Quickload and case fillers

[obiwannabe]

How would you best account for the use of a filler in Quickload?

When looking at chamber pressure, adding the filler weight to the bullet makes very little difference in the calculation. However, decreasing case capacity by the volume of the filler makes a HUGE difference.

It makes logical sense to me that you should do both. The filler is shot out with the bullet, but it also significantly reduces case volume.

So the queston is, if the charge weights are identical, would a reduced load in a large case compressed with filler behave the same as a full load compressed the to same degree in a smaller case?

Example: 458WM vs 45-70 with 54gr H4198 and the 325gr FTX (middle of the range levergun load).

The 45-70 at recommended COAL of 2.650" has a usable case volume of 3.789cc's and shows 107% compression yielding 2278fps@57,900psi

458WM at a COAL of 3.068" (seated to the cannelure) has 4.879cc's usable capacity. Adding 7.5gr of BP Original filler reduces the capacity to 3.808cc's (7-7.25gr/cc as best I can measure with my 2.2cc dipper). Then you up the bullet weight to 332.5gr. Now the 54gr of H4198 shows 107% compression and yields 2275fps@56,500psi.

Intuitively, it makes sense. The powder doesn't know whether it's in a big case or a small case, but then again I've essentially fudged the numbers to make QL spit out the same result. I'm just not sure if real life will really work out so neatly as the numbers. Any thoughts?

 

[griz]

Makes sense to me. Most fillers I have heard of are slightly compressible, but I would guess it isn't enough to make much difference. Might be interesting to try a comparison with a 357 loaded with a full case of Trail Boss versus a 35 Remington with the same charge of TB and a filler. I might try this later this year.

 

[obiwannabe]

I made up a few rounds today to try out in my 458WM.

I used H4198 and the Hornady 350gr FNSP using 45-70 levergun data from Hodgdon. The charge range is listed as 48.5-54gr. I split the difference and went with 51gr. I separated the charge from the buffer with a 0.030" card wad then added 8.75gr (~1.25cc) of BP Original shot buffer. Seating to the cannelure compressed the buffer about 10%.

Based on the Hodgdon data this load should have run about 2100fps out of the 45-70 with a 24" barrel. Fudging my Quickload data as mentioned above predicted 2156fps from my 21" barrel.

These ten rounds went over the ProChrono Digital at an average of 1949fps with an ES of 51fps. No pressure signs and the burn was clean. No unburned kernels left in the bore. Accuracy was reasonable, nothing earthshaking, but on par with what this rifle usually does with the bullet flying nearly halfway down the barrel before engaging the lands.

I'm guessing the actual peak pressure (and therefore velocity) was less then predicted because the buffer is pretty compressible. It takes up the extra space to keep the powder burn consistent but allows for a fair amount of expansion. Like a little shock absorber between the powder and bullet.

Anyway, it's a heckuva nice hunting load that doesn't beat the tar out of you then waste all that energy in the woods behind the animal.