flash hole size

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oley55

New member
Pretty sure I acted while under an extreme case of "crainial-rectalitis" and messed up 80 pieces of LC 7.62 brass. Not having the right drill bit to clean up the flash holes, I used a .0840"/2.1336mm bit. From what I have read on line, 2mm/.0787" is the maximum diameter for a large primer 308win.

Even if I am able to reduce loads and use them, for the sake of continuity with my other brass I think these will have make their way into my scrape brass bucket.
 
If you mix your brass for match loading, you should scrap them. If you keep your match brass segregated, you should be able to use them. Back when NT primers first came out, they were in both large and small pistol sizes, and 45 auto cases using them had mammoth flash holes of 0.125" diameter. This was because the DDNT sensitizer in these primers had much higher brisance than lead styphnate compounds, and could blow the primer out if the hole wasn't bigger to vent the gas faster. Guys who tried loading them with standard primers and their standard loads reported being unable to tell any difference.

A rifle may be a little more sensitive, but probably being 0.084" instead of 0.080" (the number benchrest shooters reaming large flash holes for uniformity use) will be essentially invisible except maybe in 1000 yard matches. Just to be safe, take the chronograph out and measure one of your standard loads, then take 6 of your over-reamed cases and make one 10% lower charge, one 8% lower, one 6% lower, one 4% lower, one 2% lower and one with the full charge. Fire them in that order, watching for pressure signs and for the velocity to be higher than your regular load by more than your usual spread. Keep a special eye on the primers for mushrooming appearing at a lower load level. If you get neither exceptional mushrooming nor an obvious increase in velocity (as I fully expect will be the case), then load up a full set and confirm the velocity is about the same as your usual load gives you in the same conditions.

Check for accuracy while you are at it. If it improves, you've found yourself a new flash hole diameter.
 
I'm a benchrest shooter 308 caliber , I check all my flash holes with a #45 drill bit .082 and size them to that , I read Federal is going with a small primer and flash hole in their 45ACP cases 1- will make a stronger case 2- the velocity increases 50 fps. I just prep all my cases to be as exact as possible.
 
I think the move to small primers in 45 Auto is because, in proportion to the pocket diameter, the flash hole is bigger, thus eliminating the need for different tooling for forming cases for NT primers. Just the headstamp has to change. Winchester started doing this first AFAIK, but so far, only in their loaded ammunition.

Increasing velocity requires more pressure coming from somewhere, so even if greater strength of the 45 Auto case comes from using small primer pocket, to avoid violating the laws of physics you still have to go to higher pressure to get greater velocity and ultimately that means either changing the SAAMI standard or labeling all your ammo +P+ to show it's not made to the SAAMI standard.
 
CW308,

yea these are #44s, but are smaller than what a #44 (.086") is advertised to be. With a mic I am getting .0847" on the shank, but can not get a reliable measurement over the flutes. So who knows, except for machinist types.

Guess I won't toss them yet, but they will definitely get set aside for another time. Even with a note in the container, my boys will one day say, "what the heck was the old man trying to do here?" Or so I imagine.

thanks to Unclenick and CW308
 
Most drills I have are slightly undersized so the holes they drill, which are widened by flexing and wobble and deflected to the sides of the hole by sharf, produce a hole that comes closer to actual nominal size. If you are using one as a reamer, though, your hole will be closer to the measured size unless a lot of material is being removed.

Set your micrometer up to the size you think the drill is and see if the flutes will fall between the anvil and spindle nose. If so, tighten by a tenth of a thousandth and try again until it starts to catch and drag a bit. If it stops altogether, you want to go in between the current setting and the previous tenth and try again. At that point, you are probably within a tenth if the micrometer quality is good. Conversely, if it doesn't fall through, open the micrometer wider in tenths until it just makes it with a bit of drag along the way.

Finally, if you want real precision in the holes, go to the next smaller size drill and then use an actual chucking reamer in a pin vise just to take the last couple of thousandths out of the hole diameter.
 
Guess I won't toss them yet, but they will definitely get set aside for another time. Even with a note in the container, my boys will one day say, "what the heck was the old man trying to do here?" Or so I imagine.
Click to expand...

I have had some good success with nail polish on the heads.

I have two 7.5 x 55, one is a K-31 and the other is a custom barrel. I could not get the head space to work the same so I split my brass up (I had some NNY but not enough, so PPU got colored)

Its held up well and easy to put on when it wears off.

Might work, just put a card in with the cases if someone comes across them down the road and ??????
 
oley55
I don't think you would see a difference on your target , its worth a test , only difference being flash hole . I deburr my flash holes on the inside and a twist on the pocket side , I uniform my primer pockets , only have to do it once , I use to use the Uniformer to clean the pockets but once I switched to wet tumbling with SS Pins and liquid detergent my cases clean like brand new , inside and out also primer pockets , I pop the primers first before cleaning and sizing . Hope I Helped .

Chris
 
I've got about 3K 1X fired cases, mostly all matched from same lots and/or purchased at the same time, a case of unfired Win Ranger, & a case of unfired Win PDX1, all .45 auto cal. & only Fed GM match, Win, & R-P & not a single small primer among the group, and no range brass either. I've been saving lots & large groups of 1X fired cases for about 30 yrs and it is paying off. I hate small primers and less than good quality brass.
 
I have a flash hole micrometer it is useful when the reloader measures before and again after. There was one reloader that drilled all of his flash holes out to a diameter. That allowed him to have cases with the same diameter flash hole.

And then there was the rational; it was a JIC thing as in just in case it makes a difference.

And then there is that old saying: Primers are not a good way to determine pressure. When measuring the diameter of the flash hole before and again after firing pressure will increase the diameter of the flash hole and primer hole and high pressure will increase the diameter of the case head and high pressure will shorten the distance from the cup above the web to the case head.

And then there is another method and or technique that would require reloaders to remove their hands from the keyboard so I will not go into that one.

F. Guffey
 
F.Guffey
You have me looking over my shoulder , are you following me . Only kidding .
Be Well .Chris
 
F. Guffy said:

I have a flash hole micrometer it is useful when the reloader measures before and again after. There was one reloader that drilled all of his flash holes out to a diameter. That allowed him to have cases with the same diameter flash hole.

And then there was the rational; it was a JIC thing as in just in case it makes a difference.
Click to expand...

yep, pretty sure that was my thinking. Rereading your post and as always trying so very hard to glean F. Guffy's point, for the slow of mind (like myself), in plain English what are you inferring please?
 
I guess the F.G. hook went out and we all bit
Click to expand...
.

I have flash hole gages, if I did not have one I would make one; I do not look at reloading through little beady eyes; I understand this thread is about the diameter of the flash hole. It would seem reloaders see the flash hole through small beady eyes. They tumble their brass with stainless steel pins to avoid punching media out of the primer pocket/flash hole. And then there is the diameter of the flash hole drilling without a plan. I would determine the smallest diameter and the largest diameter first knowing reducing the diameter of the flash hole is most difficult I would decide if it was necessary to apply the 'leaver policy'. Applying the leaver policy would be determined by the number of flash holes to be drilled.

Sorting flash holes by diameter is an option for me because I have a flash hole gage, again if I did not have one I would make one, but someone before me decided the flash hole gage was a good ideal.

Back to limited knowledge through looking at the world through beady eyes.

And again I understand this thread is about the diameter of the flash hole. Again, I have a flash hole gage. When determine the diameter of the flash hole after firing I am able to compare the diameter of the flash hole before firing if I measured before......firing:rolleyes:.

I have hammered cases with heavy loads, I understand reloaders examine primers for pressure; I also understand the effect high pressure has on the case head. High pressure can increase the diameter of the flash hole, case head and primer pocket and high pressure can decrease the thickness of the case head from the cup above the web to the case head.

Again: A builder of bench rest type rifles called to ask for help; he built a bunch of rifles that required cases that he did not have, he had to find a way to form them. He started out with 440 long belted magnum cases. He asked me to bring the 'other' #4 RCBS shell holder because he had 40 cases that would not fit his #4 Shell holder.

To put a plan into gear I had to determine if 'it' could be done. It took a lot of forming dies it worked. When finished with the 400 cases I started on the 40 that would not fit his #4 RCBS shell holder; I used a small gasket cutting ball peen hammer to drive his cases into his shell holder. Looking at the problem with wide vision I knew the case did not fit his shell holder because the 40 cases had heavy loads. I knew the case had expanded in front of the belt, I knew the diameter of the flash hole had expanded, the primer pocket had expanded, the case head had been crushed.

Between us we had 5 lathes, I offered to use a collet in a lathe to reduce the diameter of the case ahead of the belt. I also offered to cut the extractor groove deeper. Finally he decided it was not worth the effort necessary to save the cases.

And then there is that part that is difficult to get reloaders to do; and that is the part where they remove their hands from the key board.

My favorite brand of shell holder is the RCBS shell holder; my RCBS shell holders fit where the touch, something like a hand-me-down shirt. I have at least three sets, they are not alike.

I also have shell holders that fit, RCBS did not make the ones that fit. The shell holders that fit were made by Herter. When using a Herter shell holder the case fits, my opinion it is an excellent fit. If after sizing a case with a Herter shell holder and then loading the case and firing it I find the case does not fit the Herter shell holder I know the case head expanded because the case head will not fit the Herter shell holder.

And no that is not the reason Herter made shell holders that fit.

F. Guffey
 
F.Guffey
In your opinion , I'm using the #45 drill bit .082 to check the flash holes most are at the .082 size very few are slightly smaller , those I change to .082 with the bit . I'm shooting a 308 with the same powder charge and bullet . I am no longer looking for that accurate load , I am satisfied with the one I have now , only working on form and enjoying shooting . That's the reason I want all the flash holes the same size . Would you agree
 
If anyone was interested in measuring their flash holes they could buy a pin gage set

http://www.starrett.com/metrology/p...ools/fixed-gage-standards/Pin-Gages/S4003-250

normal is 0.080″ flash hole and Lapua Palma brass is 0.062

or buy a couple sets of pin drills

https://drillbitsunlimited.com/060-to-0799-C375219.aspx?sid=25472

but unless you are a .2 or below shooter I bet you would never notice a difference a .004 larger flash hole . I read it on pretty good authority that you should never mess with the flash hole so I just clean and uniform the pockets.
 
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hounddawg
I'm not shooting high end brass , FC , ADI & HSM , I didn't know Lapua flash holes are smaller . 082 has been working for me with no issues , I shoot only one distance 200 yards so it's simple to find the best recipe . One of these days I will give Lapua a shot or two . Thanks for the info , pin gauges are out of my ballpark but the bits will work just fine . Thanks

Chris
 
Only the Palma style brass CW. I have about 90 pieces that were bought in 2009 or 10 that have the smaller flash holes but LRP pockets. A lot of the newer SRP brass use the "Palma" style .060 flash holes. I tried some of the Peterson small rifle .260 brass with SRP's and Palma flash holes. The Peterson 6.5 CM's and several other cases also use the small flash hole. If you get ahold of any you have to use a small pin deprimer. Redding has one for their decapping dies and I use a Mighty Armory universal which has replaceable pins in both sizes.
 
dawg
I have a Universal decapper die , also a RCBS 223 die set , gave my Colt HBar to my son-in-law . Only shoot my 308 for many years , never got an etch for another shooter . Thanks for all your helpfull advice .

Chris
 
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