Formula for cast vs factory bullets on powder limits

[inline50]

Is there a formula to determine the powder limits for a cast bullet when you only have factory bullet data.
Example: say you have data for a 200gr. factory bullet only, but you are reloading a 200gr. cast. Limits
are, say 5.0 start and 6.0 max. for (X) powder. Can you apply the limit stated and use the same information
for you cast bullet or is there a safe reduction percentage you must factor in? I would assume that cast
would be somewhat less that the limits given for a factory. I use straight W.W. for my bullets so hardness
may also factor in.

[RobS]

There is no hard and fast rule here. No load data is perfectly interchangeable as the firearm tested is not the same firearm in your hand. There is a reason why there is a minimum and maximum load and with that in mind load at minimum and work up with your similar components. Without pressure testing equipment the next bet is a chronograph and loading to velocities of know powders and that will get you in the ball park of pressure associated with those velocities. Generally speaking lead boolits generate less resistance vs jacketed so there in less velocity/less presures if the powder charges do not change between the two different projectiles.

[blikseme300]

In my limited experience a simple formula won't work. Slower burning powder is usually needed and your rifle or pistol along with the target will tell you what works. Cast Boolits are unto themselves and they don't mimic j-words when shot.

[Scharfschuetze]

I agree that an extropolation between cast and jacketed might not lend itself to a formula. Pistol and revolver loads should be similar for a given weight, but rifle loads in the larger cases will vary considerably.

There are a number of "on-line" loading sites that should give you an idea of good starting loads with cast bullets in most calibres.

Castpics comes to mind:

http://castpics.net/subsite2/LoadLookup/default.html

[engineer401]

Rules of thumb or simple equations made to address complicated situations only provide rough estimates of what may work. It is always best to buy or borrow a good cast bullet handbook to start with.

[41 mag fan]

RobS had it right. You can substitute cast for jacketed on load data. Cast boolits produce less pressure.

Start at the min and work up watching for any pressure signs.
Right now I'm using data from Lyman 47th edition, on half jacket bullets 300gr, for a 45-70.
I can load to the max with no problems or noticeable pressure signs.
Use data at your own risk, if leery find a cast boolit load data book.

[runfiverun]

in handgun calibers the powders are definately interchangeable and many loads are too.
in my 44 mag i use 19.3 grs 2400 powder under a 240gr cast boolit.
i use that same load with a 240 gr jaxketed bullet when i have them.
for my homeswaged jaxketed 250 gr bullets i prefer 9.3 grs of unique. [shrug] it just works that way.
in other cartridges i do and don't use the same loads [9mm i don't, 45 acp i do]

rifles are a yes and no answer.
generally i don't use a published jaxketed load under a cast boolit even when nearly the same velocity's are achieved.

[HangFireW8]

I use straight W.W. for my bullets so hardness may also factor in.

Probably not. The full range of lead alloy hardness is trivial compared to the hardness of a copper jacket.

[pdawg_shooter]

You can use jacketed for cast...if you paper patch.

[offshore44]

Pdawg_shooter, you just crack me up...got any relatives that were missionaries? :bigsmyl2:

[Larry Gibson]

No.

Larry Gibson

[44man]

It is why you work loads. Some cast will use more powder then jacketed but aother cant do it.
It is still good to start with jacketed loads for cast but you must work.

[45 2.1]

An almost full slate of opinions above. Confusion reigns as usual.

[Scharfschuetze]

An almost full slate of opinions above. Confusion reigns as usual.

Point well made.

Why guess when there are numerous sites and manuals available that cover the whole spectrum of loading for cast boolits. I agree that a conversation is nice and that it keeps the fora going without getting boring, but in the end why guess when you can be pretty sure with tested or proven data?

[44man]

The gamut of cast is huge. Most manuals ignore cast or just use a few boolits. It is hard for a beginner. Even the Lyman manual can't be taken at face value.
After all these years I still have a problem with a new caliber.

[Maven]

"Is there a formula to determine the powder limits for a cast bullet when you only have factory bullet data?"

inline50, Actually there IS such a formula. You can find it in "Modern Reloading (1996 Ed.)" by Richard Lee, pp. 91 - 93 (p. 94 if you want squib [sic] loads). I don't know whether Lee's formula was included in later editions of "Modern Reloading."

[capt.hollis]

My formula is that I have a brother in law whom stays drunk as hell , so I hand him the bullet and say here ya go , try this one . Then I step back ... :)

[inline50]

I guess i should have stated my problem a little differently. If a reloading manual only gives information for a specific jacketed bullet of (X) weight, then a cast bullet of the same weight using the same powder charge as the jacketed bullet should be safe as cast has less friction, therefore less pressure for the same load. Correct?

[pdawg_shooter]

Correct.

[Wayne Smith]

I guess i should have stated my problem a little differently. If a reloading manual only gives information for a specific jacketed bullet of (X) weight, then a cast bullet of the same weight using the same powder charge as the jacketed bullet should be safe as cast has less friction, therefore less pressure for the same load. Correct?

Correct. That fact provides a rule of thumb. Whenever you are using explosives distrust rules of thumb! None the less for revolver, and especially low pressure revolver cartridges, this works. It also works with the 30-30 and a very few other rifle cartridges.

[grouch]

Just a small caution for the rifle crowd - if you're using a soft alloy there may be a point where pressure causes "rivetting," which, theoretically at least could drastically raise pressure. This is speculation on my part, as I've never experienced it. If you start low and work up, the accuracy falls off well before there's dangerous pressure.
Grouch

[WILCO]

Is there a formula to determine the powder limits for a cast bullet when you only have factory bullet data.

Yes.

Simply find a FMJ load listing for the cast boolit weight and powder you wish to use.

Following the rules of powder selection and reduction, reduce the load to the appropriate velocity for rifle or pistol.

Richard Lee discusses this very thing in his book, Modern Reloading, 1st and 2nd editions.

As mentioned before, there is plenty of cast boolit load data available in the reloading manuals, but sometimes a specific combination isn't listed.

I once used some Accurate 2520 powder in 8x57mm. After searching over hill and dale, I finally found some FMJ load data. Using the LEE "Shooter" program, I safely assembled the required load data for use with cast boolits.

Soon after, I discovered some well known load data using shotgun powders and followed that path to even more success.

Know that the answers are out there, but it takes time, research and much effort.

This website is no substitute for a solid battery of reloading manuals and associated computer programs.

[WILCO]

Thought I'd share a picture:

[Larry Gibson]

Inline50

You talkin handgun or rifle cartridges or both?

Larry Gibson

[Larry Gibson]

Inline50

You talkin handgun or rifle cartridges or both?

Larry Gibson