Home Forums Hunting & Shooting Ask The Gunwriters How do you determine COL?

rosco,

Using a bullet in a fired case is "close enough" for determining proper seating depth that a bunch of winning benchrest shooters use it. In my own benchrest rifle it resulted in 5-shot groups averaging around .18" with a minimum of fuss. Which is part of why I use exactly the same "tool-free" method as Steelhead.

oregontripper,

"2 in 1 out" happens because 3-shot groups aren't sufficient to really reflect the accuracy of a rifle and load. The spread of ALL shots will be larger than the average of 3-shot groups, so the "flier" is simply a shot that's part of the overall picture.

Four-shot groups are superior for testing accuracy, and more shots are even better.

I start with the bullet close to the lands because seating it deeper results in less pressure, so there's no danger involved after finding the best powder charge with the bullet seated just off the lands.

Thanks.

The quote is the reason I suggested the comparator is a useful tool,but certainly not a requirement. Just a quick way to check a lot run change BTO without starting over. Wont take throat wear into account tho, curious how often (shots) you check the wear on your more accurate rifles.

I learned this from Benchrest shooters decades ago, and as a writer who specialized in reviewing rifles and developing loads for the reviews, I proved hundreds of times it worked and this advice is being repeated and proved over and again by readers here and other sites where the advice has spilled over.

If you want to know a maximum dimension for OAL, consult you reloading manual.
If you want to know whether that dimension is relevant to your particular rifle, try it in your magazine box to see if it will really fit as a starting point but also confirm there is enough leade to chamber that dimension before running off to the range. Some rifles will house an OAL but not chamber it, Ruger, being an example.

So, how you you "know" I am wrong?

John

It depends on the rifle. I seat a bullet in a case, with the case-mouth pinched just enough to hold a bullet firmly but not so firmly it can't be easily pushed back when chambering a round. Then I chamber the test round, and most of the time find rifling marks on the bullet.

In my benchrest rifle I then shot several loads with this "jammed" seating, and after finding the most accurate powder charge, tried a few more loads with the seating depth varied slightly, using a micrometer seating die. Turned out jammed was most accurate.

In a hunting rifle I keep seating the bullet slightly deeper until the rifling marks disappear, meaning the bullet is just off the lands. This usually requires at least .02" more seating depth, but varies with the bullet, chamber, etc.

That seating depth usually results in the accuracy level I'm seeking, but if it doesn't I try seating the bullet slightly deeper with the same powder charge. I start with the bullet close to the lands because seating it deeper results in less pressure, so there's no danger involved after finding the best powder charge with the bullet seated just off the lands. Once I find the seating depth that shoots best, a dummy round with a bullet seated to that depth goes into the die box.

Of course, sometimes that seating depth will have to be tweaked, whether due to another lot of bullets with a slightly different ogive, or throat wear, or whatever.

I know you shot a crown royal box one time steelhead.somehow i doubt you could teach me much..

I know you shot a crown royal box one time steelhead.somehow i doubt you could teach me much..

Point is, measuring a bullet base to tip with a caliper aint repeatable, may as well throw the caliper away and run the test everytime you change up.

I know you shot a crown royal box one time steelhead.somehow i doubt you could teach me much..

Point is, measuring a bullet base to tip with a caliper aint repeatable, may as well throw the caliper away and run the test everytime you change up.

I know Amaxes have changed some over the years......but I don't believe bullet makers typically retool frequently just to move ogives back and forth. Or do they?

I know Amaxes have changed some over the years......but I don't believe bullet makers typically retool frequently just to move ogives back and forth. Or do they?