boolits

[Alberta Separatist]

don't know if this has ever come up before, but , has any of the mould manufacturers ever produced a bullet mould without lube grooves?
I'm thinking about boolits that are lubed with Lee alox; why would one need grooves?

[HORNET]

Grooves give the alloy that is being displaced by the rifling someplace to move to and give the lube someplace to go so that it doesn't all get scraped off during boolit seating. I don't think enough LLA would be retained on an ungrooved boolit to work at any but very low velocities.
Some molds are still being made without lube grooves, notably those intended for paper-patching for BPCR use and for use in sabots. The NRA's testing with paper-patching for .30 cal. some decades ago concluded that they had better results if the boolit still had grooves (even very shallow ones) and the Lyman paper-patch molds were cut with shallow grooves.

[357maximum]

Hornet hit is spot on.

The grooves offer rearward displacement of alloy instead of pushing all the alloy straight INTO the boolit....straight in displacement by the rifling will cause internal stresses in the boolit. This can cause varying amounts of accuracy/pressure issues. The deeper the rifling the more noticable displacement is. One of the reasons boolits with looong gas check shanks are more accurate in deep rifled toys. THEY GIVE THE ALLOY A PLACE TO GO WITHOUT INDUCING STRESS TO THE BOOLIT.

Fouling removal and holding lube are actually the two smallest reasons for grooves in cast. The fouling removal function does help keep the bore consistant from shot to shot though and of course holding lube is necesarry also, but not the only function of a LOOB GROOVE.

Them "dirt grooves" and "lube grooves" on the nose of some designs serve a similar role for the nose. They not only allow a tight well fitted nose to be unloaded if you choose not to fire it they also give a tight fitting bore rider a stress free yet tight fit.

Displacement is also why some loverins shoot so well. Stress free boolits are a good thing.

There is good reasons besides just pressure for them copper solids to be grooved.

[303Guy]

The grooves offer rearward displacement of alloy instead of pushing all the alloy straight INTO the boolit....straight in displacement by the rifling will cause internal stresses in the boolit. ....I'm not sure I understand about the internal stressess but I sure can vouch for the rearward displacement of alloy into the base edge of the boolit distorting it and giving it rifling 'feathers'. I have however, shot smooth sided cast boolits which were dipped into hot lube that performed rather well. Very low pressure rounds fired into test medium showed no signs of rifling compression stress nor base distortion as such. I have experienced paper patches slipping on hard surfaced smooth sided castings but a softer alloy gripped the paper pretty well.

[Edubya]

I have shot a lot of smooth boolits in my .22s. No lead and with 700-1,200 FPS that is equal to most of our other handguns.

EW