New Mould Question on Weight Difference

[barnabus]

i recently bought a RCBS 45-325 FNU mould thats suppose to drop around 325 grains. I bought the mould for a reduced load for my pedersoli trap door. Its dropping at 343-344 grains which is heavier than i anticipated. I was using a 405 grain bullet mould. Im using range lead and normally that alloy drop very close to advertised weight in every other mould i have. It was raining all day yday if that would matter that much.Casting temp was 750 degrees It drops at .459 Any thoughts?

[DeuceTwo]

Hard to say without a close examination of the mould itself. Try casting the "lead" in another mould and see what results you get for a comparison in regards to weight matching previous results.

[jdgabbard]

I have this problem often, and now view mold "weights" as a generality rather than a rule of law... For example, I have a 358477 that drops right at 158gr with 50/50+2%. That mold is a 150gr mold, so it's about 5% heavier than it should be dropping. My MP357-125-HP drops at 130gr with the HP pins, about 4% over.

[barnabus]

Hard to say without a close examination of the mould itself. Try casting the "lead" in another mould and see what results you get for a comparison in regards to weight matching previous results.

did you read the post entire post?

[barnabus]

I have this problem often, and now view mold "weights" as a generality rather than a rule of law... For example, I have a 358477 that drops right at 158gr with 50/50+2%. That mold is a 150gr mold, so it's about 5% heavier than it should be dropping. My MP357-125-HP drops at 130gr with the HP pins, about 4% over.

yes all my other moulds are within that say percentage window but this one is way over.

[Dusty Bannister]

The following link will take you to a thread showing the alloy standard used to establish the weight on various types of RCBS molds. Is your alloy the same as the standard?

https://castboolits.gunloads.com/sho...-of-RCBS-molds

[gwpercle]

Try mixing your "range scrap" 50-50 with COWW and see if that alloy doesn't lighten up the boolit .
Every mould is a law unto itself ... just keep adjusting untill you get where you want to be .
Gary

[mnewcomb59]

Weight changes dramatically in big 45 molds. My 453-345 WFN from Mountain Molds has cast as high as 357 grains with 1-1-98 alloy and as light as 339 with 3.5-3.5-93 alloy. This mold is specced for WW metal and the weight and diameter is spot on with that alloy. It casts larger and lighter with richer alloy, and heavier and smaller with softer alloy. I bet it would be only 320 in Linotype.

The reason you are seeing a different weight is because you are using an alloy with a different specific gravity than the manufacturer used when they designed it. I am guessing based on your numbers that it would be right on in weight with Lyman #2 which is 5-5-90.

[Larry Gibson]

RCBS moulds are designed around linotype alloy. Cast of linotype the bullets from your mould probably will drop close to 325. The higher lead content of your alloy is what makes the difference.

[gunther]

Worry more about the as cast diameter than the weight. Original TD's run over .460 very often. Don't know what an Italian copy would be, But you ought to find out.

[rintinglen]

RCBS spec'd their bp cartridge boolits with 10-1 lead/tin mix. I will bet that your boolits don't have that much tin.

[barnabus]

Worry more about the as cast diameter than the weight. Original TD's run over .460 very often. Don't know what an Italian copy would be, But you ought to find out.

i dont need to worry about cast diameter as i already know what my rifle requires.i wanted a lighter bullet for recoil reduction and maybe you dont know but weight matters when it comes to that,not diameter

[Bigslug]

Snipped from Dusty Bannister's link:

"Unless noted otherwise, all RCBS bullet moulds are double cavity type. Each mould is identified by a five or six digit number, followed by two or three letters. The first two or three digits identify bullet caliber, the last three are bullet weight in grains. (Round Balls are identified by caliber only.) Bullet weights are established by the following methods:
• Rifle & Silhouette Bullets- Linotype alloy.
• Pistol, BP Silhouette and C Sharps Arms Bullets- An alloy of 1:10 tin to lead.
• Cowboy Bullets- An alloy of one part tin to twenty parts lead
• Round & Minie Balls- Pure lead."

So your mold is going to need linotype to drop at the advertised weight. I'm pretty sure I ran into this issue with both square and round lube groove versions the Ideal/Lyman 452423. Spec was 238 grains back in the day when discarded printer's linotype was a common thing - any alloy we'd consider appropriate for pistols today - it dropped closer to 250.

If trapdoor level loads aren't "reduced" enough for you, backing off the charge and working with filler wads to maintain a safe volume for your propellant to work within are likely the better answer than simply dialing back the bullet weight. My Dad's got some skeletal issues that have made shooting his .45 single shots with full-snort loads impractical. The 535 grain Postell and other long range target bullets are often lobbed at subsonic speeds so they don't have to deal with turbulent trans-sonic airflow problems as they slow down. We used something close to the .45-70 trapdoor cavalary carbine charge (54-55 grains of Black if I remember correctly) combined with filler wads behind the Postell to get an 1150-ish feet per second load in his .45-100. Very comfortable load, and it'll reach if we need it to.

[Larry Gibson]

barnabus

If that RCBS 45-320-FN-U bullet doesn't work out for you I suggest the Accurate 46-275R. It is a close copy of My Rapine 460250 bullets [they drop at 270 - 275 gr] and is excellent in TDs when loaded over 8 gr of Bullseye (no wad or filler needed). The Accurate bullet is designed for COWW alloy so it should be just right for your alloy. Recoil is very gentle, and accuracy is excellent.

[rintinglen]

That 45-325U was an excellent boolit in my 45-70 Marlin CB. It shot very well, I used it for several years for Lever Action Silhouette matches with no complaints. 20-28 grains of 2400, somewhere in there is the charge that will tickle your fancy.

[Delkal]

I guess I don't see the problem with a 325 grain mold that actually casts 19 grains heavier. I is only a 6% difference and I doubt it will change your load or the ballistics coefficient.