Upper/Lower compatability

[WidowsSon683]

I have a question for the folks that have built their own PCC. I have an XProducts side charging upper that I want to use in my build. I have seen that a lot of the ar9 lowers say something along the lines of "designed to work exclusively with our Brand X upper receiver". Has anybody ran into any problems with just slapping on any random upper on a 9mm lower. Looking to get mine finished pretty soon.

[Aircooled6racer]

Hello: I have found that some uppers have the bolt bore in a different place than others. If the upper rides the bolt higher, then you may have some trigger reset problems. The lowers that I have seen have been pretty good on specs. The only way is to actually try it. Most problems that I have seen are with the bolt and the buffer setups. Thanks, Eric

[MickB]

2 hours ago, Aircooled6racer said:

Hello: I have found that some uppers have the bolt bore in a different place than others. If the upper rides the bolt higher, then you may have some trigger reset problems. The lowers that I have seen have been pretty good on specs. The only way is to actually try it. Most problems that I have seen are with the bolt and the buffer setups. Thanks, Eric

That is pretty sad if true. The Colt 9mm AR was designed around a regular mil-spec upper, so if an upper receiver maker can't get something as basic as the bolt bore correct then they have quality issues. 

 

Mick

[NOMADSS]

Have seen to may issues with mis matched guns or guns pieced together trying to save a few bucks only to have more issues and problems.  Id recommend buying a complete gun from a company and know that the thing will run and or have someone to go back to if it doesn't.

[WidowsSon683]

8 hours ago, NOMADSS said:

Have seen to may issues with mis matched guns or guns pieced together trying to save a few bucks only to have more issues and problems.  Id recommend buying a complete gun from a company and know that the thing will run and or have someone to go back to if it doesn't.

Not everyone has that kind of money. Also why would I pay for parts that im going to replace anyway when I can build it to my specifications the first time with only the parts I want.

[Flatland Shooter]

There may be others but the only vendor that state on their website that you need to match their uppers with their lowers is Palmetto State Armory (PSA).  In my opinion it is just marketing hype.  I have two PSA lowers (for Glock magazines) and it appears that any mil-spec upper will work.  Somewhere on the forum someone indicated the dedicated 9mm uppers are a little beefier than the mil-spec 5.56 upper but I cannot tell the difference.

 

I now have over 3500 rds through my PSA carbine.  I changed out the trigger immediately along with the safety (wanted ambi).  Due to the short leade on the barrel, I've had to develop short loads but that's just part of the learning experience.  A Miculek style comp (replacing a birdcage) pretty much eliminated reshoots due to the timer not picking up the last shot.

 

Build or buy is just a matter of preference.  Both can take you to "A" class quickly.

 

Bill

 

 

[Aircooled6racer]

Hello: The 3 PSA lowers here are all running fine with different makers uppers on them. The only way to know for sure is to try it. I have had great luck with the Anderson uppers and the QC10 upper. Building your own is fun and you do get what you want on your build. The biggest problem I have seen is trigger problems with some builds. Thanks, Eric

[JMontie]

On ‎5‎/‎24‎/‎2017 at 8:51 PM, WidowsSon683 said:

I have a question for the folks that have built their own PCC. I have an XProducts side charging upper that I want to use in my build. I have seen that a lot of the ar9 lowers say something along the lines of "designed to work exclusively with our Brand X upper receiver". Has anybody ran into any problems with just slapping on any random upper on a 9mm lower. Looking to get mine finished pretty soon.

I've heard X Products and Matrix Arms are the same. I have a quarter circle 10 lower, worked great with a 556 VLTOR upper, now I'm getting spent brass wedged about a live round feeding in the chamber. Emailed Matrix Arms, was pointed everywhere but their upper. I will take a look at everything, but I know I have a gouge in my upper where the bolt slammed on an empty case. Love the side charger layout, hate the gas in the face with a standard upper.