In my Krieghoff 450/400X3, the left barrel gives greater velocity than the right....everytime. Depending on the load, we're talking about anywhere from 3 f/s to as much as 100 f/s as measured thru the Oehler 35P skyscreens. All loads are weighed and assembled as close to tolerance as I can muster. The data is based on 16 different loads.

My question is.....is this due to different barrel deminsions i.e. is the faster barrel cut smaller thereby having a greater pressure buildup resulting in higher velocities? Or is there something else at play here.

Interestingly, while the left barrel is always faster, they are about equal in the accuracy department, sometimes the left wins and sometimes it's the right which comes out on top.

Is there any merit to tayloring the loads for the left barrel to match loads/velocity of the right? Or is this just too extreme?

Comments please.

Thanks

I've had the same thing happen with some powders/loads, but not with all. You could try a different powder.

I don't think it's reasonable for a hunting rifle to have two barrel-specific loads.

quote:

Originally posted by Antlers:
I've had the same thing happen with some powders/loads, but not with all. You could try a different powder.

Antlers,

I used1 brand brass, 7 different powders, 6 different bullets, 10 different charges and 4 different primers for 104 rounds (52 left/52 right). Left barrel faster in all cases.

I had around 30fps difference between barrels from my 470 Merkel and a friend has around the same from his 470 Chapuis.

quote:

Originally posted by bigfats:

quote:

Originally posted by Antlers:
I've had the same thing happen with some powders/loads, but not with all. You could try a different powder.

Antlers,

I used1 brand brass, 7 different powders, 6 different bullets, 10 different charges and 4 different primers for 104 rounds (52 left/52 right). Left barrel faster in all cases.

Nevermind...

How are the composite groups? Some of my best groups had the variance in velocities.

The left barrel of my Trail Guns Armory (Pedersoli) Kodiak MK IV always shows a higher velocity. The chambering is a bit tighter than that of the right barrel.

Bigfats,
Sounds like you are holding that left barrel too tight with your thumb.

Seriously though, I wouldn't worry about it, as long as regulation and groups are good...as you have stated. If you are not pushing the ragged edge of pressure, you should be safe in both barrels.

There are slight differences in the machine work, between barrels...even in the high end British doubles. My friend has a H&H .577 that is .004 difference in throat depth. Barrels can also, have .001-.002 change in bore/groove diameter at different points along the way. I have seen JJ measure many barrels at Champlins. These slight differences can easily cause 20-30FPS difference in velocity...sometimes more.

Just my 2 cents...
ND

I have a 9.3 X 74R that consisently produces higher velocity from the left barrel when using IMR4350 with F215 primers. Accuracuy from both barrels is excellent and regulation is fine. Of ten pairs I tried about a month ago, nine had left barrel velocities higher by 11 to 86 fps - most pairs had the left barrel faster by 25-65fps. The one pair that had the right barrel faster did so by 12fps.

These consistent differences prompted me to try different powder (RL15) and different primers (GM210). I got higher regulating velocities with slightly heavier 4350 powder loads and the 210 primers. The consistent left barrel higher velocities went away. The max difference of 7 pairs was 41fps - the other six pairs varied from 3fps to 26 fps. Only three of the pairs had the left with higher velocities. The 210 primers seemed to make a noticable difference with this particular rifle.

Regards,
Emory

Good lord, who cares?

I'd be much more worried about shooting the damn ________ in the right place than those differences in velocity.

My older Searcy 470 is consistantly 50-60fps faster in the left barrel. Butch told me that is not unusual. He also mentioned that the right barrel may have been shot more, opening it up a mite.

It is no different than two bolt rifles of the same make giving different velocities. No two barrels are exactly alike.

465H&H