Hello again Gent's,
The idea for a chamber adapter for the 577-450 is not a new thing but it sparked my interest. While flipping through my reloading book I found myself looking at the 45 Long Colt and remembered hearing of someone once making an adapter for that. At first I thought the 45-70 would be a good cartridge to make an adapter for but the walls of the adapter would be too thin. After a little more looking I decided that the good old 45 colt or the 454 Casull would be the best way to go. I started talking to my father about the idea and he got behind it too. He drew up the dimensions based off a fired 570-450 casing and he made two adapters to test out at the range. This past weekend we took my most recently finished Gahendra (see previous post) and my dad's smooth bore Mk. II out to the range.
I was confident in the structural integrity of both guns and knew full well that there was a chance I could damage or destroy the rifle by doing this. I was willing to take the risk and accept any consequences. For the first two shots we put the gun in a gun rest and remotely fired it to be sure of safety.
We brought with us a box of standard 45 LC, a box of 410 shot shells #9 shot, and a box of 410 slugs. After the first two shots in the Gahendra went off with no problems and no signs of pressure or structural problems I shot a group at the target 30 yards away and was very happy with the results. The next thing we tried was the bird shot out of the smooth bore and that worked very well also. Last thing we tried was the the 410 slugs and at 30 yards they all hit in a 3 inch radius of the bull's eye. Considering how open the v-notch on it is that is good in my opinion. One thing to note is that in the Mk. II there was no problem shooting the shot shells or the 45 LC. However when shooting the Gahendra there was a just noticable puff of gas when shooting what would drift across the shooters face. The Gahendra chamber is a little looser then the Mk.II and allowed a little gas to escape.
Here is a side view of the adapters.
Here is a view of the 410 shells in the adapter to give you an idea of the size they are. The 410 sticks out so when you shoot them the plastic expands slightly to fit the gap. This makes it so they dont slide of after shooting but it is not much effort to get them out. We just force it back out or use a razor to cut off the top.
Here is a side and top view of the 45 LC in the adapters. They slide in and fit well. The Gahendra I used slugged at .456 and the size of the standard 45 colt is .452 so they were a little under sized. I will hand load the next batch using .454 dia 255 gr bullets.
The few shots in the black I was very happy with but there was a string of shots that hit off to the right. Because the trigger pull on the rifle is crazy difficult I think that had a hand in the grouping. I took 3 shots at a 12" target at the 100 yard mark and hit it 1/3 times. This coming weekend I will try the larger handloads with one of the other Gahendra's that has a very nice trigger pull. I will post results.