Upper not fitting lower

[vlady]

I have a billet lower that I milled out of an 80% and just got a billet upper yesterday and am having a fitment issue. It looks like the pocket around the rear take down pin on the lower is not allowing the upper to sit all the way back. There is about a 1/16th (maybe less) gap against the front of the buffer tube slot and the same misalignment with the pivot and take down pin holes. My question is, can I safely file down the rear take down tab on the upper to achieve proper seating of the upper and lower? Seems like an easier/cleaner solution than filing the pocket of the lower, but what do I know, I'm certainly no gunsmith. Any help is greatly appreciated. I'll post pics tonight but hopefully the explanation above is enough to give the experts here an idea.

[Gutz]

I'm pretty sure you can file it down....

[vlady]

Bit the bullet and filed the notch down. Worked like a charm and everything lines up perfectly now. Thanks Gutz

[troberge]

I had exactly the same problem. I *carefully* filed down the rear take down hole in the lower. Worked like a charm.

[vlady]

I had exactly the same problem. I *carefully* filed down the rear take down hole in the lower. Worked like a charm.

My issue wasn't the hole, but rather the tab itself so I filed it down and now the holes align perfectly, both pins go in perfectly too. On to the barrel selection

[kcstott]

I know you issue is taken care of but and FYI there needs to be a chamfer on the upper rear lug. On the back side vertical surface and the bottom. that usually solves the fitment issues.

Do not file holes to fit. that will cause your weapon to rattle and possibly cause reliability issues. Some time the holes don't line up perfect. I get which ever hole looks like it will line up the best. use that one to locate off of. then I run a reamer through the holes when the upper and lower are together only if the pin fits but is really tight. This will loosen the fit enough to allow it to work correctly but not so loos as to cause issues.

[ford63man]

don't file your upper. fix the lower to fit the upper.
if you don't make your lower right, than you will have to file
all uppers that you ever try to fit to that lower.

[vlady]

don't file your upper. fix the lower to fit the upper.
if you don't make your lower right, than you will have to file
all uppers that you ever try to fit to that lower.

I did consider that, but it was a lot easier for me to file the tab and it literally took a minute to get it to fit plus I don't plan on mating this lower to any other upper in the future

[kcstott]

don't file your upper. fix the lower to fit the upper.
if you don't make your lower right, than you will have to file
all uppers that you ever try to fit to that lower.

Incorrect.
There is a large chamfer called out on the M16 upper ordinance print that is not on commercial uppers. The just break the edge. That along with the commercial cut of the lower makes the fit snug at best.

Now if the lower was cut incorrectly thats another issue.