AR10 Upper won't seat properly

[Brad V]

I recently did a new build lower AR10 with the Aero Precision M5. I used the Palmetto State Armory lower kit to complete. 

I purchased a complete AR10 upper from PSA as well....BCG and charging handle included

1) First issue- with the BCG installed, when I try to seat the upper into the lower, the BCG strikes the buffer. I will close, but I can tell the two pieces are impacting. As a result, I can engage the rear take down pin...the pin does not line up with upper receiver hole.

2) Second issue- I removed the buffer and spring, and attempted to close with only the BCG/charging handle installed. Same issue, it is still slightly off, preventing the rear takedown pin from lining up.

At first I thought the PSA buffer/spring were the problem, so I purchased the Aero Precision AR10 buffer/spring. This did not solve the problem. 

[mrmackc]

I reckon you have already called the professionals at Palmetto State Armory ,and requested to return their pieces for a refund?  What did they have to say?

It seems that a lot of folks have trouble trying to mesh a different brand of uppers to the PSA parts, did they say you needed to buy one of their propitiatory Uppers? I wouldn't do any drilling, reaming or grinding, just return the PSA stuff for a refund.

[dpete]

43 minutes ago, Brad V said:

I recently did a new build lower AR10 with the Aero Precision M5. I used the Palmetto State Armory lower kit to complete. 

I purchased a complete AR10 upper from PSA as well....BCG and charging handle included

1) First issue- with the BCG installed, when I try to seat the upper into the lower, the BCG strikes the buffer. I will close, but I can tell the two pieces are impacting. As a result, I can engage the rear take down pin...the pin does not line up with upper receiver hole.

2) Second issue- I removed the buffer and spring, and attempted to close with only the BCG/charging handle installed. Same issue, it is still slightly off, preventing the rear takedown pin from lining up.

At first I thought the PSA buffer/spring were the problem, so I purchased the Aero Precision AR10 buffer/spring. This did not solve the problem. 

 

Quote

1) First issue- with the BCG installed, when I try to seat the upper into the lower, the BCG strikes the buffer. I will close, but I can tell the two pieces are impacting. As a result, I can engage the rear take down pin...the pin does not line up with upper receiver hole.

That is exactly what is supposed to happen.  The BCG should push back slightly against the buffer.  That way when the spring slams the buffer forward it doesn't snap off the buffer retainer pin.

2) Second issue- I removed the buffer and spring, and attempted to close with only the BCG/charging handle installed. Same issue, it is still slightly off, preventing the rear takedown pin from lining up.

This should tell you that it isn't a buffer/spring issue.  If the PSA upper and Aero lower do not mate up with no spring tension at all you have a case of the two pieces not made to the same tolerances and specs.  Its not uncommon for 308ARs made from parts from different companies to have issues.  There is no milspec in the 308AR world.  (By the way, you do not have an AR10.  It did not come out of the Armalite factory in any way shape or form.  Companies that make parts for these big ARs throw around the term AR10 as if it is a universal term....IT ISN'T).

By the look of your spring/buffer picture you have a carbine spring and buffer from PSA and a rifle spring and buffer from Aero.  Do you have a carbine or rifle length buffer tube?  A carbine spring/buffer will not work in a rifle tube,  and a rifle spring/buffer will not work in a carbine tube.

There are numerous threads here on the forum detailing many of the failures of PSA in trying to put out a functioning large frame AR.  They do whatever they want with proprietary specs and parts then claim they will do things they don't.  I'm sure someone with more diagnostic skill than I will chime in and make further suggestions.  Take their recommendations to heart, listen to what they tell you and then do it.  Don't get butt hurt when a suggestion points to the fact that some of the parts you may have purchased aren't up to snuff.  These guys have been getting people's rifles to function for years if they listen to what is being told to them.

Edited December 6, 2020 by dpete

[shooterrex]

If you buy a PSA lower it will mate to the upper. The PSA upper will not fit up to an aero lower. Are you using a carbine stock or an A2 rifle stock. That answer determines which buffer and spring to use. You still will probably have a to short gas tube and a rifle that is only so so accurate. I'm not knocking PSA just stating facts. I have 2 of them and they work and shoot now. I would return the PSA upper and build an upper with Aero parts. Cheaper in the long run.

[billymagg]

25 minutes ago, shooterrex said:

If you buy a PSA lower it will mate to the upper. The PSA upper will not fit up to an aero lower. Are you using a carbine stock or an A2 rifle stock. That answer determines which buffer and spring to use. You still will probably have a to short gas tube and a rifle that is only so so accurate. I'm not knocking PSA just stating facts. I have 2 of them and they work and shoot now. I would return the PSA upper and build an upper with Aero parts. Cheaper in the long run.

Yes Sir, the Aero Precision lower gets very high marks here, and that would be your most advantageous solution to your problem, return the PSA upper and parts and go with an Aero M5 upper receiver, buy a complete upper if you can find one?? I saw that somebody had some upper's and lower's in stock just recently, but I don't remember whom?? Hang in there Brad, and please introduce yourself on the appropriate introduction thread if you haven't already. Welcome to 308 AR, the best gun forum on the internet, just ask us!

There are some very knowledgeable and helpful gents here who will help you sort these details out...

Edited December 6, 2020 by billymagg