Is bullet "bumping up" necessary

[fiatmom]

I can see why bumping up would be necessary in an original trapdoor, mine has a .460 bore. Why would it be necessary in a modern rifle with a known bore diameter and a bullet .002 over?
Also is there an advantage to hollow base bullets , would they be shot without a wad or a very thin one.

[Springfield]

It's not if you use the right bullets, I cast .461 for my Trapdoor.

[Larry Gibson]

"Bumping up" is not "necessary" in a trapdoor and is not desired for best accuracy. Mine shoot much more accurately with bullets as cast at .462 or .463 (Lee 405HBs) than they do when sized .459. My target TD's groove depth is .461. I size my Rapine 460-500 at .4615 and they also shoot much more accurately than if sized .459. This is with both smokeless and BP.

Larry Gibson

[fiatmom]

I have found this to be the case Larry. There seemed to be a lot of chat regarding bumping and started to think it was necessary. I have a lee mold that drops at 460, I may have to Beagle or leement it. I checked the diameter but was not entirely sure with 3 lands and grooves, I got a reading of 460 to 462.

[NickSS]

Generally speaking a bullet that is at least groove diameter will shoot more accurately than one that is bumped up from firing. The three groove barrels on the springfields were very carefully researched and selected by the Army when they were adopted to give good accuracy with the Government loaded ammo. The idea was to get acceptable accuracy for as long as possible during a battle not necessarily pinpoint accuracy. I own half a dozen trapdoors and they all have oversized bores by todays standards but when you think about shooting 50 or 100 rounds without cleaning it makes perfect sence to be a bit large in the bore so that the rifle will shoot longer without fouling out.

[fiatmom]

Thanks Nick
,So the general consensis is a properly fitting bullet is best so would the alloy really matter?
BTW good name
Nick