Quickload Burning rates for Retumbo and H1000

[Steveb]

Does anybody have experience with H1000 and Retumbo in Quickload. The Burning Rate listed "seem" low to me because I have to adjust the Burning Rate a large amount to match our velocities from the rifles. This makes me cautious to use the recommended powder charge weights.

Does anybody have other Burning Rates from their experience for these powders?

I have never used Quickload for large cartridges and very slow burning powders so am curious and cautious.

Thanks

 

[SeabeeKen]

Adjust the Ba until your velocity matches.

 

[Steveb]

I understand that and do that for other cartridges but the amount of adjustment is far larger than I have normally done before so I am cautious. If other shooters have found the same thing as I have then I would feel a lot better.
Thanks

 

[Straightshooter1]

I understand that and do that for other cartridges but the amount of adjustment is far larger than I have normally done before so I am cautious. If other shooters have found the same thing as I have then I would feel a lot better.
Thanks

I don't know what "normally done" is, but I do have to make what I'd call substantial adjustments in the Ba. For Retumbo that I use in my 6.5 PRC, my adjustment is ~.0600 above QL's number.

 

[Steveb]

Yes, this is normal for my smaller cartridges and I feel comfortable with this but now for both powders I have to move from .33xx to .50xx range which it a huge amount more than I consider normal.

 

[Straightshooter1]

Yes, this is normal for my smaller cartridges and I feel comfortable with this but now for both powders I have to move from .33xx to .50xx range which it a huge amount more than I consider normal.

You might find a way to measure the moisture content of your powder to see how that might play into your issue. My Retumbo runs 47-52% as measured with a Kestrel DROP (52% being from a fresh just opened bottle).

 

[PhilC]

Adjust the Ba until your velocity matches.

Just did this while working up a load using H1000 for my brother's 7RM a few weeks ago.

Did the same thing with N135 for 7BR load development, predicted velocity with QL "default" Ba was significantly different than over the chrono.

 

[Ned Ludd]

If I'm understanding your sutuation correctly, I generally use a 2% reduced load to mitigate any potential pressure issues with untested QL predictions made using the factory preset Ba. That is close enough that the load usually won't be way off if everything is kosher, but reduced sufficiently to determine an average velocity. I can then adjust Ba and "calibrate" the software to the specific rifle. It costs a few loaded rounds and one trip to the range, but I find it worth the effort, for the peace of mind if nothing else.

 

[JPB4BAMA]

If I'm understanding your sutuation correctly, I generally use a 2% reduced load to mitigate any potential pressure issues with untested QL predictions made using the factory preset Ba. That is close enough that the load usually won't be way off if everything is kosher, but reduced sufficiently to determine an average velocity. I can then adjust Ba and "calibrate" the software to the specific rifle. It costs a few loaded rounds and one trip to the range, but I find it worth the effort, for the peace of mind if nothing else.

I don't want to hijack this thread, but I was just about to post a similarly themed question. I have posted for thoughts in the past concerning what I thought was a significant mismatch in the Ba between default and what I have to reduce it to to match my MV in my 223AI. This is specifically with Varget and Shooters World Precision. My MV's are consistently about 150 - 200 FPS SLOWER than what the Default Ba predicts. I see the same on several different lots of each powder so it does not appear to be a Lot or moisture/humidity issue. BUT now for the punch line. SAME bottles of powder I started to work on some 308 loads with 168 ELDM, and the predicted MV from QL is pretty much spot on. Had I started out with my Ba derived from my 223 Use I would have been severely compressed and overpressure , so thankfully I did not go that route. But now this begs the question as to why?

Now, I am shooting Moly plated 88ELDM in the 223 and naked copper in the 308, but even if I drop the shot start pressure to zero in makes minimal difference compared to what I have to tune to match actual MV's. I've even played with the weighting factor and it makes a rather minimal effect as well. I'm just wondering it there is something else like case geometry of the 223AI or is the MOLY even slicker than Ive been thinking and it's not just shot start pressure but along the whole length of the barrel that is causing this discrepancy. And just to muddy the water a bit more, when I try Vit N140 it behaves much more like the predictions with just about a 2-3% reduction in the Ba.

 

[Ned Ludd]

Case geometry (i.e. using different cartridges) can absolutely affect the Ba necessary to match predcicted to actual velocity in QL. Likewise, it's not a great stretch to think that using a different brand of brass that had different internal volume, or a different bullet, or even a different primer might affect how one has to adjust Ba in order to get predicted and actual velocity to match. I think that almost anything that can alter pressure/velocity by definition would mean the Ba would need to be adjusted. As to by exactly how much of an adjustment, I think that only testing (i.e. calibrating the Ba to a given load velocity) can answer this question. Clearly one would expect smaller changes in Ba from things that would result in a smaller change in velocity. For example, changing brands of brass or primers may only require a small Ba tweak. Changing to a different cartridge might be expected to require a more significant adjustment.

 

[Jager]

I think that almost anything that can alter pressure/velocity by definition would mean the Ba would need to be adjusted.

This.

When we adjust Ba in QuickLoad, we inevitably think we're adjusting the burn rate of the powder. I mean, it's actually named that, right?

But in reality QL's Ba number is the primary rheostat via which we dial in what QL is modeling to what we actually see in the field. Ba is a bucket which includes everything that could affect pressure.

Got a tight chamber or a tight bore, producing higher velocities? Fix it with Ba.

Got a soft lot of powder, producing lower than expected velocities? Fix it with Ba.

Keep your powder in an unusually dry room, raising the energy potential of that powder? Fix it with Ba.

Have the manufacturer of your bullet change jacket suppliers, and the metallurgy of the new product differs ever so slightly from the old? Fix it with Ba.

The other thing QuickLoad requires for accurate output is very precise case capacity. And since case capacity varies so much from headstamp to headstamp, and even from lot-to-lot within a headstamp, It really needs to be measured. Very carefully.