Patched vs Unpatched Velocities

[yonderin]

I recently did a small trial on velocities of paper patched, teflon tape patched and unpatched projectiles and was a bit surprised by the results. I had predicted that teflon would be fastest followed by paper patched and finally unpatched lead. I was surprised when average velocities were all very close, with unpatched falling in the middle. All projectiles were hard cast from the Bullet Barn.

I used an 1873 Trapdoor carbine and am theorizing that the short barrel didn't didn't allow for complete powder burn for any of them. Therefore the effects of different kinds of patching couldn't really come into play. Load was 65 gr of FFg.

Anybody else have any experience with this? I only fired 5 rds of each so maybe not enough for a conclusive result.

 

[Ol' Flinter]

Your sample size was far too small. Ideally a hundred of each but at least 25 of each to show any statistically significant differences between the 3 variables. I agree that short barrel length might have masked a difference that might have been more evident if the projectiles had been fired through a longer barrel.

Some years ago I experimented to see whether PRB lubes might change the point of impact. My most accurate 54 cal rifle was sighted dead on at 50 yds with my target load and Moose Milk patch lube. I wanted to know if Bore Butter, used for hunting in cold weather, would change the point of impact. Fired a 5-shot group with Moose Milk lube over a sandbag at 50 yds. Then began shooting the same balls with Bore Butter lube. The first went into the original group but then successive shots were, in turn each about an inch higher than the one before until the 4th shot when the shots started to form a group and a nice tight 5-shot group formed about 4" above the original Moose Milk group. That was a good enough indicator/trend for my purposes but I would have had to repeat that process probably at least 10 times to show any statistical significance.

 

[BCRider]

What sort of speeds did you record? And did the range of speeds from each patching method overlap with the other methods?

I'd say that 5 rounds is more than enough to see a trend. I'd also suggest that if the range of results from any two patching methods overlap then you can consider those two as basically equal or of such a slight variation that it's insignificant.

 

[yonderin]

Average velocities were; 1127 - paper patch, 1138 - lead and 1143 - teflon patch. There was overlap of each velocity range.

Speculating that they would have been slowed by varying degrees of friction in a longer barrel, once powder had been more completely consumed. Paper and teflon tape came in the same order I'd expected, lead was the joker. Bullets had a BH 25 so perhaps the hardless contributed to more sliptivity?

Will fire some more and unless teflon shows a noticeable advantage, just too difficult patching with to bother.