Primer Flash Holes

R

RC20

New member
I have Lapua brass for my 6.5 Lapua Target gun (Lapua is the only one that makes brass for it). I am not interested in the argument about small and large flash holes, I am wondering about Lapua brass not adhering to what seems to be what should be (yea, verbiage) a small flash hole.

In picking out the corn cob granules (lets not get side tracked on that), I found my pin tool slid easily into some of the holes and others were quite tite.

So then I figured, ok, will even them out, 5/64 drill (.080) and like the pin, easy no resistance on some and miner resistance on others.

Hmm I think, that is kind of sucky quality control.

Then it occurred to me, what size is the flash hole on a Large Rifle Primer? Right around that same .080.

Is Lapua just that shoddy on their flash holes?

Only ref I came across was .059 for one standard and .078 for the other.
 
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I mean, sure, they're free to make the hole the size they want(anticipating fitting at least some sort of "standardized" decapping pin). But I believe most flash holes are punched, so there's not a ton of accuracy there

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Doing some searching this popped up from Lapua. Lapua sure has consistency problems with the primer holes.

We’ve also incorporated our smaller diameter flash hole (1.5mm, rather than the industry standard 2.0mm), which has proven to provide enhanced accuracy, and is used in a number of our other accuracy oriented cases.
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Add into the case mouth dents that there are 5 or so per 100 (more in the 06 cases I got some time ago). Easy to fix but??????????????
 
Honestly, I think drilling out the flash holes was a bit much, I would have just use a flash hole uniformer. And just the fact that your "pin gauge" slid easily in some and was tight in others... Did you actually measure the difference? Or just decide that Lapua messed up and decided to cram a drill bit in there to "fix" what you thought was a problem? If you were concerned, I would have contacted Lapua to get their input. They're top of the heap for a reason (but not immune to error) and even after reading that article, I think you're overreacting a bit, and not sure what you're looking to discuss, argue, or claim

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Dents occur in all the bulk brass I've ever had from the cases being poured into boxes or the boxes being bounced in transport. Unless cases are individually packaged like cartridges (ADG brass is available like this, for example) you can't really control that.

The flash hole inconsistency is interesting, but, as mentioned, it is not a precision process. If you look at Lake City brass, for example, it is drilled, but drills walk, so quite a few of them are off-center. I think you can design a drilling process that won't do that, but I haven't seen proof it is superior to punching. In either case, the reason Sinclair sells flash hole reamers is to eliminate the inconsistency.

Smaller diameter decapping pins are available from some of the die makers if you have problems with the reamed flash holes, but I don't think you will.
 
What I see the issue as being -is that Lapua says

We’ve also incorporated our smaller diameter flash hole (1.5mm, rather than the industry standard 2.0mm), which has proven to provide enhanced accuracy,
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And yet RC20 has there brass and it's flash holes measuring 2.0mm NOT 1.5mm . IMHO that's not inconsistent , being off by 25% is flat out wrong ! I'd have some questions too .
 
Honestly, I think drilling out the flash holes was a bit much, I would have just use a flash hole uniformer. And just the fact that your "pin gauge" slid easily in some and was tight in others... Did you actually measure the difference? Or just decide that Lapua messed up and decided to cram a drill bit in there to "fix" what you thought was a problem? If you were concerned, I would have contacted Lapua to get their input. They're top of the heap for a reason (but not immune to error) and even after reading that article, I think you're overreacting a bit, and not sure what you're looking to discuss, argue, or claim
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I was a technician/engineer working in the mechanical field for 35 years, so yes I know data, testing and when I find an anomaly.

I also know when I am wasting my time, so no I am not going to try to deal with Lapua. You would have better success wrestling a jello elephant.

I like the quote from Peterson Brass:

A high-quality casing will have a precisely punched flash hole which is free of burrs and tearing. It is also important that the flash hole is uniform in size from casing to casing.
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But also:

Due to the packaging and shipping process, case necks are often slightly dinged or bent and need to be rounded up and sized to give proper neck tension. New and/or fired cases must be full-length resized or have the expander ball of the sizing die run through the case neck prior to loading.
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I did not have a successful career in what I did by being sloppy or jumping to conclusions. I may get the letter drill bit sizes just to get tighter data. The reality is that Lapua taughts its precision and people talk about the small flash hole size as being optimum, Lapua brass does not come that way. I have not measured other brass.

Punch or drill, quality control is quality control. Either process can be made to be quality and either can be poor.

If there is anything to flash hole size its my opinion that uniform (same size) would be relevant, not the size itself.

A uniformer is a hand held drill that evens out the size but will do nothing if a flash hole is larger than (in this case) the small size (technically its supposed to be .059) (it also chamfers the inside to remove burrs though I suspect the first firing does that nicely)

A good 20% of the Lapua cases are of the much large hole size.

A major purpose of this forum is to pass information on and I have not seen that discussed other than in broad terms. It is now.
 
And yet RC20 has there brass and it's flash holes measuring 2.0mm NOT 1.5mm . IMHO that's not inconsistent , being off by 25% is flat out wrong ! I'd have some questions too .
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Metal God: Those are the two sizes quoted for the spec.

The larger holes in the 6.5 x 47 I have are not 2 mm, just that they are bigger than my 1/16 drill size allows me to measure. You can feel looser but it would be a guess as to how much though .070 would seem about right as my pick pin is .068 and its a fraction loose still.

My pocket pick does not go into (did not) into the flash hole on about 80%, it easily went through. The holes are not so much uniformed now but closer to the same.

I would have to get the letter drills

I did what the one test did, a 1/16 drill bit ).062 and they are now that size minimum.

The larger holes are move than that, less than 5/64 (.080)
 
If you mic drill bits, they are often a little undersized. I bit the bullet and got a set of pin gauges, similar to this one. Makes finding these numbers much easier.
 
Metal god said:
And yet RC20 has there brass and it's flash holes measuring 2.0mm NOT 1.5mm . IMHO that's not inconsistent , being off by 25% is flat out wrong ! I'd have some questions too .
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Actually, since Lapua is claiming 1.5mm, you should start with that as the base value. That makes the discrepancy of 0.5mm a difference of 33 percent, not 25 percent.
 
Guilty of ball park of the difference though I don't know what it is for sure.

I did check my drill bits and they were spot on (also top notch bits).

Dang, now I have to think about pin gauges, used about everything else at work over the years, never needed those, hmmm. Letter drills I could use for fine tuning though and I can mike them and be accurate.
 
The neat thing about the pin gauges (I have two sets that go from 0.061" to 0.025", and 0.251" to 0.500") is the increments of 0.001" all through the range. No more in between mystery sizes as long as you don't need higher resolution than 0.001".
 
Ok, in the interest of science, PM me and then send me the group from .059 to .090.

I can then give you data on the small flash holes from 6.5 x 47 as well as quality of the large flash hole in 308 and 30-06 (I have both those in Lapua as well).

I promise I will send them back!

Not inclined to buy the set as I quit work a few years ago and its a one time check thing.
 
I found this interesting, he had the same result I had. (different cartridge )

Every lot of Lapua brass for my 6.5 Grendel has needed to have the flash holes uniformed as they come with two different diameters of flash holes. I discovered this when I was poking walnut shell media out of the flash holes. My tool would pass through some flash holes, and not pass through others.

I have not tested whether I get better groups from uniforming the flash holes, but I figured anything that gives more consistent ignition can't hurt. If the flash varies from round to round because of the different diameter of flash holes, my ignition may also vary.
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I got a .070 drill bit and ran throuigh thge 100 or so cases I did not have loaded (there were two seperate lots of cases in that batch - 100 are loaded right now)

Out of the 100 I can access as it were, 8 were .070

I bought another box of 100 a few weeks back, went through those, 98 are .0625, two are .059.

1/16 (.0625) would be a good choice to size the flash holes to and will do the two odd ones to that.

I do have a query into Lapua on the other group(s) I got. I don't have a problem with the uniform of .0625 but .070 would seem to push that into two groups of different characteristics by significant in size though maybe debatable if it matters.
 
I have to admit to being asleep at the wheel, I had noticed it before but did not think a lot of it. Maybe the lack of Sunlight and cold winter got thoughts to wandering.

Agreed it is strange. Never been happy with dented mouths at 60 cents (sale) to $1 per each case (Peterson is even higher) but those are easily corrected with the sizer (though I used the M die)

I have bought other new brass, looked at a lot, never saw a dented mouth. Not saying it does not happen but ........ Last group also fewer in that regard.

While I can feel a bit of variation on the newest batch, its no more than .001 or .002 (sans the two that were probably a true 1.5/.059.

Still am plenty good with that, its consistent not wild as the former batches was.

Once it struck me I thought an interesting idea to nail down the specifics. I think its close enough for reasonable.

Be interesting (and will report) as to what Lapua has to say.
 
Thank you for bringing this topic to light. It comes up every so often.

I will do a test to put up, regarding flash hole size consistency. To see if it matters at all.
 
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