Pressure because of bullet shape?

[poon]

Hi shooters.
I was just wondering why the Vithavuori guide states two different loading data for 55 grain bullets a FMJBT and a FMJ ?.The max load of these two differs 1.6 grain! What data should I use for a Sierra Gameking/Blitzking boattail?
I have primer starting cratering with this load:
Brass: Lapua ,load;24.5 N133.primer Fed.BR Bullet :55 grain
Sierra Blitzking.
Could this be because of pressure?
Or a weak spring?
Poon

 

[abinok]

heres my 2cents...
if you are getting primer cratering with handloads, but not with factory ammo, its probably a bit warm. if it does with factory loads as well, its likley just a poorly fitted fining pin. The differance in the listed loads is due mostly to the one bullet having more bearing surface than the other. keep in mind that a 1.6gr differance in a 24.5gr load isn't very much. You will likley see that much variation from gun to gun.
Sierra shows 24.1gr as max for gas guns and 24.9gr for bolt guns with VV133.
Listen to what your gun is telling you, and don't start squeezing the saftey margin of your gun for another 50fps of velocity, even if it seems to shoot well.

 

[boomer]

There are more variables then the shape of the different bullets that affects the pressure curve. When you are working up loads and you can't find loading data for your bullet look to a similar bullet that has the same chararistics and start low and work up.
The catering is a sign of pressure, you should be able to see other signs as well, flat primers, hard extraction and others. There are other things that could be causing these problems as well Brass, primer, chamber dimensions, and more. Remember speed isn't as important as accuracy or safety.

 

[longtooth]

Partner seems to me you posted once before on high pressure problems which tells me you're paying attention to pressure signs and doing the right thing by asking questions. I agree with abinok and boomer safety is often pushed to the limit, I have seen many over the years who brought in firearms with blown barrels and cracked stocks many were hurt because they pushed just a little to much, and some who used to little in fire forming, Keep watching for pressure and when you have a close call that scares you let us know we have all had them.