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This doesn't seem to happen with monometal bullets equipped with stress relief grooves, and following the hypothesis above, they simply do not cause high pressures of examples with no stress grooves......
I wouldn't rely on "grooves" in the full calibre width of the bullet one little bit. Instead the best monometal bullet examples have RAISED bands with the 'shank' being sub calibre. The rifling can groove the rainsed bands without excessive pressure or displacement. The grooves hardly change it at all. My hypothesis.
Interesting you observed the OSR on a bolt action Weatherby. Usually the reports of it are on much thinner barrelled multi barrel firearms.
John I read an article from Barnes when they first brought out the banded bullets. It claimed the groves were cut into the full sized-grove sized - bullet to allow the displaced material from the lands to fill into. Like you I would have no real confidence in this.
I must add that I can not remember moist of that article so it may well have gone on to say that was a trail only set up. Can anybody tell me if the current Barnes X bullets are bore riders or full size.
NOTE to qualify my stated opinion on not relying on the grooves. The comment was limited to use on non raised banded monometal bullets in thin walled barrels such as might be on a double rifle, combination rifle, some single shots etc.
On MOST bolt action and modern rifles with thicker barrels and good modern steels, they probably are not an issue.
I've used some of these eg Barnes X, without an issue in bolt action rifles with thicker barrels.
However it should be noted the earlier comment where OSR was observed to occur on a Weatherby .378 bolt action rifle.
Personally I do like good old lead core projectiles on good controlled expansion design. These may not be an option in all legal jurisdictions nowadays due to the idiocy of some lawmakers.
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