Jacketed Data For Cast Bullets?

[DanLee]

Any reason not to use jacketed bullet data when loading identical weights of cast bullets? I am thinking primarily of medium velocity cartridges such as .30-30, .35 Remington, .358 Winchester, and .35 Whelen.

[stubshaft]

Other than driving them too fast and causing leading, there are no problems.

[ddixie884]

Be careful of seating depth. As long as internal capacity is not reduced you should be OK. Start low and work up..........

[Wilderness]

My experience with 170 gn .30-30s has been that cast gas check bullets chronograph about 100 fps faster than published data for the same powder charge with the same weight of jacketed bullet.

Likewise with published data, e.g. Lyman #46, 170 gn Speer + 35 gns 748 = velocity 2116 fps & pressure 30,100; 170 gn #311041 with same load does 2270 fps and 32,900 fps.

The extra pressure would suggest that cast bullets may be sealing better than jacketed - so the extra velocity is not a free ride.

[243winxb]

Having loaded the 30-30 with cast, 173 gr GC , i would never use the jacketed bullet powder charge.

Google Hodgdon reduced loads. https://www.hodgdonreloading.com/low-recoil-loads Then work up to the velocity you want, without problems.

[charlie b]

I start with Lyman's Cast Bullet data. If I have a bullet in between I extrapolate.

[quilbilly]

In most of my rifle cartridges, the velocity gain by using CB's over JB's is usually about 100-150 fps (Your results may be different) using the same load and powder. My theory is that standard lubed lead boolits are more "slippery" reducing friction inside the barrel. That gain in velocity doesn't necessarily mean better results, however. My rifles have rarely liked the same powder for both.

[Wilderness]

In most of my rifle cartridges, the velocity gain by using CB's over JB's is usually about 100-150 fps (Your results may be different) using the same load and powder. My theory is that standard lubed lead boolits are more "slippery" reducing friction inside the barrel. That gain in velocity doesn't necessarily mean better results, however. My rifles have rarely liked the same powder for both.

Quilbilly - note the Lyman data shows increased PRESSURE as well as increased VELOCITY for cast versus jacketed. Cast may indeed be more slippery but they're also generating more pressure, suggesting a better seal perhaps. Both factors could be at work. The extra pressure would work against CB results.

Most powders in .30-30 (and .308) show about 50 fps change for a grain of powder, so a 100 -150 fps velocity difference cast versus jacketed suggests the jacketed load needs to be cut 2-3 gns for use with cast for same velocity, and probably same pressure (then cut a bit more to achieve cast compatible pressures).

[Texas by God]

I have done it with several cartridges like 30-30,30-40, 8mm,& .358 Win. First, I look for a heavy jacketed bullet starting load with around 2000fps velocity, then I substitute a lighter weight cast bullet to ease the pressure a bit. I see no point of loading over 2000 fps for cast bullets and usually go slower than that.


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[GregLaROCHE]

Using staring loads and working up has worked for me using hard lead and gas checks. Over here there are not that many different powders available. You have to work with the data that’s available.

[Larry Gibson]

I've been actually pressure testing to determine whether cast or jacketed bullets of the same weight in a given cartridge with the same load give a higher pressure or even a higher velocity. The testing has been with both handgun and rifle cartridges.

I have not determined a definitive answer any better than "it depends". I've not even yet determined what it edpends on. Sometimes the pressure is higher with jacketed and sometimes with cast. The only way to know is to measure the pressure. However, most often but not always, a concurrent measurement of higher velocity means the pressure is higher.

Best stick with proven data and always work up the load as all manuals suggest.

[black mamba]

I don't have a way to measure pressure as Larry does, but in studying posted data, it seems that when using hard-cast gas-checked bullets, the pressure and velocity is closer to similar weight and bearing surface jacketed bullets. Softer cast bullets that "slug up" and snuggly fill the grooves seem to create slightly higher pressures, but their "slipperyness" also adds velocity. Many handgun loads show 50-75 fps higher velocity for cast over jacketed, even at the same pressures.

[charlie b]

This same type discussion has gone on about plated bullets and powder coated as well. Results seem to be as Larry has found. Sometimes one is the same as the other, sometimes not.

I start with Lyman's cast bullet data simply because in rifles I am using reduced loads most of the time. Lyman has that type of data for a lot of powders. The only problem is that there are so many newer powders it is hard to find data for them.

[243winxb]

I tried to compare data between cast and jacketed. See album photos of Manufactures loading data here.

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