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I'll throw in my 2 cents.....

I agree with Daryl and 500gn both. I think thin bands are probably better than thick ones.

I think the shank between the bands needs to be sufficently smaller than bore diameter in order to give the displaced metal somewhere to go. How much smaller is determined by the spacing between the bands, but there should be a positive space to deposit the displaced metal.

I think the face of the lands in the throat should be perpendicular to the bore so as to cut the band via shearing, rather than a sloping/tapered throat that presses the land into the bullet, radically increasing radial stress and doing a poor job of moving band material into the grooves between them. Fortunately most barrels are this way when NEW, but I wonder if throat errosion over the decades give the lands a more tapered profile in this area, thereby increasing radial stress. Even when new with a non-grooved bullet the bearin surface may be too long to move the sheared material all of the way to the bullet base. It has to go somewhere, and squeezing lands into all sides of a solid bullet takes a huge amount of force.

Chamber pressure is important only to the extent that if it is below the level required for the monolithic bullet to obturate, it may allow the shank of a non-undersized bullet to remain larger than if the pressure were higher, resulting in damage farther down the barrel where it is thinner even though pressure is far, far below max there. Perhaps extremely detailed testing could answer this by detailed measuring of bullets fired at varying pressure levels.

Lastly, I think barrel construction plays a role. I personally think cut rifling is the only way to go on a DR or custom/non-production gun. Having said that, the act of buttoning could strengthen the barrel steel to resist the stress of monolithics. If it is enough to prevent OSR is an open question, but the act of forcing a hardened button down a barrel with the purpose of inducing stresses beyond the metal's elastic limit should impart some resistance to similar stresses in the future. Even if so I'd still alway opt of chopper lump cut rifling if given the choice.

All of this is simply theory and conjecture on my part and could be wrong across the board. It isn't unknowable, but would take a LOT of testing to determine.

Bob

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"If we're not supposed to eat animals, how come they're made out of meat?"

Edited by Omnivorous_Bob (17/02/10 05:51 AM)

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