Bullet seat depth

[bml215]

My bullet seating depth varied between a few thousandths; I'm guessing the case lengths varied just a little. They all come withing the max the manual states though. I wanted to know if this is going to have a big impact on my grouping. Taking a shot in the dark; I'm guessing the slightly shorter rounds are going to have a higher pressure because of the difference in space. Is this going to be a noticeable difference at the range?

[Twoboxer]

Seating depth ~= COL or COAL which is Cartridge OverAll Length.

COL has nothing to do with the length of the case. Two cartridges having the same length with different case lengths and identical bullets just have a different amount of case bearing on the sides of the bullet. When I started reloading that didn't sound right to me, and I had to draw a picture.

The thing that is most likely varying is the shape or length of the bullets. When you seat a bullet, the seating stem that pushes the bullet in does not touch the very tip . . . it cups the nose and touches somewhere on the curved side (ogive). If it's a few thousandths, don't worry about it.

It is possible for two cartridges with different overall lengths to have the same . . . or more . . . or less . . . case volume beneath the bullet. Depends on the differences in the bullets.

At this point, it shouldn't be a guess for you to figure out what that means . . . you should have read that in a manual But the deeper the bullet is set, the more pressure. The shallower the bullet is set, the lower the pressure . . . until it gets to a point too close the lands where pressure starts to rise again.

Several thousandths variation will not cause a safety issue. Will it be noticeable? Probably not in recoil, maybe a bit longer ejection difference, maybe a difference in accuracy . . . but probably not enough to notice.

However if a bullet is seated considerably deeper than the published load data, and you are using max loads, the results will begin to climb toward a safety issue . . . depending again on how "too short" the cartridge is.

[frankski]

Everything TwoBoxer said.

I have one other observation: if your COAL varies a lot, it may be because your bullets have large variations in shape, particularly ogive. In a pistol bullet, unless you're shooting over 10 yards, you may not notice a difference in accuracy. However, large variations in shape (and weight) will have a very noticeable effect on accuracy in a rifle bullet.

[bml215]

Thanks guys. Towards the end I was getting pretty consistent results close to lyman's specs. There were a couple that seemed weird I was .010 off. I was using gold dots. I'm shooting 15 & 25 yds with pistol.

[DucatiRon]

C.o.a.l. can also vary if your using range brass or even well used same headstanp brass. Different brass has different elasticity when it it sized. Based on that when seating the bullet you will get varing levels of resistance. This will also lead to your length not being fairly consistent.

[bml215]

Thanks. If you guys don't seem alarmed then that makes me feel better. I will probably be at the range today testing my first batch of reloads.

Edit: So I went to the range with my reloads and a little bit of winchester whitebox I had left over. I shot the winchester first then the reloads as a comparison to see if it would tighten up my group. I am blown away with the results. My grouping was a third of the size. I had read reloading would give you a better grouping, but I didn't know by that much. I did have one fail to fully eject, and surprisingly it was with one of the reloads I was right on the money with the C.O.A.L. The ones seated a little deeper were no problem, and still very accurate. I don't think I will ever go back to store bought.

[GeneCC]

Thanks. If you guys don't seem alarmed then that makes me feel better. I will probably be at the range today testing my first batch of reloads.

Edit: So I went to the range with my reloads and a little bit of winchester whitebox I had left over. I shot the winchester first then the reloads as a comparison to see if it would tighten up my group. I am blown away with the results. My grouping was a third of the size. I had read reloading would give you a better grouping, but I didn't know by that much. I did have one fail to fully eject, and surprisingly it was with one of the reloads I was right on the money with the C.O.A.L. The ones seated a little deeper were no problem, and still very accurate. I don't think I will ever go back to store bought.

You're just getting started. Wait until you start to use more sophisticated tricks.

[bml215]

I know. First load and wow, I can imagine after awhile I will be able to make loads and put holes on top of each other. What are some of the tricks to look forward to learning?

[Remington788]

I know. First load and wow, I can imagine after awhile I will be able to make loads and put holes on top of each other. What are some of the tricks to look forward to learning?

Hmm, don't reload in a carpeted area unless you want to learn how to safely vacuum up spilled powder. I learned it the hard way.

[wanneroo]

I find for the reloading I do chasing the last few thousandths is a fruitless task. Bullets will have variations in dimensions thanks to different manufacturers or lots of production and depending on the manufacturer and their equipment you can have some size differentials in bullets. Some Winchester bullets I loaded in 9mm had up to 10 thousandths in variation of overall length.

As long as my finished rounds get within a few thousandths on OAL and fit a case gauge properly for a quality control check I'm good with it. I've never had any function or accuracy issues with my reloads.