I also have a Glock 20 Gen 4 and I replaced my barrel with a 6" KKM. It shoots great and I wanted the tighter tolerances since I reload. The KKM is easier on the brass.

I've started loading some 10mm rounds as well with Longshot and really like to performance so far. And that Longshot powder really has a bark

Yah, knock on wood, my G20 Gen4 is working the way it's suppose too. The Glocks are pretty loose tolerances compared to most steel frame guns and as mentioned earlier in this post the lower frame flexing could be some of the issue. I noticed on my Gen4 that with the gun assembled, the lower receiver is actually bending or flexing from the pressure of the spring. This has to make me wonder about the alinement of the rails during cycling and if their might be some binding going on especially under heavy loads.  I also think there's an issue with the 10 round mags feeding properly in the G20's. But so far mine's working and I'm hoping it stays that away. It will be interesting to see if the 22lb spring works as well or creates any issues. I'll find out the next trip to the range for sure.

Guys,

Was following this thread and I have a new Glock 20 Gen 4 I purchased a while back. I took it to the range this past week and fired about 250 rounds through it. I have a 6" KKM barrel and added the extended slide release and upgraded the sights. I bought a new 22lb spring from Glockmeister recently but when I went to the range I left the stock spring in. I shot about (50) PPU 10mm rounds (weak ass rounds) and then shot (200) 10mm loads I had worked up myself.

I have to say I didn't have a single FTF or any issues at all. I'm running the stock 15 round Glock mags since I've seen problems with the 10 round mags feeding for many people. But again, so far had no problems feeding. My reloads were using Hornady XTP 180 grain hollow points and also some were loaded with 180 grain Xtreme Flat nose copper plated bullets. Next trip out I'm going to swap out the factory spring for the 22lb Glockmeister spring and see how that does.

One thing to note is I polish all my feed ramps on my automatic pistols to help the feeding process and to reduce hang ups. Since I was working up some 10mm loads, my charges went from light to very stout and no problems with any feeding. 

I just happen to shoot some of the PPU 10mm I had bought a while back today. That stuff is for sure rabbit fart ammo. Was not impressed at all. Was concerned bullets were even getting out the end of the barrel:)  Might be ok for just doing a little target practice but not anywhere close to full power 10mm loads. I had some of my 10mm loads that were loaded with Accurate #9 with me as well and they stand up and get your attention. Won't be buying the PPU 10mm stuff again. 

Guys, thank's for the feedback regarding the Winchester primers and Starline brass. Just wanted to make sure there wasn't a problem before investing in some new Starline brass and finding out there was an issue. 

Guys,

New to reloading and I have a question. I saw on a different forum some guys saying that Winchester Large Primers won't work with Starline 10mm brass. Has anyone had any issues with Winchester primers not working with Starline brass? The fellow said they were to large to fit in the pocket. This was the first I heard so I wanted to get some other feedback since I was just getting ready to order a batch of Starline brass. Thanks in advance for any comments on this.