Stiff Pivot Pin-Upper receiver lug hole misalignment

[pablo2]

I’ve run into an alignment issue and would appreciate opinion(s) on how to proceed.

I’m working on a rifle project that is based on an AR15 platform. The lug holes for the pivot pin and takedown pins are properly aligned when the upper and lower receivers are separate from each other. The pins travel through the lugs smoothly.

However, when the upper and lower receivers are mated together, there is a problem. The pivot pin holes of the lower receiver do not match well with the pivot pin holes of the upper receiver. The pivot pin can be hammered through to home. But, a punch and hammer are required to remove the pin. Please note that the alignment of the holes for the takedown pin are very good when the upper and lower receivers are mated together.

I’ve mated the problematic upper receiver with another lower receiver and the misalignment persists. Thus, the misaligned holes are associated with the upper rather than the lower receiver.

I have several options (ranked from least to most risky):
1. Do nothing. Usage will loosen travel through the misaligned holes for the pivot pin.
2. Turn down the pivot pin until it travels through the pivot pin holes more easily
3. Replace the upper receiver
4. Line bore the hole for the pivot pin while the upper and lower receivers are mated together

 

[Dub]

#3

 

[nicholst55]

The pivot pin will NOT 'wear-in.' Trust me on that. Don't screw around reaming holes or turning down the pivot pin. Replace the upper. You will be time and money ahead.

 

[6ShotsOr5?]

If you go with undersize pins you may still have some alignment issue that could affect feeding, but it won’t cost much to try that. On the other hand, stripped uppers are cheap and you might be up and running faster that way.

 

[GNERGY]

Pins are cheap, sand the one down a little. I usually ream my holes and make larger pins for the ones I want really tight.
Tarey

 

[jelenko]

#3.
Uppers are cheap; AR's are lego sets - easy to put together and take apart.

 

[Dusty Stevens]

I vote none of the above (you forgot that choice). Take it back apart and fit each part until the upper doesnt fit anymore. Figure out the out of spec part (hint: its not the upper)

 

[jelenko]

I vote none of the above (you forgot that choice). Take it back apart and fit each part until the upper doesnt fit anymore. Figure out the out of spec part (hint: its not the upper)

!

 

[457ciSBC]

I’ve run into an alignment issue and would appreciate opinion(s) on how to proceed.

I’m working on a rifle project that is based on an AR15 platform. The lug holes for the pivot pin and takedown pins are properly aligned when the upper and lower receivers are separate from each other. The pins travel through the lugs smoothly.

However, when the upper and lower receivers are mated together, there is a problem. The pivot pin holes of the lower receiver do not match well with the pivot pin holes of the upper receiver. The pivot pin can be hammered through to home. But, a punch and hammer are required to remove the pin. Please note that the alignment of the holes for the takedown pin are very good when the upper and lower receivers are mated together.

I’ve mated the problematic upper receiver with another lower receiver and the misalignment persists. Thus, the misaligned holes are associated with the upper rather than the lower receiver.

I have several options (ranked from least to most risky):
1. Do nothing. Usage will loosen travel through the misaligned holes for the pivot pin.
2. Turn down the pivot pin until it travels through the pivot pin holes more easily
3. Replace the upper receiver
4. Line bore the hole for the pivot pin while the upper and lower receivers are mated together

3. What are the diameters of the current pins? If your current pins are around .247, they are already undersized.

I have tons of questions and can’t really tell from your post if the mating interference is fore and aft or up and down. I would find the offending root cause before shotgunning a upper receiver replacement.