HP and alloy questions for 20ga. (62-cal) rifled barrel only slug

[turbo1889]

Okay, so some of you may (or may not) know that I'm addicted to loading, shooting, and generally tinkering with shotgun slugs.

Currently my best mold for 20ga. rifled barrel slug guns looks like this:

http://forums.handloads.com/uploads/turbo1889/2008-10-02_161114_20ga_Slug.JPG
http://forums.handloads.com/uploads/turbo1889/2009-03-01_173219_20ga_Solid_450gr_Slug.JPG

And depending on how I load them I can push them out the end of my NEF-USH (a single-shot, break-action, rifled bull barrel slug gun made be New England Firearms known as the Ultra Slug Hunter) at anywhere between a very mild sub-sonic plinker load at about 1,000fps to velocities approaching 2,000fps using large quantities of a certain slow burning rifle powder that will produce a stable burn at low level shotgun pressures following in the footsteps of Hubel the 12GAFH guy. I took both of me deer this year with the high power loads one at 160-ish yards (paced off) and 228 yards (laser range finder).

Anyway, long story short, I'm thinking of having a HP version mold made. I'm not too knowledgeable when it comes to HP boolits and the "correct" profile to cut into the HP pin and what alloy to cast them with for what velocity etc, etc. So I was thinking about something along these lines:

http://forums.handloads.com/uploads/turbo1889/2010-01-26_174017_20ga_HP_Slugs.JPG

Am I correct that the second more aggressively tapered HP shown second in the picture would be more of a variable expansion at variable velocities type of HP? In that I'd get a little expansion at the low velocity end and full expansion at the high end due to the HP tapering off as it goes deeper. I want something that will still expand a little bit at low velocity but at the same time won't tear it's own nose off (over expand) at high velocity.

Also what kind of alloy are we talking? I was thinking maybe 20:1 or equivalent hardness mystery mix.

Need some input from guys with a lot more experienced with HP molds then I have.

[yondering]

Turbo, you're correct about the variable expansion with the tapered hollow point. A larger angle in the cavity will result in more variable expansion, so obviously some balance must be found, where you can obtain ideal expansion anywhere within your velocity range. 2000 fps is enough to expand even a pretty small hollow point, while 1000 fps will require a larger cavity and a relatively soft alloy.

For the alloy, have you narrowed down what works best in the mold you have now? Since this is a custom proposition, you can tailor the hollow point cavity to work with the alloy you are currently using (as long as it's not a brittle alloy like linotype, which won't expand so much as just break apart). If your gun doesn't have a preference, 30-1 or something in that range is good. WW alloy is a little too brittle for good hollow point results, but works fine when mixed with pure lead, at ratios containing 75% or less ww alloy. For decent hardness, if needed, 50/50 ww/pure, heat treated or water quenched, works pretty well, while still being ductile enough to prevent shattering.

Regarding the hollow point dimensions, what you've drawn up above should expand fine with an alloy like ACWW. For a softer alloy, I'd suggest shrinking the mouth of the hollow point by about 30%. Also, unless you want massive expansion that may severely limit penetration, I would reduce the depth of the hollow point cavity to about 1/3 of the total slug length. (looks like it's ~ 1/2 length now) That should still give plenty of expansion, with a reasonable amount of retained weight. Bear in mind that with a soft alloy and high impact velocity, the slug will expand enough to reduce the slug length down past the depth of the hollow point, so a 1/3 depth cavity may result in a slug that is less than 1/2 it's original length.

Lots of variables here, so it really depends on matching up the alloy to the hollow point and impact velocity.

[OLPDon]

Just my 2 cents worth why not drill out the slug you have in hand and see first if they fly right, 20 gage slugs are quite a task to get good groupings. If you get good performance the slug (boolit) as is, try hollow pointing with drill bitts/ center drill ect you could even grind down reg drill bits to the profile you like. It is much cheaper to use a drill bit then order a custom mold and if you are happy with the HPing of a Boolit you could then invest in a Mould.
Don

[Blammer]

Since I have one of your slugs on hand to actually look at....

I would recommend the HP opening at the top be .175 and the depth be .225 and end in a sharp V like your second picture.

the .175 HP opening will give you a sufficient lip around the HP that makes it easier to cast and fill out. The .175 is REALLY a big HP opening and will easily work well at 1000 fps or less, meaning that when it arrives at the deer 200 yds away it will still expand quite well.

I would go with .225 deep, which is to the bottom of the very top drive band so that when a close deer, say 30 yds, gets hit it will expand fully and then some, probably half way down the shank, but should not blow apart like a varmint boolit.

that's my best guess and what I'd do.

[yondering]

The .175 is REALLY a big HP opening and will easily work well at 1000 fps or less, meaning that when it arrives at the deer 200 yds away it will still expand quite well.


I disagree with this. .175" is a reasonable size for a hp in a .40 or .45 pistol bullet, but is kind of small for a 20 gauge slug; it's certainly not REALLY big. Heck, even my Miha 45 acp hollow point mold has a .200" wide cavity at the mouth.

Remember this: a small hollow point is more easily plugged up, and can fail to expand sometimes even with a soft alloy. A large hollow point is more reliable, giving more flexibility to tailor the amount of expansion by adjusting alloy hardness.

Also, I recommend rounding the bottom of the cavity, rather than it coming to a sharp point or having square edges as shown in your drawing. The rounded bottom of the cavity will do a better job of limiting expansion beyond that point, where a sharp edge at the bottom of the cavity can turn into a crack, allowing the expanded nose portion to shear off more easily.

[Blammer]

My estimation is based on WW alloy. (sorry, forgot to include that on the last post.)

I have several HP's in various calibers, 35 cal, 30 cal, 44 and 458. My 458 has a HP size of .125 similar to my 30 cal's.

.175 may seem small, but IMO an some feeble experience of mine I believe it is a good size. Plus if you determine it's not big enough you can always make it bigger, hard to make the hole smaller. :)

in this thread I have a 35 cal with the dish HP. Not that it's a direct comparison but this is what I'd envision the HP slug to act accordingly.

http://castboolits.gunloads.com/showthread.php?t=60958

it peels back to the end of the HP and ploughs on through.

[yondering]

.175 may seem small, but IMO an some feeble experience of mine I believe it is a good size. Plus if you determine it's not big enough you can always make it bigger, hard to make the hole smaller. :)


The hollow point size has to be proportional to the bullet. Your 458 is a good deal smaller than a 20 gauge. Your .175" hollow point would be huge in a 32 ACP, but tiny in a .730" 12 gauge slug. It's all about proportions.

Your thinking is backwards on making the hole smaller to start with. It's the hollow point pin that would be modified; it's easy to start with a large pin and make it smaller.

On that topic though, Turbo, you probably should plan to make several hollow point pins to experiment with different styles and see what works best for you.

Blammer, nice .358 bullet BTW. Wish I had something like that, but heavier, for my Whelen.

[rob45]

Just my 2 cents worth why not drill out the slug you have in hand and see first if they fly right, 20 gage slugs are quite a task to get good groupings. If you get good performance the slug (boolit) as is, try hollow pointing with drill bitts/ center drill ect you could even grind down reg drill bits to the profile you like. It is much cheaper to use a drill bit then order a custom mold and if you are happy with the HPing of a Boolit you could then invest in a Mould.
Don



It may end up costing about the same either way.
Typical cost to modify the current mold to a HP is usually around $35, and extra pins (for different profiles) are not too expensive.
Best results when drilling really needs a fixture for centering to ensure consistency.

The advantage to drilling the HP (after casting a FP) is that the depth could be varied more easily. Also, it would eliminate the minor adjustments we normally need to make when casting a HP (keeping the pin hot enough, etc.).
Contact JIMinPHX and have him make a drilling fixture if you're not comfortable doing it yourself.
http://castboolits.gunloads.com/showthread.php?t=71615

Each method has its pros and cons; both have the potential to give the desired result.

Good Luck.