Boolit Bases SQUARE - Gas Check Bases RADIUSED

We strive to cut the spru to the boolit base square yet we add a gas check that has a radius to its base - a function of "cannot get a square base from" the GC punch. Perhaps in the "heat of the moment" as the gas checked boolit is "spanked" by the high pressure spike and heated, it conforms to the inertia of the boolit and obturates to the side walls taking the shape of the chamber, rifling lands, and grooves. IDK...subtle maybe, and part of the "infinite mathematics" of the unknown Universe.

BOOLIT BASE

https://i.postimg.cc/nhgRnFZW/Boolit-Base.jpg


GAS CHECK BASE

https://i.postimg.cc/FKSPRMHH/Gas-Check.jpg

I believe that as long as the base is concentric and perfect in its entire diameter, it will be sufficient.

As the boolit leaves the muzzle, the expanding gases will "blossom" evenly, and the projectile will have a good "launch" , all else being equal.

If the expanding gases are interrupted or altered by an uneven base, a gouge in the boolit base, or a damaged barrel crown, a "wobble" or uneven launch of the projectile can result in inaccuracy.

Just my thoughts....but not written in stone!

I have noticed that many gas checks wind up concave after running the GC Boolit through a lube sizer. The phenomonon described by OP would explain it.

Quote:

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Originally Posted by Jim22

I have noticed that many gas checks wind up concave after running the GC Boolit through a lube sizer. The phenomonon described by OP would explain it.

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I regularly size .322" #U321297HP bullets down for .30-30. I lube and gas check in Lyman .323" die, then run them through Lee .314" and .311" dies. With springback they end up at .3125". Before any of this I scrape the bullet bases with a knife to remove the little high spots around the sprue rim. Coming out of the .323" die the gas checks are nice and flat on the bases. After the Lee dies, the gas checks are dimpled and the shanks slightly elongated. I believe the dimpling is part of how the gas checks accommodate the diameter reduction.

If I do not scrape the bases, the dimple may be half moon shaped instead of circular, but the circumference remains even. With or without scraping, these bullets shoot very well in .30-30, even better than they did in .32 Special.

Bullets recovered from pigs, despite being reduced to stubby wadcutters, nearly always have the gas checks still attached. Dimpling in no way represents a loosening of the gas check on the bullet.

Maybe gas check shanks should be beveled. Why worry about nice square edges if they don't stay that way?