Projectile Length

[Dmbjr]

Stupid question but after being out of it 20 years got to ask. Is the length of projectile the same on a 7mm mag from 160 grain to 175 grain?
Reason I ask is just thinking out loud if the diameter is the same I figure length would have to be different to make bullet heavier or lighter. Can someone elaborate for me?

 

[Rich M]

Sounds like you answered your own question.

Diameter doesnt change so length must to produce an extra 15 gr weight.

 

[A382DWDZQ]

It depends on the profile of the bullet and the material. Monos are longer than lead because the material is less dense. Some bullets have a longer taper. So you could have a lighter bullet that is longer than a heavier bullet.

 

[TxLite]

Also have to consider bullet shape. They could be the same length but different weights depending on the overall bullet shape and location of ogive. Boat tail vs flat base etc

 

[Dmbjr]

They are both 7mm mag partition from a 175 grain to 160. Wondering if I can leave the bulllet seating die the same?

 

[z987k]

They are both 7mm mag partition from a 175 grain to 160. Wondering if I can leave the bulllet seating die the same?

In that case it will give you the same COAL, but the 160 is shorter than the 175, so the amount of bullet seated into the case will be less. Which means more available case volume, which means less pressure for the same powder and weight.

 

[Keith Stone]

Do yourself a favor and buy a comparator set. As others have mentioned shape and length are most likely different so optimal seating depth is likely to change depending on the bullet ogive.

 

[Dmbjr]

I’ve always did what I did years ago. Work the bolt so rifleing seated bullet. Not sure if that’s correct but a old timer showed me that 30 years ago.

 

[Wapiti1]

I’ve always did what I did years ago. Work the bolt so rifleing seated bullet. Not sure if that’s correct but a old timer showed me that 30 years ago.

I am assuming you mean, I seat a bullet in an empty resized case, but leave it long, then put in the rifle and close the bolt to find the max seating depth to the lands. Yes, that is a valid method. Then you subtract a little (like 0.020") to get your initial seating depth because jammed into the lands is not great for hunting or pressure. You'll eventually pull a bullet with the lands and have a fun little mess to deal with.

There are other methods as well. Most of the time the depth that hits the lands won't fit in the magazine. A comparator is best so you can work with bullets of different shapes and seat to the same distance to the lands.

If you just use one brand/line of bullet, then COAL will get you there too.

Jeremy

 

[TaperPin]

They are both 7mm mag partition from a 175 grain to 160. Wondering if I can leave the bulllet seating die the same?

If you can drop a bullet into the seating die, use calipers to measure to the bullet base, repeat for the other bullet, and a little subtraction math should tell if the seating overall length is the same for each bullet.

 

[hunterjmj]

Do yourself a favor and buy a comparator set. As others have mentioned shape and length are most likely different so optimal seating depth is likely to change depending on the bullet ogive.

I second this. Great tool to measure your lengths. I also use the shoulder gauge as well to check fired cases, new brass, and after sizing.