MP 462-420 HP Mold

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Aaron posted this 17 February 2026

Made my first casts with the new MP 462-420 HP Mold tonight. Again a beautiful brass mold sent from Europe to NC in 2 1/2 DAYS. Heads up UPS and FEDEX.

This mold definitely likes to be fed from the bottom spout of the Lyman Mag-20 furnace. Being a large bullet, both the mold and the alloy must be super hot to cast correctly with full fill-out of the bullet. Casting with Lyman #2 alloy produced HP bullets of 380 gr at .460" on the nose. These plain base bullets are a tad heavier than the Gould Express bullet at 330gr with its rather small HP opening. These MP bullets will feed well in the lever action 45-70 guns as well. I can't wait to load some of these rascals up and test them.

With rifle in hand, I confidently go forth into the darkness.

mp-molds

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Wilderness posted this 17 February 2026

Aaron - nice looking bullets, but MP definitely like their big hollows. These should be pretty deadly on Racoon sized stuff.

How deep are the hollows, how long are the bullets, and how much material (weight) does the hollow remove?

I wonder if anyone has done any work on slowing down the action of these big hollow points. Maybe some softer-than-lead material in the hollow, tested in Ballistic Gel.

The only method I have tested is to punch in a tight fitting pellet or pellets of soft shot into the base of the hollow. Definitely provides a means of graduating the HP action to less than 100%. Only test was on hogs.

Then again, BHN on its own may be enough to regulate the HP action at mid-teen velocities.

You are only as good as your library.

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Aaron posted this 17 February 2026

Aaron - nice looking bullets, but MP definitely like their big hollows. These should be pretty deadly on Racoon sized stuff.

How deep are the hollows, how long are the bullets, and how much material (weight) does the hollow remove?

Bullet weight with no hollow is right around 460gr. With the HP, bullet is 380gr. Bullet length is 1.021" and the hollow depth is a tapered .340" into the nose.

These should be interesting to test in various alloys and at various velocities in the 45-70 and 45-90 rifles.

With rifle in hand, I confidently go forth into the darkness.

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Wilderness posted this 18 February 2026

Aaron - that should leave a fair slug to do the deep stuff. The proof of the pudding will be in the eating. I keep thinking back to your blown up .44 Magnum bullets.

You are only as good as your library.

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Aaron posted this 18 February 2026

Those photos were pretty telling. Bullets became frangible. This bullet, a tad slower and softer, should perform well. Of course for now, I can only test it in a proxy medium. Will be fun to do….

With rifle in hand, I confidently go forth into the darkness.

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Aaron posted this 18 February 2026

I mentioned before in a previous post that molds have personalities. I have observed that most of my molds can be ladle fed after I had previously used the bottom spout of the Mag-20 furnace. There were a few that could easily be ladle fed and cast great bullets. I have since migrated to mostly ladle feeding, but here I have a mold which demands spout feeding. It simply will not cast well with the ladle. When I ladle feed, I have always mated the ladle spout to the mold, turned upright to allow gravity to work its wonders, then turned the pair and removed the ladle from the mold. This mold simply will not cast well with the ladle either with the pair mated or not. I have noted in my casting log book, this mold needs to be spout fed from the pot.

Like Wilderness, I do try to maintain good data on my hobby. Makes life a lot easier to keep good records especially as I get older...

Now if I could only remember where I have placed (for safekeeping of course) my small pistol cleaning kit. I have searched everywhere and simply can not locate it or think where I have placed it. An enigma for sure.

With rifle in hand, I confidently go forth into the darkness.

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Aaron posted this 25 February 2026

Well....dead in the water. This bullet, like the 312-170-HP bullet will NOT CHAMBER due to full diameter measurements in front of the crimp groove. To accommodate short throats, these bullets need to be BORE DIAMETER ahead of the crimp groove, not groove diameter like they are. Unfortunately this will be my last MP rifle bullet mold. Comments, photos, and suggestions were sent to MP Molds in the hope they will be used to improve the product.

This bullet may work in a long throat single shot but it won't work in a lever action rifle when the crimp groove must be used. Dang.

With rifle in hand, I confidently go forth into the darkness.

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Premod70 posted this 25 February 2026

I wouldn’t give up until I tried a taper crimp die.

Dale Flinchum

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Aaron posted this 25 February 2026

Dale,

A taper crimp die won't fix the bullet diameter forward of the crimp groove.

Seating deeper will throw chamber pressure through the roof. Lee figured out this trick decades ago.

These bullets won't even seat fully in the chamber of my Uberti 1885 High Wall. Won't seat in a Marlin 45-70 or the Uberti 1885 in 45-70. They simply have too much bullet diameter ahead of the crimp. I even sized them to .451" with the same result. That nose NEEDS to be .450" or .449" for these rascals to seat in most 45 caliber guns if using the crimp groove.

They WILL chamber in the Miroku (Winchester) 1886 in 45-90 with its generous throat. MP Molds needs to shrink the bullet diameter ahead of the crimp groove.

Have the exact same issue with their 312-170-HP bullet. The nose is too fat, to far up, to chamber in most rifles with a normal throat whereas the Lee C-309-170-F, with its .300" nose, slides right into the chamber due to its bore riding nose.

With rifle in hand, I confidently go forth into the darkness.

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Wilderness posted this 25 February 2026

Aaron - if you have a Lyman or RCBS lubesizer you can part size the bullets, just the noses. Bullets go in nose first of course. The first band may get some slight reduction also from the lead-in of the die, but I can't imagine this being an issue. For this you will also need a flat faced "top" punch to push against the bullet base.

You may be able to buy a .449" or .450" die, or get one made.

https://www.buffaloarms.com/449-custom-sizing-die-for-ly-bac449.html

Someone on the Forum might even oblige.

For this job you don't need the lube holes in the die, or the groove for the O-ring, or the groove for #45 screw, just a naked piece of steel of the right diameter and length, with the right bevel on the bottom, and the right sized hole through it, part tapered hole of course.

Or you could find an unwanted die of lesser diameter and have it drilled and reamed out.

And you'll need to rod/punch to push the bullet back up out of the die if you haven't already got one that could do the job.

I read somewhere also of someone attacking oversized bullet noses with a Lee Factory Crimp die, working on loaded cartridges of course.

All of this could apply equally to your .30-30 mould, though I expect finding a ready-to-go lube sizer die for the .30-30 nose would be more difficult than finding something suitable for the .45-70.

You are only as good as your library.

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Aaron posted this 25 February 2026

Bill,

Tried to size the nose to .451, my smallest 45 caliber size die. Didn't work. Sizing the entire bullet to .451 was fun to try too. Obviously it didn't work and the bullet went back to the melting pot.

I am just not in the mood to modify any equipment to make a custom sizing die for the nose when MP Molds can adjust the software to make a bore riding nose just like RCBS, Lyman, Lee, and others do to allow the bullets to fit into multiple throats by multiple gun makers. I appreciate your comment regarding this but a 45 caliber bullet is a pretty standard thing in the industry. It's not like it is some obsolete or metric caliber nobody makes a mold for.

I have sent comments to that effect to MP Molds hoping they may listen and adjust accordingly across the mold family for rifles. Hope it works. This mold and the one for the 30-30 rifles will sit on the shelf unused.

With rifle in hand, I confidently go forth into the darkness.

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Wilderness posted this 26 February 2026

Aaron - do I detect a touch of SOL?

Come on, where's your sense of adventure?

I've done some modest forward bullet sizing to get #311407 bullets further up the throat in a .308. It was no big deal.

You are only as good as your library.

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Aaron posted this 26 February 2026

Bill - truth be told, I am a bit, no, more than a bit frustrated with this situation. The mold does not produce usable bullets for any of my 45-70 rifles, either lever action or single shot, and only one of my 45-90 rifles, the Miroku 1886 lever action can use it as is. My expectation was not realized with this mold or the 30 caliber mold. Fool me once - shame on you. Fool me twice - shame on me.

I have the technical ability to tool my way around this but actually do not wish to spend any more time, money, or effort doing so. I'm getting cranky in my older age and want to avoid stressful situations. That's why I do NOT watch or read the "news" on any venue. I avoid ALL political garbage (propaganda) and "government" issues as well. Makes life simpler for me as I cast bullets that chamber in my guns.

These molds, with shipping, are not cheap. They are great molds - the bullets aren't designed well for rifles, especially lever action rifles where the crimp groove is used.

So....I move on. No good story to write up here.

With rifle in hand, I confidently go forth into the darkness.

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rjmeyer314p posted this 15 March 2026

OR you could just seat the bullet deeper and decrease the load by 1-2 grains to overcome the pressure. Then work up gradually. Honesty makes a tool to vary how the bullet is seated wrt the lands.

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rjmeyer314p posted this 15 March 2026

That should read Hornady, not honesty.

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Aaron posted this 15 March 2026

Since these bullets are (were) to be used in a lever-action 45-70, the crimp groove is integral to the cartridge construction. Seating the bullet deeper would allow them to be pounded even deeper into the case under recoil. While deeper seating may work in a SS rifle, it's really not an option here and the crimp groove needs to be used for its primary purpose. Other mold manufacturers like Lee, Lyman, RCBS, Saeco, and more, have learned over the decades that bullets designed for lever-action rifles and bear a crimp groove, need to have the nose smaller to slip into the bore creating a "bore riding" nose whilst the main body, behind the driving band is groove diameter. Of course these bullets function perfectly in SS rifles as well. Why do you suppose Lyman made the 535gr Postell (457132) mold with a bore riding nose? Otherwise the bullet would seat as deep as the primer hole in the case with 5gr of propellant under it. I'm being facetious here but there is a reason these bullets have a bore riding nose and some have crimp grooves.

Putting a full groove diameter nose in front of a crimp groove on a heavy rifle bullet is senseless and obviates the lack of understanding of the manufacturer for their product and its intended use.

With rifle in hand, I confidently go forth into the darkness.

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rjmeyer314p posted this 15 March 2026

Try seating them deeper and use a Lee factory crimp die. It might hold in a lever action.

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Premod70 posted this 15 March 2026

Never say never on the taper crimp until tried. Try casting 20-1 to lessen the resistance and the crimper, you may get lucky. Good luck.

Dale Flinchum

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Aaron posted this 16 March 2026

Dale, I use the crimp groove on this bullet with a slight roll crimp. Actually I use the Lee Factory Crimp tool on these for the 45-70 and 45-90 Lever-Action rifles.

With rifle in hand, I confidently go forth into the darkness.

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Aaron posted this 20 March 2026

Against my better judgement and absorbing another $62 hit, I ordered a .449" size die from Buffalo Arms to size the nose of the MP 462-420 HP bullet down to fit in most 45-70 and 45-90 rifle throats whilst using the crimp groove provided in the bullet. Use of the crimp groove is essential in lever action rifles with tubular magazines. While I could seat the bullets even deeper into the case and use an aggressive taper crimp, that reduces case capacity for Black Powder loads, which was what I mostly use in these rifles.

I just tried the nose reduction to .449" making the nose a "bore riding" nose profile and when cartridges are crimped into the bullet crimp groove, they now chamber in ALL of my 45-70 and 45-90 rifles. Miracle of miracles. Actually it's not. The MP bullet design is very poor. Emails sent to Miha Prevec have gone unanswered. His bullet design for rifle bullets with a crimp groove NEED to have a reduced "bore riding" nose profile to allow chambering in most rifles.

RCBS, Lyman, Lee, Saeco and a host of other mold manufacturers figured this out decades ago. Miha just doesn't get it. He also refuses to answer my email messages regarding this. Perhaps someone on this forum who has Miha's ear can point out this design flaw to him? While MP Molds are generally well designed, this particular error means the cast bullets are show stoppers when trying to use the crimp grooves. His handgun bullets are fine, but these rifle bullets need to be redesigned with a bore riding nose profile.

Below are images of the resized nose to .449" up the nose .150" above (before) the crimp groove. These now chamber perfectly. The bullet shank of course, is sized to .458 or .459" depending on the rifle. Problem solved but at another $62 expense and more time to prepare the bullet after casting.

Bullets shown are rejects from the casting batch but serve here for test purposes.