Weight variations in my cast 45-70

I mixed up a batch of 50 lbs ww and 50 lbs pure. Added a few pounds of Linotype. Made new ingots and put in my Lee 4-20. Ladled some and bottom poured some. Air cooled and water quenched 50 of each. Weights this morning 24 hours later are from 388.2 to 389.7. Few culls at 387 but going back in the pot again. No defects I can visibly see. Temp at around 750 which seems to work best with the Noe mold. Are these variations enough to throw off accuracy? I would think weights to be more consistent. Good sprues. Good fill out. No frosty from running too hot. Let mold cool after each 10 casts or so. Weights are pretty much same whether ladled or bottom pour. Confused.

You are running about 1 1/2% variation, Not as bad as you think. Most say 1% variation on your weight that's 3.8 grns. In 45-70 I doubt you eill see the 1.5 grn variation. As a test load a 10 shot test group 5 rounds 388.2 and 5 rounds 389.7 and shoot from a solid rest, see what effect it has.

My 45 caliber bullets run in the 500-550 grn range and when Im up to temp and running my basic spread is .5 grns over a 4-5 hour run. These bullets have no visible flaws, good clean square bases and shoot very good out to 500yds.

I start the pot Propane fired with 100-125lbs capacity. Set the first 2 moulds on the warming shelf usually Old West brass moulds on cabin tree handles. this helps a lot with starting out.

Once up to temp I remove thermometer and flux well with wood chips and wax or paraffin. stiring so the ally is pushed thru the flux and the flux is worked thru the alloy good scraping sides and bottom to remove sticking crud. This helps keep the alloy clean and blended.

I then replace the thermometer and start casting I run 2 2 cavity moulds at a time. The first 10-12 drops from each mould go back in the pot with out a glance. Im now casting for "keeps" and these drops are very nice. Take care to not drop new bullets onto others in the tray. I use a paint roller pan lined with 5-7 hand / bar towels. I lay these flat in the pan and push bullets down every 10-12 drops when towel gets full posk up the 4 corners of the top towel and set aside leaving next in line ready to go. I use a small 8 ounce dead blow mallet to cut sprues, loosen bullets and seat blocks. I pour a little differently than most.I fill my rcbs ladle with lead from clos to the bottom of the pot in a swirl motion around the pot. I then fill the farthest cavity and then closest letting the whole ladle run of the edge back into the pot keeping bases and sprue molten a lot longer. I set this mould on the warming shelf and repeat with the second mould. Alternating as I cast. When closing the blocks I set them on the straight edge of the pan close then 2 loight taps on mould handle at blocks to make sure they are "seated" fully closed. Brooks gives this procedure on his sight. This "over pour" seems to really aide consitancy for me. When casting these big long heavy bullets a 10 or 20 lb pot empties way to fast hence my big pot. I have made 5 hour session of 600+ bullets with on 4-5 culls for visual defects.

Experiment with fluxing temps pours angled straight fast slow just a sprue and overfilled cadence you can get down into the 1/2 grn area also. It takes some practice and experience

I think the variation is about half a percent, not one and a half. I think the culls were 387, not 287. I'd cull them too if they were over a hundred grains light. I don't think your variation is going to have much, if anything on your accuracy. You have some variation in your scale to begin with. Probably not much, but some if you did a gage R&R study. I think you're OK with what you have. Big question is whether or not that bullet shoots in your gun.

I'm using a bottom pour and another 20 lb pot on a camp stove for ladling. I'm also using 2 molds but one is 45-70 2 cavity and other is a 4 cavity 45 colt. It takes a little longer for the big bullets to get set up in the mold verses the 45s. I pour a huge sprue and shake around a little as its poured. I don't put any sprues or add more lead until I'm left with about a 1/4 pot on the bottom pour or ladle won't dip in the cast pot. Like you I always just dump first 5-6 casts in my sprue pot because the mold is never hot enough to get wrinkles out if I don't. I'll have to shoot some from lowest to highest and see impact for sure. I know the topic is ongoing but most people I've watched post don't like a 1/2 grain deviation in there bullets. Im new and love casting but I want to make sure I'm getting it right. I'm not sure if 1.5 grain difference in this big bullet would be noticeable but I guess only shooting will tell for sure. It was getting ready to rain in a few hours and I'm curious if humidity plays any hand in weight differences.

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Originally Posted by NSB

I think the variation is about half a percent, not one and a half. I think the culls were 387, not 287. I'd cull them too if they were over a hundred grains light. I don't think your variation is going to have much, if anything on your accuracy. You have some variation in your scale to begin with. Probably not much, but some if you did a gage R&R study. I think you're OK with what you have. Big question is whether or not that bullet shoots in your gun.

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Typo on my part. Was supposed to be a 3 not a 2. The first batch I ran with lyman#2 give me around 2.5 inch groups at a 100 yards. They are casting .461 but I'm sizing to .459 and lubing with bac.

I shoot a lot of 405 and 500 grs. My alloy is pretty soft range scrap 10-12 BHN. Not sure what you’re ending up with hardness, but you should check and maybe you could save the linotype for faster boolits that need to be harder. I’ve found adding more tin makes the alloy flow better. Maybe that will lower the difference in weights.

Some people have their molds taped for thermocouples so they can maintain an exact mold temperature, I'm beginning to believe that this is the only way to get exact weights on all your casts IF you do everything else exactly the same and keep your pot above a 1/2 or 3/4 full with the same alloy.

I don't think you will notice a difference in accuracy between .387 and .3897.

Some say 3% weight variation does not affect accuracy for normal shooting.

You relieve your fears, you could try a side by side comparison 10 shots each with the same load of powder of the .387, .3882, .3897

I ladle pour . I have from a 460-543 NOE triple down to a Lee 457-340 and a Mountain Molds 453-350 via a single 458193 and a double M-P 462-420 . Typically with no visible defects for 120-+ bullets I end up with 2 piles of Lee's at 340 and 342 +-.5 , 1 pile of Mountain Molds of 349.7 to 351.1 , 3 piles of NOEs at 535,531 ,and 533 . The M-P could have 2 piles but at 416.9 and 417.5 I don't worry about it and the Lyman if it throws odd weights out by more than .5 over/under it's my fault . It does throw at 412 vs it's assignment at 405 . Typically out of 110+, 60+ , 35+ pours I draw 90-105 keepers by visual inspection . In these 3-5 gr would be nominal normal . But I get consistent .7 per cavity variation with the NOE hinge side cavity probably being my biggest offender at 4gr under on a 535 gr mould .

Through the yrs and more so in my casting I've weighed mountians of bullets , looked at deviations and 1.5% case weight makes about 10 times as much difference as 1.5% in bullet weight especially inside 200 yd .

We want perfection and we can get pretty close but honestly sprue cut timing and the exact pressure angle in little bullets probably causes more variation than mould variation .
Master your rhythm and mould temp control with that and you'll have cavity variation definition .

None of this is probably of any help but there might be a useful bite in there somewhere .

My mistake there 1/2%

I keep my 458s to within 1%...so for a 405gr, I have 4gr spread to play with. I do NOT notice a difference in accuracy at 1%. I also shoot 340grs...so I keep the spread to 3gr (less than 1%)...again...no noticeable difference in accuracy for me for hunting boolits. If you are shooting competition target...yeah...you might notice...but for a hunting boolit and you said you are getting 2.5" at 100yrds...you're fine.

redhawk

This is the effect of a 402 - 404grain weight span/variation in a 45-70 at 100 yards...

http://i60.tinypic.com/5evgoy.jpg

I have the Lee 457-405 RF and cast for the second time with it. I only cast about 50 boolits with it and they were beautiful.
I cast them with 50-50 coww/soww aircooled. When I weighed them, they weighed between 418gr and 421gr.
I am not sorting them out. I am going to work up a load for a cow elk hunt in Oct and call it good.
I’m betting that heavy of a boolit isn’t going to care about that little a variation.
Nor will the elk. :Fire::-D