I am chambering a 308 case and 180 gr bullet bullet into a 308 chamber to the point that bullet hits lands. I'm getting 2.880. How much should I back off ( how far back should I seat the 180 gr bullet) on the charged round so that pressures does not build up excessively? Is there a general rule here?

I saw on a tv show last night that the recommendation was ten/thousandths off the lands. I can't recall the show but do remember Jim was the host.

Start with a low powder charge and seat the bullets .015 off the lands. Load 5 at that measurement, load 5 at .020, 5 at .025, and 5 at .030. The rifle will tell you which it likes best. Then, and only then start building your powder charge to the desired load. Always start low and increase the charge slowly. This has always worked for me with all calibers.

Thanks guys. Much appreciated.

I think it depends on what bullet you use. Call the Barnes people and they tell you to seat 50 thou off the lands. That's for their bullets. Others may like different distances. I use the magazine length a lot of the time if it doesn't end up jamming the bullet into the lands. I seat it out as far as the mag will allow and not hang up while trying to feed the chamber. Remember, the farther you can seat it out the more powder you can get into the case. The 308 case doesn't hold a lot of powder and if you use a slow burning powder with the heavier bullets then you have a less likely chance of being too hot.

Bullet choices determine seating depths as does your individual rifle. Berger bullets like being in the lands, Sierra's IMO do best about .010" out. What is important, however, is that there are no hard and fast rules as each gun is an individual and will show you on paper what it likes best. Experimentation is the answer.

Experience has taught me that when changing seating depth, one should do it in increments of .010" as anything less is a waste of time IMHO. It also has taught me that a good place to start is about .025"/.030" out of the lands.

Something else to keep in mind is that hunting rifles probably shouldn't have bullets seated into the lands. Hunting rifles are loaded/unloaded so frequently that one shouldn't risk sticking a bullet in the lands while out in the field.

If the magazine length will permit, I load all of my rifles with bullets seated .010 off the lands. There is nothing that says another depth will not also shoot well. But, after 59 years of reloading, I have come to know that .010 works for my rifles. So, I go straight to .010 and never do any testing as I used to do years ago to see what depth works best with a given load.

Don

I go .010 off also. With 180s in my 308 I like the lapua 185s or other 180s without a long tip(round nose even) so they fit in the mag and also can be seated out to the lands

we'll, ive only every really used plastic tipped bullets, A-maxs ballistic tips and accubonds are the 3 I use most. i start around a 5 thou jump and see what powder charge shoots the most accurate. I do 5 shot groups. 5 thou, 15thou,25thou. if its getting more accurate and more accurate id continue till it started opening up again. I think moving in lots of 10thou increments exaggerates and changes your having,example: if it shoots the same sized groups at 15 thou and 25thou id try them at a 20thou jump.


Amazingly ive had 1 shot kills with A-maxs, ballistic tips and accubonds with the ones shot with a-maxs dropping straight away from a chest shot. although some would have you believe that a partition and a barnes bullet are the only 2 bullets that could kill an animal

quote:

Originally posted by Exit31:
...How much should I back off ( how far back should I seat the 180 gr bullet) on the charged round so that pressures does not build up excessively?

Hey Exit31, You can leave it right where you have it, but there is an occasional chance the Bullet could stick in the Barrel when the Case is removed. That being something to avoid when Hunting, it is your option on how far back to go. Some Bullets do extremely well when way back off the Lands.

If you were using a "Straight Wall" Case such as a 357Mag, 444Mar, 45-70, etc, when you Seat the Bullets into the Case farther than what is typical, the Pressure tends to rise very quickly. This is because of the relatively High % of Case Volume which is being affected. With a Bottle Neck Case, the % Change is less, but you are correct to be cautious about how the Pressure reacts.

quote:

Is there a general rule here?

Yes there is, Always watch ALL the Pressure Indicators when ever you make a change. If only one of them indicates something strange - STOP - and determine what has happened.

As for me, I still like to use the time-proven, never-fail, highly-repeatable, inexpensive and easy to understand CHE & PRE Pressure Indicators. PRE works with every Cartridge. CHE has some limitations, but can be used with a majority of Cartridges.

If you learn to use CHE & PRE, then you can make adjustments to your Cartridges and easily "compare" how the Pressure is affected.

Best of luck to you.