Hollow Point: Round cavity vs multi side cavity

[ghh3rd]

I'm in a group buy for a MiHec H&G #503 Cramer Style Hollow Point mold. In addition the two types of round pins, there will be a pin to make five sided cavities.

I wonder if multi sided cavities perform differently than round cavaties.

Randy

[gray wolf]

Yes they do, in a few different ways. One way is that the round hole flattens to a round slug with the propper load. The hex head hollow points tend to petal with separate cutting edges,
also if driven at the right speed and not to hard a metal is used.
There will be other comments I am sure.

[fredj338]

Not a Mihec, Erik did this Lyman & RCBS for me, but the faceted pin works great. Much like skiving on a JHP.
http://img.photobucket.com/albums/v703/fredj338/45-215gr.jpg http://img.photobucket.com/albums/v703/fredj338/9mm-136-1200.jpg

[mpmarty]

This must go back into ancient history. As I recall several centuries ago there were round balls and square ones. Round balls were used on "christians" and the square ones on infidels and barbarians (my kind of folks).

[Buckshot]

..............The sharp inside corners do 2 things. One is the lead is thinner at each 'Point' or corner. The inside corner also acts as a stress riser, and if a crack is to occur in the wall of a tube, it will happen at a stress riser first.

................Buckshot

[MtGun44]

Bingo for Buckshot!

I think that you should be able to get failure (tearing) at the corners at lower force level,
so you can likely get expansion at a lower velocity with a given alloy hardness. If the
nose stays intact (round pin) you need enough force to stretch the intact hoop of metal AND to bend
the nose over. If you separate it into petals, there is no force required to stretch the
hoop because it is broken, you are now just bending a little beam over. Should be easier.

I would expect more expansion with faceted cavities, up to some limit where they angle
is large enough that it doesn't act as much of a stress concentrator. Imagine 12 facets,
not much stress concentration, it is starting to look a lot like a smooth circle. So, my guess
is more than about 5 or 6 would start to act like a round cavity again.

Theory, not actual testing. Frank has some actual test data (photos) above.

Bill

[fredj338]

Theory, not actual testing. FRED has some actual test data (photos) above.
Erik & I talked this over & though going for 6 would start acting like a round cav. The 4 sided one (9mm) works great down to about 1000fps w/ the alloy shown. The larger 5 sided 45acp will still show expansion to 800fps, but better @ 850fps. I haven't tested @ 900fps yet, but should do well. I agree w/ you mtgun, the skiving acts as stress lines for an even upset, less tearing. When I shoot the Lyman 45 Dev, they want to come apart @ higher vel. yet you can see the 4 sided cav 9mm still looks good @ 1200fps. All were tested in wet phone books @ 15ft.

[MtGun44]

Sorry, FRED !!

Thanks for the tested slugs. I still owe Erik some, just been too crappy weather here
to get out and play with buckets of water and wet newsprint! Almost got stuck at the
range today just shooting the .22 rifle.

Bill

[yondering]

Search through the "mihec 45-200 hp re-re-run" thread from last summer, we discussed this in detail. I lobbied for 3 or 4 sided HP pins, others wanted 6 sided (for looks I guess). We compromised and settled on 5 sides. I believe I posted pics of the performance of a 4 sided hollow point on that thread.

[thx997303]

I searched those exact words and all it came up with was this thread.

[yondering]

yeah, those key words were just from memory. Here are a couple threads:

MiHec .452 - 200gn Cramer Re-Re - run (http://www.castboolits.gunloads.com/showthread.php?t=56639&highlight=miha)
Discussion of the faceted pins starts on post #5, continues over quite a few pages.

Casting with the MiHec .45 Hollow point re-run (http://www.castboolits.gunloads.com/showthread.php?t=55775&highlight=miha&page=3)
Discussion of the faceted pins starts on page 3 or 4 of this thread.

Hope that helps.

FWIW, I'm still hoping Miha will produce a pointed 5 sided top punch to match the pins in his molds. This would be a top punch that fits inside the hollow point cavity, rather than around the bullet nose.

[dakotashooter2]

This has gotten me wondering if a person could just use an appropriately sized hex, torx or even philips bit (or cheap screwdriver) for the HP pin. HMMMMMMMM

[yondering]

This has gotten me wondering if a person could just use an appropriately sized hex, torx or even philips bit (or cheap screwdriver) for the HP pin. HMMMMMMMM

Yes you can!

A phillips bit works great as a nose punch in your lubrisizer to modify round hollow point cavities too. You'll have to do a little grinding, but it's not difficult. A torx bit will work too, but you'll need to grind some taper on it, or it will stick (straight sided bit in a hollow point = sticking).