Schwing
Member
I have a GP100 and have a similar issue. From what I have read, this is almost universal with the GP100. I still believe it is due to carbon buildup in your cylinder from shooting .38s. Ruger does not leave much wiggle room at all. In some ways, this is not a bad thing since it is great for accuracy. Like some others have mentioned I also shoot a 686 and my GP100 side by side and have never had any issues with the same rounds in the 686.
Right out of the box, I took it to the range, fired about fifty .38s through it and then tried unsuccessfully to seat any .357s. The .357s I was shooting were factory ammo and they still would not seat all of the way. I was convinced that there was a problem with my gun until I did some research about this problem. This was before I even had .357 loading dies so a problem with the ammo didn't even occur to me. After a cleaning, the same ammo had no issues.
I have found that I have to keep the cylinder 100% immaculate to avoid this problem. This means thoroughly cleaning it every time after shooting .38s. Even shooting 6 rounds of .38 is enough to stop mine up. I have never had the issue just shooting .357s. I have also started using an over sized brush to clean out the cylinder and have had much better results since then.
Right out of the box, I took it to the range, fired about fifty .38s through it and then tried unsuccessfully to seat any .357s. The .357s I was shooting were factory ammo and they still would not seat all of the way. I was convinced that there was a problem with my gun until I did some research about this problem. This was before I even had .357 loading dies so a problem with the ammo didn't even occur to me. After a cleaning, the same ammo had no issues.
I have found that I have to keep the cylinder 100% immaculate to avoid this problem. This means thoroughly cleaning it every time after shooting .38s. Even shooting 6 rounds of .38 is enough to stop mine up. I have never had the issue just shooting .357s. I have also started using an over sized brush to clean out the cylinder and have had much better results since then.