I've not done any real testing to confirm how eroded nipples effect accuracy but have suspicion-ed as well as read of it's deleterious connection. I'm wondering if any of you have had experience with this?
I suspect this is the cause of a sudden accuracy drop in my underhammer match rifle. I have some new nipples coming so will get a read on it soon in this rifle.
Funny you should mention nipple problems in your under hammer rifle.
Shortly after I was asked to be the Team Armourer for the U.S. International Muzzle Loading team, I attended a preparatory meeting for the World Championships in 1996. I had many years of working guns at the Spring and Fall Nationals of the North South Skirmish Association as well as having been a Team Armorer for Nationals using unmentionable rifles. So I made up an "Armorer's suggestion sheet" for the Team prior to leaving for the World Shoot.
I can't even begin to think of how many times I've seen eroded nipples cause accuracy loss; mostly in NSSA Rifle Muskets and Revolvers, but also with standard rifle nipples that were shot in competition. So I most strongly advised the percussion shooters to have TWO brand new nipples for each gun and that both caused the same group size and placement of group. That way if the nipple went bad at the World Shoot, they could instantly change it and get right back in the competition.
Actually, I strongly suggest putting a new nipple on a gun when you put it up for the winter, after a season of shooting. That way you will have a fresh nipple every year. Now if it is just a hunting rifle you don't shoot much except in BP Season, then at least every three years replace the nipple, before it causes an accuracy loss.
OK, so we are at the World Championships in Wedgnock, UK and I am set up best as I can on my picnic table work bench and vise already C clamped to it. I laid out a bunch of Original and Repro Musket tools each day, just outside my common working tools. I did that for speed in case someone needed a nipple changed and for them to use in case I had to use the necessary or was "walking the line" while my Team Members were shooting.
About 10 AM, I made a trip to the Necessary and when I got back, our best Female Shooter was frantically going through the nipple wrenches during the second day of practice. She was the wife of the of a very good friend of mine and we were also very good friends, besides. As I walked up I calmly asked, "Nancy, what seems to be the problem?" She had her original .45 caliber Underhammer Rifle with which she had won two gold medals at World Championships with in the past, plus other medals earlier in her career. I KNEW that rifle would shoot extremely well. So when she described how the group size had gone to Heck, I looked at the nipple and sure enough it was eroded too much.
However, BECAUSE it was an original rifle, I was a bit worried about the nipple thread size not being of a modern standard size. So I told her I would take care of it and suggested she get a cup of coffee or tea while I worked on it. FORTUNATELY, it had been re-threaded for the modern standard 1/4 x 28 I found when I got it out and checked the thread size. So I quickly got a new nipple installed. (I found out a couple days later a good friend of both of ours had re-threaded it for modern nipples about 4 years earlier.) I was just about finished checking everything else on the rifle when she came back with her coffee. As I finished, I informed her everything was fine with "her Baby" and she should now be able to shoot good groups.
HOWEVER, then I noticed she had laid out the little plastic/glass vials that held individual powder charges for her rifle on the 2x4 horizontal beam that supported our overhead plastic fly. She had done that to count how many she had left. The sun shone right through them, or I may not have noticed. I could EASILY see the powder charges were different by eyeball alone. It took a few minutes to explain she had to have done something wrong when measuring the charges and she had to separate and empty the ones that were different.
OK, we got that corrected and off she went to shoot. She came back later on that afternoon and said her rifle was right back to shooting as good, if not better than new. Now BECAUSE she was a long time personal friend, I asked her, "Nancy, you were in the meeting when I discussed changing nipples before we came here, what happened?" She admitted her rifle was still shooting well with a nipple the other shooter (the one who had re-threaded it to standard size) had replaced in the rifle 1 1/2 years before, so she thought it would be OK. I rolled my eyes and she said, "Yeah, I know...."
She wound up with the Silver Medal for the Ladies 100m shoot that year. Unfortunately the rifle that beat her belonged to the Wife of the Swiss Team Captain and I had resurrected that rifle a few days before. Nancy wasn't real happy with me for that.............Grin.
Gus