Why Deep Chamfer on Barrel Chamber?

[gunsandgunsmithing]

That chamfer is a good .040 deep
A PPC case is solid for about .150. This is off of a Panda. On these, there is .135 case protrusion plus bolt to bbl clearance. Kelblys tenon print allows .007-.010 for this clearance and at that, it would have .145 unsupported case protrusion..all solid.
This much chamfer does nothing good and leaves a great deal of thin unsupported brass protruding. I usually just polish that edge with 320 grit paper on a small rod. Never a feeding issue nor scratched brass.

 

[Fuj]

I always just break the edge and polish for single shots. Mag fed,
I would do a 1/32nd inch chamfer, since your force feeding. Maybe
it was done to help fast feeding (in conditions) of those sharp shoulder
improved cases ??

 

[gunsandgunsmithing]

I always just break the edge and polish for single shots. Mag fed,
I would do a 1/32nd inch chamfer, since your force feeding. Maybe
it was done to help fast feeding (in conditions) of those sharp shoulder
improved cases ??

It's a ppc. I pretty much always just break that edge with 320 grit. They feed fine in a coned breech action.

 

[Dusty Stevens]

Yea dont do that

 

[AckleymanII]

I have always broke the edge with 320 grit also on a split 1/4" wood dowel, no issues. Some may chime in with a much better method.

 

[Dusty Stevens]

I have always broke the edge with 320 grit also on a split 1/4" wood dowel, no issues. Some may chime in with a much better method.

I use 320 crocus cloth on my finger tip. It rounds the edge over a lot nicer than a hard backed object. I use the dowel in the chamber though

 

[GenePoole]

That chamfer is a good .040 deep
A PPC case is solid for about .150. This is off of a Panda. On these, there is .135 case protrusion plus bolt to bbl clearance. Kelblys tenon print allows .007-.010 for this clearance and at that, it would have .145 unsupported case protrusion..all solid.
This much chamfer does nothing good and leaves a great deal of thin unsupported brass protruding. I usually just polish that edge with 320 grit paper on a small rod. Never a feeding issue nor scratched brass.
View attachment 1349355

Are you going to let us know who did this (or is it unknown)? I know it's not functional, but I also don't like to see such a rough cone. It just screams amateur. Try a little wet-or-dry there too.

 

[tobnpr]

Think I posted this one a few months back- customer sent in a shortie for a re-chamber from .300 Whisper to Blackout. The only conclusion I can come to is that the "smiths" that do these extreme chamfers are looking to improve feed reliability- which it will of course do- and must be totally ignorant to the consequence of potential case head separations. I think this one was .060 or so- with the .125 protrusion needed for the Savage, way too much exposed for a .556 parent case.

 

[Dusty Stevens]

Think I posted this one a few months back- customer sent in a shortie for a re-chamber from .300 Whisper to Blackout. The only conclusion I can come to is that the "smiths" that do these extreme chamfers are looking to improve feed reliability- which it will of course do- and must be totally ignorant to the consequence of potential case head separations. I think this one was .060 or so- with the .125 protrusion needed for the Savage, way too much exposed for a .556 parent case.

Everything about that from the stamps to the finish screams amateur, not to mention that spot drill center cut. I wonder if he actually did a whisper or found out thats another name for a blackout?

 

[AckleymanII]

amateur or Don't give a rip.

Most want as much case head support as possible

 

[gunsandgunsmithing]

Are you going to let us know who did this (or is it unknown)? I know it's not functional, but I also don't like to see such a rough cone. It just screams amateur. Try a little wet-or-dry there too.

No, I'm not gonna say who did the work, but I didn't like seeing it that way.

 

[gunsandgunsmithing]

 

[LVLAaron]

Most want as much case head support as possible

Or... all of it right up to the rim.

 

[AckleymanII]

That chamfer is a good .040 deep
A PPC case is solid for about .150. This is off of a Panda. On these, there is .135 case protrusion plus bolt to bbl clearance. Kelblys tenon print allows .007-.010 for this clearance and at that, it would have .145 unsupported case protrusion..all solid.
This much chamfer does nothing good and leaves a great deal of thin unsupported brass protruding. I usually just polish that edge with 320 grit paper on a small rod. Never a feeding issue nor scratched brass.
View attachment 1349355

The Old Sako balloon head 220 Russian brass may rupture due to the chamfer!

 

[gunsandgunsmithing]

The Old Sako balloon head 220 Russian brass may rupture due to the chamfer!

I prefer not to find that point, but I believe that even the Lapua will do the same at some pressure/unsupported case scenario. The last pic shows just that, imo. I have to wonder how far from rupturing, that case was, though. It had been re-sized when I got it so I'm sure the die make the sharp edge and probably pushed it downward a bit, too. You might need to zoom in on it to see what I'm talking about, near the web area.

 

[AckleymanII]

I purchased a second hand Panda. Someone put a barrel on a Right Bolt, left port panda, and There was too much bolt face to barrel clearance. I was shooting the Sako balloon head cases. I am right handed, so my face is near the ejection port.

I pulled the trigger and found myself sitting on the concrete floor. My body's impulse was to get away from the gasses, totally subconscious muscle reaction. The balloon head case was in two pieces. I was wearing safety glasses, eyes were ok. This event shook me up a bit.

The Panda has no vent holes in the side of the action to vent gas in case this kind of thing happens. All the gases were vented out the ejection port in my face.

The cases had been fired in a different rifle, but they head spaced perfectly in this rig. The slight difference in Web dia(.001), balloon head case, plus the excessive bolt face clearance set me up for a disaster.

 

[gunsandgunsmithing]

I purchased a second hand Panda. Someone put a barrel on a Right Bolt, left port panda, and There was too much bolt face to barrel clearance. I was shooting the Sako balloon head cases. I am right handed, so my face is near the ejection port.

I pulled the trigger and found myself sitting on the concrete floor. My body's impulse was to get away from the gasses, totally subconscious muscle reaction. The balloon head case was in two pieces. I was wearing safety glasses, eyes were ok. This event shook me up a bit.

The Panda has no vent holes in the side of the action to vent gas in case this kind of thing happens. All the gases were vented out the ejection port in my face.

The cases had been fired in a different rifle, but they head spaced perfectly in this rig. The slight difference in Web dia(.001), balloon head case, plus the excessive bolt face clearance set me up f

I purchased a second hand Panda. Someone put a barrel on a Right Bolt, left port panda, and There was too much bolt face to barrel clearance. I was shooting the Sako balloon head cases. I am right handed, so my face is near the ejection port.

I pulled the trigger and found myself sitting on the concrete floor. My body's impulse was to get away from the gasses, totally subconscious muscle reaction. The balloon head case was in two pieces. I was wearing safety glasses, eyes were ok. This event shook me up a bit.

The Panda has no vent holes in the side of the action to vent gas in case this kind of thing happens. All the gases were vented out the ejection port in my face.

The cases had been fired in a different rifle, but they head spaced perfectly in this rig. The slight difference in Web dia(.001), balloon head case, plus the excessive bolt face clearance set me up for a disaster.

Glad you're ok. How much excess clearance

 

[liljoe]

This is the result of to much clearance. He said the first round seemed a little hot because the bolt opened a little hard. This was the second shot.
This was in a Borden action 6 PPC , 68g bullet and 28+ grains of H 4198.

Joe

 

[338 Mollett]

I shoot for 5 thou clearance all the way around the bolt nose .

 

[boltfluter]

I see this quite a bit lately. I believe it is from lack of knowledge about the whole process. Not good, and will eventually get someone injured. Do the research or don't do the job, as this is not child's play.

Paul