Regulating my double rifle

[Fred]

I have been using the S&B bullets and 41gr. of 4064. Does a good job in my Drilling and stalking rifle. I like the S&Bs but haven't been able to get Midway to get them for me.

[Diz]

Fred,

That looks like an excellent load for a 9.3x72R. The pressure looks to be just about 21,700 psi and the velocity 2017 fps. A nice low pressure loading at least that's what my program says. I have used 3031 which is a bit faster with good results too. It's an interesting cartridge in a drilling.

Thanks, Diz

[Leatherman]

Thanks, I may try this load in my 9.3x80 Collath too. Diz could you run that through your program for me. Again I have no idea what difference the fatter and longer 80mm Collath case will Have when loads for the 72mm are used.

[Diz]

Sorry for the delay I was reconfiguring the computer that the QL program is on. The CIP Max pressure for the 9.3x80R is listed as 1800 bar or 26107 psi but I have no way to verify that with other references. I expected the pressure to go down in the longer case and it did. Here are the CALCULATED numbers for a 24" barrel with 42 grains of IMR-4064:

PMax = 18163 psi
Vel = 1915 fps
Fill = 68.5%
Burn = 76.48%
BalEff = 20.2%

I'll try to run one with the same charge weight but with IMR-3031 to see what that looks like. Do you want me to change the barrel length?

Thanks, Diz

[Leatherman]

My double rifles and Drillings have 27" barrels. Looks like I have some room in the 9.3x80 for some more powder. I'll start with 2 more grains and see what spread in velocity I get. I am going to a gun show today to see if I can find some 4064. I will be interested in what you come up with useing 3031. That has always been my standby powder in the 9.3x72R. I am starting to load my 11.3 X 83 double rifle this weekend. Got my .444" cast bullets today from Buffalo Arms and some .60" wading material. Going to start with black powder loads and see what velocity is needed to regulate the barrels. Then I am going to load up some nitro loads starting with 4148 and 5744 powder. The case capacity is 5 grains less 2f black powder than a standard .450 nitro case after sizing down to my chambers. So I am taking the .450 BPE loads and dropping a few grains to start with.

[Leatherman]

Sorry I meant to say 4198 powder not 4148.

[Diz]

Leatherman, will all the new powders coming out it's hard to keep up with all the numbers. What velocity are you looking for in your 9.3x80R? I could try to run for it with 27" barrels and see what come out. Thanks, Diz

[Leatherman]

Well that's a good question. If It were a single shot it wouldn't matter but it is a sxs double and I have to find that majic velocity to regulate the barrels. I have shot it once with VW powder but if you remember I had a 300 fps spread in velocity that I think was effecting my groups and regulation. At that load it was around 2100fps and my spread was about 4" apart at 50 yards with open sights. So I am thinking around 2200 fps might be my next goal. I have a scope mounted on the rifle now so that should help my groups if I get the velocities to be more consistent .

[Diz]

Leatherman,

I adjusted the barrel length and ran the calculations to get as close to 2200 fps as I could. I ran both IMR-4064 and IMR-3031 and an interesting phenomenon occurred in the numbers. The "faster" powder (*) showed a lower PMax than the "slower" powder. My educated guess is that it has more to do with fill ratios than anything else. Again these are only calculations so exercise caution when working with this information.

27" barrel with 47.0 grains IMR-4064 and 193 grain S&B bullet

PMAX = 23263 psi
Vel = 2197 fps
Fill = 76.6%
Burn = 83.89%
Bal Eff = 23.7%

27" barrel with 43.5 grains IMR-3031 and 193 grain S&B bullet

PMax = 20839 psi*
Vel = 2199 fps
Fill = 71.7%
Burn = 91.47%
Bal Eff = 25.7%

This outcome is very interesting to me and what I like about this program but it all must be taken with a certain amount of caution. The pressures predicted are getting closer to the CIP Max and other factors can work to raise or lower the actual pressure. This data is also just for the 9.3x80R and no other. I provide this information as an example not as proven data and those of you that are not very experienced handloaders must understand the difference. These are numbers produced by a computer simulation and not proven. I have found this program to be very reliable but it is still just calculations and a great deal of experience and good judgement are needed to correctly interpret and safely use it for load development.

Thanks, Diz

[Leatherman]

Thanks Diz. I'll load up the 3031 and see what results I get and com pair with your program. I expect it will be a little different as my 9.3x80 is the Collath version which has a slightly fatter base than the standard 9.3x80R.

[Diz]

Leatherman, hope it works out as planned. Keep us posted. Thanks and good luck, Diz

[Leatherman]

I loaded the 9.3 X 80 Collath with 43.5 grains of 3031 with the 193 grn. Tesla bullet and useing the newly installed scope shot this target today. I used 2 ounces of Dacron filler. The velocities were not as high as Diz's program predicted but I expected it to be lower as the Collath cartridge has more capacity than the normal 9.3 X 80R. With the exception of shot #2 and 8 it isn't too bad a group for hunting in my neck of the country where shots are well within 100 yards. The barrels are shooting 1" apart at 50 yards but I need to shoot it at 75 and 100 to get a clearer picture of what trajectories the barrels are doing. I am going to put another grain of powder in next time. I think this caliber should be over 1900 fps with this bullet. I still have something strange going on with the velocity spread. Shot #6 was lowest at 1797 fps and #8 was highest at 1950 fps both out of the left barrel but I did have some consistency within acceptable range with the rest. I am separating the brass and seeing if that may have anything to do with it. When trimming the rims down I had a couple that I got a little thinner than others so the head space may be the problem.
http://s828.photobucket.com/user/Lea...e_12.jpeg.html

[Diz]

Leatherman,

Thanks for the update. It seems to be shooting fairly well but it is certainly slow to predicted. Better to start off a little low anyway. I was thinking about the variation you are seeing and when you mentioned thinning the rims I immediately thought that there may be a firing pin strike issue. A light blow due to excess head space can lower pressures and increase velocity spread. The position of the case against the face or further in the chamber could make it more erratic. I would suggest measuring the rim recesses in the barrels as well to see if one is deeper than the other but I wouldn't go so far as to suggest adjusting rim thickness accordingly if they are different. You would end up with different cartridges for the left and right barrels and more trouble than it is worth. Take a very close look at the primers to see if you can find a difference in the indent.

Also, did you mean 2 grains of filler? I think you are making good progress.

Thanks, Diz

[Leatherman]

Ha, yes I meant 2 grains of filler. I am going to go through my brass and pick out any with rims that are thinner than what they should be and set them aside. Then load the next round with the more uniform rims and see if the velocities and groups improve. I'm sure there is nothing wrong with the gun itself.

[sharps4590]

Where's shot #1 on the target or did I miss something? Your velocity numbers don't look too bad except for #6. #8 might be a little high but I don't know that it is that far out.