New to Quickload, question about seating

[Thor2j]

I just bought quickload. I am trying to figure out a way to set distance to lands. One of my main objectives was to see by adjusting seating distance from land what the pressure results would be. Is this possible with quickload??

Thanks!

[SL1]

No.

QuickLoad does not have any way to adjust for bullet travel before engraving on the lands.

There is an adjustable "start pressure" that you can play with to see what effect it has on peak pressure. But, it does not seem to have that much effect on peak pressure. And, you would need to know the answer to the question that you are asking in order to set the start pressure to the "right" value.

This is one of the things that I don't like about QuickLOAD (and all other programs available, today).

[mehavey]

You'd probably need to resort to 3D hydrocodes to get all the answers to all the possible variations and permutations inherent to what goes on inside the chamber, along the barrel, ...and for several feet out the muzzle too

And having used such codes (a lot) at Eglin in calculating bomb-stacking interactions -- you aren't going to get much better answers than QL's ± a few perecent.



post:
And then you'd need to know so many characteristics of the bullet design, the exact throat dimensions, the clearance between neck and chamber, then leade angle, bore condition... etc, etc, that you'd spend more time in data entry than shooting.

[Brian Pfleuger]

If you hold the cursor on the "Shot Start (Initiation) Pressure" window it will give you a list of suggested pressures and tell you to add a certain amount for touching the rifling. It stands to reason that the pressure would be no less than the starting value (as an estimate) and would increase toward the maximum value as you approached the rifling. It's probably closer to an exponential increase than linear, with only a little change until you get really close to touching and then rapid increases.

The effect on max pressure is usually 8,000-10,000psi for typical rifle cartridges.

[SL1]

The effect on peak pressure from bullets touching the rifling might be a lot higher for small cartridges that use quick-burning propellants and relatively large diameter bullets.

So, I would not take the 10,000 psi as an upper limit.

I think that the "start pressure" in QuickLOAD is more a matter of getting a finite-difference numerical equation to perform reliably in a computer simulation than it is a tool for investigating the pressure effects of bullet travel distance to the restriction in the bore created by the rifling.

SL1

[Brian Pfleuger]

I checked 3 cartridges today, .204Ruger 32gr, .243Win 95gr and .308 150gr and used QuickLoad's predicted max load with the powder that produced highest muzzle velocity. The lowest of the 3 was around 8,000psi, the highest around 10,000. I know from experience that 7mm-08 is similar.

I'm sure the number is more of a "play nice with reality" figure than a cold, hard fact but I think it's instructive too.

It certainly worked out when I accidentally mismeasured my 7mm-08 and had the bullet jammed in the rifling. The action on my Encore popped open a few increments below predicted max charge. First I thought IMR3031 wasn't playing nice, until I remeasured. After I made the adjustment in QL, I saw that what was supposed to be an upper-50k PSI load was probably closer to upper 60k.... oops.

[Clark]

The way I improve my results with Quickload is to:
1) Get the predicted velocity to match the chrono velocity when not touching the lands, by changing the powder charge. Then I know the offset percentage for the powder in the library of QL offset from the powder I bought.
2) Using the above adjustment, then change the start pressure until the predicted velocity matches the chrono velocity when jammed into the lands.


For example in I may find my jug of H4350 is 1.5% wimpier than QL thinks it is and I may find that 2,000 psi is a start pressure for off the lands and 4,000 psi is a start pressure for jammed into the lands.