Live and learn--primer-flashhole size--large and small?

[jeffreybehr]

I learned today, after trying my Lyman flashhole deburring tool on my Peterson 6XC cases, the the tool's pilot snout will not enter my 6XC cases' flashholes.. Discovered that my 6Creed cases' flashholes are about 0.077" diameter while my 6XC cases' flashholes are about 0.65".. I can't find a flashhole deburring tool that is spec'd for that.. What am I missing?

...been reloading for 60+ years and dint no this...

 

[Rook 6]

Yep. Large primer flash hole is supposed to be .80 and small flash hole .59 I believe. I'll defer to others if my measurement quotes are wrong. Watch out for decapping pins.

 

[jeffreybehr]

Yep. Large primer flash hole is supposed to be .80 and small flash hole .59 I believe. I'll defer to others if my measurement quotes are wrong. Watch out for decapping pins.

I figured that, but both my primers are Small Rifle size.

 

[M-61]

I figured that, but both my primers are Small Rifle size.

Sure but we are talking about the FLASH HOLE size, NOT Primer size

Look for one that fits Lapua brass

 

[Iowa Fox]

I think Starline has 0.080 on there small pockets

 

[kvd]

I've had similar problems with Lee's universal decapping die pin. The easy fix there was to mount the decapping pin in a drill press and use some emery paper to turn the pin down to about 0.060". Unfortunately in your case, the hole pilot of the tool appears to be part of the cutter. You may need another tool for small flash hole deburring. The 21st century 6mm small flash hole deburring tool might be an option. They ain't cheap but they do work well.

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

 

[6ShotsOr5?]

Yep. Large primer flash hole is supposed to be .80 and small flash hole .59 I believe. I'll defer to others if my measurement quotes are wrong. Watch out for decapping pins.

Yeah, I think you missed a 0, probably meant to say 0.080” and 0.059”.

 

[jeffreybehr]

I've had similar problems with Lee's universal decapping die pin. The easy fix there was to mount the decapping pin in a drill press and use some emery paper to turn the pin down to about 0.060". Unfortunately in your case, the hole pilot of the tool appears to be part of the cutter. You may need another tool for small flash hole deburring. The 21st century 6mm small flash hole deburring tool might be an option. They ain't cheap but they do work well.

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

Ordered one of those from 21st.. TYVM for the link.

 

[Dusty Stevens]

Best trick is to just not touch the flash holes

 

[wkdickinson]

Have a read of "Modern Advancements In Long Range Shooting" Vol. II by Bryan Litz. Especially the last paragraph on page 140 - "If you are dealing with flash holes that a drilled vs. punched, it's unlikely that you will see any difference in the magnitude or consistency of muzzle velocity by deburring or chamfering the flash holes".

Lapua cases have their flash holes drilled, according to their website. I emailed Peterson to ask if theirs's are drilled or punched. They responded that they are punched, but then deburred and chamfered.

 

[Dusty Stevens]

Have a read of "Modern Advancements In Long Range Shooting" Vol. II by Bryan Litz. Especially the last paragraph on page 140 - "If you are dealing with flash holes that a drilled vs. punched, it's unlikely that you will see any difference in the magnitude or consistency of muzzle velocity by deburring or chamfering the flash holes".

Lapua cases have their flash holes drilled, according to their website. I emailed Peterson to ask if theirs's are drilled or punched. They responded that they are punched, but then deburred and chamfered.

Is deburring the flash hole necessary/helpful for lapua small rifle cases?

My understanding is lapua 6.5x47 cases, and I think all lapua cases, have their flash holes drilled, not punched, meaning there is almost no (I think) likelihood that a burr would form in the drilled flash hole like it can for other cases whose flash holes are punched. Since I am having...

forum.accurateshooter.com

 

[Rook 6]

Yeah, I think you missed a 0, probably meant to say 0.080” and 0.059”.

I sure did.

 

[55fairlane]

Most of the flash hole debur tools are center drills.....look up dimensions and companies like msc or McMaster carr stock them.......but I agree with everyone here, leave it alone.....

 

[Laurie]

Going back to basics, there are four permutations 'out there':

1) Small primer (SP) + small flash-hole (SFH). Originally, this was only found in a small number of high-precision cartridges - 220 Russian/PPC, BRs, and Remington's UBBR 308 brass designed as a 'basic case' for reforming. When Lapua introduced its SP 'Palma' 308 Win case around 10 years ago, it adopted this form and again with the later 6.5X47mm Lapua, 6.5 Grendel, and its SP Creedmoors. Peterson and one or two others have picked up on the concept where they make SP versions of what are usually large primer numbers (243 Win, 260 Rem, 308 Win, Creedmoor). SFH dia. is nominally 1.5mm / 0.059".

2) All non-specialist SP designs such as 222/223 Rem, Hornet, Hornady version of 6.8mm Rem SPC etc use a small primer but the standard larger flash-hole (nominally 2mm / 0.079"). Surprisingly nobody has made special SFH variants to date.

3) Some makers of SP brass options such as Starline and PPU (Grendel brass) have stuck as per 2) with the larger flash-hole. There is a handful of cartridges where ammunition factories use either primer size, but again always with larger flash-holes - 6.8 Rem SPC SP if Hornady / LP if Remington; old Remington made UCC headstamp 7.62X39mm SP, the norm LP

4) 'Traditional' large case Large primer / large flash-hole. AFAIK, nobody makes an LP/SFH variant.


For an SFH reamer/uniformer, look up PPC/BR versions. (Sinclair Intnl, K&M and other specialist tool suppliers).

http://bulletin.accurateshooter.com/2007/03/brppc-flash-hole-deburring-tips/

http://bulletin.accurateshooter.com...rst-aid-clearing-obstructions-in-flash-holes/

I still use a Sinclair tool (in appropriate size) on Lapua brass of either type. I've found the very occasional undersize example. This tool only uniforms the hole being indexed from the primer pocket and doesn't cut out punch-edges/spikes on the inside of the case. I gave up worrying about those in Lapua brass of either type a long, long time ago. Interestingly, for years we were told that the benefits of the exit-side debur operation wasn't just fraze removal but putting a small bevel or venturi onto the flash-hole, but the Litz book / chapter @wkdickinson mentions also looks at that. Whilst the punch spike removal was very valuable in improving ignition consistency, there was no benefit found in bevelling the flash-hole.

 

[LVLAaron]

Best trick is to just not touch the flash holes

Agree. The quality brands have excellent flash holes to start with. Lapua, Alpha, Peterson, and I'm sure others. Absolutely no need to remove material.

Hornady on the other hand... Those flash holes are full of boogers and what looks like lathe chips dangling around the holes.

 

[NorCalMikie]

If they arn't broke, don't fix them.

 

[tsyarnall]

Grafs or PMA has the .062 and .059 flash hole deburring tools

 

[rjtfroggy]

My first step in prepping new brass is to drill out the primer hole to 0.071, solves the primer punch problem. I see no difference where it counts the target.

 

[M-61]

I see no difference where it counts the target.

I have. Years ago the original PMA offered 22-250 brass with small flash hole.
I'm talking 70's. Using their small flash hole brass MY 22-250 ( not a BR rifle) suddenly produced smaller groups.. From that time on I convinced myself the smaller flash hole helped.
Additionally I have no intention in altering the size of the hole. Or that angle of exit. I've no clue and don't care how Lapua drills, punches, or shoots laser beams to make their flash hole. What I do care about is a small burr being left there after the flash hole is made. I merely want to remove an imperfection. I'm not changing the hole size either, as I'm sure Lapua or Peterson etc., just didn't pick that size out of a hat.
I am relating MY experience with MY rifle and MY handloads.

 

[LHSmith]

Best trick is to just not touch the flash holes

I remember from Jack Neary's video seminar from one of the SuperShoots that he and Darryl Loker tested different flash holes in Lapua brass prepped for 6 PPC- in Loker's Tunnel and results showed that Lapua did their homework - the untouched flash hole brass produced the best accuracy.