I can't find a single reference to shooting a deer in billk's original question! :wink:
How come so many posts on this board regarding load, caliber, etc. seem to degenerate into a discussion of what it takes to kill a deer? :rotf:
billk, IMO, you have encountered the biggest problem most shooters have in gaining accuracy and consistency in their shooting. Most patch material has a load point at which it will fail. Not all patch material, but most. Your load of 80 gr 3f is just enough increase in pressure to blow your patch. The straw that broke the camel's back, so to speak.
Patch material will fail if it is not tough enough or if it is not tight enough, or, if your barrel is not broken in and the sharp edges of the rifling are cutting the patches. The material you are using might hold up better if you go to a .535 ball, providing it is not too difficult to load in your barrel. OTOH, tightening up with a larger ball may not solve the probelem if the patch material is not tough enough or if your rifling is too sharp and is cutting the patching.
A high quality patch material is a wonderful thing and should be bought in large quanitities and selfishly hoarded in a secret place!
FWIW, I'll iterate my own method of arriving at the "perfect" load.
First, If you think your barrel may be overly sharp and cutting patches, you should lap it. There are several ways to lap a barrel but I find the easiest and fastest way to do it is to firelap it.
Always use a genuine lapping compound as opposed to a homemade concoction. Twnty or 25 shots with lap impregnated conicals and with the bore wiped thoroughly between shots will take care of any overly sharp rifling.
Once I know that the barrel will not be a problem, I head to the range with a large variety of patching materials and usually two ball sizes. For a .54, for example, i'd take along .530 and .535 balls. I start out by arbitrarily deciding what is the heaviest charge I would ever shoot in the rifle at hand. Check your manufacturers max load recommendations and use that, for example. Start shooting your patch material at that max charge. Shoot about five of each patch material with each of the two ball sizes. Recover your patches from each test
before you start with another patch material. so as not to confuse which patch is whcih. Usually the various patch materials will have some distinctive marking such as a stripe, but not always. Use colored marker pens to identify the plain ones that could be confused. "Read" your patches and determine which patch and ball combo held up the best, then start with you load work-up for either target accuracy or hunting accuracy.
Most shooters simply start in with load work-up and usually hit a point where their group is opening up. It's assumed that the barrel won't shoot anything higher than such and such a load and they settle on a load beneath the one that began to open up. What is often happening is the patch ball combo has reached a pressure limit and is blowing.
My own experience with the above method has shown that with the best and toughest ball/patch combo shot from a good quality or at least properly lapped barrel, just about any load will shoot with reasonable accuracy. Some charges will be more accurate, but the differences are often hard to see.
I have a .45 that will shoot with equal accuracy with a charge of 20 to 60 grains of 3f or 2f. There is probably a "sweet spot" or two in there but 30 or 35 grains is all I need for that gun for small game or targets and so that's what I shoot.