I'll try to make a long story short. I have a Model 70 super Shadow in .270WSM that has never shot well with factory ammo. If I got a group under 2" at 100 yards it was a good day. So I decided to try some reloads and see what my rifle would like.

To start off with, I tried to figure out my OCL and the bullet's distance from the rifling. I used the cleaning rod method and got a measurement of 2.860. I figured that was wrong so I did the split case method and got a measurement of 2.867. So now I'm stumped and still not confident in my measurements. I bought a Hornady OCL gauge, a modified case and also the ogive adapter for my calipers. Using the same 140gr Accubond I did the other tests with, I got an OCL measurement of 2.880 and with the ogive adapter a measurement of 2.310. I measured all of the factory ammo I had from the case base to the bullet ogive and I got measurements from 2.210 to 2.272. I got OCL measurements from 2.725 to 2.755. The SAAMI OCL for this caliber is 2.860.

It appears that I will never get the bullets close to the rifling in this gun. Am I doing something wrong? Should I take it to a gunsmith? Sell it? I'm totally stumped.

How long is your magazine? Good luck.

Forget OCL, it is meaningless as long as the rounds fit in your magazine. It is the cartridge length measured to the ogive that matters.

If I read what you wrote right, you're figuring that the factory ammo has to jump around half an inch (2.860-7 minus 2.272-2.210)??? Something doesn't seem right, I've never heard of a chamber that long.

If this is correct you are right, most bullets will probably not be seated deep enough in the case and certainly won't fit your magazine if you try to reach the lands.

Alternatively, either I'm misunderstanding your numbers or your chamber measurement is off. The split case method is usually reasonably accurate. The other method that I prefer is a unmodified dummy cartridge with the bullet colors in black Sharpie. Seat progressively deeper until the bolt will close on it, then carefully creep it back re-covering the rifling marks on the ogive each time until the bullet is no longer marked by rifling when you chamber it.

I have a Ruger in 300 WM that has somwhere between 5/8" and 3/4" of free bore. It took me a really long time to find something that would shoot in it and now I can shoot groups in the 3/8" range and on regularly shoot in the 3/4" range.

May take some shooting to figure it out. If you have the money I would talk to a smith to remove some of that freebore but you'd be better off putting a new barrel on it.

I was pretty upset when I measured my Ruger. I didn't do it until after a I found a load. I kind of learned to reload with that Ruger. So some of it could have been bad reloading practices.

Tom

Thanks for the replies.

handloader1, I never thought about it that way. Thx

spaniel, sorry to confuse you. That was a lot of measurements I put out there. The ogive measurement I got with the Hornady gauge for the 140g Accubond in my chamber was 2.330". The ogive measurement with a factory load of the same bullet is 2.210". The jump would be 0.120". I have heard that you want between 0.010" and 0.020". Don't know if 0.120" would be one of the causes for poor accuracy. If I seat the bullet to attain maximum OCL, it would give me 0.020" bullet jump with the 140g Accubond.

statjunk, thanks for the reply. I guess I will just have to reload some and see what I get.