Seating depth

[Wheeljack]

COL is used in most data charts, but not the seating depth. Lyman does a good job in that you can see it uses a different COL for different bullets. We don't load a WC at the same COL as a RN. So what is important to me seems to be the seating depth. A change in depth is a change in the pressure of the round. Even RN bullets from different manufacturers have a different length. I think that if the COL is listed in the data, the length of the bullet should be included too. We buy bullets by weight and caliber, can it be so hard to include length in the description? Am I just over thinking this?

Edited January 29, 2015 by Wheeljack

[Sarge]

I think you are.

This is why we start low and work our way up looking for pressure signs. After a while of reloading and comparing bullets you will realize when a bullet needs to be seated deeper or it can be seated longer. You will also learn when and by how much to lower or raise the charge weight. There are hundreds of bullets out there and there is no way to list a load for each and every one. It just takes experience and a lot of caution.

[Hi-Power Jack]

if the COL is listed in the data, the length of the bullet should be included too.

You'll also find that the OAL will depend on the specific shape of

the bullet, in YOUR gun.

E.g. two different round nose bullets of the

same weight, may require a different OAL in YOUR gun based

on the specific shape of the round nose.

One might touch the rifling before the other.

[superdude]

Sarge and Hi-Power Jack are correct. See figures 7 and 8 at this link: http://38super.net/Pages/Overall%20Length.html

[Wheeljack]

They are right. So it makes all the posts with information on how many grains of this or that that they use, worthless. First, find out what length of what bullet fits your gun. Than you have a maximum COL, but is it the most efficient COL. Does it load most efficiently. Then start with the lowest charge you can and work your way up to the maximum charge. Then when you have all this data, minimum and maximum, go back and determine the charge that is most accurate. When you have collected all this information and not before, let us know the bullet you are using, it's length, the COL you have found that chambers best, in what gun and the power and charge for the most accurate shot.

And I thought that just asking for the seating depth was enough to help.

[Steve RA]

I'd start with a Plunk Test in your barrel, with the bullet you are going to use. Then make a dummy round and see if it fits your mags and how it loads from the magazine. After that you can start on the powder charge.

[Wheeljack]

Correct. I think I'm just being lazy asking for too much information instead of using the information available as a guide to build my own "perfect" round. Thanks.

[Wheeljack]

Superdude, that is a great article. Thanks.

[IDescribe]

Once you have a lot of load data with a particular powder, seating depth can be quite useful with new bullets for which there is no published data. I'm still going to determine my max COL with a push test, but after making that determination, I'm going to calculate the seating depth and compare it to data I've already developed with whatever powder(s) I will use. And seating depth is one of the data points in all of my reloading data. Given that there are some bullets in my personal data with the same surface type -- plated, jacketed, moly, etc.. -- and the same diameter and weight, seating depth has proven to be a far better predictor for what the powder will do with the new bullet than simply finding the "closest" bullet I can in whatever published data I can find and using that data.

An example to be clear here: if I have a new Bullet X, and there is no published data for Bullet X, I'm going to push test, and let's say it's a 9mm 124gr plated HP, and it seats to 1.13 in my CZ-75, with a seating depth of .205. I want to load it with N320, so I look into my load data spreadsheet for N320, and hurrah! there's a plated 124gr Bullet Z with a seating depth of .198. In my experience, that load data for Bullet Z is going to be very reliable for predicting what that powder will do with Bullet X. I am of course still going to start low and work up, but I'm going to use that data I already have with bullet Z to determine my starting point.

Edited January 31, 2015 by IDescribe