Re: Which manual is correct- Hodgdon, or Sierra?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wannashootit</div><div class="ubbcode-body">Thanks for the posts. Bob, what you say is certainly logical.
I don't have a chrono yet. Certainly not because of the $$, they're cheap. Just didn't think I needed one...
It is my understanding that velocity is not related to accuracy,at least at the short (100-200) yard distances I'm working now.
So, is velocity a way of determining pressures? If so, then buying one is a no-brainer, right?
Please- don't tell me to read the manual. If you don't want to answer- don't....
It's even worse for the 175 SMK's I started loading tonight. The max load from Sierra is less than the minimum load from Hodgdon.
I understand it is a complicated science. That's why I decided to visit the reloading depot here... for the 175 SMK's, most are shooting 43-45 Varget out of similar bolt guns (Savage).
So, I'm loading 42, 43, 43.5, 44, and 44.5 for the weekend. </div></div>
Wannashootit,
Your simple statement "...your understanding that velocity is NOT related to accuracy" and your question "..is velocity a way of determining pressures?", are far more complex than you might realize.
Let's address your first statement: "...your understanding that velocity is NOT related to accuracy".
First off, velocity of some sort is necessary to get the bullet out of the barrel. Then the bullet must have sufficient velocity to reach the target.
All this must take place before we can measure a bullets accuracy on a target. So velocity is related to accuracy, and is close coupled with it.
If ultimate accuracy @ 100 or 200 yds is all that is required, then we only have to contend with the minimum velocity necessary to reach that target. So if the bullet leaves the muzzle @ 2400, 2500, 2600 or 2700 FPS is immaterial, if the desired accuracy is achieved at some point.
But if we are concerned about the relative accuracy of that bullet at say 1000 yds. then velocity is very much a player.
For example a 1/2" group @ 100 yds, means nothing, if the bullet cannot reach the target nose on @ 1000 yds, if that is the goal. Better to suffer a load that delivers a 3/4" group @ 100, but can also reach the target and still deliver acceptable accuracy @ 1000 yds.
I hope I made that understandable.
Next your question: "..is velocity a way of determining pressures?"
Yes, but only within a narrow set of circumstances:
If you loaded 5 rounds with 44, 45, 46, 47, and 48 grains of Varget, in a new Lapua case, with a Fed 210M primer, and a Berger 155.5 Grain 308 bullet, at a COAL of 2.810", and fired them each over a chronograph:
I would expect to see, increased velocity with each increase in powder. With each increase in velocity there had to be an increase in pressure, because without pressure, there is no velocity.
But that's all it really tells you. If your goal was to reach say 2900 FPS, and the 48 grain load yields only 2850 FPS, then your faced with upping the load, or being satisfied with what you got. But the velocity in and of itself tells you nothing about whether that 48 grain load is generating 58K PSI or 65 K PSI, or something else.
Change any component, change seating depth up or down, and you have introduced a new set of variables, and you will also changed the velocity, pressure, accuracy, curve sometimes for the better, and sometimes for the worst.
The good news out of all of this is, if you use prudent reloading techniques, and start from below and carefully work up, the brass cartridge case will tell you where to stop long before you reach the point of a self disassembling rifle.
A Chronograph is a tool in reloading, and most helpful in reloading for long range, but not the only tool, nor is it the most important tool. You can get by nicely without one. I reloaded for more than 20 years, before I got my first chronograph. But I've used one for the last 18 years or so, and would feel a bit uncomfortable now reloading without one.
Having another tool in your tool box is never a bad thing.
Have fun,
Bob
