Cast bullet sizing question

[hard88cast]

I am looking for a gas checked bullet for a rifle I am having built that is almost done. Smith will size the bore for me but at this point i am going with what the manufacturer of the barrel stated as the barrel size as .510.
From past experience I have learned the value of gas checks when pushing bullets faster then BP can. So am looking for a gas checked bullet of .512 diam in the 450-525gr range with a shorter then normal nose to crimp groove to be able to work in a lever gun. So if anyone knows of any bullets like this for sale please let me know. So far have not found any with the correct profile to match up with the original 50-100-450.

My main question is bhn hardness combined with a gas check.
Some of the bullets on the market I am finding are up around 25bhn, seems pretty hard, must have some tin in it I guess.
Does that hardness along with a gas check cause concern shoving a hard .512 bullet down a .510 bore in a modern built rifle.
Thanks

[243winxb]

https://www.buffaloarms.com/510-440-grain-rngc-hard-cast-510440gc.html

And https://www.midwayusa.com/product/1988311889


Both are .510" diameter. I dont see 25 bhn being a problem when working up.

512" 340 Grain RN Gas Check Qualty Hard Cast Lead Bullets SPG Lube from Box of 50 https://www.buffaloarms.com/512-340-grain-rngc-hard-cast-512340gc.html

[hard88cast]

243.
I have seen the .510 bullets, been looking for .512 bullets which is what I want to start with. The other issue is the nose to taper groove needs to short to match the original 50-100 bullets in order to feed correctly. Thanks for your thoughts on the bhn.

[Thin Man]

Many molds will drop a cast boolit a few thousands over their target diameter. If your mold does not get you up to the diameter you need, read a few of our threads about how to beagle the mold to help it give you what you want. Lots of really good info on this topic throughout these pages.

[reddog81]

My main question is bhn hardness combined with a gas check.
Some of the bullets on the market I am finding are up around 25bhn, seems pretty hard, must have some tin in it I guess.
Does that hardness along with a gas check cause concern shoving a hard .512 bullet down a .510 bore in a modern built rifle.
Thanks

Hard lead is still very soft compared to most metal and especially soft compared to any steel being used to make a rifle barrel. And you’re not going to hurt a barrel with a gas check.

[mehavey]

Go no harder than Lyman#2/BN-15.
Paradoxically, harder than that that has trouble bumping up/sealing
-- leading big time -- espcially if slightly small in diameter to start.

OOC: What cartridge/what pressure/what weapon?
50-100? Win 1886?


.

[405grain]

NOE bullet molds makes just what you're looking for. Go to their site and check out their 512-475-RF-BT6. Other bullet mold manufacturers also make good designs that will fit your needs.

Cast bullet companies that mass produce bullets with automated casting machines almost always use very hard alloys. They do this to prevent damage during shipping. For a 50-100 cartridge your going to be better off with a softer alloy - something like 11 to 13 BHN. The harder alloys will not seal the bore at the velocities that your going to be shooting. The softer alloys will bump up and seal on firing, and will be much better at preventing leading. Gas checks are beneficial for several reasons: better bore seal, can be used at higher velocities, improve accuracy, etc.

A good rule of thumb is to size the cast bullet .001" above groove diameter. But a better rule is to size the bullet to match the throat instead of the bore. All things being equal, a .512" diameter bullet should work fine in your rifle. If it's slightly too large it can easily be sized down a little bit. If it's too small, try powder coating to increase the diameter before trying to alter the mold.

[mehavey]

I'm pretty sure the OP is looking for this bullet/mould:
293607
https://www.accuratemolds.com/bullet_detail.php?bullet=51-450CG

[Hanzy4200]

I have 350 and 500 gr FN bullets sized to .512, but plain base, no GC. I would contact Accurate Molds. He will cut you whatever mold you desire.

[tja6435]

You can have Accurate or LBT make a mold to your specs.