6br flash holes/current lot
- Thread starter chris308
- Start date
Sinclair used to sell a flashhole deburring tool designed especially for cases with the smaller hole, but I see it's no longer listed in their catalog. I recently did a very rudimentary test with new 6.5x47 Lapua brass necked down to 6x47 - I loaded 20rds. - 10 w/flashholes deburred; 10 w/o deburring. ES & SD of the cases without deburring was less than half what it was with the deburred cases!?? 600yd. groups were nearly identical out of both samples, but what would they look like at 1000?
There's no depth stop on the .060" Sinclair tool, so the depth of the deburring cut can & will vary. This in itself could account for some or all of the increase in ES & SD I saw in this example. Trimming cases to uniform length and installing a stop to index on case mouths would take care of the variations in deburring depth.
I'm gonna HAVE to repeat this test, just to make sure it wasn't a fluke. I've religeously deburred flash holes in ALL my match brass for the past umpteen years - would hate to think that the results with small flash hole Lapua could've been counterproductive. Also need to try the same sort of test with typical U.S. cases w/punched .080" flash holes - here, I would expect deburred cases would show some improvement over unmodified cases.
There's no depth stop on the .060" Sinclair tool, so the depth of the deburring cut can & will vary. This in itself could account for some or all of the increase in ES & SD I saw in this example. Trimming cases to uniform length and installing a stop to index on case mouths would take care of the variations in deburring depth.
I'm gonna HAVE to repeat this test, just to make sure it wasn't a fluke. I've religeously deburred flash holes in ALL my match brass for the past umpteen years - would hate to think that the results with small flash hole Lapua could've been counterproductive. Also need to try the same sort of test with typical U.S. cases w/punched .080" flash holes - here, I would expect deburred cases would show some improvement over unmodified cases.
Forum Boss
Administrator
Dennis,
I never had the 6BR brass with the little slivers occluding the hole, but about 2 years ago I did use a K&M tool to "uniform" flash holes. This was supposed to take them to .062, but in fact it opened them to about .067.
I found, with Varget powder, the "uniformed" cases showed pressure with a lower charge, and the ES/SD also increased. The difference in ES/SD wasn't as dramatic but it was there, with ES going from about 12-13 to about 20-22.
The "uniformed" flashholes also seemed to collect carbon faster than untouched flashholes. I attribute this to the fact that you are adding fine machining lines to the walls of the flash-holes.
Lapua flash-holes are NOT drilled. They are formed by a punch coming from the top to meet another coming from the bottom.
I never had the 6BR brass with the little slivers occluding the hole, but about 2 years ago I did use a K&M tool to "uniform" flash holes. This was supposed to take them to .062, but in fact it opened them to about .067.
I found, with Varget powder, the "uniformed" cases showed pressure with a lower charge, and the ES/SD also increased. The difference in ES/SD wasn't as dramatic but it was there, with ES going from about 12-13 to about 20-22.
The "uniformed" flashholes also seemed to collect carbon faster than untouched flashholes. I attribute this to the fact that you are adding fine machining lines to the walls of the flash-holes.
Lapua flash-holes are NOT drilled. They are formed by a punch coming from the top to meet another coming from the bottom.
Chris -
I got 400 pieces of Lapua 6BR brass from Brunos just about 2 months ago. They all had small burrs in the flash hole. I used the SHANK end of a number 53,.059) drill to just sort of swage out those little tits. The pin vise I have is a little too small to hold a #53 bit, so I just grabbed it by the fluted end and used it by hand - worked ok.
I usually examine the inside shoulder by feel with a inside flash hole tool,other calibers). This is my first go-round with Lapua brass, so if the mod's advice above is correct regarding inside-outside punching, it may not be necessary. However, I'm currently waiting for a small hole tool from Possum Hollow to arrive, and will see for myself. I understand most of the various tools will enlarge the hole, either a little or a lot...
From using the shank end of the .059 bit to punch out the holes, it appears that they are quite uniform in size. I don't plan to enlarge the holes at all. When the PH tool shows up, I may just dress the bit down a little, and use it as a pilot only. Depending on what the inside shoulder feels like, I may not use it at all.
I got 400 pieces of Lapua 6BR brass from Brunos just about 2 months ago. They all had small burrs in the flash hole. I used the SHANK end of a number 53,.059) drill to just sort of swage out those little tits. The pin vise I have is a little too small to hold a #53 bit, so I just grabbed it by the fluted end and used it by hand - worked ok.
I usually examine the inside shoulder by feel with a inside flash hole tool,other calibers). This is my first go-round with Lapua brass, so if the mod's advice above is correct regarding inside-outside punching, it may not be necessary. However, I'm currently waiting for a small hole tool from Possum Hollow to arrive, and will see for myself. I understand most of the various tools will enlarge the hole, either a little or a lot...
From using the shank end of the .059 bit to punch out the holes, it appears that they are quite uniform in size. I don't plan to enlarge the holes at all. When the PH tool shows up, I may just dress the bit down a little, and use it as a pilot only. Depending on what the inside shoulder feels like, I may not use it at all.
AlNyhus
Silver $$ Contributor
I just made up 50 30BR cases on some of the 'new' lots of Lapua 6BR cases. The flash holes measured .058-.059 on these. No burrs or swarf in any of the flash holes. I use a Ron Hoehn tool that indexes from the primer pocket side to open the flash holes to .062, then cut a slight chamfer on the inside with a tool that indexes in the .062 flash hole with a non-cutting pilot.
If you're shooting a coated bullet, you may see some significant improvements by enlarging the flash holes. -Al
If you're shooting a coated bullet, you may see some significant improvements by enlarging the flash holes. -Al
Personally, fooling with Lapua flash holes is a waste of time in my opinion. If it makes you feel better to uniform, de-burr go for it, damn all that work. That's why when I build a new gun/caliber it has to use Lapua brass. I like shooting them myself! Now if they would make some 20 Vartarg brass........
Varmints For Fun
Varmints For Fun
the last 2 lots of 6mmBR lapua brass that I purchased had flash hole burrs. K & M makes a deburring tool with a stop designed for the small flash holes of the ppc and BR cases. I have used this on most of the cases, I will save the rest and run a test to see if it makes a difference with my ES and Standard deviation.
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