.40 cal questions/Bullet type questions

[Keeperfaith]

Hello,

I have 155 grain sierra FMJ bullets.

My Lymans 49th only shows data for the 155 grain Jacketed Silvertip.

Is this data compatible with my FMJ's or will I have to get specific data for FMJ 155 grain bullets?

Im still new to reloading so please help me out here.

So my second question:

Is the data in the manuals only applicable to the specific type of bullet listed (ie: FMJ, JHP etc...)?

Or is that just the bullet the testors used and I am free to use any type of bullet (FMJ/JHP/TMJ) as long as the grains are the same as the data they specify?


Thanks again

Steve

 

[1SOW]

The bullet weight and nose shape needs to be the same to use the same oal and loads listed in the manual.
EG: a 155gr Sierra FMJ (RN) vs a 155gr Zero FMJ (RN), the book oal and load data will work for either bullet as long as you work UP from the low end of the data..

If the nose shape changes, say a JHP vs an FMJ, then the OAL will be different. The JHP may be .60" long and the FMJ may be .75" long. You can't use the same oal for both.

The 'real issue' is "seating depth and pressure". With Two bullets of the same weight and type (jacketted, plated, lead), but different nose-shapes, IF they are loaded to the same seating depth, you can use one's load data to work up a load for the other. You can't use the same oal

If you know the bullet's length you can compute the seating depth from the data's oal. Then with a bullet of the same "weight" but a different nose shape, you can seat it to the same depth in the case and use "that" new oal with the listed bullets charge data.

example: 9mm load data= 124gr FMJ, oal 1.150. This bullet is .60" long.
Case length = .750" Bullet length= .60" Seating depth = OAL- (bullet length +case length) Seating Depth= 1.150" - (.60" + .75") Seating depth = .015"
New Bullet is 9mm 124gr JHP. This bullet is the same weight and also jacketed. 124 JHP Bullet length = .55"
To seat it to the same depth in the case, the oal will need to be .004" "shorter than the 124FMJ data, because the bullet is shorter. So the new bullet's oal will be 1.100" and can use the other bullets charge data to work up the load. Seating depth = .015" @ 1.10" OAL


Just be sure to start the load at the low end of the data and work up. Sounds complicated, but it's not. The same seating depth with a bullet of the same weight and type will give very close to the same "pressure"

I hope this makes sense.

 

[ArchAngelCD]

ALSO, do not mix lead bullet data and jacketed bullet data. they are not compatible. You usually need less powder to achieve the same velocity with a lead bullet than a FMJ or JHP bullet.

As long as the bullet composition is the same along with the same weight and profile, the load data is also compatible.

 

[Keeperfaith]

Makes sense, but so far the OAL for my 41 magnum loads were actually shorter than the manuals OAL. Not significantly shorter but the cannalure fit perfectly into the top of the mouth. I crimped it and they shot perfect.

Can anyone give me a xerox or pic of a Relaoding manuals data for the .40 S&W. Specifically for 155 grain FMJ bullets? I have the Lyman's 49th reloading manual FYI.

Thanks all,
Steve