.300 win mag o.a.l.

[moooose102]

so i have read that a degree of accuracy can be gained by seating the bullet a couple of thousandths of an inch away from the rifling. so i did a little experiment today with some hornady a-max bullets. i purposly kept seating them longer until i got one that the bolt wouldnt close on, and started shortening it by .005" at a crack until the bolt closed. once i reached that point, i lengthened the next 3 until i got it to hit the lands. that point is at an oal of 3.560". according to the books normal aol should be 3.340. i know that a-maxes are quite long, but is it really sound right to go out to 3.558" oal (.218" longer) (and .002" off the lands) for these? actually, believe it or not, they will clear the magazine walls at that length! fyi, its a remington 700 rifle. also, should i start @ the lowest powder recomendation, or reduce it further than that for the extended length? i will be using IMR 4831 powder w? 178g a-maxes.

 

[Cypress]

The longer length should lower pressure not raise it unless the bullet is contacting the lands. I usually seat mine betwwen .010-.030 off the lands and then test rounds in .5 grain increments using regular load data. Some guns have shown improvement some haven't.

 

[ranger335v]

Book OAL figures seem to cause a lot of angst. That length is no more "engraved in stone" than the powder charges. Use the length you want and develope your charge accordingly. Not too many years ago NO loading manual listed any OAL at all, we survived nicely then and still can.

You will likely find that seating to touch the lands, or nearly so, is simply another "old wives tale" repeated until it has become "fact". It's not though, most sporters will shoot best with bullets well off the lands but we have to try it to find out.

 

[MMCSRET]

This procedure is a boon to accuracy, however most of the rifles I have done it for had magazine boxes too short to allow the longer rounds to be inserted into the box. Consequently I seat as long as the box will allow. Guess thats why I like single shots.

 

[Clark]

My 300WM VZ24 mag box started out shorter, and I worked hard to make it big enough for 3.34" cartridges tipping up on the edge of the base.

 

[Afy]

Ranger335

With all due respect almost every in benchrest seats to touch the land. I presonally seat to about .002 away.. and yes the accuracy did go up.

It might not make too much of a difference if you're using the rifle to hunt primarily... but when you are shooting for groups it does make the difference between a .75 MOA and .5 or better MOA 5 shot group.

Simillarly I consider a .300 WM to have a barrel life of about 1200 rounds, while most hunters would laugh at this and continue to shoot and successfully bring down game at 5 times that number.

Also some of us dont care about what will fit into the magazine. We're happy loading one at a time.

 

[Der Verge]

Most loaders say that pressures increase as you get closer to the lands. I would back off the load a bit when legnthening the OAL. My $0.02

 

[243winxb]

You will likely find that seating to touch the lands, or nearly so, is simply another "old wives tale" repeated until it has become "fact". It's not though, most sporters will shoot best with bullets well off the lands but we have to try it to find out.

+1 also, if the base of the bullet is at the neck/shoulder juncton, with the bullet just out of the lands, that would be perfect. Custom chambers/throats/leeds are cut this way. Having the round centered in the chamber is the most important.

 

[Jim Watson]

Bullet noses are not always consistent within .002". Unless this is a target rifle - 178 A-max, maybe it is - I would pull them back about .020" to insure clearance.