You've gotten good advise already and the one I would second is to back off on your loads. I suspect the leading of the bore is what is ruining your patterns after a few shots and the leading is caused by excessive loads for the 20 gauge bore. The pellets at the bottom of the shot column are being squashed between the "irresistible force" of the burning powder and the "immovable object" of that long column of lead shot. They are forced outward to rub very hard against the barrel walls. Those misshapen pellets then fly off wildly once free of the confining bore.
There is a notion that you can load as much powder and shot into a muzzleloading gun as you wish because "it doesn't have to fit a shotshell".
Well, yes, you CAN but that doesn't mean it's a good idea. For centuries there have been charts to show sportsmen the proper load for their guns of various gauges. Generally the recommended weight of shot was about the same as the weight of a bore size round ball. In the 20 gauge the standard service load has always been 7/8 ounce with 70-75 grains of powder.
When gunmakers began developing the breech loaders and ammunition for them they didn't just make a shell of arbitrary length and then load whatever fit. They made the shells to hold the load that had already been accepted as a standard load for muzzleloaders of that gauge. The 7/8 ounce remained the standard 20 gauge load until we got into the "magnum" loads in the 1950's. Even in the 3" magnum 20 gauge 1 1/4 ounce is the heaviest load available today. With all the advantages of progressive burning powder and plastic shotcups in modern shotshells my own pattern testing concluded that I could put as many pellets on target with one ounce loads as with the 3" mag 1 1/4 ounce loads, and I'm not alone in that conclusion. It's not how many pellets you load but how many actually hit the target that counts.
I'd suggest you back off to one ounce of shot over 70 grains powder and you may well find that by reducing the number of pellets in your load you actually increase the number hitting the target. That is after you've gotten all the lead out of your bore. I'm fond of one ounce loads in everything from 12 to 28 gauge guns, there is surprisingly little range increase from heavier loads, especially with a cylinder bore.
Keep at it and I'm sure you'll find a deadly load which doesn't lead the bore, good luck! :thumbsup:
There is a notion that you can load as much powder and shot into a muzzleloading gun as you wish because "it doesn't have to fit a shotshell".
Well, yes, you CAN but that doesn't mean it's a good idea. For centuries there have been charts to show sportsmen the proper load for their guns of various gauges. Generally the recommended weight of shot was about the same as the weight of a bore size round ball. In the 20 gauge the standard service load has always been 7/8 ounce with 70-75 grains of powder.
When gunmakers began developing the breech loaders and ammunition for them they didn't just make a shell of arbitrary length and then load whatever fit. They made the shells to hold the load that had already been accepted as a standard load for muzzleloaders of that gauge. The 7/8 ounce remained the standard 20 gauge load until we got into the "magnum" loads in the 1950's. Even in the 3" magnum 20 gauge 1 1/4 ounce is the heaviest load available today. With all the advantages of progressive burning powder and plastic shotcups in modern shotshells my own pattern testing concluded that I could put as many pellets on target with one ounce loads as with the 3" mag 1 1/4 ounce loads, and I'm not alone in that conclusion. It's not how many pellets you load but how many actually hit the target that counts.
I'd suggest you back off to one ounce of shot over 70 grains powder and you may well find that by reducing the number of pellets in your load you actually increase the number hitting the target. That is after you've gotten all the lead out of your bore. I'm fond of one ounce loads in everything from 12 to 28 gauge guns, there is surprisingly little range increase from heavier loads, especially with a cylinder bore.
Keep at it and I'm sure you'll find a deadly load which doesn't lead the bore, good luck! :thumbsup:
