Need someone to check my math . . .

R

Rangerrich99

New member
Okay, here's the deal: I bought some Alliant 300 MP powder to try out with some .357 mag 158 grain hardcast lead bullets. Unfortunately, Alliant doesn't have any data for lead/plated bullets with this powder. Now, as I understand it, what I need to do is first reduce the max load they give for my bullet weight by 10% to find my starting load weight for the jacketed bullet listed and the max load weight for a lead bullet. Then, because I'm using lead bullets, I need to further reduce this number by 10% to find the starting load charge weight for a lead/plated bullet. So, that should go something like this:

Max load weight: 18.6gr
18.6gr x 0.1=1.86gr
18.6-1.86=16.74gr, max powder charge weight for lead/plated bullet

16.74 x 0.1=1.674
16.74-1.674=15.066, or 15.1gr; starting charge weight for a lead bullet.

Did I figure this right? Or should I subtract a full 20% (3.72gr) from the max charge weight listed to find my starting charge weight for a lead bullet?

Thanks for your replies in advance.

P.S. Sorry, I got my bullets mixed up, these numbers are for 158 grain .357 mag bullets, not 240 grain.
 
Your math looks right. However I have no idea if you logic is sound. What cartridge are you loading for.

Using 10% and 10% you're at 15.1 and using 20% you're at 14.9.... Probably not a huge deal.
 
Loading for .357 mag: Missouri Bullet Co. .358 cal. 158 grain SWC Keith style, Brinell rating 18.

I'll be launching these bullets from a Ruger GP-141.
 
I see you added the cartridge while I was typing. Hopefully someone can give guidance. I'm not very familiar with that powder.
 
Using a slow powder like that doesn't always work out so simply. The lead bullet may offering enough less engraving resistance in the forcing cone that you end up using the same amount of powder a jacketed bullet would, just to keep the pressure high enough for reliable ignition. Loading a slow powder down too far can result in it extinguishing during firing, leaving a bullet stuck in the barrel. That warning for 296/H110 has been around a long time, but as a Hodgdon tech told me long ago, it's not the only powder on the planet that can do that.

I also note the bullets in the on-line data are all Speer Gold Dots. These have plated jackets that are softer than a standard cup-and-core bullet jackets. A Speer tech told me they sometimes have Gold Dot data that does not overlap jacketed bullet data for the same powder, so they are a somewhat difficult information starting point. I would also read this.

Since 300-MP powder is still on the reloading community's learning curve, I would give Alliant a buzz and ask for an opinion ((800) 379-1732). My sense is that reducing by 10% twice¹ is going to knock pressure down over 40% and that's probably too much for reliable ignition and burn. You would want to check after every shot that low to be sure a bullet wasn't stuck in the bore. You could try a compromise like -15% (multiply the maximum by 0.85) which is Western Powder's general recommendation for handgun starting loads, but be very careful to check for stuck bullets after each shot. If you fire the next round into a stuck bullet, that's usually the end of the gun, not to mention the potential to be the end of you, if a gun fragment heads the wrong way.


¹ A simpler way to calculate a 10% reduction twice is to multiply the maximum by 0.81, which is 0.9². 0.9 gives you 90% of something, or -10% of the maximum. Multiplying by 0.9 and then by 0.9 again is the same as multiplying by 0.9², or 0.81. Multiplying the maximum by 0.85 gives you 85% of maximum, or -15%.
 
It's often very tempting to get creative with reloading, especially when components get scarce.
But if the powder manufacturer doesn't have info on a particular load in their data, maybe there's a good reason.
 
That can be true. It can also be true that because testing is expensive and they don't happen to make the type of bullet in question, that they just never try it and, for liability reasons, they won't recommend something they haven't tested.

I know at Beartooth Bullets, which makes a number of extra heavy-for-caliber BHN 21 cast bullets, they have a number of 296/H110 loads that fill the case completely or are even a little compressed under their cast bullets. It turns out that as the powder space gets smaller (think, 300 grain bullet in a 44 mag case, for example) the peak pressure from a same % fill gets smaller because the expansion ratio has increased.
 
Loading for .357 mag: Missouri Bullet Co. .358 cal. 158 grain SWC Keith style, Brinell rating 18.

I'll be launching these bullets from a Ruger GP-141.
Click to expand...

Do NOT reduce by 20%. You are headed towards squib city.

I load those bullets in 357 to jacketed max with 296/110 (17gr) in my GP100 and those bullets handle it just fine.

Use Alliant's 16.7 starting load.
 
No doubt the recommendations from Beartooth (and all the other component makers) were arrived at by thorough testing in ways unavailable to us mere amateurs.
We have to trust someone about reloading data, while still keeping our brains on full alert.
Hopefully the folks making the components are them.
Kind of like trusting the fastener torque settings in service manuals.
 
CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

This is my history of handloading:

8x57mm 1905 Mauser necked up the 1889 7x57 case to 8mm, put powder in it the case until the head failed, back off a tiny safety margin and 150 gr 2900 fps is still the practical limit 111 years later.

270 win 1925 Winchester necked down a 30-06 [with Mauser case head] to fit a Chinese .277" bullet, put powder in the case the until the case head failed, backed off a tiny safety margin, and 130 gr 3150 fps is still the practical limit 91 years later.

357 mag 1934 Elmer Kieth [trying to help the FBI kill gangsters wearing bulletproof vests] put so much powder in a 38 special cartridge, that the cases were stuck in the cylinder. He backed off a tiny safety margin and 82 years later 158 gr 1400 fps is still the practical limit with finger tip extraction.

7mmRemMag 1962 Remington wanted a good April fool's joke. They took a 300 win mag case and shortened it from 2.62" to 2.5" for no good reason. They necked it down to 7mm. They shortened the OAL from 3.34" to 3.29" for no good reason[3.34" is what the 300WM and 30-06 and everything else uses] . Then they reduced the pressure from 64 kpsi in the 300WM to 61 kpsi for no good reason [crazy, given the belted magnum case head is stronger than the 270 case head registered at 65 kpsi for the previous 37 years.] They designed the Rem 700 at the same time. It was just like any other rifle, it takes a 3.34" cartridge in the magazine. "That cartridge and rifle will NEVER sell. Ha Ha ha." [evil laugh at Remington] 54 years later the Rem 700 and the 7mmRM are not quite dead yet.
 
My first reloads were 125g TC hardcast over 300-MP in .357.
I can not for the life of me find where I found the recipe, it's been three years(or around there) since I worked up to that load.
For my 18" Rossi R92 I'm using 17.7 or 18.3 grains(depending on who I'm going shooting with). Again, I don't know if these loads are safe. I can't find where I originally found this recipe but those loads have proven accurate, reliable(over 1000 rounds loaded and all have fired), and have no pressure signs on my gun, the cases or primers(I know those mainly subjective and precise). In nickel plated and brass, the cases eject just fine.
I wouldn't recommend this load because it was a SUPER new reloader that worked it up from where ever I found it.

There is cast data out there for this powder...I just can't find it anymore, if you do please share the location because I have some 158g that I want to use since I have 5lbs of 300-mp.
 
Alliant powders... good and bad.

The GOOD: easy to find, seemingly in stock most anywhere that typically sells powder, the price is decent and options for 4 & 8lb containers about. Also, their ballisticians typically answer e-mails fairly quickly.

The BAD: their published load data sucks, it is the WORST of all the known powder brands. Hodgdon (and IMR/Winchester) has them whupped, Western (and Accurate/Ramshot) has them whupped, Vihtavuori has them whupped, and it's not close.

Alliant's online and currently published load data is almost all based 100% on Speer bullets and no others. It's absolutely LAME and more than annoying. For long established Alliant powders (and former Hercules powders), I refer often to my 2005 printed Alliant guide... which is the very last printed guide before Alliant really dumbed down all their data and made it all Speer bullet specific. So for the most part, I simply refer to my 2005 Alliant guide when I need some more ideas and professional published data for an Alliant powder.

This, of course, does not work for Power Pro 300-MP which was not on the market in 2005. This puts 300-MP in an annoying place... a seemingly useful powder with precious little published load data behind it. :mad:

Hornady's current manual has a little bit of 300-MP published data in it... but nothing for a cast lead bullet in .357 Mag with 300-MP.
 
Thanks for all the replies.

Okay, so it seems my options are to wait until Alliant does more testing (not holding my breath on that), or to do as TimSr says and start at 16.7 grains (Alliant's starting load for a jacketed bullet). So, I'm thinking I'll just load 5 rounds at 16.7 grains, load/shoot one at a time and inspect each fired case after firing. If there aren't any signs of over-pressure and IF for some reason I want to load more powder I'll step up 5 more cases by 0.3 grains, and so on.

Personally, I don't think I'll step up much from 16.7 grains, as at a certain point I'll probably run up against that wall of too much recoil for my purposes.

Anyone see an obvious logic flaw with this plan?
 
Rangerrich, there is no magic formula used to compute starting loads for lead bullets from starting loads for jacketed. Cast bullets can be finicky creatures, but they're really not that tricky most of the time. First off, in almost 95% of cases, the starting load for a jacketed bullet will be safe (safe as in your gun won't blow up) for a lead projectile of like weight. This assumes that the lead projectile isn't seated any deeper than the jacketed one, and it passes the plunk test. These are assumptions, and that is why I say 95% of the time. So... Do your homework before making these assumptions. In most cases, a lead bullet will display lower pressure than a jacketed one, with all other variables equal.

The main purpose in lowering cast data is to prevent leading. There is no simple equation to predict leading. That takes experience. Velocity, pressure, and the burn speed of the powder are all contributors to leading... But to varying degrees. Using starting loads for Mid to heavy for caliber bullets mitigate leading by keeping both pressure and velocity under control. Just ensure that the loaded round passes the plunk test and has equal case capacity to the MOAL of the round that you are using data for. Then check for lead fouling and ensure it isn't an issue (extreme leading can lead to build up in the barrel and pressure spikes.

I think you will be OK with trying the standard starting load for these cast bullets. Just make sure you aren't having to seat deeper, and in turn reducing case capacity. And check for signs of pressure
 
Thanks guys. This experiment may have to wait until after the 4th, but i feel a little better about the whole thing after getting some feedback from all of you. I'll post my results when I get a chance.
 
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