Inconsistant loaded round COL?

[Chopaka81]

This past weekend we measured the bullet to rifle barrel lands engagement and adjusted the bullet seating depth. We adjusted my 300 RUM standard RCBS bullet seating die for 0.003" off the lands.
What we are seeing with loaded rounds now are variances of +/- .002".
I am using a RCBS Rockchucker press. The bullets are Hornady 208gr A-Max's.
Is +/- .002" all the better I will get with this press/bullet seating combo? The press seems to be pretty tight.

 

[Jinx-)]

Probably stupid thing to ask, but did you sort your bullets by ojive length

 

[Chopaka81]

good question. no we did not sort the bullets.

 

[Delta Hunter]

So, you're measuring to the tip of the bullet and not to the ogive? The differences you are noting are normal if you're measuring to the tip of the bullet.

 

[Chopaka81]

We are measuring to the ogive.

 

[bigngreen]

You can also get that if your not very consistant with your method of seating and hitting the bottom of the stroke differently when seating.

 

[Boss Hoss]

I have used this for years----COL does not mean SQUAT except in a magazine anyone who tells you different does not know what they are talking about and you should just smile and walk away lol!!!

Measure Bullet Bearing Surface and Bullet Sorting for 6mm Benchrest Precision Shooting

 

[Boss Hoss]

You can also get that if your not very consistant with your method of seating and hitting the bottom of the stroke differently when seating.

Agreed -- that is one of many reasons why I use a Wilson Seating Die and an Arbor Press...

 

[Delta Hunter]

One more thought, are you compressing the powder when you seat your bullets? I've had bullets back out of the case a bit after seating them over compressed charges.

 

[Boss Hoss]

One more thought, are you compressing the powder when you seat your bullets? I've had bullets back out of the case a bit after seating them over compressed charges.

That is correct----one reason why I never compress loads (just build a bigger rifle or use a different powder) and the people who do that and seat too close to the lands can get a very ugly surprise when they least expect it. .

 

[Delta Hunter]

Yea, I no longer use compressed loads either.

 

[woods]

IMO .003" is too close to the lands to seat the bullets. Any variance will make a larger difference and it is possible that some of the bullets will be seated on the lands which will make a difference in POI. Not too much pressure difference unless jammed into the lands, but a minor pressure increase which will cause the POI shift.

Better to seat .030" off the lands and find a good load by varying powder charge weight. There are a lot of rifles that have a tremendous jump to the lands nowadays and many of them shoot lights out. Most Weatherby's and Ultra Mags have as much as .250" jump to the lands when you seat to fit the magazine. Barnes bullets recommend a jump of .050" (not .005"). Now this is mainly for hunting guns and not benchrest.

YMMV

 

[boomtube]

I strongly agree with Woods that 3 thou, even if that precision were possible, is "too close for comfort." You're loading for a hunting rig, not a bench rifle.

Reloading for common rifles ain't like making a watch; seating within +/- 2 thou IS precision for what you're doing.

 

[Boss Hoss]

FWIW---I load my hunting ammo for my rifles at about 3-4 thou off the lands and have never had a problem. Still sort bullets by bearing surface but that being said there is still the possibility of a surprise but so far after many years no problems. One reason I feel comfortable in doing this is my rifles were all chambered correctly meaning absolutely square… This quickly gets to be a situation where is a tiny bit of accuracy in most cases worth the possibility of missing a shot because of a stuck bullet…..