Flash holes for 6mm Dasher

[BigDaddie]

Hi All,

what is the go with the flash holes for a 6mm Dasher? I am using Lapua brass.

I have uniformed the pockets with my Sinclair tool and de-burred them internally to create the 'small cone.'

Should the flash holes be left as they are,after de-burring) or do they need to be opened up? Pros & cons would be good.

 

[Bob3700]

Leave the flash holes alone. They are drilled not punched so there should be no reason to uniform them.

The size of the flash hole is deliberately smaller than you normal 308 sized brass. It copies the 6mm PPC flash hole diameter.

You can get a PPC sized flash hole uniformer, but it is not needed on Lapua brass.

RGDS

Bob

 

[Moderator]

I generally agree that it's best to leave Lapua Flash holes alone--provided they are not obstructed or out-of-round.

Contrary to popular belief, Lapua flash holes ARE NOT DRILLED.

They are formed by a punch,mandrel) coming down from the top, meeting another steel shaft that comes up from the bottom. This is much better than a one-way punch, but occasionaly you'll see a flash hole where the circle has not been completely removed by the top and bottom punches.

 

[BigDaddie]

Thanks fellas...I wont touch them!

 

[RDavies]

How about the Sinclair uniformer, which only takes them out to .063'?

 

[MarkS]

cr500,

Leave them as is. I get better SD and ES, with them as they come.

Mark Schronce

 

[jb1000br]

Repeat: Leave them alone. I have a K&M deburring tool that Ken hand picked to be under 0.059' This way it only takes off the bur and doesn't touch the diameter. Works perfect. Only certain lots of the Lapua brass need it.

JB

 

[memilanuk]

Mark or Jason,

Could you give some example numbers of how much 'better' you are getting with un-touched flash holes as compared to ones that have been reamed with a PPC sized cutter?

Thanks,

Monte

 

[MarkS]

milanuk,

My first 6BRX with opened flachholes, ran 20 to 25 ES. without they were runnung 9 ES.

Mark Schronce

 

[memilanuk]

Interesting...

I am still on my first Dasher, so relatively limited experience. I didn't do any before/after chrono testing, but I did hit the flash holes with a PPC uniformer from Russ Haydon. It opens up the flash holes to 0.062 or 0.063, don't recall which. I recently ran several 10 shot strings across my CED chrono and got SD of 3-4 and ES of 10-12.

Monte

 

[jb1000br]

Monte, I have not opened mine and any 10-shot group that I have chronoed ran 8-15fps IIRC. 5-shot groups are always under 10fps ES.

JB

 

[RDavies]

HHMMM, I was expecting that opening the flash holes from std to .062' and having them all exactly the same would have made it more uniform than having some variance in flash hole sizes.