Land Depth/Clearance

i bolted in the cartridge with split neck and 100Gr btsp test round, OAL from base cartridge to tip of round 2.775". reload info calls for 2.63" OAL on loaded round. thats an about 1/8 of an inch clearance to rifling lands. Does that seem right or am I getting bogus test readings from cartridge I made.??

Tried it several times, the Bullet is going back in from where it set it in cartrigde after I close bolt and lock bolt. then unlock and withdrawl cartridge and catch by fingers as ejector pushes it over to eject.

Put a cotton plug in the barrel just beyond the chamber where the rifling starts and pour molten Cerrosafe, woods metal or sulfur an find out for sure.

Forgive my ignorance but, why does it matter? Is this a custom rifle of unknown safety?

I am under the impression that closer to lands is more accurate for target shooting. To far back bullet is centered by impacting lands unevenly and bullet looses its optimum profile. like a spiralling football end to end unbalnce in spiral, and closer to land elimainates or minimizes that.

On the other hand, too close to lands there is an increase in case pressure before bullet completely exits cartridge.

Guess I will dry load a case or two at varying lengths several thousands below below measured OAL, and see how they chamber in.

Powder charge is going to have more effect on accuracy. Also, shoot a lighter bullet such as 85-90 for starters, going to the ends of the variety, 55-105gr, ain't gonna help make it easier. Also, are you neck sizing these cases? You should be for accuracy. Also, wipe all case lube from finished rounds before firing.

If you're using that split case you made, chamber it, measure, back off 10 thou, then set your die there and forget it, work on the powder charge till groups tighten up, if not, try different weight bullet and repeat.

mozz wrote:If you're using that split case you made, chamber it, measure, back off 10 thou, then set your die there and forget it, work on the powder charge till groups tighten up, if not, try different weight bullet and repeat.

Thats what I used to find OAL of 1ooGr bullet when contacting land. So back off .010 thousands should be good? working up some loads for up coming deer season. I won't have a lot of time to go out... MAYBE 40 minutes a night after work. So I want something bigger than 85Gr for a longer shot, more impact energy. Of course I will reset scope for round I like the best. 55Gr I loaded for chucks, but nver got up to farm to shoot them.