260 Rem AI and QuickLoad

[Joe R]

Hi Guys,
I'm getting my stuff together to build a 260 AI. I finally got my hands on a fire formed case and wanted to start loading info into QuickLoad and much to my surprise the 260 AI is not among the case choices. This is uncharted waters for me. What do I do now? Can anyone offer any help?

Kindest regards,

Joe

 

[ShootDots]

Joe, just give me a call and I'll tell you where to start and how to get where you want to be..

 

[alphapygmy]

On mine I use the 260 Rem case data and adjust the water capacity to what mine measure. Mine have a capacity of 55.7 grains water, my cases are 2.010" long. I use a charge of 46.8 H4831SC over a 142 SMK loaded to a COAL of 2.865. My quickloads shows a velocity of 2801 at 60 degrees and my true average over 50 shots has been 2806 fps at the same temp. It's about 15 fps off with H4350 depending on powder lot but that's still pretty good in my book.

 

[savagedasher]

It depends on what brass you are using. My Remington brass was 47.8 GR of h20
My best powder was Norma MRP with 140 GR bullets . Larry

 

[Joe R]

Thanks alphapygmy,
I started doing exactly what you suggested, so it's good to know that I'm on the right path.

I spoke to Ben (he's a walking encyclopedia) and what he told me is consistent with the QuickLoad output. So now all I have to do is get my barrel chambered and start shooting with my LabRadar close by and refine things.

My Lapua brass has a water capacity of 55.950 grains.

 

[fredo]

Question to the gents who adjust inputs in QL to account for an unsupported "Improved" case:

Do you find that adjusting the cartridge 'weighing factor' is another data point to consider when tweaking QL for a cartridge that is not covered in the database?

 

[Joe R]

Question to the gents who adjust inputs in QL to account for an unsupported "Improved" case:

Do you find that adjusting the cartridge 'weighing factor' is another data point to consider when tweaking QL for a cartridge that is not covered in the database?

Fredo,
I like your question, it made me stop and think a little (a dangerous thing, I know).

I've only been using QL for a couple of years, and lightly at that. I had not given much thought to the cartridge weighing factor because I've been only concerned with the .308 (I shoot F-TR). But given that the .260 can be considered an overbore caliber, maybe an adjustment in that factor is something to consider, more so with an AI version.

What is your experience in playing with this factor? What calibers? Any advice you can offer?

Joe

 

[fredo]

Hi Joe.
I asked, because that's what I've done on occasion, for some wildcats.

'Weighing factor' is a representation of a case's powder burning efficiency in a certain shaped case. Seeing as how wildcat mods like changing shoulder angles and/or necking up/down purposely change the shape & volume of a parent case, it only stands to reason that 'weighing factor' might needs adjusting...

By simply messing around with it, you can see how it might affect projected data for your case.

I've done a bit of tweaking of weighing factor for a few wildcats in hopes of getting QL data to jive. For necked down, overbore cases like: .17Predator (.17-223 Improved), .22-243AI, .30-338 Norma Mag Improved...I've found that decreasing weighing factor below that of parent case to be beneficial to making #s jive. Seems like the more overbore & wacky the chambering, the more it needs 'tweaking', LOL. However, along with adjust Ba (burn rate factor) of a particular powder, one can get surprisingly close to matching projected data with actual measured data...

As for simply changing shoulder angle, as in your case with the .260AI, was curious as to whether gents were tweaking 'weighing factor' to account for the sharper shouldered case. I'd think that "Improving" a case would warrant a small adjustment, maybe a couple/.02?

The .260 & AI aren't terribly overbore, so you may find that your data is pretty close...

Good luck!
Fred

 

[Joe R]

Thanks for responding Fred,
You gave me some good info above and I also learned of another variable that I can massage to get QL to more appropriately reflect real world results.

Good man!

Joe

 

[alphapygmy]

Concerning adjusting the Weighing Factor, I don't play with it and have results very close to my Labradar. I looked at the WF for other cartridges with approx. the same bore case ratio and some more towards being overbored and most were still listed as .5. The few that weren't I couldn't quite get a good feel for how much to adjust so I just left it alone. I mostly adjust the Burn Rate Factor to hopefully compensate for different lots and burn characteristics at different pressures. That virtually always gets QL and my chrono very close as long as all the data I entered was accurate.