Ok, so due to my lead mix my Lee 158 grain rnfp mold is dropping bullets that are almost 169 grains. Would I load these as 168-170 grain bullets or can I still use the 158 grain rnfp load data?

Sounds like you are using pure lead. Add 10 --12% hardener to get the weight down. If using a full charge back off 1 grain in.357 or 1/2 grain in 38. Lead is easier to go down the barrel. Most of the cheaper molds will not make a round bullet and you need a sizer unless you are just throwing lead.

Using wheel weights or at least I bought some lead that was supposed to be wheel weights that were cast into ingots. I loaded a few using 13.5 grains of 2400, very slight leading and seemed to have a little powder left behind. Just didn't know if I had to use load data from a 170 grain bullet or load for the bullet that the mold is supposed to drop.

Normally a heavier bullet has a longer bearing surface. Use 170 data to be on the safe side if a full charge load. A Lee or Lyman manual is your friend. Lee has more loading data high and low.

Several factors pertaining to bullets will affect performance, pressures, and safety.

Bullet weight is an important factor; essentially defining the weight or mass of the object to moved, accelerated, and expelled. The greater the weight the greater the pressure, assuming a fixed propellant charge.

Bullet shape is another factor. Bullets having longer bearing surfaces result in greater friction (resistance), thus higher pressures.

Bullet composition (cast, swaged, specific metal contents, solid, jacketed, etc) also affect resistance to movement and acceleration, thus resulting in different pressure levels.

Bullet diameter is another factor. While factory bullets (particularly jacketed or swaged) are standardized at 0.357" there can be some variation due to manufacturing tolerances, tool wear, or other factors. Cast bullets will also vary considerably, both because of mold dimensions as well as specific alloys in use having differing final results, and sizing dies are also subject to manufacturing tolerances, tool wear, and wear during use. Further, while bore and groove diameters are generally standardized (0.357" for .38 Spl and .357 Mag), there is actually quite a bit of variation among production firearms (commonly 0.354" to 0.360"). The fit of the bullet in use in relationship to the actual dimensions of the firearm in use may affect pressures and performance.

The 12-grain difference you have experienced (158-grain mold specification, 170-grain cast bullets) is a bit unusual, but not without precedent. I have a .358" 150-grain SWC mold that drops bullets at 146 grains with wheelweights (at .358") and at 142 grains with linotype (at .3585"), so differences in both weight and as-cast diameters can be expected with different bullet metals. The results you have reported might indicate a high lead content, but also might be due to a mold produced with a new "cherry" cutter that has not worn down in use.

Since you are dealing with a 170 grain result that would be the appropriate place to start in working up loads. If you have not yet slugged your bore you should do this to determine what other factors you need to take into consideration (1. lube the bore lightly, 2. take a lead slug or buckshot that requires a bit of force to start into the barrel. 3. tap the slug through the bore using a wooden dowel. 4. measure that slug to determine actual groove and bore diameters).

Lyman Reloading Handbook #46 provides several loads for the Lyman #358429, a long SWC weighing 168 grains in linotype metal:

Powder Start Max
Bullseye 2.8 4.2
Unique 3.8 5.0 (most potentially accurate load)
Blue Dot 5.5 7.3
231 3.0 4.6
HS-6 5.0 6.4

This should give you a reasonable starting point to begin working up a load. Consult all other available data sources, particularly the powder manufacturers' published data, before beginning. Beginning with the starting load you can evaluate results for any signs of excessive pressure (difficult extraction, micrometer measurements of case bodies and webs, primer appearance, etc), and work up in small increments to desired results without ever exceeding max recommended loads.

Have fun with it.

FYI - I have that same mold and I melted down wheel weights to get ingots. When I drop the bullets out of the mold, I drop into a bucket of water. I think the hardness of the bullets is in the range of 16 + or -. My bullets are weighing, on average, 161 grains. A few at 163 and a few at 159. That Lee mold makes beautiful bullets. Smoother than a baby's butt!! My last run of 400 bullets turned out 5 or 6 rejects due entirely to my pouring mistakes.

Also, water quenching will not increase the hardness of pure lead. For that the lead needs some Antimony, some Tin, and some Arsenic. Arsenic content less than 1%. I'm not sure that wheel weights made in the last 30 years have any arsenic content??

I've got moulds from NEI,RCBS,Lee,Saeco,Lyman and even a custom made mould.Most manufacturers will give the weight of the bullet with the equivalent of Lyman no2 mix.Since I cast softer than Lyman no 2(and no I don't have leading problems in my magnums),the moulds will drop heavier than announced weight.My moulds all drop heavier than announced wieght.

My Lyman SWC is announced at 158gr and drops at 166gr.I use 170gr load data and never had a problem(.357Mag full load H110).Have fun and play it safe!
Qc

I thank you you guys for the info, I loaded 50 of them as 170 grain 13.5 grains 2400 gonna test them out.