I know other people have had the same issue. I could really use the help of an internal ballistician to figure this one out. I have two G20's one Gen3 and one G20SF, both currently stock guns, and the problem happens with both of them. Here's the problem: with any full power load (180 or 200gr. above 1200fps., verified with a chronograph) the slide fails to catch the next round in the magazine at about the sixth or seventh shot in a 15 round magazine. In other words, at about the 7th round in a 15 round magazine, the slide will eject the empty case, but catch the next live round in the magazine on the cartridge wall between the rim and case mouth. The live round "stovepipes" vertically with the nose of the bullet jammed against the top of the chamber. It doesnt' make any difference what magazine I use (I have about 10 of them- old and new ones) nor does it make any difference what ammo I use provided it really is full power - chronograph verified. (Some ammo. manufactures brag about full-power loads, but the chronograph indicates otherwise.) CCI blazers, Hornady 180gr., Remington UMC 180 gr., all function flawlessly. I've tried stiffer recoil springs all the way to 24#s and the problems gets worse. The same problem happens with a 5.5 aftermarket Jarvis barrel. The problem wont happen if I rapid fire the pistol pretty much as fast as I can. If I slow fire the gun jams almost guaranteed at about round 6, 7 or 8. In diagnosing the problem, and speaking with a Glock technician, it appears slide speed could be an issue. One thought is that a stronger magazine spring would help. (They are on order and should be here within a day or two though others with the same problem have stated the magazine springs helped, but did not solve the problem.) I am also thinking that it could be the slide is not going back all the way and therefore not able to catch the rim of the next round. In playing with the gun using a spent reload case (180 XTP bullet at 1250fps.) and live rounds in the magazine, it takes an extraordinary amount of effort to eject the spent case from the chamber and rack the slide all the way back. Heres where a ballistician could help. Is it possible that the higher pressure from the full power load is keeping the slide and barrel locked longer (i.e. the slide can not open due to the super-expanded shell in the chamber) and when it does open it doesnt have enough energy to push the slide all the way back? Or is it that the expanded case (very slight bulge) is catching on the next live round and slowing the slide down? Why does it happen only in slow fire? Does the brass have more time to expand due to a heated barrel and therefore create a tighter fit again slowing down the slide while trying to extract the empty case? Please people, do not tell me this is limp wristing, or bad ammo., or I need a stiffer recoil spring. Ive tried all to isolate all of those conditions and the problem still happens with a weak wrist or fully braced, reloaded ammo. or commercially manufactured, and with various recoil springs all the way to 24lbs. I could shoot the 10mm target ammo. in the gun, but then why have a 10mm? Thanks for all your help.