gents

While waiting for a McMillan stock to arrive, I sacrificed 2 bullets and cases to see how deep I have to seat the bullet in the case and still be able to chamber the cartridge.
I seated the bullet shallowly, then put the cartridge in the magazine and cycled it through the chamber. When i could turn the bolt down to its locked position the bullet was pushed back into the case, but still touching the bore grooves, right?
I then ejected the dummies and measured the length with my digital caliper, which gave the Maximum Over All Length for the particular bullet in this particular rifle.

The COAL for the two different bullets in my CZ ZKK602 are as follows:
3.823 " for the Barnes Banded Solid 300 grain
3.665 " for the Swift A-Frame 300 grain

This is 0.218" longer than the length of a factory loaded Swift A-Frame of 3.447"

My question is then if a part (not all) of this length difference would allow for a more shallow seating of the bullet in order to reduce the freebore and increase accuracy? I would guess that around 0.04" freebore will be minimum?

In the case of the longer solid bullet, more space in the cartridge could then be used for gunpowder since this length also fits the magazine.
Is this a way of creating a poor mans "improved" .375HH?
Or will the pressure of having a solid monometal bullet close to the lands/grooves go through the ceiling?
Shall I take advantage of the long magazine box in the CZ or stick to factory OAL?

So far am I still using factory ammunition for hunting, while plinking is reloads. As the new stock arrives and when it is all bedded and done, then will I start reloading these solids too.

Sincerely
Daniel

Daniel,

My procedure is as follows: I work up loads with the bullet seated out as far as it can, while still fitting in the magazine, and not touching the lands. When I have settled on a load (I normally look for small extreme spread in a reasonable velocity range without pressure signs), I load up a couple of batches, reducing the OAL by 0.5mm increments, shooting only for groups.

If using monolithic solids, you should not use less than .040-.050 freebore. Start there and reduce OAL until you get the best groups.

Hej Daniel

I used to have the exact same model (perhaps you even have my old rifle!), and my loads were 95mm long if I recall correctly -- in any case, bullets were seated about 5.5mm out compared to what their cannelures indicated was 'normal'.

Go ahead and take advantage of the long magazine box! Just make sure that you don't jam the bullets into the rifling or pressures can climb and this can also result in a mess if you eject a loaded round and the bullet is pulled, dumping the powder.

I started to experiment with differing seating depths to see which gave the best accuracy, but to tell the truth the rifle shot damn near everything so well it was just not worthwhile. Those bullets were expensive, and it takes a lot of concentration to shoot tiny groups with the .375 Ouch & Ouch off the bench! :0

John

Gents

Thanks for replies and suggestions!
I will take it easy and try to find a load where the 2 bullets are finding their way to the same point of impact. Hopefully, this can be done without too much shooting. The bullets ARE expencive, and it sure is a bit of pounding in trying to get small groups from the bench.

JPB
It might be your old rifle, if you sold it in Luleå a few years ago? The rifle is made in 1985. It kicks like a mule right now with the bent monte-carlo stock and a hard factory pad. I keenly await the arrival of the McMillan stock.

Sincerely Daniel

quote:

Originally posted by Huglu:
JPB
It might be your old rifle, if you sold it in Luleå a few years ago? The rifle is made in 1985. It kicks like a mule right now with the bent monte-carlo stock and a hard factory pad. I keenly await the arrival of the McMillan stock.

Sincerely Daniel

Hej igen Daniel

I sold my rifle to somebody in the south of Sweden, so it is not likely mine. I should not have sold it really -- it shot great, and many loads to the same point of impact.

It was just that I was tempted to buy a friend's Sako in .375 H&H -- McMillan stock, pillar bedded, great trigger job... so I had to sell the Brno (hard to justify 2 .375's in Sweden! :-)

The Sako cost me a lot more than the Brno. It didn't shoot any better than the Brno (which is to say: great!). The Sako is a bit lighter is all...

John

quote:

My question is then if a part (not all) of this length difference would allow for a more shallow seating of the bullet in order to reduce the freebore and increase accuracy? I would guess that around 0.04" freebore will be minimum?

Please note that seating bullets closer to the rifling, "to reduce freebore", does NOT necessarily increase accuracy. Some of my most accurate .375 H&H loads have been with bullets seated a lot deeper than you would generally seat them!

Just one note that using 2 different bullet styles and designs will have a different COAL. Some bullets have a differen ogive and lengh to them,so your COAL will change according to your chamber. van