Hi, I just bought a used Glock 20 and have a few questions.  

There's a fair amount of what I'm assuming is powder residue in the polymer frame.  Is it okay to use Hoppe's #9 to clean it out?  I remember reading about some sort of solvent which melts the polymer and can't remember which it is; last thing I need is to ruin this gun cleaning it.

When I insert the magazine, it locks up just fine when the slide is locked open.  With the slide closed, however, it takes some real force to lock up.  It looks as though the round is pressing up against that little bar in the center of the slide behind the barrel and next to the extractor (firing pin housing?) as there's a fair amount of brass coloration on it.  Is this normal?

Finally, this was planned to be my carry pistol, so I'm thinking of installing night sights.  How much would it cost to order them and have a gunsmith or Glock armorer install them?  Does it make more sense to send it to Glockmeister and have them do their free installation?

Thanks for your help.

Quoted: When I insert the magazine, it locks up just fine when the slide is locked open.  With the slide closed, however, it takes some real force to lock up.  It looks as though the round is pressing up against that little bar in the center of the slide behind the barrel and next to the extractor (firing pin housing?) as there's a fair amount of brass coloration on it.  Is this normal?

I don't know if it's normal, but I noticed the same thing with my new G22.  This is my first Glock, however, so I am comparing it to other semi-autos.  I also don't know how much "real force" it took for you to lock the magazine.  On mine it was just a little stubborn resistance that was solved with a light-to-moderate tap.  After that first magazine, I don't think I even noticed that anymore.  Maybe a tap is all it takes.

Again, this is my first Glock.  I'm curious to hear what the experienced Glockers have to say.

Quoted: Hi, I just bought a used Glock 20 and have a few questions.   There's a fair amount of what I'm assuming is powder residue in the polymer frame.  Is it okay to use Hoppe's #9 to clean it out?  I remember reading about some sort of solvent which melts the polymer and can't remember which it is; last thing I need is to ruin this gun cleaning it.

It's safe to use but a bit unnecessary.  A few cleaning patches, qtips and some CLP will remove it just as well.

When I insert the magazine, it locks up just fine when the slide is locked open.  With the slide closed, however, it takes some real force to lock up.  It looks as though the round is pressing up against that little bar in the center of the slide behind the barrel and next to the extractor (firing pin housing?) as there's a fair amount of brass coloration on it.  Is this normal?

Yes, this is normal.  It will take a fair amount of "umph" to lock up a full magazine on a closed slide.  

Finally, this was planned to be my carry pistol, so I'm thinking of installing night sights.  How much would it cost to order them and have a gunsmith or Glock armorer install them?  Does it make more sense to send it to Glockmeister and have them do their free installation? Thanks for your help.

I believe Glock still charges $58 for factory night sights (plus shipping) but I think they still use a chrimp style front sight instead of one that screws one.  If that is the case I'd either send my slide to Glockmeister or find a local shop to install a set of Mepros, Trijicons or several of the other high quality sights.

I would personally do the sights myself. They are probably the easiest pistol sights to replace IMHO.
For the rear sight a plastic or brass drift with a plastic mallet and thats about it. Mine required very little effort to remove but they were also new guns so a older one may be a bit stiffer. Front sight I just yanked off with a pair of pliers, it's just cheapo plastic anyway.

Thanks for your help everyone.  I've decided to go ahead and get the Meprolight sights and try to find an armorer around here if I don't do it myself.  Now I all I need is to start handloading and I'll be all set!

Quoted: Thanks for your help everyone.  I've decided to go ahead and get the Meprolight sights and try to find an armorer around here if I don't do it myself.  Now I all I need is to start handloading and I'll be all set!

Is this your 1st 10mm?