I have an lmt upper and a cheap ballistics advantage lower that due to the lower possibly being out of spec wont line up correctly with the lmt upper or a bushmaster upper that I also tried.

Ive seen posts on here about having super tight fitment issues on their rifles but in my situation though possible to get both pins together takes so much force that obviously there is something wrong with the lower.

Could i not just take material off the front takedown pin until it will go through and leave the rear one alone?

The rear takedown pin goes in fine without the front one pushed through which when the rear pin is pushed through seems to hit up against the upper receiver hole for the takedown pin which makes it impossible to get
through.

Wouldnt just taking material off the front takedown pin ( like a 3 dollar part)  keep me from having to remove material from the upper or lower takedown front pin hole.

There is nothing wrong with the upper so i would leave that alone im not opposed to taking material off the lower takedown pin whole but if i were to what would i use? Just sandpaper and a bunch of elbow grease?  This seams like a common problem from cheaper lowers not that their junk or anything like that but this is just how it is sometimes with them.

once the back pin is in the front doesnt want to go through and this also happens when putting the front pin in first where the lower now wont close. The front pin looks like its hitting the receiver and not going through i can see a spot of aluminum where the front pin seems to be hitting on the upper receiver.

its possible to get this together but the force it takes to do so is not right at all.

There is something definitely wrong with the lower, i cant send it back since its had an m16 pocket machined into it. So im stuck with it for now and just need a way to get the pins to go in without feeling like im going to break the rifle everytime i put it together.

If it was my rifle, I would take a little bit off each hole to align them.  That way the amount removed from each hole would be reduced.  I have had upper/lower combinations so tight that I had to grease both pins and gently tap them into place.  After a few times to the range and tapping the pins in, they now fit tight, but aren't really obvious.  Some times, the misalignment is due to heavy anodizing and just removing a little anodizing will fix things.  I wrap some fine abrasive paper around a pencil or chopstick, and work it back and forth to remove some of the anodizing.

Life is about tradeoffs.  You can indeed drill out misaligned holes, and then you get corrosion.  But it is cheap and easy.

Couldnt i just take a metal file to the front takedown pin to make it fit and smooth it out with a bunch of sandpaper.

Ive already worn out the finish from screwing around with this for a while. Like i said it was possible to get these to go together it just takes a stupid amount of force. Ill just try to shoot it as much as i can and see if that helps at all.

I had one lower that would not mate to an upper properly. It had a hump in the middle on both sides of the fire control group pocket that kept it from closing fully.

My solution was to use a flat file to make the upper surfaces of the lower perfectly flat. A little flat black paint made it look good and it now mates up perfectly to an upper.