LAPUA BR FLASH HOLE IS .062" NOT .059"

[billslatteryjr]

Posted in the 6BR forum also.

The Lapua .059" flash hole has been gone a long time. Most likely since the switch from the gold paper to blue plastic box. Unless my pin gauges and mics are wrong the flash hole on the last 10 or so blue box lots I've bought is now somewhere around .062". I've got old untouched brass that measure under .061, which is the smallest pin gauge I have, and have tried numerous times over the years to notify this site and Sinclair Inter to correct their info pages and product descriptions but have got nowhere. Figure their pin gauge sets aren't small enough to measure for themselves or they're in cahoots with the fake news folks.

 

[Ned Ludd]

This is not a direct answer to your question, but all my lots (including the most recent) of Lapua Palma (.308 Win) brass have the smaller flashhole. As expected, my .223 Rem brass has the larger flashhole. I did not actually measure the holes with pin gauges, but a "standard" decapping pin will not fit into the tighter Palma brass flashhole, so I had to obtain the smaller decapping pins sold for the decapping tool. As I didn't actually measure them, I cannot say what the exact diameters of the two different sized flashholes are, but clearly Lapua is still providing different sized flashholes in their brass. Of course, it is possible that this is a cartridge-specific phenomena. Have you contacted Lapua directly with this question?

 

[billslatteryjr]

Ned, No I never asked Lapua directly.

Just know there's a lot of guys that are still taking the written word that it's best to leave the 6BR flash hole as is when they may be better off uniforming the things. I know it ticked me off when I discovered it had changed a couple lots in. Use the Sinclair tool now.

 

[Ccrider]

Posted in the 6BR forum also.

The Lapua .059" flash hole has been gone a long time. Most likely since the switch from the gold paper to blue plastic box. Unless my pin gauges and mics are wrong the flash hole on the last 10 or so blue box lots I've bought is now somewhere around .062". I've got old untouched brass that measure under .061, which is the smallest pin gauge I have, and have tried numerous times over the years to notify this site and Sinclair Inter to correct their info pages and product descriptions but have got nowhere. Figure their pin gauge sets aren't small enough to measure for themselves or they're in cahoots with the fake news folks.

This is fact. I don’t know that the difference in size matters, but I know that the holes are not .059 and are mostly .062. Never understood why all the written specs say .059.
I do seem to remember reading where Litz I believe tested and found that there was no benefit to uniforming the SRP holes.

 

[Murray Brook]

I have 2 lots of Lapua 6mm BR Norma brass and they easily take my collet die decapping pin measuring .062. Lot #'s of the brass are P01188206/1261919 and P01143001/1151718

 

[billslatteryjr]

This is fact. I don’t know that the difference in size matters, but I know that the holes are not .059 and are mostly .062. Never understood why all the written specs say .059.
I do seem to remember reading where Litz I believe tested and found that there was no benefit to uniforming the SRP holes.

I don't know about that. Looking back I'm figuring that's why I lost all those matches.

 

[Evan]

Maybe it was when they switched from drilling the flash hole to punching them?

Drilled flash holes was and always has been a rumor. No brass maker has ever drilled them; the setup to do so doesn't exist and would be expensive and too slow for production levels. All flash holes are punched, some are just punched to a much higher standard.

 

[ppaul]

Posted in the 6BR forum also.

The Lapua .059" flash hole has been gone a long time. Most likely since the switch from the gold paper to blue plastic box. Unless my pin gauges and mics are wrong the flash hole on the last 10 or so blue box lots I've bought is now somewhere around .062". I've got old untouched brass that measure under .061, which is the smallest pin gauge I have, and have tried numerous times over the years to notify this site and Sinclair Inter to correct their info pages and product descriptions but have got nowhere. Figure their pin gauge sets aren't small enough to measure for themselves or they're in cahoots with the fake news folks.

Yes, the ones I've measured have been .062 not .059. Posted something along those lines a couple years ago. Really did not get any meaningful responses, finally dawned on me that if no one else cared why should I.

 

[carlsbad]

My guess is the spec say .059 since that will ensure you use a decapping pin that will fit though the smallest hole.

 

[Texas10]

Posted in the 6BR forum also.

The Lapua .059" flash hole has been gone a long time. Most likely since the switch from the gold paper to blue plastic box. Unless my pin gauges and mics are wrong the flash hole on the last 10 or so blue box lots I've bought is now somewhere around .062". I've got old untouched brass that measure under .061, which is the smallest pin gauge I have, and have tried numerous times over the years to notify this site and Sinclair Inter to correct their info pages and product descriptions but have got nowhere. Figure their pin gauge sets aren't small enough to measure for themselves or they're in cahoots with the fake news folks.

Ok, you made me look. My 2017 blue box of Lapua 6mmBR brass measures .059. My newest box purchased in 2019 measures .062.

 

[Ccrider]

Ok, you made me look. My 2017 blue box of Lapua 6mmBR brass measures .059. My newest box purchased in 2019 measures .062.

Have you seen a difference in performance?

 

[Texas10]

Have you seen a difference in performance?

Nope.

 

[KMart]

In my case, my decapping pin measures just slightly smaller than .062 with a micrometer. It may measure exactly .062 depending on how I was holding it. In some instances, I have had brass that fit very tightly on that pin and has pulled the pin out if the retainer nut has gotten a little loose. If that happens, I get out my uniformer for an 062 hole and wallow it out a bit. At the temperature and velocity of the primer flash going through the hole, I don't think .003" is going to amount to a hill of beans in the performance of the round. I do however, like all of them to be the same diameter.
I do think that the biggest advantage of the small flash hole is that it helps allow us to operate our chamber pressures at a much higher pressure level without pressure signs on the primer or blanking them. It seems that the small flash holes came into being when everybody started designing and using smaller more efficient cartridges at higher velocities.

 

[338 dude]

Posted in the 6BR forum also.

The Lapua .059" flash hole has been gone a long time. Most likely since the switch from the gold paper to blue plastic box. Unless my pin gauges and mics are wrong the flash hole on the last 10 or so blue box lots I've bought is now somewhere around .062". I've got old untouched brass that measure under .061, which is the smallest pin gauge I have, and have tried numerous times over the years to notify this site and Sinclair Inter to correct their info pages and product descriptions but have got nowhere. Figure their pin gauge sets aren't small enough to measure for themselves or they're in cahoots with the fake news folks.

There was a post a while back about Lapua drilling their flash holes I actually shot them an email and got a response to which they said that they punch all their flash holes now I wonder if the change from drilling to punching had anything to do with the size of the flash hole

 

[Texas10]

I'd like to see any authoritative or confirmable reference on the subject of drilling of flash/spit holes. As far as I've been able to research, no manufacturer of cartridge brass drills or has ever drilled flash/spit holes. Drilling is way too time consuming whereas a punch gets the job done in a micro-second. I would be surprised to learn the throughput speed of cartridge brass during the punch operation was less than 200 pcs per minute. Try doing that with a drill operation.
http://forum.accurateshooter.com/threads/lapua-does-not-drill-their-flash-holes.3909883/

Upon opening a fresh box of Lapua 6mmBR brass last week, I took time to inspect them. Regarding the flash holes, all were uniformly centered in the pocket and all had been deburred inside. Close inspection with 20x showed no smearing of brass within the flash hole indicating a good sharp punch and proper fit to the die.

The only thing I had to do was fireform them and they shot very well even then.

I have seen many flash holes that were cone shaped and blown out on the inside with much smearing of brass internally and a large burr on the exit side of the hole, especially on factory produced ammo I have purchased on sale. I have never seen that on premium brass sold separately.

If you have questions regarding the flash/spit hole of your newly purchased brass all you have to do is have a close look using magnification. You'll quickly find out whether the mfg. held good tolerances and kept dies sharp.

 

[Laurie]

Have you seen a difference in performance?

Tests that people did decades back on the smaller capacity small flash-hole cases usually found that 0.070" was the tipping point. Hit or exceed that and things went downhill. So, a move from from 0.059 to 0.062 shouldn't have any effect other than a possibly tiny increase in pressures / MVs as long as the holes are consistent between cases.

 

[Laurie]

I have seen many flash holes that were cone shaped and blown out on the inside with much smearing of brass internally and a large burr on the exit side of the hole, especially on factory produced ammo I have purchased on sale. I have never seen that on premium brass sold separately.

Chippings from flash-hole uniforming / deburring early production Hornady 6.5mm Creedmoor brass. The two big spirals would have had interesting effects on ignition consistency if left in place!

 

[RedfootRanch]

The two big spirals would have had interesting effects on ignition consistency if left in place!

View attachment 1199739

Please tell of these interesting effects on ignition consistency that you have seen!?

 

[rjtfroggy]

Guess I am in a minority. As soon as I get mine I take out the .072 drill bit and open them all up. No misfires, no blanked primers, no problems with pressure and when I check (not often) velocity, es, sd are well with in reason.
I also don't get chunks of carbon or unburnt powder when I clean.

 

[Laurie]

Please tell of these interesting effects on ignition consistency that you have seen!?

Well I didn't in this case as I removed them before using the brass! Having those stuck in the path of the primer flame / hot particles would almost certainly block and/or skew their path to a greater or lesser extent affecting how the charge then burned.

There have been many studies on the effects of deburring flash-hole outlets over the years and there is across the board agreement that there are benefits in reducing ES/SD values with some makes and qualities of brass. The most recent I've seen is in Bryan Litz's book of precision shooting and handloading essays, Modern Advancements in Long Range Shooting Vol. II

https://store.appliedballisticsllc.com/Modern_Advancements_in_Long_Range_Shooting_V_II_p/0008.htm

The many studies in the book includes one with the Applied Ballistics team looking at the effects of flash-hole uniforming / deburring on ES/SD using multiple groups, also fired from a variety of different size / calibre cartridges with both sizes of primer. It unequivocally found across the board benefits. (This is unusual in that many of his other exercises give a mixture of results and some show few if any benefits at all.)

So far as Lapua goes on both size of primer and flash-hole, I've never bothered deburring and gave up on primer pocket uniforming many years back as I just couldn't see any benefits from these two practices. I do still carry out a once only flash-hole diameter uniforming exercise on new brass using Sinclair rear-entry reamers. This is partly because I have the tools and it's an easy exercise, but more because I once (and once only) discovered a small percentage of undersize 2mm/0.079" holes in new Lapua 223 Rem brass. This was two or three cases in a 100-ct box in 'gold box' days. They were so tight that the tool would barely enter and took multiple turns against significant resistance before it stopped cutting. Unlike the other 97 or 98 cases, there was also significant discarded brass.

I've always wanted to try some of the case-prep tests on 'ordinary' factory brass that you'd see years ago in gun magazines. However, I never reckoned you could draw meaningful conclusions from their three round groups fired in 30-06 Rem 700 BDLs and similar. I intend to do it with an FN SPR rebarrelled to 260 Rem with a Bartlein Heavy Palma barrel and have collected several makes of brass to see how much difference they make (if any). As part of this I did some load development with Remington brass (actually pretty consistent and reasonably well made on inspection) and just before Covid lockdown started loaded some 40 rounds of out of the packet R-P brass, half as supplied / half F-H deburred and uniformed to see what the group averages and LabRadar say at 100 yards off the bench. Sadly, that's still on hold along with many other projects as my club has still to get covered firing points back into full use. (My expectations are, no noticeable short-distance group benefits, but as per Litz, ES/SD reductions.)