Using jacketed data for cast

[sse]

As a basic rule of thumb, I have always felt that you could use jacketed load data for cast boolits and be safe.
I am not saying you would want to, but that you could. If load data is not available for the cast load, then you can at least start with jacketed data to give you an idea of where you want to go. Just not the other way around. Am I correct in this idea?

[Winger Ed.]

Sort of.
It would be safe since cast won't develop the pressures of jacketed bullets.
However; your accuracy will probably be in the toilet.
And I'd count on some major barrel leading too.

Look at some random pages in the Lyman cast book, and any listed data for jacketed.
There's good reasons why the powders and charges are so different for the same bullet/boolit weights.

Rather than spending your time & efforts re-inventing the wheel:
You're ahead of the game using cast data for cast loads.
If for no other reason than they usually use less powder, and have already been researched and developed.

[ShooterAZ]

You can generally "extrapolate" cast loads for handgun cartridges using jacketed data, but I personally wouldn't recommend using jacketed data in cast for rifle calibers. Some might work, others will give terrible accuracy.

[wv109323]

For some rifles, no. I don't think you could obtain the velocity with accuracy with most bottleneck rifle cartridges. Safe yes but barrel leading, especially with a compensator or silencer may get dangerous.
For pistols ,the cast bullet bore fit and hardness would need to be ideal.
Powder burn rate and selection may vary as you increase velocity.

[P Flados]

As far as expected chamber pressure, cast vs. jacketed is probably less significant than seating depth.

Seating depth can be difficult to determine for published load data unless you know the length of the bullet.

I have seen experimental data that seemed to indicate that pressures with cast can be higher or lower depending on the situation.

Any time you are not using the exact bullet listed in published load you are increasing the uncertainty for resulting pressure. The more difference in bullet (shape, material, etc) the larger the uncertainty.

I like to use all available published load data and Quickload together to estimate a maximum charge. I also tend to avoid putting much faith in reading "pressure signs" unless the rating for the round is over 30 ksi for pistol and 50 ksi for rifle.

[AlaskaMike]

For handgun cartridges I've never had any issues, leading or otherwise, using jacketed load data with cast bullets. This includes plain base (non-gascheck) bullets in a .454 Casull Rossi 92 carbine with 50k+ psi loads.

For bottleneck rifle cartridges, things become very different very quickly. Any time I've tried to push a cast bullet over 2200 or 2300 fps, things started to get much more complicated.

[rintinglen]

For rifles, as a general rule, no. 40,000 to 65,000 psi loads are pretty sure path to a leaded barrel and miserable accuracy.

For pistols and revolvers, especially non-magnum guns, you can almost always take a starting load for an equal weight bullet and use it with your cast safely. The one caveat is that such loads may be too light and not function well in your autoloader. Now there are some exceptions, rifle caliber hand guns, and the like, but as long as you don't start at the max, you can safely use that jacketed data.

[quilbilly]

Early on some years back, one of the things I noticed when comparing LLA lubed rifle CB's with the same load in jacketed of similar weight is that the slippery CB's would be often be 150 fps faster. I quickly reduced the loads for CB's and since accuracy was much better at lower velocities for CB's, I would start at about 20% below factory charges. What was said above about autoloaders above has been definitely true for me. My accuracy CB loads in a 223 are 400 fps lower than will function my semi-auto.

[Martin Luber]

Data for iacketed in a pistol would be too hot for lead. Compare them in a load data book.

Lead data used with jacketed pistol loads would be too light

[Wilderness]

As a basic rule of thumb, I have always felt that you could use jacketed load data for cast boolits and be safe.
I am not saying you would want to, but that you could. If load data is not available for the cast load, then you can at least start with jacketed data to give you an idea of where you want to go. Just not the other way around. Am I correct in this idea?

My experience with cast in .30-30 is that I expect MORE velocity from cast than from jacketed with the same load.

Example: LeverEvolution powder, 36.3 gns with Sierra 170 gn bullet in my rifle gets 2300 fps (chronograph). My cast 175 gns bullets get 2300 fps with just 34 gns LVR.

Nor is it a free ride. Velocity requires pressure, so the extra velocity from cast is probably a function of a more efficient gas seal.

Example again, this time from Lyman #46 with .30-30: Hornady 170 gn with 35.0 gns #748 gets 2116 fps with 30,100 C.U.P. Cast #31141 with same load gets 2270 fps and 32,900 C.U.P.

My rule of thumb with .30-30 is to expect an extra 100 fps from a cast bullet using jacketed bullet data. That is about 2 grains worth of velocity (and pressure).

A few months ago this same question was asked. Larry Gibson's reply indicated a more diverse relationship than my limited .30-30 experience.

https://castboolits.gunloads.com/showthread.php?440346-more-or-less-powder-when-going-from-jacketed-to-cast&highlight=larry+gibson

Bottom line: Do not expect same results from same load with cast and jacketed.

[P Flados]

For rifles, as a general rule, no. 40,000 to 65,000 psi loads are pretty sure path to a leaded barrel and miserable accuracy.

My experience has been that there can be a definite velocity threshold for a given gun but I have never run into what looked like a pressure threshold. And with my powder coated boolits, it has been a loss of accuracy, not onset of leading. Yes I have had leading with PC, but it was not because I pushed too hard.

I have several rifles and a good number of TC contender bottle neck rounds that I have pushed pretty hard. Most of these have been rounds based on 223 brass. I have probably run these up to the mid 50,000s for pressure with no problems.

[243winxb]

Compare handgun data here https://www.thehighroad.org/index.php?media/albums/load-data-lead-vs-jacketed-bullets.265/

Many are MAXIMUM, reduce for a starting load. Some old data, check all current data.

[sse]

Thanks guys. I needed to check before passing this along to others.

[mdi]

My first reaction is "Why?" Cast bullet load data is as readily available as J bullets. I haven't run into a cast bullet handload that I could not find cast bullet data. (we're communicating with computers which are tools to reach the world's largest library and with a few taps on a keyboard will locate info on anything imaginable to man)...

[schutzen-jager]

the first edition + some later ones published by Lee made no distinction between cast + jacketed bullets at all - i still use some of that data without problems -

[stubshaft]

I use the lower end of J word loads for starting loads in my cast bullets if no other load data is available.

[P Flados]

My first reaction is "Why?" Cast bullet load data is as readily available as J bullets. I haven't run into a cast bullet handload that I could not find cast bullet data. (we're communicating with computers which are tools to reach the world's largest library and with a few taps on a keyboard will locate info on anything imaginable to man)...

For popular cartridges. looking for cast specific load data is one thing.

There are a lot of cartridges with very limited pressure tested load data of any kind.

I have a number of guns where I have been collecting data for years. For some, the total number of available published loads is for less than a dozen different bullets and all of them are jacketed.

Also realize that most loads assembled more than a decade ago was done with the standard assumption that cast bullets were very limited in how hard they could be pushed.

With improved understanding of "fit is king" and with powder coating, people may want to try cast bullets at performance levels well above what was considered reasonable in the past. I have done this for a number of rounds and achieved full power or near full power performance with zero available cast specific load data.

[charlie b]

Just use the book data same as you would for jacketed. Start low and work up. From what I have seen two different jacketed bullets vary as much as jacketed vs cast.

[Harter66]

Use the slowest available powder with heavy bullets and it works ok .
But the too slow to get hurt model doesn't always convert well .

Be sure you're using data for what your bullets actually weigh not what they are supposed to weigh .
I have a 405 gr 458193 that pours at 415 gr .
A 462-420 MP that casts .460-417.
A 27-130 that drops 141 .
A 7mm- 168 that just dropped at 179 gr.
My 2nd 452-255 that casts 454-265
And a 45-500 that drops 530 gr .

I didn't get any signs in the 6.8SPC bolt gun until the primer was gone and the pocket was .215 dia using 130 gr data about 1.7 under max .