Tip on flash holes that can ruin your ES

[Jim Hardy]

Some flash holes are punched and some are drilled. Drilled it better. With punched, you can sometimes find a lot with off center flash holes! Not good for uniform ignition and ES. Dont assume that Lapua drills all their flash holes. They do not. Be diligent with brass that you paid big money for.

Jim Hardy

 

[mikecr]

I didn't think Lapua drilled flash holes. Only Norma.

 

[Homerange]

Won't matter if drilled or punched it still leaves inconsistencies on the inside of the case to disturb an even flash from the primer. Use a chamfer tool by hand and all the little dags of brass remaining from manufacture can easily be felt.
Flash hole chamfer internally or put up with larger variations in ES. Period.

 

[LHSmith]

I didn't think Lapua drilled flash holes. Only Norma.

I believe Lapua punches from both ends, minimizing burrs.

 

[LHSmith]

Won't matter if drilled or punched it still leaves inconsistencies on the inside of the case to disturb an even flash from the primer. Use a chamfer tool by hand and all the little dags of brass remaining from manufacture can easily be felt.
Flash hole chamfer internally or put up with larger variations in ES. Period.

According to Jack Neary, leave the flash holes alone. In a blind test in Daryl Lokkers tunnel, they determined untouched flash holes shot smaller in 6 PPC Lapua cases (220 Russian parent case). This test was done @100 yds.

 

[243winxb]

 

[dmoran]

Some brass have thin flash-hole "meat", which can easily get over chamfered and made to thin - IME.
I myself use drill bits to make the internal chamfers, and only the slightest of a chamfer.
Below is a sectioned 6BR Lapua case, which flash-holes are only around 0.050" thick.
Donovan

​

 

[Ledd Slinger]

Used to chamfer flash holes. No noticeable difference. Now I just look through them in the light when I uniform or clean the pockets. If I see a nice round hole, good to go. If there is a blockage, I'll chamfer it out.

 

[Homerange]

According to Jack Neary, leave the flash holes alone. In a blind test in Daryl Lokkers tunnel, they determined untouched flash holes shot smaller in 6 PPC Lapua cases (220 Russian parent case). This test was done @100 yds.

My emphasis.
Yes, blind as in can not see.
Any influence from a disturbed primer flash is very unlikely to affect grouping at 100 yds. Period.
Velocity ES will have little effect at that range however at 500+ well that's an entirely different affair.....

 

[Rust]

I don't like a chamfer at all. I reground a chamfering tool to have virtually no chamfer, just knocks the burrs off without removing any more metal.

 

[Coolhand]

Warren Page Benchrest Hall of Fame " uniform your flash holes " thats all I do, since reading about this in Warren's book, the " Accurate Rifle " my ES & SD in my Palma Rifle have reduced remarkably. Get some appropriate sized gauge pins and sort out what diameter your flash holes are. For Lapua .308 Brass ( big primer ) I use a #45 drill bit which is 0.082" or 2.08mm. Four flute chucking reamers work really well to, of the appropriate size of course.
You can buy a flash hole uniformer but #45 drill bits are cheap by the 10 pack.
I found a block of aluminium at work , drilled it out 13/16" tapped a 7/8" x 14 thread, screwed a .308 file trim die into it tightened the lock ring, put the block and die into a machine vise on a mill drill upside down, stick a new case in and lower the #45 drill, one pass and your flash holes are uniformed.If there are any dags inside the case the drill bit takes them out, and I have yet to find any dags in Lapua Brass, not to say that is does not occur.
New drill bits like to 'pick up ' on brass, so get some emery paper and just take the 'edge' of the rake. Sometimes I will run a new drill bit into a block of mild steel, just to dull the edge a little.

regards
Mike.

 

[LHSmith]

My emphasis.
Yes, blind as in can not see.

Blind test - where someone gives the shooter cartridges of known characteristics and records the results while the shooter has no idea what differentiates the batches of cartridges.

 

[LHSmith]

Any influence from a disturbed primer flash is very unlikely to affect grouping at 100 yds. Period.

I'll take real testing over WAG/theory every time. Did I mention that SR BR groups are measured to the ten thousands of an inch....and at the 2016 Super Shoot that 0.0005" was the difference in group size between 1st and 2nd in the 2-gun agg. That's five 5 shot groups @100 yds. and ditto for 200 yds. (50 shots for record)
My point is that if the flash holes are consistent as received from Lapua, I prefer to leave them untouched.....remember #1 rule in BR : eliminate as many variables as possible.

 

[JimPag]

I'll take real testing over WAG/theory every time. Did I mention that SR BR groups are measured to the ten thousands of an inch....and at the 2016 Super Shoot that 0.0005" was the difference in group size between 1st and 2nd in the 2-gun agg. That's five 5 shot groups @100 yds. and ditto for 200 yds. (50 shots for record)
My point is that if the flash holes are consistent as received from Lapua, I prefer to leave them untouched.....remember #1 rule in BR : eliminate as many variables as possible.

Tony Boyer in his book and I quote, The flash hole is either punched or drilled in either case a small burr CAN FORM on the inside of the cartridge. FOR BEST ACCURACY, this burr should be removed. Guess I'd rather take his advice than all the other Tony Boyer's out there.

 

[ttfreestyle]

Ok so what's the best tool for performing flash hole deburring? Is one brand above the rest? Mainly 6ppc and 6br cases is all I use.

 

[jlow]

This is what I use, except I have it chucked onto a drill. Works well.

http://www.brownells.com/reloading/...48114c&gdfms=26BE2DE20E6547DCA06068AE05F725EE

 

[243winxb]

There are as many as 3 or 4 flash hole diameters. Buy the right one.http://bulletin.accurateshooter.com/tag/flash-hole/

 

[Comrade Terry]

Ok so what's the best tool for performing flash hole deburring? Is one brand above the rest? Mainly 6ppc and 6br cases is all I use.

http://www.xxicsi.com/flash-hole-debur-tool.html

 

[Homerange]

My point is that if the flash holes are consistent as received from Lapua, I prefer to leave them untouched.....remember #1 rule in BR : eliminate as many variables as possible.

Then I presume you trust brass manufacturers to produce brass to such fine tolerances that no case prep is necessary?

What planet are you on?

 

[Homerange]

This is what I use, except I have it chucked onto a drill. Works well.

http://www.brownells.com/reloading/...48114c&gdfms=26BE2DE20E6547DCA06068AE05F725EE

Looks the same as this one:
http://www.sinclairintl.com/reloadi...ersal-flashhole-deburring-tool-prod34127.aspx