bore diameter bullet

[Hank45]

Will a breechseated bore diameter bullet (.277) upset enough to fill the groove diameter (.286)?: Thanks for your answer, Hank :coffeecom

[MikeS]

Why would you want to shoot a bore diameter bullet? If you're shooting lead boolits, if your groove diameter is .286 then you really should be shooting at least a .287 diameter boolit. I'm assuming that you're shooting a single shot rifle for target shooting, so why use a boolit that HAS to upset to fill the groove diameter to seal, which means that the boolit base, the most important part of the boolit for accuracy is getting all out of shape.

[NoZombies]

To answer the question;

Probably not, almost certainly not with any accuracy.

A better option would most likely be paper patching.

[uscra112]

Doctor Mann proved conclusively that a bore-diameter boolit of reasonably soft alloy WILL upset to groove diameter, but his boolit design had a base band that was throat diameter to do the initial sealing, and was usually breech-seated.

"The Bullet's Flight from Powder to Target". Franklin W. Mann.

[grouch]

It's possible, though I don't think it's likely. As USCRA said, it's mentioned in "The Bullet's Flight" and it would be interesting to know the answer to that. Remember that Mann was using a VERY soft alloy and Pope's barrels with a rifling system that gave bore diameter bullets far more support and far less space to expand into than conventional rifling. I look forward to hearing how this works out.
Grouch

[MtGun44]

This can work with very soft alloys and hard pressure rise powders - best example is
BP. While it can work, it is a problematic design - so if you have a choice, I would want
a throat that will accept the design as close fit and align it to the bore well, and have the
base already larger than the groove diameter. This will probably be more forgiving in
the long run.

You didn't say if you were making a gun or have one that you need to satisfy. The two
cases are very different. Many of the old leverguns had no throat and chamber would
not hold a groove diameter boolit. Yet with soft lead and BP they worked well. But usually
with smokeless and harder alloys results were extremely poor.

Bill