K&M Chamfer Tool

[mdmp5]

I have a Giraud, but I don't trim my brass every firing. I currently use a carbide bit on my drill with a 28 degree chamfer on cases I am not trimming. I was on the K&M site one day and saw their chamfer tool. They make this claim that every other chamfer tool on the market cuts too sharp and potentially fucks up the base of the bullet. Then they validated the need for their tool by telling some anecdotal story about some dude who took a bunch of bullets and destroyed the tips and they shot fine, but when he fucked with the base of the bullet, it became a flier.

Anyway, their tool cuts a 4 degree chamfer. I was wondering if anyone here has used it and if so, how do you like it?

 

[AMG04]

You have me hooked for an interesting conversation. I'm in...

4 degree or 24 degree angle? In a game where 1/1000 of an inch is significant, a 24 degree angle change seems extreme.

Conceptually, I think the standard 45 degree angle or vld 22-28 degree angle creates a flat surface inside the case neck that the boat tail contacts and exerts pressure against. That pressure expands the case mouth gradually and allows the bullet to slide into the case.

On the other hand a 4 degree angle is creating a razor's edge with the outside edge of the case mouth, which would likely cut into the jacket more depending on the angle of the boat tail.

With that said, as long as the bullet diameter is less than the outside diameter of the case mouth (cut at any angle), how or where is there a sharp enough edge to cut into or deform the bullet's jacket?

 

[mdmp5]

It's 4 degrees. No it is a very subtle cut that wouldn't hurt the jacket in the least bit

check out the picture and you can see what i am talking about

 

[mdmp5]

This is what I am using now, the sinclair tool. The whole thing is 28 degrees, as you can see. The K&M tool counts one side as 4 degrees, so comparatively speaking, the sinclair bit is 14 degrees

 

[mdmp5]

With that said, as long as the bullet diameter is less than the inside diameter of the case mouth (cut at any angle), how or where is there a sharp enough edge to cut into or deform the bullet's jacket?

If the bullet diameter was less than the inside of the case mouth, it wouldn't fit. It would just slide in and out with zero resistance

 

[AMG04]

The picture helps alot to confirm the angle. Each side cutting at 14 vs 4 makes alot more sense. Long day at the office so I'm not as sharp as I should be.

I still dont see where a boat tail will contact a sharp enough edge to become deformed. I've used the standard 45 degree cutter which is 22.5 degrees on each side and pulled alot of bullets during load development due to reaching pressure signs.

Under a magnifying glass (not microscope) I could not see any deformation. I loaded the bullets again to retest promising powder charges with very good results.

 

[AMG04]

Agreed, the bullet needs to be less than the outside diameter (neck tension). I typed too fast and didn't proof read.

 

[mdmp5]

I still dont see where a boat tail will contact a sharp enough edge to become deformed.

Yes, the base of a boat tail is not the part that will ever get scratched. It is the caliber section at the junction of the boat tail. Flat based bullets are a different story

 

[AMG04]

Caliber section being the bearing surface. So K&M is claiming the sharper 22 degree angle is gauging into the bearing surface?

Again, I've not seen that happen on bullets I've pulled from loaded ammunition.

I have never tested this on target so I'm interested in what the rest of the community has experienced.

Great opportunity to learn. Thanks for kicking off the discussion.

 

[mdmp5]

So K&M is claiming the sharper 22 degree angle is gauging into the bearing surface?

Pretty much why I started the thread. It is a bold claim, but semi plausible on the micro scale. Question is, does it make a damn difference or are they racketeering?

 

[AMG04]

Do I really have to buy another tool!?

 

[mdmp5]

Idk, waiting for some more input hopefully from someone who has one

 

[SPAK]

I have two of them. One large and one small.
I also have a Redding that cuts a 15deg chamfer I believe.

They’re nice tools, cut really well.

I honestly don’t know that I can tell a difference on target between the 15 deg or the 4deg using boat tail Bullets. What both the Redding and the k&m do however is have a pilot that centers on the flash hole to hopefully keep you from chamfering the mouth unevenly. It’s not as fast as without the pilot but I do feel the added step is worth not cutting an uneven chamfer.

I honestly can’t see how the base of a boat tail bullet would get scratched from seating from a poor chamfer. Bearing surface maybe, but the rifling is sure to do more to the bearing surface than a scratch would.

 

[mdmp5]

The website talks about the heel of the bullet, which is the junction between the base and bearing surface

 

[spife7980]

My question isn’t on the angle but rather the application: if you have a giraud why would you ever use another chamfer tool over it?

 

[mdmp5]

Sometimes my brass gets too short, either by slight overtrimming due to variance with the giraud, or from peening due to tumbling. I minimize the peening by only tumbling for less than 2 hours, but still get some. I try to get the cases to grow enough so that every one can be trimmed with the giraud. Not every case headspaces exactly the same, so I get some variance of about 3 thousandths or so

 

[winniedonkey]

I got one to use for my bolt gun loads. I have it set up so I do a bunch watching something. It's been on my list to do a side by side with my carbide tool on my rcbs prep station. I have some range time coming up and I'll report back with what I found, if anything.