Using formula's in Quick Load

[TheSnake]

I am starting this thread to continue a conversation from another post as not to steal that post. Please let us know if you have developed formulas to use in Quick Load to narrow down the variables entered to bring velocity closer to actual Chronograph readings. Below is an example from Louielouie from the other post to show the kind of thing I am looking for. Let's also assume other variables like bullet length, cartridge length, barrel length, twist rate, H2O case capacity and such fixed variables have all been entered correctly. Even after entering fixed variables accurately, the QL velocity always seems to have been off more than I want it to be after I shoot them. Please share your magic.

I still use the recommended 'jammed' pressure but have changed the initial start pressure of the bullets based on the bearing surface length of my 6.5 mm bullets. Pressure = ((1420 * bearing_surface_length) + 2853) - which is about 3630 for 123 Amax and 3756 for the Sierra 140 SBT. This is based on Wolf LR primers - I add 100psi for BR2's, 200 for GM210M's & 400 for Winchester LR's.
Think of this as a guideline to manage variables along with actual case capacity, bullet weight, powder burn rate and that nebulous 'weighting' factor. I'm usually within 10 ~ 12 fps of predicted velocities using H4350 & h4831sc. RL17 & A4350 are close but the temp variable doesn't track as well.

 

[Nomad47]

A question I have for louielouie is: Are you saying you use the formula for jumped bullets and you add 7200 PSI to your formula for jammed bullets? And I'm guessing adding about 600 for 215Ms would be about right?

First of all, I prefer to 'jump' my bullets, so my comments are based on the bullet being seated short of the lands.
This isn't a formula but I have found that if I enter COL to lands as my actual cartridge length regardless of what my loaded length is, then QL's predictions come out closer. My theory is that the bullet reaches the engraving point very quickly and that is the case volume (along with fired case capacity) that QL is working with. The only error this produces is the box for case filled percentage which has no bearing on velocity, pressure or barrel time.

 

[RDavies]

I would like to know when do you start using the jammed pressure setting, is it when the bullets are jammed in hard, how about if bullets are just touching, or .005-.015" off the lands, when do pressures stop going down from extra case capacity, then go up for higher start pressures?

 

[Nomad47]

Just my opinion, but I would say when a bullet can't get a "running start" is when QuickLoad says to add 7200 PSI to the Shot Start Pressure. Obviously a couple thousandths on either side of "touching" the lands is a gray area.

 

[louielouie]

Yes, I add 7200 psi when I seat to/into the rifling with the 'init start pressure' for each bullet as follows:

Bullet	weight	MAX COL	Bearing length	Init pressure
Hdy Amax	123	2.838	0.5465	3629
Sierra SP	120	2.758	0.579	3675
Hdy Bonded	129	2.880	0.617	3729
Norma Golden	130	2.847	0.6175	3730
Nosler CC	140	2.775	0.625	3740
Hdy BTHP	140	2.847	0.6335	3752
Sierra SBT	140	2.758	0.636	3756

Of course the max COL is for my chamber only and the init start pressure for each bullet is based on using the formula quoted elsewhere AND WOLF Large Rifle primers which seem to produce the least pressure.
I add to this if I use different primers:

CCI BR2	100
Fed GM210M	200
Win WLR	400

This is from measuring the velocity difference of JUST the primer change from a known load and using QL to predict it by varying the init start pressure. My Winchester 243 brass holds 56.0 gr of H2O and the Remington 7-08 has 55.4

I'm using a 'weighting' factor of 0.44 for 260 Remington and have adjusted the 'Ba burn rate' a few percent too for certain powders. I have not messed with 'long barrel friction' but for the record I'm using a 25.5" Shilen 4-groove with 'ratchet' rifling.
I have posted this data from my observations of components I've used and measured and like all 'reloaders code', it's just a guideline.

 

[Nomad47]

Quote "I'm using a 'weighting' factor of 0.44 for 260 Remington and have adjusted the 'Ba burn rate' a few percent too for certain powders. I have not messed with 'long barrel friction' but for the record I'm using a 25.5" Shilen 4-groove with 'ratchet' rifling."

Hmmm, "long barrel friction" is a new one for me. Are you adding to the bullet weight for this?

Chris Long says he limits his 'Ba burn rate' adjustment to 5%, but I found for my .284 w/ Berger 180 Hybrids jumped .020" that I had to increase Ba burn rate by 7% and shot start pressure to 7500 psi to get QL to calibrate for my H4831/215M load. How much is a "few percent" for your burn rate adjustment?

 

[louielouie]

• I don't know if 'long barrel friction' is new to v3.6 but I get the impression that it doesn't come into play with my rifle - too short a barrel. I think it's likened to a .22 rimfire where the bullet loses velocity after a certain barrel length because it does not have enough gas pressure to accelerate or maintain velocity of the projectile.
• Hodgdon states in one of their manuals that they hold their burn rate to +/- 2% variability from lot to lot and I have not had to change burn rate values of Hodgdon powders in QL more than 3% after I got the other variables addressed.
• I do input the actual bullet weight but I don't use it to compensate for anything else.
• Chris' work is fabulous to read and his proof to back up his opinion about using hotter primers here in the great NorthWet compared to people shooting in Arizona is why I switched to GM210M from Wolf or BR2's. That said, he advocates adjusting bullet weight & powder burn values until QL matches measured velocities - which works for that one combination and maybe others. I think we can do better by managing more of the variables.
• QL v3.6 uses a 'weighting' of .5 for the 284 Win but when I look at http://bulletin.accurateshooter.com/2011/04/overbore-cartridges-a-working-definition/ plus the 35 deg shoulder, etc., I'd be inclined to use 0.43 (since I use .44 for a 260 Rem). I certainly don't agree with some of the 'stock' values QL supplies.
• Too bad http://www.shootforum.com/forum/bulletdb.html doesn't include bearing surface length-this would allow tailoring the "shot start/init pressure" for each bullet within a caliber. Perhaps that could be compiled by people who have many different samples of a caliber? My 6.5's were measured with a couple Hornady comparators on a Frankford Arsenal digital caliper.

 

[Nomad47]

I need to update, my version of QL is pre Windows 7.
Over on the wssmzone forum, Chris stated he adjusted Ba by no more than 5%, then WF by no more than 10%, and finally bullet weight by no more than 4% to calibrate his loads. At least that is what I have in my notes. Chris says adjusting bullet weight compensates for varying barrel friction. But QL changes shot start pressure to compensate for a change in barrel friction caused by bullet coatings.
BTW, Berger has the bearing surface length for all their bullets on their website.

 

[TheSnake]

Back up. QL users please step forward with your tips.