What is the diameter spec for 556 flash hole. Can’t find hard data. Thinking 078-080,but have seen the 082 which I think is large rifle. I know different brands will be diff dia, but I want to uniform some LC22 range pickup…
I’d suggest you purchase a pin gauge set and determine what you already have, then decide what median diameter you want to settle on. I’d imagine that there would be some potentially wild variations out there. SAAMI shows specs for .223 cases, but since NATO specs aren’t necessarily the same as SAAMI you may have some leg work to do. I looked briefly and didn’t even see a SAAMI spec for flash holes.
Yeah. Some of that damned import ammo has flash holes so small, my decap pin won’t fit. I was going to open them up, but it became too big of an ass ache.
Honestly if uniforming flash holes became THAT critical, I’d just buy some LaPua brass. The proverbial juice isn’t worth the squeeze. Getting the same year headstamp should be good enough.
I pin gauged some once fired LC 90 and 12 and they ranged from between .077 and .081.
I’d use .079 as my nominal goal based on this data set as measured by me.
But I don’t fuss about primer pockets anymore, I don’t even clean them as I’ve seen zero evidence it has any impact on accuracy. I do have evidence that case volume impacts repeatable accuracy potential for a given loading and I do spend the time to sort by head stamps, when loading for accuracy.
Still looking for some new Lapua cases to measure. So I may be back with more data.
ETA: All my Lapua is sitting loaded in boxes, the single once fired case I was able to find measured .080 so maybe I’d shoot for that instead.
Unless the flash holes were really wild and all over the place, I’d bet that the primer quality would be more significantly impacting consistency.
GI mil-standard is .080 ~ +.004
Thanks, guys, esp sinister, and yes, I too doubt FH dia makes any diff for AR accuracy, but it’s the easiest part of working brass (for a bored old man). I was drilling 080 and ignoring the loose holes. And now I may start using my old Sinclair fh deburring tool since 082 seems to be within reason. And the only reason I uniform pocket depth is in hopes of reducing shallow pockets interacting with civvy primers and floating firing pins… I waste a lot of time in reloading so I can blame poor performance strictly on myself for not having my eyes closed or on not pulling the trigger hard enough…
Sinister for the win! That makes sense based on the readings I was taking and that LaPua was right on the money.
Wasn’t trying to tell you not to do it…Your brass, your process. Just letting you know I didn’t for a single data point that is probably meaningless.
I was! 
No sweat HK. I try to check a lot of boxes that, in the end, have absolutely no effect on the results, especially given my equipment and skills. It is mostly about making honest effort through each phase of the journey for me at this point…
Was typing as markm posted, so, how bout this:
I think you’re both right!
When I was modifying some Lapua 6.5cm brass with the small flash hole, I used a nice brand new TiN drill bit to open the holes up from .060 to .065 or so. The flash holes did get cut nice and clean. But I was just doing that to accommodate the decap pins in almost all my dies.
But I really have no faith in primer pocket uniforming, flash hole deburring, etc. for the level we shoot.
I wonder if Sinister will reveal his source?
I checked all my reloading manuals prior to breaking out the Pin gauges and none of them had the flash hole documented.
Allegedly smaller flash holes or primers (is/was it Lapua that made small rifle primer 308 cases?) Allowed more even progress of the powder burn. Allegedly, someone even installed a tube in the flash hole so the primer flame ignited the powder towards the front of the case for more efficient progress of powder burn/pressure curve. Maybe adopted from the artillery shell guys? Can’t remember. Precision Shooting out of print for some time. Maybe all this does help some guys shoot .09in at 100 or sub 2in at 1000…
Oh, yeah: and now I don’t feel so bad about my googliefie not revealing the requested specs above! Thanks yet again…
For some reason I got it in my head that we may see greater consistency with deburred flash holes because some powders could potentially have issues from being inconsistently segregated by the burrs as they’re different in all cases. Or maybe I should avoid spicy foods late in the day? I have a couple of different uniformers/deburrers because I load a fair amount of 357 SIG and also have a lot of Speer brass with the small flash holes that have trapped my decapping pins, sometimes pulling them out of the decapping stems. For 223/5.56, deburring is just something I do to make myself feel better.
I think my match shooting days are behind me now, so maybe I won’t uniform primer pockets anymore. I never was a big fan.
Consistency is always good in shooting/ammo. It’s just a matter of picking your battles. If I shot lower volume, I could make room for more steps in the process. I just try to get away with the least amount of ass ache possible.
I have to admit that loading 50 or 100 rounds at a time for a bolt gun was an intriguing challenge, but loading lots of 500 or 1,000 for the AR is a tedious pain in the ass (still on a 1974 model single stage rcbs…). Problem is I load bottle and can ammo like I’m loading it for a thousand yard shot at a high value target. Good thing I don’t have a job (retired) and the kids are grown…
No sense putting forth the effort if there isn’t at least a little reward for it. Personally, I’m not at a proficiency level where I’d know the difference.
I’ve made attempts in the past to load the BEST little batch of .223 ammo I could… using the chargemaster, and Lapua brass, etc. Then the ammo didn’t shoot a bit better than my blow an go stuff. I quit right there before I got sucked into driving myself nuts.
Same here.
What really has me messed up is the different components (due to availability ) I’ve been working with for 3 different rifles. A thou best for this one, a thou best for that one, but haven’t worked towards a single across the board load. I do have a couple of loads pretty good in both of 2 rifles. Oh wait, even more loads fine for bottle blasting, and the Hanson barrel is just gonna be 2-3 minutes, regardless…