Penetration as a function of cast bullet design.

[Bill*B]

The author of this web site (http://www.rathcoombe.net/sci-tech/ballistics/methods.html#round-nosed) states that "there is something inherently efficient about the penetration of very broad flat nose solids", noting that an "abrupt transition" favoring penetration occurs when nose flat diameter exceeds 50 to 70% of bullet diameter. If I read this right, he is saying that a hard cast wadcutter should out penetrate a round nose of the same weight, impacting at the same velocity. Has this been your experience?

[Bigslug]

I haven't done a whole lot with round noses, and I don't have true apples-to-apples. However, what I do have:

I've water-shot the LBT 230 grain LFN (.32" meplat) at the standard .45 ACP GI velocity of 830fps and gotten nine milk jugs out of it. Proof that you could hunt elk with a 1911 if you were hungry and determined enough.

I've done the same with the 265 grain .455 Webley MKII bullet at the regulation speed of a bit over 600fps. That one was typically a five to seven-jugger.

I've shot the Lyman .358 195 grain round nose into an 18" FBI gel at about 570 feet per second. Went completely through in a straight line and stopped on the hard rubber backing plate.

I've milk-jugged the somewhat pointier 14BHN NOE 200 grain round nose at 630 fps. It stopped in jug #4 and showed no definitive evidence of tumbling.

I've milk jugged the 220-ish grain full-wadcutter .455 Webley MKIV at @600fps into thicker-walled jugs (milk jug shaped, but originally containing swimming pool chemicals). Dented jug #5, bounced back into #4. Confident that actual milk containers would have given another jug or two of depth.

For comparision's sake, I've found that the typical police duty hollowpoint is usually a 3-jugger, sometimes 4.

Surely a leading factor in this discussion has to be exactly WHAT you're trying to penetrate. If flat noses have an advantage is softer materials, I might surmise that the displacement of media off the meplat serves to reduce friction on the sides of the bullet. On a harder substance, focusing the energy on a pointier tip will have an obvious edge. After all, the M1 Abrams tank is firing big, pointy darts at its enemy counterparts, not upscaled Keith SWC's.

[Wayne Dobbs]

Flat nosed bullets tend to remain stable in flesh penetrations; many, perhaps most, round noses will yaw (which limits penetration).

[Outpost75]

Flat nosed bullets tend to remain stable in flesh penetrations; many, perhaps most, round noses will yaw (which limits penetration).

This is key.

Long, round-nosed bullets have a greater overturning moment and longer radius of gyration which encourages tumbling.

Ogival flat noses and blunt FMJs with shorter ratio of length to diameter, such as .45 ACP hardball have their center of gravity closer to their center of pressure (shorter radius of gyration) and tend to remain point-forward.

242641242642242643242644

[Bill*B]

Interesting data. Thank you, gentlemen.

[am44mag]

Very interesting. It's certainly something you'd want to keep in mind if you plan on using your cast boolits on dangerous game.

I presume this is why a lot of dangerous game ammo has a flat or nearly flat nose?

https://cdn3.volusion.com/kcks2.jk6t3/v/vspfiles/photos/90375300DGXB-2.jpg?1553240800

[SSGOldfart]

How about ballistics? Isn't the flat nose going to fall more and quickly vs the pointy darts :groner: so again one must select a boolits base on what it's purposes.

[pettypace]

The author of this web site (http://www.rathcoombe.net/sci-tech/ballistics/methods.html#round-nosed) states that "there is something inherently efficient about the penetration of very broad flat nose solids", noting that an "abrupt transition" favoring penetration occurs when nose flat diameter exceeds 50 to 70% of bullet diameter. If I read this right, he is saying that a hard cast wadcutter should out penetrate a round nose of the same weight, impacting at the same velocity. Has this been your experience?

Here's a gel test of 5 rounds of a two-projectile .38 Special load. The bullets were all 95 grain Lee 356-95-RF's loaded base-to-base. The front bullets flew as intended and the back bullets flew base forward like a boat tail wadcutter. Same bullet weight and same velocity with the "round flats" out-penetrating the "wadcutters" by 3" on average. (One of the front bullets penetrated the full 22" of the gel.)

242691

[Bill*B]

There is no question that wadcutters have the worst possible ballistic coefficient. Yet here is another site (http://www.gsgroup.co.za/articlepvdw.html) proclaiming that they are a different beast in tissue, and discussing why that may be. I found the "shoulder stabilization" theory interesting - had not heard that one before.

6/2/19 update: Re - reading this article, it is saying what Outpost75 wrote: bullets tend to tumble in tissue. Flat point bullets "cavitate", i.e. push the tissue aside with their blunt meplat, and have a greater resistance to tumbling.