Deburring Flash-hole Observation

[titanxt]

I was just messing around while cleaning some cases and decided to see if any more material came out if I stuck the flash-hole deburring tool back in some cases that had been fired. These cases were deburred initially before firing. No extra brass was removed from a good portion of the cases, however, about half of the cases did. I was kind of surprised at the amount of brass that was removed. What causes this? Incomplete deburring on the initial attempt? Brass flowing after being fired in areas where the cutter can engage? When I initially deburred the flash-holes I took my time and made sure that I had removed all of the bur, so I am a bit surprised that anything would still be there???

Thank you!

Andy

 

[CatShooter]

I was just messing around while cleaning some cases and decided to see if any more material came out if I stuck the flash-hole deburring tool back in some cases that had been fired. These cases were deburred initially before firing. No extra brass was removed from a good portion of the cases, however, about half of the cases did. I was kind of surprised at the amount of brass that was removed. What causes this? Incomplete deburring on the initial attempt? Brass flowing after being fired in areas where the cutter can engage? When I initially deburred the flash-holes I took my time and made sure that I had removed all of the bur, so I am a bit surprised that anything would still be there???

Thank you!

Andy

Flash hole cutters work differently - you didn't say which you have and how it was adjusted... and if you did anything to the cases like trimming.

 

[Shynloco]

Andy,

I'm not in the least surprised by your find. If you consider, some folks clean their primer pockets (as do I) after each firing. That means a run through of some brand of primer pocket cleaner device that likely forced crap back through the primer pocket, though isn't necessarily attached to the inside of the flashhole itself. Now I don't run the deburring tool back down the neck of the casing, but visually look down the flashhole to make sure nothing is there. My next move is to tap the casing, neck down on a hard, but padded surface expecting whatever loose stuff is in there to fall out. Then after deburring and chamferring the mouth of the casing, plus a light scrubbing of the outside of the next with 0000 steel wool, I lastly run a bore brush of the caliber I'll be loading to clean the inside of the neck from loose whatever and then wipe the casing exterior. Bottom line, between unburnt powder and the crap I shoved down the flashhole during cleaning, I'd expect that unless I bath or retumble my brass FOREVER, you can't possibly get everything out of that casing or even expect it to be like virgin brass. Just my .02.

Alex

 

[titanxt]

I used the Sinclair tool.

Thank you!

Andy

 

[jlow]

It's the same reason why primer pockets gets loose after firing i.e. the pressure causes the dimensions of the chase to change.

 

[CatShooter]

I used the Sinclair tool.

Thank you!

Andy

I have the same tool - it is a good one.

Do you adjust the top piece so it rides in the neck to center the shaft??

If so, that is probably your problem - when cases are fired, most of the time they change length - sometimes they get longer and sometimes, shorter... depending on a few variables.

That is why it is suggested that cases be fired once before being trimmed or turning (or most anything else)... so the case can "settle" into it's new home

If you set the cone part to firmly touch the case mouth, it will act like the stop, and if the case shrinks, the tool cuts more.

The tool has it's own stop at the cutter, and if properly set, the first cut is all it will cut - it will not continue to cut.

When you set the alignment cone, leave a little space - don't bring it down onto the case mouth.

 

[243winxb]

Lyman tool- Deburring Flash-hole

Fired

Done wrong, IMO.

Correct way >

 

[bloc]

Intuitively, it seems as if de-burring flash holes would be good, but is there a measurable performance gain from it?

Has anyone ever actually tested whether or not there is a practical benefit? And if there is a benefit, what might it be and what might be its magnitude?

 

[CatShooter]

Intuitively, it seems as if de-burring flash holes would be good, but is there a measurable performance gain from it?

Has anyone ever actually tested whether or not there is a practical benefit? And if there is a benefit, what might it be and what might be its magnitude?

I think people have done tests and found no difference - but it is psychological, and that is enough reason to do it.

 

[Patch700]

Intuitively, it seems as if de-burring flash holes would be good, but is there a measurable performance gain from it?

Has anyone ever actually tested whether or not there is a practical benefit? And if there is a benefit, what might it be and what might be its magnitude?

On the other end of the spectrum , on one instance out of sheer boredom I had taken 40 pieces of 243 brass from one of my varmint rifles and conducted a test.

With these 40 pieces of brass (ww) I had worked up a load that was pushing 70 grain B tips to the tune of 3425 fps and was giving me velocity spreads of just under 15 fps.

The cases were all uniformed etc however for this test I went in with a flash hole uniformer and re-cut the flash hole , I then ran those loads over the chronograph and noticed a slight increase in velocity spread... I then de burred them yet again (so in essence they were deburred 2 more times after what would normally be considered good enough)

That same load then had a velocity spread of between 35-40 fps.

I went a step further and then took a drill bit and "uniformed" all the flash holes to a specific diameter , that was worth another 10fps .

Final verdict for me... don't over do it and in some instances just don't do it at all.

The biggest mistake some people make particularly with Lapua brass is to mess with the flash hole... It is drilled not punched and therefore there is no flap as per say to deburr.

 

[243winxb]

Lapua or Norma brass http://bulletin.accurateshooter.com/tag/flash-hole/