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Alstone · Moderator & Site Supporter

Thanks Griff I didn’t think about reversing the process, the only thing is deciding where to split the mould. Thumb Up!

Looking at it logically I think I will have to split it just before the nose starts, that way I can lift the nose part of the mould off leaving the pellet sat in a hole, with a pin up the base to make the internal hole, if this part of the mould is removable I could push the pellet out through the bottom of the mould.

Cheers Brutuz for the Tin design, It will take a bit of sweat filling it. Laughing

Slavia The twist is 1.25 in 12"

Al

Alstone · Moderator & Site Supporter

Ok then! I got the reverse mould made so that the lead could be pored from the head of the pellet, I also incorporated a sprue cutter. But all to no avail the problem is that when you pour the hot lead in from the head of the pellet, as the lead reaches the skirt which is quite thin, the lead cools down to fast and sets before reaching the base, I have tried increasing the temperature of the mould but because air is trapped below the lead it goes no further.

I have a friend who has a die cast injection company, so I went around to see him for any tips he could give me. The first was that the lead needed to be injected to get a good finish, the second was that I was wasting my time doing it that way, and go back to the original method of pouring the led from the base and drilling out the hole.

One thing he did tell me was how commercial pellets are made, evidently on his travels he visits many exhibitions of moulding machines, and at one of these there was a stand making airgun pellets. The way it was done was that reel of lead wire is fed in to an extruding machine and finished pellets are spat out of the other end, evidently cold forged.

These are the parts making up the mould for feeding the lead in from the nose end

The same parts assembled. The silver bar on the top of the mould is the sprue cutter.

This is a pellet produced with an unfinished skirt.

I don’t intend to pursue this method any more, which is a shame as it seemed to have potential.

I think I'll go back to the first mould and incorporate a hole drilling jig.

Al

dogon1013 · Member

alstone,

I just remembered this link about molding pellets, maybe you have allready seen it.
http://airgundevelopment.com/mold.html

Alstone · Moderator & Site Supporter

Griff1950 · Member

Al, I'm afraid you misunderstood me. Split your mould blocks vertically just as you were doing in the beginning, just invert the bullet in the mold. Your moulds will have to be very hot to make a good pour, and you will have to engrave vent lines so that the base can fill completely. The vent lines are easily cut in brass, in tougher metals, you can use a triangle file. You can make any type base plug you desire, and make the skirt as thin or as thick as needed. It can also be helpful to make a sizing die, as pellets don't always come out the same size as the mould. Differences in temp in the mould blocks can sometimes have a pronounced effect on bullet diameter.

Alstone · Moderator & Site Supporter

Cheers Griff, I did think about doing it that way but was concerned about flash from the vent holes, as I didn’t want to have to finish the pellet after moulding.

Al

Alstone · Moderator & Site Supporter

I decided to go back to my original mould idea as it was simple and worked ok, it just needed a bit more care and getting the centre hole equal and deeper.

This is the MK 4 pellet mould and I hope the last one. It is similar to No 2 but as the addition of a sprue cutter and hole boring jig

The sprue cutter trims off the spare lead from the back of the pellet.

It is then swung around and used as a drilling jig to drill a hole up the base of the pellet.

The pellets come out quite well and need no further finishing, the pellet from my TX collected a few rifling marks from the barrel choke. The finished weight is 10 grain.

Grouping is not bad 10mm but could be better, this target was five shots using a TX at 20m from a bench.

A very interesting project and I have enjoyed making the bits and trying out the pellets, but I think it is easier to go out and buy pellets than make them. Unless of cause you want something special?

Al

Brutuz · Senior Member

Very impressive Al Cool

fritz · Silver Status Member

Very impressed with the accuracy.

Do you plan to chrono them, and figure the BC anytime soon?

EDIT: adding a space to the headspace would make for easy hollowpoints

dogon1013 · Member

Looks good.

and you can easilly change the weight by not drilling as far, or changing the drill size.

BBGun Bob · Veteran Member

A small waist is required(a must) on pellets because of the slow twist rate. I read somewhere that a small waste is required behind the head of a pellet.This reduces drag along the pellets side surface and concentrate's air passing by the pellet to the skirt.This action is what creates drag on the rear of the pellet and allows head first flight at all times.Without some sort of bottle design followed by a skirt a pellet's flight will tumble .
A pellet is much like a shuttlecock(think badminton birdy) rather than a dart.Because of the slow twist rate of pellet gun barrels there is not enough spin on a straight sided projectile to keep in from tumbling in flight no matter how fast it travels(FPS).
I just thought I'd pass this along while your racking your brain.LOL

Best Regards
BBGun Bob

PS:
Even the old Sheridan Cylindrical pellets had a small waste incorporated into there design if you look real close.

Alstone · Moderator & Site Supporter

Hi Bob, hope your keeping well?

Thanks for the tip, I’ll alter the mould and give it a try, I was trying to get away from waisted pellets so that I could get them to auto feed into a breach, stacked side by side instead of end to end.

The last batch I made were pretty good regarding quality and finish, but the best grouping I could get was 10mm, so you could have something there, I’ll try a small waist first and see what happens, the thing is to protect the skirt from damage.

Al

jlwilliams · Veteran Member

Are they making neat holes or keyholes? If you shoot them at a box, do they make round holes in both sides of the box? Or do they make a round one in the front and an oblong 'keyole' in the back? The box trick will help you see if they are tumbling in flight.