[scowens]

I have two questions:

1. Is the C.O.L. listed in manuals a min, max, or "target" dimension?
2. What is the normal variation from this?

I'm wanting to work up a load and not sure which way to go, possibly longer.....

Thanks!
Steve

 

[Range Junkie]

The COL listed in the manuals is usually the minimum length. You can go longer and it will decrease pressure due to the fact it increases case volume when you do so but going shorter will decrease case volume and increase pressures. Many people load there rifle cartridges longer in an attempt to make them more accurate (trying to find the sweet spot if you will). It decreases the jump to the lands but if you want to be able to load them through a magazine then the magazine dimensions will usually dictate how long you can actually make them.

 

[Saskshooter]

You need to check each COL you read to find out what it means. It may mean the COL listed is simply the one used for the testing the manual writers did to get the data. It may be the SAAMI listed maximum length. It may be a dimension a reloader is using in his specific rifle. It is unlikely to be a "minimum" of any sort.

Reloaders do vary COL quite a bit, but only after careful consideration of factors like the maximum length of the chamber in the specific rifle, amount of bullet "jump" to reach the lands, length of bullet being held by the case neck, intrusion of the bullet into the case powder space, magazine length, and other factors.

Before you use a listed COL as a basis for your decisions, make sure you understand what it means in the specific case you are reading about, and in your own specific rifle.

 

[broom_jm]

By and large, the COL you see mentioned in reloading manuals is the SAAMI spec and the longest length you could reasonably expect to cycle cleanly in any gun/action chambered for said round. In many cases this length can be exceeded with the end result of better case capacity, slightly improved internal ballistics and, potentially, greatly improved accuracy.

Many experienced reloaders use a gauge, or mechanical methods, to determine the longest allowable seating depth for a given bullet in their gun, and then back off .010" - .020" to see where accuracy is best. If this load is to be cycled through the action (as opposed to strictly being used for target shooting) then you would need to determine whether or not your gun will reliably feed a cartridge of this length. If it will, and the accuracy is there, you're all set. If not, you'll have to find the best compromise of COL that will feed reliably vs. best length for accuracy.

It's all part of the fun of reloading!

 

[zb338]

Most of you know about it. There is a gauge called the Stony Point
O.A.L. gauge. It's not very expensive and it is very simple to use.
They have two types. One is for bolt guns or anything where you
can get at the chamber, and the other is bent so you can use it
in lever actions and pumps.

Zeke

 

[unclenick]

Not anymore. Stoney Point sold out that line to Hornady a couple of years back. It is now the Hornady Lock-N-load Overall Length Gage, though some vendors are good enough to put "formerly Stoney Point" in parentheses in the name.

The COL in a manual that is specific for a bullet is sometimes the minimum for their load recommendations, as seating deeper may raise pressure? This is tricky in rifles, as seating longer will also raise pressure if you go far enough. There are also two instances in which manual COLs may be maximums: in a revolver load that cannot be allowed to stick out beyond a cylinder, and with a load that has to fit a magazine that has no extra room available and must feed smoothly (the SAAMI cartridge length number is a maximum for that purpose among guns complying with SAAMI or CIP specs, which modern non-custom guns typically do). Other times the COLs may correspond to the location of a crimp groove or a crimp cannelure on the bullet, and you will need to use it if you want to roll crimp the case to maximize start pressure, which is often especially desirable if you are using a powder on the slow side for the chambering and bullet combination.

 

[scowens]

Thanks for the replies!

One more question: Let's say I finally find the magic bullet depth. I'm not shooting bench rest, so I'm not looking for that accuracy. However, once I find the depth, will that stay the same, while going from one powder to the next? From one bullet weight to the next (55gr to 62gr.)? Shell to shell?

Thanks all!

Steve

 

[Saskshooter]

Thanks for the replies!

One more question: Let's say I finally find the magic bullet depth. I'm not shooting bench rest, so I'm not looking for that accuracy. However, once I find the depth, will that stay the same, while going from one powder to the next? From one bullet weight to the next (55gr to 62gr.)? Shell to shell?

Thanks all!

Steve

No it may not stay the same. Reloading is always a giant experiment with more variables than can be controlled. Any change in any one of those variables can produce changes in results. Or it may not.

If you change a variable, you must expect to start again with the "work up" process, and you cannot predict the consequences with just logic. Only experimentation will work.

 

[cvc944]

Without getting too technical, bullet profile is the only variable in your question. If you switch to a sleeker bullet and use your existing seating die, you will end up farther from the lands than you originally were. If you switch to a more blunt bullet, you will end up closer to the lands than you originally were. At this point I don't worry about it. I just go to the range and see how they fly.

 

[unclenick]

In addition, if you read the sticky with Walt Berger's comments, you will find some bullet styles don't want the same distance off the lands as others. It's all individual.

 

[dmsbandit]

I load to the magazine length of my gun if the throat will allow it. Most of the time, the base of the bullet is sitting at the neck-shoulder junction. Seating bullet out too close to the throat will raise pressures, and doesn't guarentee the best accuracy. Weatherby rifles have VERY long throats to keep pressures in check, and few people complain about bad shooting Weatherby rifles.

 

[MikeG]

I start with the same seating depth as one that's known to work well in that rifle, but it may need tweaked, yeah....