Wild Cat Load development.

[mikegaiz]

I am in the process of developing two wild cat cartridges which are very different than any other current cartridges. I have bought reamers, had custom dies made, barrels chambered, fire formed brass, selected several bullets and powders and am ready to do load development. The problem is where do I start. I have measured the case capacity and it is very close to current cases which are one caliber larger or one smaller. Is it save to start with the load data from those cases which are for the same bullet weight, but not same caliber? I have been told by shooters I respect to measure the case capacity and start loads with 80% of that volume. So if it holds 100 gr. Full start with 80 gr. And work up.

Has anyone done this? Which method should I use?

 

[savagedasher]

I am in the process of developing two wild cat cartridges which are very different than any other current cartridges. I have bought reamers, had custom dies made, barrels chambered, fire formed brass, selected several bullets and powders and am ready to do load development. The problem is where do I start. I have measured the case capacity and it is very close to current cases which are one caliber larger or one smaller. Is it save to start with the load data from those cases which are for the same bullet weight, but not same caliber? I have been told by shooters I respect to measure the case capacity and start loads with 80% of that volume. So if it holds 100 gr. Full start with 80 gr. And work up.

Has anyone done this? Which method should I use?

I would get QL and Quick design With the two you should be able to choose the powder and amount . Larry

 

[ireload2]

What are your mystery wildcats that you think are so different?

I am in the process of developing two wild cat cartridges which are very different than any other current cartridges. I have bought reamers, had custom dies made, barrels chambered, fire formed brass, selected several bullets and powders and am ready to do load development. The problem is where do I start. I have measured the case capacity and it is very close to current cases which are one caliber larger or one smaller. Is it save to start with the load data from those cases which are for the same bullet weight, but not same caliber? I have been told by shooters I respect to measure the case capacity and start loads with 80% of that volume. So if it holds 100 gr. Full start with 80 gr. And work up.

Has anyone done this? Which method should I use?

 

[Brians356]

What are your mystery wildcats that you think are so different?

Yes, pray tell. At least divulge the similar ones of different caliber. Why the reticence?
-

 

[jfseaman]

@mikegaiz

If it's a secret Wildcat, get QuickLoad and QuickDesign.

You have to be careful of which powders you use at %80 of available case volume. I like %90 better if you have guys helping follow their guidance.

 

[338 Mollett]

I,m working on another one myself.But to answer your question the case that has caliber smaller go to a slower powder and faster powder on the other.On the necked down version it got tricky for me in calculating case capacity with the powder burn rate for optimal velocity .Those wildcats can fool you on pressure. Good Luck!

 

[Shaggy357]

Quick Load is the smartest way to go....or do a little digging through the archives. If you are using existing brass, the wildcat, or a close twin, is likely available to compare data. Every military case ever made has been necked up, necked down, shortened, and/or straightened to make a wildcat. I have probably 10 wildcats made from .30-30 brass.....equal number from .223 brass....

Good luck and stay safe.

Steve

 

[dedogs]

If you don't know any one with QuickLoad/ Quick Design then get a hold of Ken Howell's book "Designing and forming Custom Cartridges" and read it. Very good info. dedogs

 

[gunsandgunsmithing]

As has been mentioned, bore diameter has a lot to do with powder choice and how much to use. No, you can't assume same powder charge as a similar case but different bore diameter, even if the bullet weight is the same. The larger bore gives more area to allow pressure to drop faster. I like to think of the chamber plus a couple of inches of the actual bore as being the "expansion area", for lack of a better term. Just think about it...If you consider it as I just mentioned, breech face to cartridge length plus 2 inches, obviously, the larger bore will have more area.

 

[Brians356]

Do you have any idea which powder you prefer to start with?

Read the Richard Lee reloading guide, Chapters 9 and 10 I believe, the sections about cast bullets and reduced loads. In the load data sections for different cartridges, Lee lists "1-gr Reduction Factor" for certain powers which are safe to reduce loads by as much as 60% below the "Never Exceed" charge weights. The most well-know powder for reduced loading (besides purpose-built Trail Boss) is H4895, but there are many similar powders which are suitable, obviously IMR 4895 but many others. If you find a cartridge in Lee's manual which has a case capacity close to your wildcat, and find any powders listed for it with the "1-Gr Reduction Factor" included, you should be able to choose any one of those powders and start at 80% of case capacity.

Edit:

Might be safer to start at 70% case capacity, or 70% below the "Never Exceed" load for your bullet weight under that similar cartridge, assuming you found one.

PS
If you don't have access to the Lee manual: If you reveal the approx. case capacity, bullet diameter and weight, I could suggest a few powders which would be safe to start at reduced charge weights. But one of the 4895s would probably suit, and they tend to work very well in a variety of cartridges.
-

 

[SheepDog]

Two bottle neck cases with the same volume but in different bore sizes can be used to extrapolate a starting load with the same powder and same weight bullet. The cartridge with the smaller bore will generate more pressure than the case with the larger bore. The larger bore case can also use a slightly faster powder than the smaller bore but now you have to be real careful.
Lets say that you have a case that has the same volume as a 243 but your new case is fatter and shorter and shoots a 30 caliber bullet. (think a short magnum case cut down to the same volume as a 243.)
Using the starting load for the 243 as a starting load for your case with the same powder and the same weight bullet is a good starting point (usually). The difficulty comes in recognizing a maximum load. There is no accurate way to tell that you have reached a maximum pressure for your rifle. However if you get ten reloads without difficulty with primer pockets stretching or case failures you are probably not hurting your gun. If you are properly sizing the brass and not "over sizing" it so that the cartridge fits the chamber each time it is used then the only indicators that show excessive pressure are hard bolt lift or primer pockets stretching. Either of these indicators tell you that you are well beyond safe limits in your gun with this load. If either of them occur then you need to drop the load by two grains or 4% whichever is less.
Fatter cases burn more powder faster than skinny cases and can go with slower burning powders. The opposite is also true. Fatter cases can build slightly more pressure because more powder is burning at the same instant so be aware of this when extrapolating data from one to the other.

I don't have Quick Load because it doesn't run on Linux and I refuse to use MS operating systems or software that requires it. I might attempt to write an internal ballistics program someday if I find a burning need for it but so far the exterior ballistics programs I have written are all I need.

 

[mikegaiz]

Thanks, to all of you really trying to help and to the others I say whatever,,, I will give feedback ounce the bullets start flying.
Thanks
mike

 

[Cool Tool]

Thanks, to all of you really trying to help and to the others I say whatever,,, I will give feedback ounce the bullets start flying.
Thanks
mike

Good luck mike see you in the spring lord willing maybe you will bring out another record breaker.

 

[Catfish]

If your going over bore with your cases just start with with the next smaller case you can find in that caliber. I load for the 17 AH and with that case .1 gr. powder increase can raise pressure from safe to sorry. I also load for the 300 WSM necked down to 6mm and with that round 1 gr. don`t mean much. BUT, with the 6-300 WSM even the slowest of powders like H-1000 will not fill 80% of the case capacity with with 105 gr, and up bullets. If you are in doubt don`t do it! Years ago I was talking with a guy that necked a 50 BMG down to 6MM. He could barely get 5,000 fps. with it burning all of that powder, and he was trying to sell that barrel. While the 6-300 WSM is far less extreme, I`m thinking it is still to much over bore for any gain.