7x57 - long throat chambering question

[SkullKeeper]

I’m having a barrel made in 7x57 (using a VZ 33 action) and I will be using primarily 160 gr North Fork bullets and older 175 gr Hornady. I’d like to know what distance should the best in terms of JTL (jump to lands) ?
The original magazine on this rifle was for a 270 Win so I have a little bit of room to seat bullets out more than standard if need be. This will be a hunting rifle (not target/match) if that makes any difference.
Thank you for any input.

 

[Rare Breed]

I remember @redleg when he bought his Highland Stalker in the same caliber (275 Rigby same as 7x57) only made the addition and I think it had to do with the lengthening of the magazine throat for larger bullets. I would check with Joe

 

[Areaonereal]

I would think 20 thousand to lands to start for best accuracy and increase 5 thousand from there until it shoots acceptable groups.

 

[Dean2]

Throat the gun to SAMII specs. You do NOT want a round that jams the bullet into the lands, too many potential problems from feeding to extraction to pressure in the heat. For a Hunting load I start .015 off the lands, load up 3 rounds starting just above min and going up .5 grains at a time, determine max load. Back off 1 full grain load 3 of each seated shorter .01 at a time to find best group. Most of my cartridges like jump of about .05 with Barnes and .03 with Hornady. My current 7x57 likes jump of .040 with the Hornady 175 and the 154s.

 

[Joker12]

Good advice from Dean! My experience is the same, a #1 Ruger that is properly throated for 175s so anything else is a substantial jump to the lands. It just doesn't seem to matter as it shoots 154gr Hornady very accurately. My experience is that for the folks playing the accuracy games bullet distance to the lands may be important but not so much for the rest of us.

 

[fourfive8]

I believe a standard 7x57 reamer will have throat specs to handle the older style 175 gr round nose bullet. Ask whomever reams your chamber the type of reamer they are using. Some special order reamers may have shorter throats. If standard, you should be good to go. Seat to cannelure if bullet has one or for a minimum .025-.035” jump to lands. If the chamber and throat are reamed plumb and on axis, a little excess freebore will have minimal negative effect on practical accuracy and a bonus of some insurance against over pressure surprise.

 

[Clodo Ferreira]

Hi SkullKeeper
The following link has the 7x57 C.I.P. dimentions of the chamber and the cartridge https://bobp.cip-bobp.org/uploads/tdcc/tab-i/tabical-fr-page33.pdf
I recommend to use that dimentions for the chamber of your rifle barrel. They are the right ones for all the bullets you will use. More so if the magazine has the 30-06 / 270 Win lenght!

Good luck!

CF

 

[Clodo Ferreira]

I add that with that chamber jump-to-the-lands dimention and that magazine lenght, you can load the 7x57 with a much longer OAL. This allows to use all the case volume even with 175 grs bullets. This is what I do with my 7x57 made with a M98 1935 Mauser action and 175 Nosler Partition bullets, my all around favorite. I reach velocities very near the 7x64 (also made in a Std. M98 Mauser...) with R22 or R19 powders at absolutelly safe presures.

 

[SkullKeeper]

Thank you VERY MUCH to everyone that has contributed so far !!

 

[WAB]

I would decide on the optimal length for the bullet you want to use. Make up a dummy round to work from. I would then chamber to be 50 thou off the lands as long as that is SAMII or longer. It’s OK to be longer than SAMII, it’s definitely not OK to be shorter. Once you start loading, if it doesn’t negatively affect accuracy, 100 thou is better.

I have 3; 7x57’s. One is SAMII, two are longer.