Reading bullet bases

[kwilliams]

Was able to recover a few bullets I shot today at 600 yds from my new rifle I am dialing in. Its a .40 cal using 30:1 alloy. The bases show no gas cutting but have just a very small bump at each land imprint, no fins or wings. Using .030 poly wads. My question is just how perfectly flat can one expect a fired bullet base to be? Tried .060 poly but accuracy seemed to be not as good, and I did not recover any to have a look at.
thanks
kw

[SchuetzenDave]

The lands cut a groove into the bullet translocating a bit of metal that results in the bumps you noted.

A fired bullet will never be perfectly flat on the bottom.

What is most important is you have square bullet base edges; that seal and prevent any gases cutting around the side of the bullet.

[semtav]

How much larger than groove dia are your bullets kim
I only used 1 .030 ldpe with my 40-82 loads also. Accuracy didn't suffer.

[Woody]

I've noticed with .030 LDPE wads I got clean edges with no gas cutting, but I did observe powder grain imprinting on the base. With .060 LDPE wads, I did not observe any gas cutting and no powder grain imprinting. I also have found that with my .40-65, with .030 fiber wads I observed both gas cutting and powder grain imprinting, and best of all, my best accuracy. Go figure.

Woody

[Woody]

I've noticed with .030 LDPE wads I got clean edges with no gas cutting, but I did observe powder grain imprinting on the base. With .060 LDPE wads, I did not observe any gas cutting and no powder grain imprinting. I also have found that with my .40-65, with .030 fiber wads I observed both gas cutting and powder grain imprinting, and best of all, my best accuracy. Go figure.

Woody

[kwilliams]

Brian
GG bullets are .4085 in a .408 bore-14 twist, have not seen any trace of leading. Yup its the 40-82 silhouette, thinking I am going to really like it. Have not seen any powder kernel impressions with the .030" poly. Just getting brass fire formed and some basic sight settings today.
Kim

[kwilliams]

correction its .408 groove dia.
kw

[kenny sd]

LDPE? what's that
I'm using veggie .060 and have used poly in the past, but veggie seems to work best.
what think...

[TAA]

Low density polyethylene?

[bruce m]

recovery of bullets breech seated rather than seated in the case shows differences in the base.
both my 40/72 and 45/2.4" shoot breech seated best with about a 1/8" airgap.
this puts the base of the bullet into the leade angle of the rifling.
these are bore diameter + 0.005" pp bullets.
fired bullet bases are flat with no finning.
I wonder if similar happens with bore diameter pp bullets fired from a proper pp chamber?
if so there is accuracy potential to be had from fixed ammo in such chambers.
bruce.

[Woody]

LDPE = Low Density Polyethylene = Poly Wads

I cut my own wads from .060 LDPE that I purchase from McMaster Carr. It's the same stuff. When I use fiber wads, I cut them from automotive gasket material that I purchase in bulk. It adds a few seconds to the reloading process, but saves a cents too.

Woody

[kenny sd]

at $20 for a thousand, I think I'll go to BA....
However, I've heard that the poly is not as good as the veggie.
what think?

[kenny sd]

at $20 for a thousand, I think I'll go to BA....
However, I've heard that the poly is not as good as the veggie.
what think?

[Aviator]

However, I've heard that the poly is not as good as the veggie.
what think?

Not really sure what thinking will do in this case!
Trying both will probably get better results!

[Kurt]

Here are some typical bases using different wads and alloys types and hardness. Alloy temper plays a large roll how the base will end up.
Using .06" wads, polly or fiber makes a difference in the direction it is placed in the case. The thicker wads have a sharp and rounded edge when they are cut and this shows up especially with softer alloy like 1.30 or softer also you will find the fins increasing.
You can enlarge this photo for a closer look.

IMG_3520.jpeg