bullet substitution in formulas


PDA






tkpinsc
March 4, 2010, 11:18 AM
I'm new to handloading. So far I'm loading 357 and 38 on my Lee 50th kit.

I've been searching for loads using Herco and cast bullets for the 357.

Is it ok to substitute a bullet of the same weight and type for another with the same powder charge and primer?

Example: Are 158gr cast swc, 158gr cast lead rn, 158gr cast lead fp, and 158gr copper washed (not jacketed) lead hp interchangeable in the printed formulas if I stay 10% or so under the maximum load?

If not, how does the bullet profile affect the powder charge?

If you enjoyed reading about "bullet substitution in formulas" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
jcwit
March 4, 2010, 11:30 AM
I sub jacketed bullet data using cast bullets every so often. But I load nowhere to max, usually somewhere in the middle to light side. I load for accuracy "which means nothing the way I shoot" and for mild recoil because of arthritis in my wrists and hands.

Really see no problem using jacketed data for cast bullets as the cast should not create as much pressure anyway.

rcmodel
March 4, 2010, 12:13 PM
Yes, No, maybe.

A 158 SWC, 158 RNFP, and a 158 RN all have different bearing surface lengths & seating depths.

A bullet with two or three grease grooves has less bearing surface and less friction then a bullet with only one.

A plated jacket 158 has higher bore friction then either because copper is not as slick as greased lead.

If you compare a 158 - 160 SWC & RN in Lyman #49, there is about a 0.2 grain reduction in Max load with the LRN in .38 Special.
Maybe as much as 1.5 grains in .357 Magnum.

Your best bet is to buy a Lyman #49 manual or Lyman cast bullet handbook, and match up the exact bullet type to the one you want to reload.

Or just stay in the middle with the data you have.

rc

Steve C
March 4, 2010, 01:05 PM
You can substitute same type and weight or slightly lower weight bullets safely HOWEVER the loads need to be worked up. That means you use the start load, either published or the calculated 10% reduction from maximum and work up looking for pressure signs and best accuracy.

When talking about the .357 mag and the .38 spl there are 2 distinct pressure levels. The .357 magnum is at high enough pressure that you can get into trouble if you load at or near maximum so its important to work the load up from a start level.

The .38 spl has a standard and a +P pressure loading level. The pressures of the .38 spl are low enough that you can exceed allowable pressure standards without observing any of the typical overpressure signs like hard extraction, flattened or cratered primers that you would in the high pressure magnum. Typically load development in the .38 spl is about accuracy or velocity and not about watching for pressure signs.

With equal loads a lead bullet will have higher velocity than a jacketed bullet of the same weight. This is mainly due to the less resistance of lead in the bore and some of it can be a better bullet to bore gas seal. With hard lead bullets load data is very similar to jacketed bullet data. After a cursory analysis of lead/jacketed data and my own chronograph results using both I make it a general rule of thumb to reduce jacketed bullet data by 20% below maximum for a lead bullet start load and consider the -10% from max jacketed bullet "start" load as maximum for lead.

With lead there are many issues related to size and fit in the bore and hardness of the bullet alloy. Push a lead bullet too fast and you get leading at the muzzle. Keep soft bullets under 1K fps. Load a hard bullet too light and you get leading at the other end. It takes some experimenting to get the right load and then change manufacturer with different bullet alloy or hardness and you may have to do it all over again.

tkpinsc
March 4, 2010, 01:25 PM
I mostly load 148gr hbwc for the 38 with 2.9 or 3.0 bullseye, and I've found plenty of other 38 load formulas for the other bullets I have on hand. I'm shooting these in a 642 and a 640. I'm using factory Speer gdhp Short barrel 38+p for carry ammo in these two snubbies.

I just got a 3screw Blackhawk 357 6.5" that the 357 loads are for. Not trying to reach maximum looking for around 1000 to 1200fps to control leading and be accurate at the range. The interest in Herco is I bought a pound before I knew what I know now, and the few loads I'm finding don't match the cast bullets I have on hand.

jcwit
March 4, 2010, 05:45 PM
Perusing the Lee Reloading Manual they give a load for a 158 gr. lead bullet "no shape given" using HERCO 7.2 gr for start with 7.9 gr. max. They also go all the way to a 200 gr. lead "again no further info" with HERCO starting load of 5.5 gr with a max of 6.1 gr.

ranger335v
March 4, 2010, 07:37 PM
"Is it ok to substitute a bullet of the same weight and type for another with the same powder charge and primer?"

I do, and have for 45 years. In fact, when I started, much of our reloading data didn't specify anything but bullet weight.

Jesse Heywood
March 4, 2010, 09:08 PM
Lee's Reloading Manual has most of one page for the 148 WC IN 357 magnum. First one is for Herco.
Herco 6.1 gr, 1386 fps, 6.7 gr, 1510 fps, 33,900 PSI.

That gives a BHN of 24 at 33,900 psi which means that without a gas check you will lead the barrel.

helg
March 4, 2010, 09:31 PM
According to Quickload program bullets of the same caliber and weight may differ in bullet length (WC is shorter than TCN of the same weight), OAL (bullets with short ogive are seated to shorter OAL), and material (lead bullets experience less bore tension than jacketed). All the above affects results of internal ballistic calculations. External ballistics adds ballistic coefficient to the game.

357/38 rounds are not that short as 9mm/40/45, and the length factors should not affect the ballistics too much. I would safely assume that standard recommendation to back by 10% and work up should work fine with any recipe on 357/38 for different bullet of the same weight.

If you enjoyed reading about "bullet substitution in formulas" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!