Can someone tell me if rechambering a drilling will have a major effect on where the bullets land relative to the shot/slug pattern?

The conversions I'm contemplating are either .30'06 to .30R Blaser or 8x57IRS to 8x75RS depending on what I can find. Has anyone been down this path?

I went from 8X57-360 to 8X57 IR in a wonderful pre war Triebel drilling. It shoots low a bit now, so I set the Bottom of the front bead even with the top of the rear sight, and everything is dead-nuts on at 100 yards. I have the advantage of a tang peep in this gun, so I was able to adjust the peep to zero at 175 yards...as far as I like to shoot iron sights anymore.

I don't know that a 8x75RS will clean up a 8x57R chamber.

I would look into that one.

Maybe these pictures helps:

8x75 RS


8x57IS

What is the difference in pressure between the 8x57R and the 8x75R??

Thanks for the responses

Luv2safari: how many fps did you gain with going from the 8x57-360 to 8x57IR?

Moa & Igorrock; I'm still not 100% sure on this which is half the reason for the post, according to the CIP figs the P1's of the x57IRS and x75RS are 11.92 & 11.90mm respectively..

Here's an idea, you could build some kind of wildcat 8mm on a 405 WCF case. I had originally though the 9.3x65 Colath was a good idea, but I don't actually know how big it is.

9,3x65R Collath is the left one, on the right is 8x57 IS.

Hmm, I guess it isn't big enough.

From my last look at the CIP diagrams I'm fairly certain the 8x65R Brenneke was designed to clean up 8x57IRS chambers (presumably they learnt their lesson with the 7x65R & 7x57R). No that's fine and dandy if you have access to 8x65R Brenneke brass and ammo...

If on the other hand you live where the 9.3x74R is the most commonly available rimmed metric, you end up pondering just how important 0.02mm is Anyone know a source of oversized 9.3x74R brass

Isn't a 405 WCF oversized 9.3x74R?

quote:

Originally posted by MOA TACTICAL:
Isn't a 405 WCF oversized 9.3x74R?

Based on Rim and case head dimensions, no. The .405 has a wider rim than both the 8x57IRS and 9.3x74R but is narrower at the all important P1 dimension across the head at 11.73mm

quote:

Originally posted by N E 450 No2:
What is the difference in pressure between the 8x57R and the 8x75R??

Good point and a post I somehow missed

x57R is 3300 bar x75R is 3800 bar

quote:

Originally posted by Gun_Barrel_Ecologist:
Thanks for the responses

Luv2safari: how many fps did you gain with going from the 8x57-360 to 8x57IR?

:

600 FPS...it makes it a viable big game drilling now. I have taken several pretty big mule deer with it in the present form and love the gun.

quote:

Originally posted by luv2safari:
600 FPS...it makes it a viable big game drilling now. I have taken several pretty big mule deer with it in the present form and love the gun.

Did you figure the 8x57 wasn't big enough for mule deer and blk. bear??? I'm just wondering how fast is was going origionally??

DM

I went from 8X57-360 to the full sized 8X57 IR. At 1,700-1,800 FPS out of the little 360 I didn't have any more than a 100 yard rifle, and the deer I have taken with the gun have all been 200-275 yards. The 8X57IR isn't a hot rod, but it is a good medium range round at 2,400 FPS that has readily available factory ammo.

It was an easy re-chambering job.

Yup, that made a big improvement!

DM