QL Education! Cool stuff.

[Bonz]

Thanks for all this great help and discussion since i have joined the forum. I posted this in an existing thread, but am adding to it and giving it a new thread so as not to hi-jack the other thread.

Question: RE IMR4320 and QL vs. developed load for 30-06 and 130 gr TTSX. Developed load in this case equates to no traditional pressure signs of increased bolt lift or primer pocket looseness, after multiple firings.

My developed and chronographed load with IMR4320 gives a good bit more velocity than the same powder charge theoretically gives via QL inputs for my rifle and fired case.

By the same token, my load developed with the same caution for the 35 Whelen AI and the 200 TTSX is essentially identical to what QL says it should be for velocity with a given powder charge.

So, both loads worked up with the same procedures and one is overboard by QL and one is well within safety margins by QL. Let's say the difference is the 10% lot-to-lot variation in burn rate. At what point do primer pockets get loose on multiple firings or at what point does bolt lift start to be noticed?

I know there are not hard answers to those questions. Each rifle, cartridge and lot of brass, is a rule unto itself, however with the Whelen load showing 57k psi (QL) and the '06 near 69k psi (QL), is that a window within where outward pressure signs would show no difference?

I know where I WANT to be on this issue. For a hunting load in the field I want to bring as much to bear as possible in a safe load, which I feel is what I have done from years of safe loading experience in working up this load.

Where I SHOULD be on this is what I am searching for.

Can a safely developed load that exceeds QL predictions truly be called a safely developed load? Are there such things as "fast" barrels that we hear about?

Love my 130 TTSX load. It is fast, accurate, and safe by traditional pressure signs.

Thoughts? Thanks guys.

 

[RiverRider]

I do not believe there is such a thing as a "fast barrel."

The approach I've adopted and feel pretty good about is to set the load up as best as I can in terms of case capacity, finished cartridge OAL, etc. and look for the velocity that shows at around 62000 psi (in most cases) in the QL predictions. Then, when I go to the range to try pairs (I don't bother with three-shot groups when I'm looking for the pressure limit) I make sure and chronograph them. If QL tells me that with H4831 my velocity should be 3100 fps at a pressure of about 62000 psi, I consider 3100 fps to be my limit. Whatever the charge is, I won't exceed it (by much at all, anyway).

 

[SJB358]

I do not believe there is such a thing as a "fast barrel."

The approach I've adopted and feel pretty good about is to set the load up as best as I can in terms of case capacity, finished cartridge OAL, etc. and look for the velocity that shows at around 62000 psi (in most cases) in the QL predictions. Then, when I go to the range to try pairs (I don't bother with three-shot groups when I'm looking for the pressure limit) I make sure and chronograph them. If QL tells me that with H4831 my velocity should be 3100 fps at a pressure of about 62000 psi, I consider 3100 fps to be my limit. Whatever the charge is, I won't exceed it (by much at all, anyway).

Agree with all RR said. Some rifles can vary a little due to the land and groove diameter, but if QL shows a certain speed to be over a certain PSI then that is what I try to stick with. All that excluded RUMS AND WBYS though. Freebore or extra leade changes it a bit as well.

If your getting 7-10 firings out of brass then I'd say your probably okay most of the time. If your stretching primer pockets on the 2nd or 3rd firing I'd bet your up into the 70K or better range.