Just wondering, thinking about building a glock using a g17 frame

Make sure it is a 3 pin Gen 3 if you plan on putting a different upper on it

ok will do i thought they were all 3 pin?

No, early Gen3 9mm frames were 2-pin, curiously you can see a molding line where the locking block pin would go:


As long as the frame is Gen3 3-pin or Gen4, the following models all use the same frame:
1. 17,17L,22,24,31,34,35,37
2. 19,23,25,32,38
3. 20,21
4. 26,27,28,33,39
5. 29,30

You can't use a Gen4 slide on a Gen3 frame, and I wouldn't try it vice versa either.(you can swap between Gen3 and Gen4 in the sub-compacts) The ejectors are different for each caliber, and the 45GAP models use a different trigger bar and slide stop.

Also, curiously, all Gen 3, 3pin frames aren't reinforced for .40 & .357Sig.

All the 3-pin 9mm frames I've seen had the extensions on the front frame rail insert to stop frame battering. Do you know approximately when those extensions were added to 9mm frames? I always thought it was at the same time the locking block pin was added to the 9mm frames.

I believe I recently saw on another forum that the frames were reinforced in 2002.  I don't know how many 3-pin frames were made that weren't .40/.357 compatible.  Glock will give you that info over the phone, by serial #.