Reloading manual data differrences

[lrrifleman]

Greetings! I realize that reloading manuals are the holy grail of handloaders, and I have no challenges against them. However, I do have a question.

I know that seating depths can have a significant effect on chamber pressure. Theoretically, bullets of similar weight and profile MAY have similar bearing surfaces.

In my quest to develop a 380 load for my G42, and build a 9mm load with my available powders, I am noticing that Sierra is seating comparable bullets 0.010"-0.030" deeper than Hornady. I am finding that if I lean more towards the top end loads in the Sierra manual for the 380, I am getting a greater degree of reliable function in the G42.

My question is: how much of a difference is this slight difference in seating depth going to impact my loads?

As always, thanks in advance for your help!

 

[BillBro]

Which bullet are you using and which bullet are you comparing it to?

Oh wait, you're using a hornady bullet? The XTP?

 

[lrrifleman]

BillBro,

For the 380, I'm looking at the data for the Sierra 90gr JHP V Crown vs the Hornady 90gr XTP.

For the 9mm, I am comparing the Sierra 124gr JHP to the Hornady 124gr XTP, with the intention of loading the Precision Delta 124gr JHP.

 

[Nevada Ed]

You have two main OAL lengths to account for.

OAL of your chamber........... &
OAL that lets you ammo work in your magazine.

Then you can fine tune these to see what your pistol likes.

Most JHP bullets have a cannelure, to set the OAL at.
Ball ammo is usually set for Full loads that will function in all weapons.....
or longer OAL that has slower powders (flake) used for slower tartet loads.

It might not come down to OAL but a certain powder that works in your weapon.

Ah.......
the joys of owning a "New" pistol
or working with a new, never used bullet.

Have fun.

 

[Nevada Ed]

Some 380 ACP 90 gr JHP have a OAL of +/- .935"

I saw a 100 gr HDY FMJ listed at a OAL of .980".

If you bullets are of a "HAP" smooth wall design you might set your OAL
to the type of loads that you will be shooting.

For full power loads I would try .935" if the manual ok's it......

for target work, I like the longest OAL to get the bullet closer to the lands
if possible, if the bullet has good support......
and if using a ball powder like Unique.

Later.

 

[lrrifleman]

@ respondents:

I just spoke with Sierra, and was given some insight. For their 90gr V Crown, they recommended either CFE Pistol or Silhouette, since they felt these powders have a wider loading range. When questioned, they felt seating depth variations (of a few thousandths) would have negligible effect on pressure. The above, only for locked breech pistols, not blowback pistols.

 

[WR Moore]

About your question on overall length/seating depth.......the differences between bullet brands may be due to the ogive forward of the bearing surface of the bullet. Ogive being the curve of the bullet shape. The few XTPs I've seen have a shape similar to a round nose bullet, the Sierra's I use are more of a truncated cone shape. Therefore, the Sierra would be seated to a shorter OAL.

 

[Nevada Ed]

@ respondents:

I just spoke with Sierra, and was given some insight. For their 90gr V Crown, they recommended either CFE Pistol or Silhouette, since they felt these powders have a wider loading range. When questioned, they felt seating depth variations (of a few thousandths) would have negligible effect on pressure. The above, only for locked breech pistols, not blowback pistols.

If you don't have any Sihouette powder, I have found out in 9mm
that a second powder that is a kissing cousin that can work is.......

BE-86.