Quickload info for Dasher, 6BR

[BOB LEE SWAGGER]

I recently purchased Quickload v.3.8.0.3. I am completely new to this program. Does it contain data for 6BR and/or 6Dasher? Is there a fairly agreed upon set of data for input?

Thanks in advance,

Dave

 

[SDDasher]

Yes, click on the pull down menu: select cartridge- file; it will drop down all the different cartridges; select 6BR or 6 Dasher.
It will then enter default numbers for generic use. Do not use these numbers; go measure from muzzle to bolt face an accurate number and enter it as the barrel length. Go measure the H2O volume of your case and enter that in the appropriate box. Do the same for the overall length of a loaded round and the length of your case in the appropriate box. The more data you can put in specific to your gun/round the more closely the program can predict the OBT.

 

[jrm850]

... The more data you can put in specific to your gun/round the more closely the program can predict the OBT.

Speaking of OBT, do you guys find that the barrel time from 10% Pmax , or the actual total barrel time more closely matches your real world nodes?

 

[Nomad47]

... The more data you can put in specific to your gun/round the more closely the program can predict the OBT.

Speaking of OBT, do you guys find that the barrel time from 10% Pmax , or the actual total barrel time more closely matches your real world nodes?

Wow, that is an excellent question. 10% Pmax has worked for me in the past, but I may look at actual.

And be sure to enter the case length BEFORE entering case capacity. Otherwise, case capacity will change when case length is changed.

 

[techshooter]

Always use the 10% of PMax to exit time, the QL default as the measure of the barrel time. I standardized the OBT model and equations to that method of measurement to be consistent with QL. Ignore the case length when figuring your barrel length, use the bolt face to muzzle crown for the OBT length input. Ignore muzzle brakes or suppressors as well. And as was said, getting your actual case volume in grains H2O and setting your actual seating depth are the best things you can do to get QL to track your range results.

Cheers,

 

[Nomad47]

Chris,

It is great to see you on this forum. I guess you can see that there are quite a few shooters on here that subscribe to your OBT.

 

[jrm850]

What an honor to have a question answered by the author himself. Thank You!

Would you have time to talk about one more? I'm curious why the pressure wave split times between the nodes shows acceleration between nodes 3 and 4 after deceleration between nodes 2 and 3?

An example from my Dasher: 90uS between 1 and 2, 152us between 2 and 3, and then back to 90 Microseconds between 3 and 4.
barrel length 28 Split Time

Node 4 1.27946230 -0.09024778
Node 3 1.18921452 -0.15179925
Node 2 1.03741528 -0.08970504
Node 1 0.94771024

I apologize if this is covered in the white paper.

 

[techshooter]

JRM850:

I'd be glad to try and answer your questions.

There is nothing special at all about the odd or even nodes, it was just a convention that I made up when building the set of linear equations from the data extracted from the physics simulations for each barrel length. There is a definite pattern to the times when the muzzle bore diameter is changing the least, due to the way the shock strain folds back on itself as it reflects from the end of the barrel. These times tend to come in pairs (see figures 4 and 5 in the original paper), and when I built the equations, it was simpler to build a set of equations for every other time. I ended up calling these times nodes (not a precise usage of the term, but it seems to work), and broke them into even and odd to represent the set of equations for the alternate OBTs. No rhyme or reason to this, I just started calling one time node 1, and the rest is, as they say, history. Having said that, I really, really wish I had spent more time thinking about the implications of the nomenclature, as I get tons of emails asking about the node numbers and the differences between odd and even nodes.

Hope that this helps!

Cheers,

 

[Phil]

Glad to see you back Chris....

It`s been a while..

 

[jrm850]

JRM850:

I'd be glad to try and answer your questions.

There is nothing special at all about the odd or even nodes, it was just a convention that I made up when building the set of linear equations from the data extracted from the physics simulations for each barrel length. There is a definite pattern to the times when the muzzle bore diameter is changing the least, due to the way the shock strain folds back on itself as it reflects from the end of the barrel. These times tend to come in pairs (see figures 4 and 5 in the original paper), and when I built the equations, it was simpler to build a set of equations for every other time. I ended up calling these times nodes (not a precise usage of the term, but it seems to work), and broke them into even and odd to represent the set of equations for the alternate OBTs. No rhyme or reason to this, I just started calling one time node 1, and the rest is, as they say, history. Having said that, I really, really wish I had spent more time thinking about the implications of the nomenclature, as I get tons of emails asking about the node numbers and the differences between odd and even nodes.

Hope that this helps!

Cheers,

I appreciate your reply, and your patience. I'm sure you must have answered this question beyond a reasonable number of times.

Most of my confusion came from my simplistic mental image of a pure ping bouncing back and forth, instead of the energy collisions between the following harmonics which would be travelling in different directions at certain points in time. I re-read the white paper today and you spelled that out very clearly, but for whatever reason it obviously did not sink in.

 

[techshooter]

No problem at all, glad to help. I get really busy with the day job and don't have much time for shooting these days.