Bullet Seating Length

[BABore]

I load for many different rifle calibers, mostly bolt guns and single shots. I usually seat my bullets to be 0.010 to 0.020 off of the lands. This is measured with a Stoney Point gauge. I understand the magazine length aspect and pressure differences. What I would like to know is, is there that much difference in accuracy if I were to start seating the bullets to standard depth. These are all hunting rifles. My typical accuracy is 1-1 1/4 inches at 100 yards.

[Bullseye]

Every gun is different and you will not know untill you test ammo loaded each way.  Some guns actually shoot better with the bullet farther away from the rifling.  I load all my rounds to the COL in the reloading manuals.  I have experimented some with a couple calibers and could not see enough difference to justify the time.  Now I am not a benchrest shooter, just a target shooter and hunter but I can get 1" or less groups with all my guns that should using the COL and that is good enough for me.  Your testing and the testing of others could prove different.

[Questor]

I have one contender barrel where it made a difference, but that was for the finicky-est barrel I own. It didn't like anything except one particular load that tamed it to be a 1" gun.  It might make a difference for you, but I caution that this game can get expensive, because the next step is to fool around with a multitude of powders and bullets.  It's not worth it, unless you like that sort of thing.

[bullet maker]

Every gun is different and you will not know untill you test ammo loaded each way.  Some guns actually shoot better with the bullet farther away from the rifling.  I load all my rounds to the COL in the reloading manuals.  I have experimented some with a couple calibers and could not see enough difference to justify the time.  Now I am not a benchrest shooter, just a target shooter and hunter but I can get 1" or less groups with all my guns that should using the COL and that is good enough for me.  Your testing and the testing of others could prove different.

Hello bullseye
  What is COL? I know that OAL is (overall length), but I never heard of COL.  Please explain.
thanks
bullet maker

[Questor]

They're both exactly the same thing. COL stands for cartridge overall length.

[longwinters]

My, limited experience, seems to go with the thought that OAL/COL does make a difference. I would go so far to say that all of my rifles shoot better with my reloads, with a longer OAL, than factory load lengths.  Well, except for my Tikka 243 that does not seem to care.  Of course this is not a scientific testing: just a guy shooting his rifles and seeing how close his groups are.

[KN]

I have a 700VS that prefers the rounds short. Set for magazine length. And a Contender carbine in 223 that prefers them short. In fact if I set them out to about .025" off the lands the thing will start vertically stringing. As was stated earlier every rifle is different. Find a load that works pretty good and experiment from there.  KN

[paperpuncher]

My understanding is that the logic to seating bullets close to the lands is to minimize the jump so that the bullet starts off relatively well aligned with the rifling. In fact, a number of bench rest shooters seat there bullets to touch the lands.

I agree with Bullseye. Every gun/cartridge is different and you will need to experiment with the OAL (along with many other variables) to determine which works best in a particular rifle

Most of my reloading is for heavy barreled bolt action varmint rifles and I find the best accuracy with the bullets seated .010 to .020 off the lands. If you are reloading primarily for hunting, then I strongly recommend not exceeding the published OAL for your bolt guns. In this case, it is important that the cartridges feed smoothly from the magazine.

Also, if you are concerned with seating your bullets close to the lands, a great tool is the Sinclair Bullet Comparator. For a given rifle, you only need to determine the best seating depth for one bullet make/type. After you determine the comparator measurement for that bullet, you can change to another bullet type/make and just seat it to the same comparator reading - and the jump will be the same.

[Donna]

BABore-

The main reason for OAL/COL specification is to insure that the cartridges will fit into the magazine of the firearm. What a person is actually doing when they are changing the seating depth of the bullet, whether or not they are aware of it, is performing a vibrational analysis of the load/firearm system. I have found that seating depth changes causes the single most important variable in the load/firearm system. Some firearms are more sensitive than others to variations in loads acting as vibrations in the total system. But any time a component or a combination of components are changed the load development of changing seating depth. What I like to do is start at the minimum load charge and just touching the lands then backing off to a max of 0.020 inches off the lands before I change any components. When I find a seating depth I like then I start increasing the load charge till I get the velocity I want, within the proper limits. Then I recheck the load by changing the seating depth plus and minus 0.005 inches. By this time I have a really good load for my firearm. But this is only after the firearm is free from variable affecting its own shooting ability.

Donna

[longwinters]

Donna,

What you have said makes sense to me.  I have been looking for a better system of looking for those "magic loads" and from your comment here I think that I will have a more logical methodology in my search.

Long