Floorplate questions:
1.  Is there a difference between floorplates which go on USGI 20 round mags & USGI 30 round mags?
2.  If there is a difference between the two, what is it?
3.  If there is a difference, will 30 round floorplates work on 20 round mags and vice versa?
4.  Anybody know a good source for 20 round floorplates?

Thanks.

20 round mag floorplates have a small slot cut for the retention spring to engage.  30 round mags lack this cut, but have two protrusions that keep them in place.  So yes, a 30 round floorplate will work on a 20 round mag.  You can see the difference in the pics.

I always keep the correct floor plates on the correct type of mags.  Eric's information is correct but he left out that while a 30rd FP will fit and lock onto a 20rd magazine, a 20rd FP won't lock onto a 30rd.  This is in regards to the old straight bodied USGI 20rd mags.

There are always exceptions to the rule...  Although I don't own any- it's my understanding that the new curved 20rd mags utilize the exact same FP found on the 30rd magazine.  This obviously  increases available parts and simplifies the production of  the newer style mags.

HTH.

Sly

Eric & I-M-A-WMD, thanks for your answers.  And Eric, your picture was worth a 1000 words!