Hollow Point Pin Design Basics Inquiry

[OnHoPr]

Back 40 years ago when I use to cast a lot there were different designs in the actual HP pin. Some were basically straight drill rod with a radius on the tip and some had the V taper going down into the nose of the boolit. These were basically all Pb molds for BP & subs. With the high power handgun and rifle boolits and their alloys is there a basic line in the characteristics of these two styles of the HP pin? Are both styles adjustable for depth to compliment your boolit's alloy and speed for your personal shooting habits or characteristics? Is there basic preferences, for instance, taper & depth for 1000 fps handgun and straight medium depth for 2200 fps rifle? As the title stated this in just a basics info inquiry.

[Outpost75]

The core pin must have some draft on its sides in order for the bullet to release.

Major diameter of the cavity should be about 0.6 to 0.7 of the meplat diameter. Larger than this and you will have trouble getting good fill-out of the thin nose section near the meplat.

A 60 degree draft angle gives a cup-point as deep as its diameter.

A 30 degree draft gives a conical cavity twice as deep as its diameter.

A 15 degree draft gives a long, narrow, conical cavity four times as deep as its diameter.

A core pin with 15 degree draft, with the point ground to a smooth hemispherical shape 1/2 the major diameter of the cavity opening works well in most cases.

Considerations are the alloy hardness and velocity level. A shallow cup-point 0.7 of meplat diameter expands well in soft 8 BHN alloy down to about 900 fps in cartridges like the .45 Colt. The same shape expands nicely and holds together at 1400 fps in 12 BHN alloy in the .44 Magnum.

The .45 Colt "New Manstopper" bullet below has a half hemispherical dimple in the nose and expands well in 1:40 alloy at black powder revolver velocity.

The .30-30 plainbased bullet shown below was modified from an RCBS 30-180FN truncating the nose to provide a 1/4" meplat and has a .15" diameter conical cup point with 60 degree draft. Expanded bullet was cast 1:20 tin/lead and fired at 50 yards into water jugs at velocity approximating the .32-40 WInchester. It is a proven deer load.

The .35 Remington 200-grain cup point has a similar .25" meplat with .15" diameter conical cavity with 60 degree draft and was cast from wheelweights and driven about 1700 fps and shot into water jugs at 100 yards.

Original black powder .44-40 cartridges with soft, nearly pure lead, solid nosed bullets do not need to be hollow pointed to expand well, as this test from W44WCF shows.

Alloys harder than about 13 BHN tend to break off the expanded nose in fragments. This isn't necessarily bad, if the solid shank below the cavity edges has sufficient weight to ensure adequate penetration.

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[OnHoPr]

Ah, a good post with a plate full of good base line info for the noodle to digest into the memory banks even though they skip and spin.