Recently I bought a VLTOR MUR1 Upper to fit on my spikes blem lower. When I fit the MUR1 on to the spikes lower I noticed that I have a gap that you could fit about 1 or 2 index cards through for reference at the rear of the receiver around the receiver extension and just above the takedown pin. As you make your way towards the front end of the receiver the fit is great between the upper and lower. The gap is just at the rear. I understand that it probably wont cause functional issues. It is just annoying because I am a bit of a perfectionist. Should I invest in some accuwedges, I have also heard of putting an O-ring around the “takedown pin hole”. Some tips would be great. Thanks.
If you’re a perfectionist, I really think you should ditch that spikes blem lower for something first rate. A stopgap solution won’t make you happy.
So are you implying that the spikes blem lower is possibly out of spec? or just that its a blem. The blem is in the mag well, which is something I am okay with.
What he said… Lowers are so cheap these days… Why stick a Spike’s blem on a choice MUR? I love MURs… Mine mates up exceptionally well to a CMT billet lower as well as a Seekins forged… I haven’t tried it on anything else, since that would be violating the law. Don’t use an Accu-Wedge. The gap and wiggle won’t affect function, but if it bothers you that much, just buy more uppers and lowers. Then you can match up ones that fit well together. All of my rifles are SOLID!
I originally bought the blem lower because Im a poor college student and didnt think lowers mattered all that matter. I certainly see where your coming from. I guess i’ll start up that FFL process again. Do you think it would be easy enough to pull out the parts out of my lower that I built and move them into a new lower?
If you put them in you can get them out. Just watch out for your pivot and take down detents/springs. Oh yeah… and watch out for your buffer retainer and spring. Those are all parts which I’ve spent too many hours than I care to think about crawling around on the floor with a flashlight looking for after they shoot out on me that I will never make those mistakes again.
Solid, Thanks again!
Play between the upper & lower have no affect on performance or accuracy. Save yourself a couple of bucks run what you’ve got. Shooting now is much better investment of your time than fretting over the fit between the upper & lower
My buddy just put a MUR1 on a non-blem BCM lower. Same issue. Hasn’t affected function.
I have the opposite issue. My MUR-1A and Seekins forged lower fit so tight I have to tap the takedown pins in/out with a punch. I think I can remedy this buy taking a little material off the top of the lower, or the bottom of the upper. My only questions are: which one do I sand down, and will doing so have any ill effect?
Sorry to hijack the thread… If mods or the OP feel this is too far off topic from the original question let me know and I will remove it.
Don’t sand them. They’ll break in over time as you use them
What he said. One of my Seekins forged lowers needed a nylon punch and hammer to separate from its chosen upper for the first few weeks of its life. Now it’s just right.
Add a little grease or CLP and work the piss out of it.
Grease will delay the “break-in.” Polishing compound will accelerate it. You can even use toothpaste, if it makes you feel better.
Definitely don’t go trying to sand material off the bottom of the upper or the top of the lower. You’ll end up with disfigured parts and likely won’t even fix the problem.
OP - be a perfectionist about things that matter, and ignore things that don’t. Use the lower you have with the upper you have.
The point I was trying to make is lube it so there’s less friction and be done with it.
In spec includes the allowance for some play between the upper and lower; this is much better than having them fit so tightly that you need tools to get the upper off that lower - I had to rotate around some of my Noveske Gen2 (Blem) lowers with MUR1A’s before I found which pairings didn’t require tools - still rather tight, but at least I don’t need tools to break down any of those three carbines.