lower velocity interval

[tipiguy]

I am reloading for a 358jdj.  The barrel is a 17" tube so I expected a little better velocity than was published.  I am using AA2520.  The max load is 53 grains with a 225 grain bullet.
 
I started with 47 grains and the velocity registered 2150fps.  With 47.5 grainf velocity rose to 2210.  48 grains got me up to 2240.  48.5 got me up to 2255.  49 grains got me up to 2260. 
 
I am new to using a chronometer but is it normal for the velocity inverval between .5 grains to reduce as the load increases?  There were no signs of excessive pressure but I do not think I have any need for more velocity.  Could there be something wrong with the chrono?  Could another .5 grains result in a larger interval of velocity?
 
This all just seemed a little strange to me.
 
Thanks for the help.
 
tipiguy
 
 
 

[us920669]

It would if the barrel is too short to permit all the powder to burn.  That's just a hunch, I've had no experience with that cartridge or powder.

[Graybeard]

Yes it's normal and yes your barrel is a little slow. You don't say which 225 grain bullet you are using and it definitely does matter.

When I was loading for the .358 JDJ in a .35 Remington Contender 14" barrel rechambered by SSK Industries I used the Nolser 225 PT, Nolser 225 BT and Sierra 225 GK. Using everything else the same I got as much as a 100 fps spread between those three bullets. I was able to reach 2300 fps from my barrel using the 225 BT with one grain less AA2520 than JD's data said was max. Since his data said I should expect 2250 fps at max load I felt that was plenty so stopped there.

A few more fps isn't gonna make any difference at all so find what is most accurate in your barrel and live with it and don't go chasing a few fps one way or another. The .358 JDJ is a hammer and doesn't need more velocity than you are getting. Sierra says their 225 GK will not expand at those velocities and my testing confirmed that. Use the Nosler 225 BT or AB and take anything that gives best accuracy in the 2250 fps or so range and expect whatever you hit correctly to die real fast.