Switch barrel/pet load advice

[chino1969]

I'm looking for advice for people who have had some experience with switch barrel rifles and load development data.

My rifle is a Savage single shot action with a Douglas 1:10 barrel in .243 A.I. with a standard neck diameter. I have developed several very accurate pet loads for groundhogs with this rifle. There is a brand new Pac-Nor 1:10 barrel sitting in my safe that I had made with my .243 A.I. reamer with a .270 neck diameter to replace my original barrel when it stops performing. My question is this:

1) Can I expect pet loads that I've already developed in my old barrel to be fairly close in my new barrel? I know to back off my powder load some during load development for safety, but is it reasonable to expect the load that worked in my old barrel to be fairly close in my new 1:10?

Any info. or experience would be greatly appreciated.

 

[Forum Boss]

In our experience the PacNor tubes tend to be on the tight side in bore diameter, which is normally good for accuracy. But it may mean more pressure with less powder. Assuming identical chamber dimensions,since the reamer is the same), we'd start a full 1.5 grains low compared to what you're using now.

Also, if the PacNor is a three-groove, you may find enhanced accuracy going into the lands.

Starting in the lands can increase start pressure. On the other hand, moving the bullet up and away from the powder column effectively increases case capacity. Therefore it's somewhat hard to predict what will happen to your pressure. There are too many variable. You didn't mention what bullet you're shooting, but if you try the 95gr BIBs, I suggest .010-.015" into the lands.

If you have a load for the 87gr Hornady V-max I would start 1.5 grains off that for the BIBs, then work up in .2 or .3 grain intervals.

 

[chino1969]

To Editor in Chief:

Thank you for the info. and reply. The bullets that I am using are the 70 gr. Nosler Ballistic Tip, the 80 gr. Berger MEF, & the 87 gr. Hornady V-Max. The Pac-Nor is a three groove barrel. The only reason that it is not on my rifle currently is that my old barrel,approx. 1500+ stiff loads) is doing so well, I can't find a reason to take it off. The 70 gr. Nosler velocity is 3675 ft/s and the 80 gr. Berger is 3550 ft/s. I've been able to put five shots into a .357 group @200 meters with the Bergers. Bear in mind this is a live varmint rifle, not a benchrest gun and i couldn't be happier with this type of performance. I've shot equally impressive groups @300 & 400 meters with the 80 gr. Berger MEF. I am still fine tuning the 87 gr. V-Max load. Maybe I've just been lucky, but I did not expect this barrel to last this long.

I also have a Pac-Nor super match 1:12 made with the same reamer that the Pac-Nor 1:10 was made with. I'm chomping at the bit to try either of these two barrels, but until I see some degradation in my old barrel I don't want to mess with success.

Any ideas or suggestions would be greatly appreciated. By the way, this web site is excellent. The threads are full of technical acumen by experienced professional shooters.