Upper to lower fit too tight

[Shao]

Don't jerry rig the weapon like this unless its an ipsc gamer gun and not for serious use......

I think sometimes the holes in the lower aren't drilled right or the anodization collects and pools in certain holes causing tolerance issues. It's usually not the pins, upper, or lower that cause the "I have to use a punch and hammer" crowd to pop up. From my experience, it's a problem more akin to the hole in a pistol grip not being drilled or molded correctly, causing a mushy or impossible to nearly impossible to activate safety. I agree that it's not ideal, but the alternative would be to find shorter and weaker springs, smoother detents, or a combination of both. You've never clipped a coil or two off of a safety spring to smooth out a tough to flip safety????

[GH41]

Please explain to me how "anodization collects and pools"??? I love the internet!

[556BlackRifle]

Sure it's not a gen III with the adjustment screw just next to the grip screw? If that baby's up, it's gonna be tight. If it's a gen II, try some different pins and after some time it will loosen. I prefer them on the tight side so it wouldn't bother me too much. Good luck!

[556BlackRifle]

Please explain to me how "anodization collects and pools"??? I love the internet!

Stacking?........ That was a joke.

[Shao]

Please explain to me how "anodization collects and pools"??? I love the internet!

Yeah after I posted it I realized that isn't possible. Chalk it up to tolerance stacking. Ano could be thicker on some lowers causing pins to be tighter and springs to add tension.

[Iraqgunz]

I have seen this as well with some Noveske lowers. I have also seen some uppers that were machined incorrectly in the rear section and would not allow them to close. The MUR uppers have been some of the better ones when it comes to fitment. I would also give the Battle Arms pins a try as well. They worked for at least 2 people I know.

[P2000]

I put together a noveske gen 2 lower with a MUR upper for a buddy almost a year ago. Getting the rear pin to push in (while upper and lower were together) was very very tight and required a rubber mallet. The pins felt fine sliding in and out of just the lower, but assembling the upper and lower was where the it got tight. After a few hundred rounds it is still tight but you can get the pins in and out by hand...some people love a fit like this.

ETA: The LPK was Daniel Defense

[Shao]

I put together a noveske gen 2 lower with a MUR upper for a buddy almost a year ago. Getting the rear pin to push in (while upper and lower were together) was very very tight and required a rubber mallet. The pins felt fine sliding in and out of just the lower, but assembling the upper and lower was where the it got tight. After a few hundred rounds it is still tight but you can get the pins in and out by hand...some people love a fit like this.

ETA: The LPK was Daniel Defense

That sounds like a detent/spring issue. Like others have said it will eventually correct itself, but that's usually because the detents start to round off or the detent springs take a set. Both would be just as bad if not worse in my opinion than just carefully modding it yourself. If someone's recoil spring in their 1911 was too strong and didn't allow the weapon to cycle, the obvious answer would be to buy a weaker recoil spring. I don't see how clipping a few coils off of detent spring would hurt anything. Guns take tuning and fitting. If gunsmiths thought the same way some of you folks do, we wouldn't have custom trigger jobs and all of those bells and whistles. Every gun and every problem is different. Detent springs, pins and lowers are manufactured by all manner of makers - just like most 1911 parts aren't drop-in, you shouldn't expect every AR part to be drop in. Sometimes they need fine tuning. If you're impatient, try my "ghetto" fix. I've put thousands of rounds through a rifle that I fixed the exact same way and guess what? It's still tight as a drum and the takedown/pivot pins pop out under deliberate finger pressure as they should. Nothing has catastrophically failed. Spring cutting is a normal procedure for fine tuning firearms and I find it a bit ludicrous that people would disagree.

Out of spec parts, tolerance stacking... whatever... I have 4 different takedown detent springs in front of me now. All vary in composition, length, strength, and even diameter. To force people into a "one-size fits all" mentality, and claim that if you do any home fixes your gun is now a "range toy" is both counterproductive to our hobby and an insult to fine-tuners everywhere. If my upper and lower can't be separated with my bare hands, something needs to be done. They will wear in EVENTUALLY, but you may be worse off in the long run with damaged springs/detents. I for one would hate to have to try to service my weapon in the field just to discover that I couldn't get it apart.

You do what needs to be done to make a functional and reliable weapon. If you trust your work, then awesome. I know that I've pulled my fair share of bent and twisted springs that were left "stock length" in hopes that the problem would correct itself. Use your better judgement and CLIP ONLY ONE COIL AT A TIME or as mentioned earlier, knock the sharp tip of your detents down slightly for a smoother engagement with the safety core.

[mtdawg169]

That sounds like a detent/spring issue. Like others have said it will eventually correct itself, but that's usually because the detents start to round off or the detent springs take a set. Both would be just as bad if not worse in my opinion than just carefully modding it yourself. If someone's recoil spring in their 1911 was too strong and didn't allow the weapon to cycle, the obvious answer would be to buy a weaker recoil spring. I don't see how clipping a few coils off of detent spring would hurt anything. Guns take tuning and fitting. If gunsmiths thought the same way some of you folks do, we wouldn't have custom trigger jobs and all of those bells and whistles. Every gun and every problem is different. Detent springs, pins and lowers are manufactured by all manner of makers - just like most 1911 parts aren't drop-in, you shouldn't expect every AR part to be drop in. Sometimes they need fine tuning. If you're impatient, try my "ghetto" fix. I've put thousands of rounds through a rifle that I fixed the exact same way and guess what? It's still tight as a drum and the takedown/pivot pins pop out under deliberate finger pressure as they should. Nothing has catastrophically failed. Spring cutting is a normal procedure for fine tuning firearms and I find it a bit ludicrous that people would disagree.

Out of spec parts, tolerance stacking... whatever... I have 4 different takedown detent springs in front of me now. All vary in composition, length, strength, and even diameter. To force people into a "one-size fits all" mentality, and claim that if you do any home fixes your gun is now a "range toy" is both counterproductive to our hobby and an insult to fine-tuners everywhere. If my upper and lower can't be separated with my bare hands, something needs to be done. They will wear in EVENTUALLY, but you may be worse off in the long run with damaged springs/detents. I for one would hate to have to try to service my weapon in the field just to discover that I couldn't get it apart.

You do what needs to be done to make a functional and reliable weapon. If you trust your work, then awesome. I know that I've pulled my fair share of bent and twisted springs that were left "stock length" in hopes that the problem would correct itself. Use your better judgement and CLIP ONLY ONE COIL AT A TIME or as mentioned earlier, knock the sharp tip of your detents down slightly for a smoother engagement with the safety core.

Dude, please let up on the detent & spring shenanigans. If you re-read the post you quoted, the pins moved freely in the lower before the upper was attached. It is very common for tolerance stacking to create this issue, whether it is the size or location of the holes, anodizing thickness or pin size, doesn't matter. The solution is the same. Isolate the problem part and replace if possible. Otherwise, shoot the gun and let nature take its course or work the pins back and forth a gazillion times (essentially lapping the pin & receiver holes) until the fit improves. Oh yeah, and lubricate the pins.

I've only had two lowers that were a real problem. They were so tight that one simply would not accept Colt pins and the other was only marginally better, requiring an armorers hammer and punch to insert and remove the pins. Both were Noveske Gen1 chainsaw lowers. The uppers AND Colt pins worked fine in other lowers from BCM and KAC. With those two particular lowers, they would also not accept Geissele trigger pins or BAD levers. Some folks have 100% success with them, others do not.

[Shao]

Dude, please let up on the detent & spring shenanigans. If you re-read the post you quoted, the pins moved freely in the lower before the upper was attached. It is very common for tolerance stacking to create this issue, whether it is the size or location of the holes, anodizing thickness or pin size, doesn't matter. The solution is the same. Isolate the problem part and replace if possible. Otherwise, shoot the gun and let nature take its course or work the pins back and forth a gazillion times (essentially lapping the pin & receiver holes) until the fit improves. Oh yeah, and lubricate the pins.

I've only had two lowers that were a real problem. They were so tight that one simply would not accept Colt pins and the other was only marginally better, requiring an armorers hammer and punch to insert and remove the pins. Both were Noveske Gen1 chainsaw lowers. The uppers AND Colt pins worked fine in other lowers from BCM and KAC. With those two particular lowers, they would also not accept Geissele trigger pins or BAD levers. Some folks have 100% success with them, others do not.

..and that's probably why I shouldn't try to offer help before I have my morning coffee. I was trying to help with a problem that I run into a lot more than out of spec receivers. Most of my takedown/pivot pivot pin issues are caused by the problem I described. I have no experience with Noveske lowers, but plenty with MUR uppers... and you CAN damage your detent springs if they're too long and you constantly have to hammer your takedown pins to get them started. I have a small pile of ruined springs caused by listening to the "hammer it in, it'll loosen up" advice that 99% of members (myself included at times) give when this problem occurs. I was simply trying to give an alternative explanation as to why pins can be tight. I admit that without caffeine in the morning my comprehension levels are significantly lowered.

The post that I quoted however didn't specify whether or not the pins and detents were installed when the poster stated that the pins slid freely in the lower. He could have just meant that the pins were of the proper size for his lower.

I will add though, if you hit the pins with ballistol and tap them with a nylon hammer and they still haven't loosened after 20-30 whacks, you either have a VERY out of spec lower/upper or if the detents and springs weren't installed - that could still be an issue.