Keith, let us know how that load works out. I once shot a couple of RST 1oz shells and man they were nice, soft shooting shells. They were as nice as my 3/4oz loads. I was really impressed. That's a little bit of difference between 16.5 and 20grs. It still doesn't sound like a 20gr load at under 8000psi is anything to worry about. I wish I had some to try. I think I'd try around 18grs to start.

In my 2 1/2" 12 gauge guns I use a Cheddite hull & primer, 19.0 grains of Hodgdon International Clays, a Gualandi 1222 wad, 1 oz of shot with a 6 point star crimp at 1150 fps. Pressure should be around 7300 psi.
This load is my modification of a Hodgdon published load using 20.1 grains of International Clays, Gualandi 1225 was in a 2 3/4" Cheddite hull at 1235 fps @ 7700 psi.

This is an old thread on 2.5" loads. Tom Ambrust did pressure testing on this load according to Dave Miles. The pressure results for International Clays are different than listed on Hodgdon's website.

http://parkerguns.org/forums/showthread.php?t=1589

Ken

I had opportunity to shoot some of the 1oz. loads with 20 gr. international this past weekend. My "test" gun is a 3 1/2" mag Winchester X2 with a 28" mod barrel. Considering the rhino roller 3 1/2" steel goose loads I shoot out of it, I figure it'll handle ANYTHING I want in one of my fine SxS shotguns or anything else for that matter. These chrongraphed at an average of 1260 FPS X 5 rounds with folded crimp and about 25 FPS less roll crimped. All were Cheddite paper hulls. Hard to judge but seemed little or no difference on recoil and report than the RST rounds. Will be sending some of them and several other recipes off for testing (including my best effort/guess at a duplicate of the RST) and share the report with all. Ken, FYI, the thread you mentioned was my source.

Keith,

Are you reloading 2 1/2" shells or 2 3/4"? I didn't like using the Win209 primer in the 2 1/2" shells because the firing pins on a couple of guns were sticking. I now use the Cheddite primers for the 2 1/2" shells.

Thanks,
Ken

These loads are all 2 1/2" in Cheddite paper hulls with Cheddite primers. I shot some similar loads worked up with bismuth shot in 2 1/2" Cheddite plastic with Fioche 616 primers, roll crimp, first in my Winchester then in one of my 12 ga. Parkers. The bismuth was 18 gr. Green dot. Mild, and chrony at 1060 FPS. Had no issues of any kind other than they didn't want to cycle well in a 3 1/2" magnum gun, insufficient recoil/pressure to properly operate the mechanism. No surprise there, did cycle in a Winchester 1400 I have that will eat anything 2 3/4" or 2 1/2", dirty, sandy, mildly rusty, or generally disgusting ( a tried and true duck killer I've shot for years, a saltwater gun ugly as post hole diggers)!

Ken, I used Cheddite primers for years without problems. I've read threads where some guys complained about them being softer and firing pins going through and having to replace them after awhile. This is usually with O/Uers where one pin was hitting on a angle. Well, the left barrel on one of my Parker hammer guns and both with a 1873 Remington hammer gun blow primers. So I traded 10,000 Cheddites for 10,000 Winchester primers and took care of the problem. The Fed and Win have a stiffer primer surface and don't have the piercing problem. Just something to keep in mind.