil. I think a slightly larger diameter pin might lock things up tighter. Has anyone played with this?
2. Has anyone come up with a more elegant solution than the key chain looking circular retaining pin that prevents the block pin from coming out unintentionally?
I guess both questions might have the same solution. I'd really like a pin that fits tight enough that it needs to be driven in and out with a punch. Then it could be flush -- more like the trigger pins etc. of the lower. I almost wish this stock block utilized the original USC screws.
Any insights would be appreciated.
Hokey religions and ancient weapons are no match for a good blaster at your side, kid.
Hmmm,,, I use a pin I got from HKParts which had a thicker hole on the left side that threaded in to tighten. I have to tap it in and out with a plastic mallet of some other type of LIGHT tapping tool. Not much, just a little something. ZERO wiggle and the hole on the left side is big enough to get my clip-on sling on.
I went on the website and I don't see it offered anymore. Not sure why...
This might be the part. Their website has had issues for a while (for me at least) and sometimes won't resolve. YMMV
Last edited by LeeMajors; 04-18-2017 at 04:27 PM.
Best of luck. Let us know if you get ahold of HDPS. I've been emailing them to order some stuff since around Christmas and no response. He told me back around Christmas that his shop had burned down and he was relocating, but no news since then.
I may be switching back. Got the BT stock in and will do a comparison this weekend.
I used to have a supply of these. They're an odd size, 13/64 or something like that, I'd have to check and see what I have around.