bullet's- profile vs. weight?

[1858rem]

I'm using a 255g bullet mold, but the bullets im casting weigh in at 243.5 grains, do i need to use load data for a 255g bullet or for a 240grain bullet? i would prefer that of a 250g bullet really because of more information on it, there are only a few loads listed for 255g but lots for 250, but being 244gr weight do i need to expect any velocity/pressure increase? basically what im wondering is what is load data based on..... the shape, like how much of the lead slug is actually in contact with the bore or the weight the bullet is dropped at upon casting...... this question is more specifically for the 124g tumble .356 mold from lee(using it in .38 special:banghead and .45 colt 255g RNFP from lee as well. i have been following load data for 250g for the .45 and 125g for the .38(both lead cast bullet) but i just wanted to check up on this....oh yah, the 124 tl drops at 117.3 grains

 

[Galil5.56]

Wow, drops at 117... Harder alloy than woodpecker lips. My Lee 124 TCTL dropped 128 with WW. I tend to load what the weight dictates. Some of the TL bullets have a long shank, but not much bearing surface because of the numerous shallow micro grooves. IMO, actual seating depth if extreme would be a concern, but note a lot of Lee bullets I have used have to be seated to what seems a "short" OAL because of their design (long shank/short ogive).

 

[bullseye308]

Unless you are loading hot, I wouldn't worry about 10 grains of bullet weight. If you wanna worry about it, use 1/4-1/2 gr less powder. A chrono would be great if possible.

 

[1858rem]

well, i have the lee safety scale and for the 255'ers i gotta cut em into 3 pieces and the 124's in two, maybe i lost a hunk? i was not willing to sacrifice many of my freshly cast bullets so i only avg'd 3 of each.... maybe i should do ten or something?.... and it was ww, recently i started mixing 50/50 ww/plumbers soft lead to "heavy up" the bullets a little. im just a strait soft lead kinda guy from casting muzzleloader-only bullets since i was 14, so this shindig is still new to me with the alloys and whatnot.

 

[rcmodel]

If you are using a 255 grain bullet mold, you need to use 255 grain load data regardless of the actual bullet weight dropped by the mold.

It has more to do with bullet bearing surface (driving band friction) then it does with a few grains differance in the weight.

On the otherhand, it probably won't make any differance whether you use 240, 250, or 255 data unless you are loading maximum pressure loads.

rcmodel