Not enough chamfer?

[Suther]

I was reloading some flat base Sierra 60gr bullets in 243win and had some odd brass/copper buildup at the neck:

Left one is pretty clean, but middle and right ones have obvious signs of... something...?



Is this from not enough chamfer? If not, what causes this?

Thanks!

 

[zaprosper]

Are you working with clean brass?

 

[boxhitch]

wag here, but is the die set too low and trying to crimp in the last mm's of seating travel?

 

[zaprosper]

I think it's shavings from the bullet, which is have only seen when dealing with clean, unlubed brass necks that have too much friction/interference as the bullet is seated

 

[Thunderhog]

Suther, it appears you have copper shavings built up, or maybe even brass shavings as zaprosper has stated.
It looks like your brass has not been trimmed to length?
In addition, a nice chamfer also helps to eliminate this.
Brass should be cleaned very well in a stainless steel pin tumbler, or walnut shell media before loading.
Yours don’t look clean, trimmed, or otherwise….

 

[708fan]

Yes. Been there done that. Case mouth looks blunt. Chamfer til it’s nearly sharp to get down to the bottom of that factory crimp.

 

[Suther]

Brass is once fired from Rem factory ammo, that was cleaned and resized a while ago and then put up. I wash with water and soap so they don't get that shiny polished brass look that you get with a tumbler or vibrator.

They were checked for length before loading, all are under 2.045. Brass from the same batch was loaded (and shot) with 100gr Hornady btsp without having this issue.

Die is a Lee die that doesn't crimp, and I played with the die to confirm its happening regardless of how the die is set up.

I've never had this issue before, but like 99% of my loading has been boat tail bullets. Another reason my first suspicion was chamfer. These Sierra bullets are quite sharp compared to even the other flat base stuff I have like 7mm hotcors which have a more rounded off edge to the base.

 

[9.3mauser]

Even with brand new brass I usually deburr the inside of the case mouth. I've had that problem a few times.

 

[Suther]

Yes. Been there done that. Case mouth looks blunt. Chamfer til it’s nearly sharp to get down to the bottom of that factory crimp.

Chamfer that much eh? I've done that a few times by accident and it always felt like I've gone too far...

 

[708fan]

Chamfer that much eh? I've done that a few times by accident and it always felt like I've gone too far...

Ya it makes you wonder alright but sometimes those factory crimps are tight quite a distance from the case mouth. An inside neck turn machine would be ideal but good Lord ya draw the line somewhere. I had to get pretty aggressive with some nickel plated rifle brass to stop the shaving as well.

 

[jethunter]

More chamfer might be needed. You could also try dry neck lube.

 

[Suther]

Now I'm thinking I need to size up some more, apply a heavy chamfer this time, and see how it goes. We'll see if I can get back to the "bench" before bed...

 

[zaprosper]

It also helps to have a VLD profiled tool. You are correct that it makes a big difference when the bullet isn't a boat tail design, I also found most issues with Sierra as well. It isnt a huge issue, these bullets will still shoot and it's an easily fixable issue. Lubing inside of necks for seating would be the last solution to throw in.

 

[Suther]

It also helps to have a VLD profiled tool. You are correct that it makes a big difference when the bullet isn't a boat tail design, I also found most issues with Sierra as well. It isnt a huge issue, these bullets will still shoot and it's an easily fixable issue. Lubing inside of necks for seating would be the last solution to throw in.

Any recommendation on a good chamfer tool? I currently just use the basic RCBS one:

https://shop.rcbs.com/deburring-too...oNMSEvY8OuE_DsYAbGJWiC7I4E2d_iB4jUFhQ_5jexG6D

 

[Smokinyotes]

Even new brass that is ready to fire I do an inside outside chamfer. Seat a primer and dip the neck in imperial dry neck lube, charge and then seat the bullet.

 

[DGY]

I’ve been using the Lyman one that is really nice!

 

[yomomma]

I'll take a different approach.
Since you already chamfer.
I use a flaring die for my flatbase .223 bullets.
Just a very light touch

 

[WhelanLad]

I get it a fair bit...
Was using Lee zip trimmer an Lee chamfer deburr tool Cap thing but have just changed to Lyman lathe and Lyman deburr tool....

I just figured it's flat bases, minimal tolerances and Resized brass..... Not really a big deal if you clear it off ..
I noticed I guess it has complications

 

[GrizzlyJester]

Way too much chamfering. Just do like 3-5 turns on the inside chamfer, and then 3-5 turns on the outside deburr.

 

[STR8 Shot]

I've had the same result with Sierra flat base. Chamfering helps considerably, I've since switched to Hornady Interlock flat base, no issues with jacket peel.