Loading to lands for new rifle

[jpwilly]

Background:
Okay, I'm working up some loads for the range tomorrow. I have the standard Ladder Loads with varget and 168gr Match, 150gr BTHP, 155gr AMAX and some Federal 150gr SP factory ammo for barrel break in. The rifle is new a new Savage 10FP 308 Win.

I made up 10 dummie rounds with 155gr A-MAX and seated them long. Chambered them then measured the COL/AOL. They averaged from 2.8285" to 2830".

Question:
Normally I load 308 Win to 2.800" AOL so the above would indicate that with there AMAX 155gr pills I'm going to have a .030" jump to the lands. Would you recommend that I make some ladder loads to try different seating depths?

 

[jbkebert]

I have been using a hornady OAL gauge. I make up ladder loads at .010, .012. and .015 off the lands. Making up batches of 5 rounds. So my loads for a .308 would be using RL-15

38.8, 39.3, 39.8, 40.3, 40.8, 41.3 grains RL-15 168 gr A-max match

5 rounds each so 30 rounds loaded at .010, 30 rounds and .012 and so on. I clean the barrel between each group and fire one fouling shot of cheapy stuff then shoot for groups. I find the best groups in each length and narrow it down from there.

Not nearly as picky with hunting rounds and usually just seat them at .015 off the lands find the best group, fine tune and call it good.

 

[Ol` Joe]

If the cartridges will fit the magazine at 0.03" over saami max you can load to the lands and work back from there. If not start at the max lgt that fits your mag or hits the lands, which ever is shorter.

 

[something vague]

Not sure what Ol' Joe is saying? I would go through with your ladder test looking for the best powder charge weight the first time out. And I would load all these loads around .010"-.015" off the lands, pick one. As always pay attention to pressure as you get close to the higher end of the charge weight. After you find your best load with the certain powder weight then I would start experimenting with how far off the lands your rifle prefers them. I would use the measurements that jbkebert gave you but I would also throw in .000", .005" and .020". And ALWAYS start with group that is the furthest away from the rifling and again keep a close eye on pressure signs the closer you get to the lands. The less bullet jump, the higher the pressure gets especially with zero bullet jump. Some people's rifle prefers the bullet into the lands but I have yet to come accross one of my own that likes them this way. I usually end up around .005"-.010".

 

[jpwilly]

Assuming there is at least .010" jump is the pressure more than say a .030" jump?

 

[jbkebert]

Assuming there is at least .010" jump is the pressure more than say a .030" jump?

Yes the smaller the jump the more pressure will build. As previously posted start with the farthest out and work in closer checking each and every casing for pressure signs. If you get them don't go any closer or any hotter.

 

[Bullet]

While this is not what you asked for you might consider this (copied from another forum)-

“There are some pretty universal rules about seating a bullet. You first seat the bullet to a given depth and then work up with the charge. To do otherwise might lead to a pressure excursion. Do you know how to read pressure in a rifle case??? If the radius of the primer is gone,the bolt lifts hard,you can see the extrusion of brass back into the elector hole,see the machine marks on the bolt face in the brass or the primer flat falls out of the case the load may be a bit hot. BUT, this can and will happen regardless of where the bullet is seated if you tip the powder bottle too much. Here's a very easy way to develope a load:
1)-Set the bullet into the lands(if you can reach them) as much as the neck tension of the case will allow.
2)-Start with a minimum listed powder charge or -10% for the bullet weight
3)-Work the powder charge up till the groups get as small as they will get.
This depends on the rifle.
4)-After getting as small a group as the rifle will shoot at the jam,back the bullet off.002/.003 at a time and see if the groups improve.Depending on the rifle they may or may not.
5)-If you decide on trying another bullet back the powder down and go back to the jam length and start again.
What this saves is guesswork. If the bullet is seated HARD into the lands then the only way to go with it is shorter. If the bullet is seated HARD into the lands and you have a safe working load pressures will NOT increase as the seating depth is shortened. If you, at any point,. get pressure signs, STOP. Back off the powder and start up again and see if it repeats. Be aware that a load shot at 70 degreesF. may not be a safe load at 100 degrees F.Back a load off when you change ANY part of that load including changing lots of the same brand of powder. Never assume anything;prove it to yourself. There is not really a lot of rocket science in rifles; experience is much more important”

If you load long enough to reach the lands the cartridges may not fit in your mag.