Sight in problems with prb

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Widows Son

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Hello all,
I'm looking for some advice getting my rifle to group at 100 metres. It's a Pedersoli Plainsman .45 percussion made in 1976.
At 25 metres it is dead on and at 50 metres, if I do my part, it groups around 2 inches. The problem is that off a rest my groups at 100 metres the rifle just won't group but prints randomly, with as much a 12 inches between bullet holes. I'm beginning to wonder if it it's the barrel/rifling?

I've experimented with round balls of 440 and 445, with .445 giving a better result. For patching I'm using pillow ticking something like .015. I'm also using a lighter cotton fabric (used for baby swaddling) that is something like .005-.008 thick (my calipers are manual and my eyes aren't what they used to be). Interestingly, I get the same accuracy at the 25-50 metres using either patch material, and recovered patches show no tears or excessive fraying, with a brown scorch mark under the ball.

For powder I'm using 45grains of Wano, (Schutzen??) which seems is all we can get in Australia. I've used as little as 40 grains and as much as 60. The 45 grain charge seems to be way to go.

The rifle is in good condition and the bore is very good. The rifling seems to have a 1:48 twist, however it looks quite shallow, more akin to the depth of rifling found in a modern cartidge rifle. I've got a couple of CVA's from the 1980's and their rifling is prominent (and they are tack drivers!)

As you can see I've experimented with various ingredients, however I'm getting nowhere. Any advice would be appreciated. Thank you
 
I am not familiar with this gun. Does it have a full length stock? Your accuracy problem could be how you are benching the gun. Too much pressure on a ram rod ferrule could affect barrel harmonics such that the shot will be off. You also may need to up your powder charge for 100 m shooting.
 
It is a half stock. It seems to come from the era when interest in muzzleloaders was being reborn. It looks like a full stock Kentucky style rifle that has been made into a half stock. It has those kinds of "lines"
 
Make sure the wedge pin is tight in the stock, and try to rest the gun on the forearm and not the barrel when shooting from the bench.
 
Shallow rifling prefers a pretty tight patch. How easy does it load? I have a TC that has shallow rifling and it requires a patch thick enough that I have to smack the short starter very firmly to get it into the barrel, and then it is pushed down the barrel with the ram rod about 8" at a time...it isn't possible to just continuously push it down the barrel in one go. It sounds like your patches are holding up pretty good, but are they really frayed around the edges? The edges almost always have some fraying, so it can be difficult to determine if it is too much and allowing "blow-by" or not. Very, very light lube greatly improves my accuracy over having a "normal" amount of lube that fills the weave of the patch. My patches you can barely tell there's lube on them. So try playing around with the amount of patch lube you're using. I'd also try a bit higher powder charge to see if you stopped too soon at 60. Try a few shots at 65, 70, 75 and see what you get. Oh, and you didn't mention if you're swabbing between shots or not? Mine absolutely has to be swabbed or groups are terrible. I do one damp patch down and back and then one dry patch down and back every shot.
2" at 50 yards doesn't sound too bad to me, so perhaps at 100 it is something to do with you. The way the rifle is rested like Grimord said, or even just a slightly varying sight picture between each shot. Holding open sights exactly the same at 100 is a task, at least with my eyes that aren't 20-20 anymore. I have good luck with a target that has a large plus sign (+) on it, it really helps me to see it and hold the same every time. I use a 6 o'clock hold so that I can see the point of aim clearly instead of covering it up at 100. The front sight covers a ton of it at 100 and that will also lead to a different sight picture between shots.
 
How is the wind? A round ball will move something like 1/2" per MPH wind at 100-yards. If the wind is inconsistent it can be moving the impact 2-inches one shot and 5-inches another.
 
My eyes have gotten so bad over the past few years that it seems impossible for me to shoot good groups any longer. The loads I use are very accurate and used to make those tiny groups past 50 yards around 4" at 100. So I know the problem is with me. Sounds like you are in about the same place as I. And thick patching is definitely the way to go.
 
I have never tried, this but have seen guys with your rifle place a wad (same size as the bore) over the powder then load the patched round ball. They shot good groups at different distances with no issues.
 
Thank you all very much for your advice. I do appreciate it.
Yes, I was swabbing between shots, just one patch. The way you describe loading is about what I have to do, I have to whack the short starter to get the ball in the muzzle, then I have to load it 6 to 8 inches at a time using a brass range rod.
The rifle requires sufficient lube on the patch or it just won't load without a mallet, even from a clean barrel. I tried using minimal lube, using both greases and ballistol/water. No joy. Gotta have enough lube.

Its fun to experiment and try out what the rifle likes. I've had CVA's, a Uberti Santa Fe Hawken and a T/C Renegade (back in the day) and none of them were this fussy in their feed and fettling. However this is all I have at the moment and I'd rather lose a shooting match with it than not shoot at all.
 
It is a nice looking rifle! Yes, shallow groove rifling can be an adventure at long range when using PRB; shallow grooves usually excel at firing conicals for extended ranges. With shallow rifling, imparting enough spin to stabilize the ball with patch is touch and go in some weapons. I noticed Buck mentioned an over-powder wad, and I found this helps lessen "blow-by" and "burn-through" on patches, as well as providing a bit of cushion to the projectile. If you can obtain .45 wool felt wads, great! Otherwise, cut some 11.5 - 12 MM discs from thin packaging and stack into a column about equal to bore diameter. Not sure if that would be a game changer for your case, but it might give some improvement.
 
A different lube can change your accuracy too. I have two .58 cal rifles the shoot fantastic with patches lubed with olive oil but don't shoot very good at all with a paste type lube.
I have a friend that uses Liquid Wrench as a lube but I don't like it because it stinks.
Something to think about.
 
Trying different things will get you where you want to be. That said i would try an over powder patch. Its very simple and will not cost only another patch to try. There is a post by an outstanding shooter Idaho Lewis about it. Good luck my friend…
 
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