Getting higher velocity than predicted by QL

[BCBRAD]

OK, for the 280ai load I put up.
COL was 3.349" and the total psi for the load and COL is 57,994 psi

Now change the COL to 3.354", the total psi is now 57,848 psi

Subtract the 0.005" difference from the total pressure

57,994 - 57848= 146psi

The 0.005"/146 psi difference works with some variance going up or down....to a point of diminishing returns.

 

[savagedasher]

You get a spike in starting pressure when the bullet is close or in the lands
QL says as much as 5000 psi

 

[BCBRAD]

You get a spike in starting pressure when the bullet is close or in the lands
QL says as much as 5000 psi

I haven't found that, as stated earlier run them 10-15 off.

Experimenting with jammed, I just use the 10,825psi for jacketed bullets.

My velocity basically does not reflect such an anomaly.

Maybe the 7200psi extra for jammed over the default of 3625 psi has something to do with it.

Something to research for sure tho.

 

[JFrank]

I have an old friend that always says-your rifle didn't read that book!
You gotta test for yourself with that implanted in my head I just simply preform a ladder test with Bullets on the lands, find my flat node then proceed with a seating test. No computer or chrono involved, just read the target.
Quick and simple.
Just me of course

 

[Ned Ludd]

I haven't found that, as stated earlier run them 10-15 off.

Experimenting with jammed, I just use the 10,825psi for jacketed bullets.

My velocity basically does not reflect such an anomaly.

Maybe the 7200psi extra for jammed over the default of 3625 psi has something to do with it.

Something to research for sure tho.

The increase in pressure probably isn't anywhere near that large unless it's a bullet seated to hard "jam" (perhaps .020" to .025" into the lands). I have experimented around a bit to come up with an estimate that bullets seated at .005" to .010" into the lands probably increase pressure somewhere in the range of ~500 to 1000 psi.

 

[JFrank]

The increase in pressure probably isn't anywhere near that large unless it's a bullet seated to hard "jam" (perhaps .020" to .025" into the lands). I have experimented around a bit to come up with an estimate that bullets seated at .005" to .010" into the lands probably increase pressure somewhere in the range of ~500 to 1000 psi.

How would a reloader measure that?
Just curious

 

[Shrek]

I’ve come to the conclusion that shooters would be much better off if Quickload and bore scopes were never invented...

 

[savagedasher]

I have had QL 15 years
It is the best thing sense slice bread

 

[Ned Ludd]

How would a reloader measure that?
Just curious

It's a rather crude method based on velocity measurements; velocity is determined for loads with bullets seated at ~.010" off, .005" off, "touching", .005" into the lands, and .010" into the lands. The average velocities can then be entered into QL using a common set of other inputs including bullet OAL, case volume + trim length, charge weight, and adjusted Ba. The estimate is based on the notion that an increase in pressure should be reflected in an increase in velocity. Initiation pressure can then be adjusted in the program until the measured velocity and predicted velocities match. In my hands, the slight increase in velocity observed for bullets seated into the lands required a modest increase in start pressure of approximately 600-800 psi for bullets seated .005" and .010" into the lands, nowhere near the 7200 psi figure mentioned in the QL user manual.

I'll be the first to point out that there may certainly be some caveats to this approach. Most notably, the pressure spike [increased energy] caused by seating bullets into the lands may solely go into overcoming the bullet's static friction against the lands, rather than increasing velocity. Nonetheless, when I first started seating bullets into the lands, I initially used the the large increase in initiation (start) pressure suggested by QL. The resulting peak pressure output values suggested the loads were WAY over MAX pressure. In fact, when using the 7200 psi value, the predicted pressures for the loads I was testing should have destroyed the primer pockets in a single firing. However, they did not. That's when I started playing around with things and came up with this approach for estimating start pressure. Using it, I have obtained pressure outputs for loads with bullets seated into the lands that match up pretty well with values obtained for loads with jumped bullets and how they impact brass life. It's not a perfect approach by any means, but it seems to correlate much better with loads in my hands than using the 7200 psi value suggested in the user manual. Unfortunately, there is not a great deal of information associated with that value in the manual. I would not be surprised if that value corresponds to a "hard" jam; i.e. bullets seated at least .020" to .025" into the lands. It would also not surprise me if the actual increase in start pressure was not linear with respect to distance bullets were seated into the lands up to a "hard" jam. Although these are merely guesses on my part, they seem to fit better with other results I have obtained for loads with bullets seated from .005" to .010" into the lands. YMMV.

 

[Ned Ludd]

From actual pressure traces when testing seating depths, your estimate of 500 to 1000-psi increase in pressure is a likely range to expect in actual traces. Even say .025-In verses say -.015-Off, likely would be less then a 3000-psi in actual pressure increase.

With QL it is easy to adjust the propellant properties to match either the velocity or the pressure to actual chronographed or pressure traced results. But I find it almost impossible to get both to come out right. And often, to get one spot on, the other will be farther off.

When I first got QL (2004) I thought it was the neatest thing. After getting a pressure trace system (2006) I realized how poorly QL was at getting both Mv and PSI to come out right, and I lost a lot of faith in it's prediction. To me QL is a good reference and starting points. But do suggest that when one gets the velocities to match actual chronograph data, it is likely the pressure predictions are not accurate (typically to low) and/or vice-versa.
My 2-Cents

Like you, I find QL to be a useful predictive tool, but it is definitely not the end all, be all, IMO. It can certainly expedite the load development process when used properly, but actual testing and empirical observations are still essential. Nonetheless, I still like to use QL, particularly in the beginning stages of a new load workup. I usually don't have too much difficulty tweaking the program to get the predictions to match up with actual velocity data; however, I do not have access to actual pressure testing equipment. So in fairness, the only measure I have to estimate whether the predicted pressure values are close to actual pressure values is to compare case pressure signs and brass life for loads with bullets seated into the lands for which I have monkeyed around with QL to get some outputs, to loads with jumped bullets and SAAMI specs where I have a much better feel for how different pressure loads affect brass life. It is not a hard science by any stretch, but so far has worked reasonably well in my hands for making useful estimates.

 

[savagedasher]

I can’t tell you the days I have we to the range to regulate the bullets on a double rifle And have to come back a and pull the bullets and load again
QL solved that problem

 

[JFrank]

Jesus"
I just feel a tad more recoil when seated on the lands.

 

[can1010]

is there a way to figure out what the proper weighting factor should be. I have asked elsewhere but cant get an answer to save my life. I have a couple wildcats that I shoot that are not in quickload. I entered reamer dimensions in quick design then imported to quickload but nothing makes sense case is not showing those kind of pressures

 

[savagedasher]

What was the parent case you made the wildcat off of

 

[can1010]

338 rum shortened and necked down to 308 with 40 degree shoulder and less body taper 108.8 case capacity built this years ago before quickload and used educated guess to start load development. think of it like a fat 300 win mag because it was shortened to fit there cip length mags