Small primer brass on larger cases

[Patch700]

What did it look like on the target ? Better or worse ?

To be perfectly honest with you I don't believe my results were achieved in a way that could be used to definitively say one way or the other if there was a decline in accuracy... The tests were done over two days , both days were if I remember correctly -28 celcius with about a 5-7 mph wind.. So you can see that this was not conducive to great shooting.. The numbers I retrieved were merely a byproduct of the ignition test.

At those temps I was experiencing the odd ftf and was interesting in finding out if a larger flash hole would overcome this issue.. in that case it did not.

 

[Texas10]

I recently bought two batches of 6mmBR brass to try out, Norma and Lapua. The Norma brass has a .062 flash hole and the Lapua is 1.5mm or about .057. Everything I read about the Lapua says don't enlarge the hole to fit the standard de-capping pin, or accuracy will suffer. Instead, buy an undersized pin. My RCBS Gold Medal micrometer dies came with the undersized pin.

 

[TAJ45]

I am curious if the Palma 308 has the same flash hole size as the 6BR as well as the "normal" small bolt face/small primer cases.

As to the garden hose physics, would not the smaller orifice, with the same force/pressure behind it give a longer, stronger? more focused stream?
My Boyle's Law principles escape me...it's been to long.

 

[JRS]

To me the top picture looks like a different primer, it looks like the test done in Precision shooting magazine years ago. The reason I am saying this is because the too picture is showing way more particulates. Like when they compared Federal to CCI, Remington, and magnum to non magnum. Look like what I saw with a magnum verses non magnum pictures. Matt

The photos are copied from German Salazar's site. German clearly states the primers used were the Remington 7.5. The Remington 7.5 is a hot primer. If you want to challenge German Salazar's word, go for it. The experiment was performed to test the "jet stream" theory with small flash holes and large flash holes.

 

[JRS]

Wolf 223 Primers.

 

[spclark]

The tests were done over two days , both days were if I remember correctly -28 celcius...

-28C?

Really?

You were out doing testing at that temp? That's -18F for us here, way too chilly for anything but feeding the cattle maybe. Now if that - was an error & you meant 28C (82F) I'm curious as to any ftf evident.

I shot a Fullbore match last April using Lapua's Palma brass (flash holes opened ever so slightly to 0.062" with a 21st Century reamer) & KVB223REM small Russian primers. That day it was 18F (-7C) when we started @ 300 yards, warmed to 26F (-3C) by the time we were done. I didn't have any problems with ignition, accuracy was normal though my usual zeroes were a little low.

I've decided I probably won't shoot under conditions like those again unless maybe the targets are shooting back....

 

[butchlambert]

I recently bought two batches of 6mmBR brass to try out, Norma and Lapua. The Norma brass has a .062 flash hole and the Lapua is 1.5mm or about .057. Everything I read about the Lapua says don't enlarge the hole to fit the standard de-capping pin, or accuracy will suffer. Instead, buy an undersized pin. My RCBS Gold Medal micrometer dies came with the undersized pin.

1.5mm is closer to .0591. I think the majority uniform them to ,0625. The last batches of Lapua in 220 Russian and 6BR accept my .0625 decapping pin. I mean brass that has been purchase from 2000 to present. I doubt that .0034 plus on size means anything.

 

[Larryh128]

It's easy to look at the flame and think that the larger flame spitting sparks everywhere is going to be the best, but give me a small round ball of blue flame at the base of the charge. Ignition should be a burn bottom to top not a burn starting everywhere. My opinion only based on my observations.

 

[AckleymanII]

Different powders will like different primers. They like what they like. Steve Chernicky took pictures of all kinds of primers like German did years ago and posted in Precision Shooting Magazine.

Putting a chamfer on the inside of the flash holes creates more of a straight stream vs a small ball. Coatings on powders create some challenges for primers, you had better experiment, assume nothing.

 

[jfseaman]

If you want to play with flash holes I have a couple thousand rounds of new Remington 6BR brass with out the flash holes. I believe a lot of the old cartridges used large flash holes.

We may not get anywhere with this as a negotiation but I am interested.

 

[jfseaman]

This is my understanding.

Facts: (correct me if I have the facts wrong)

• Smokeless powder is not an "explosion" but a burn, a fast burn but still a burn. In absence of containment it can take a long time to burn.
• Primers are an "explosion". Each brand and style/type has it's own performance characteristics in this explosion.
• The BR or Match primers have a more consistent "explosion".
• The small flash hole channels and restricts the hot gases from the "explosion".

Effect:

• The effect of small flash holes is to control over ignition of the smokeless powder.

Result:

• A more consistent burn of the powder.
• A more consistent build of the pressures associated with the expanding gasses.
• Lower ES/SD.
• More consistent muzzle velicity.

This is just how I understand it. It may not be not what it actually happens. This is what I got from German's primer studies, other primer studies, powder burn studies. Head scratching on my own.

 

[Jeff A]

Recently I was looking for a tool to remove any burrs that MAY exist above the flash hole on my 6.5x47L cases. I was unsuccessful in finding a tool with a smaller than .59" (1.5mm) pilot for the cutter but I did find several sources that said the 1.5mm flash holes are responsible for the small ES & SD I enjoy on my 6.5x47 loads. I do not have any other gun/cartridge other than the 6.5x47 that can match the low numbers I get from this cartridge. I won't modify these small flash holes. Thank you, Lapua!

 

[SheepDog]

There are several reasons not to increase the size of the flash hole beyond some point.
1. a larger hole "weakens" the head of the case. (perhaps but to what degree?)
2. a larger hole allows more gases from the burn to build faster in the primer. (it can cause pressure signs to appear faster)
3. in can affect the primers ignition potential. ( to what degree?)
4. larger flash holes can push a bullet out of the case easier and may adversely affect the pressure curve resulting in hang fires.

The safest way to handle this is to find the largest flash hole in a given lot of cases and bring them all to that dimension. This operation should be moderated with the knowledge that the largest primer flash hole might be a mistake if it is considerably larger than the rest or outside the acceptable margin of the bulk of the cases.

 

[Patch700]

-28C?

Really?

You were out doing testing at that temp? That's -18F for us here, way too chilly for anything but feeding the cattle maybe. Now if that - was an error & you meant 28C (82F) I'm curious as to any ftf evident.

I shot a Fullbore match last April using Lapua's Palma brass (flash holes opened ever so slightly to 0.062" with a 21st Century reamer) & KVB223REM small Russian primers. That day it was 18F (-7C) when we started @ 300 yards, warmed to 26F (-3C) by the time we were done. I didn't have any problems with ignition, accuracy was normal though my usual zeroes were a little low.

I've decided I probably won't shoot under conditions like those again unless maybe the targets are shooting back....

Yes that is correct , -28 degrees Celsius ... I know, not the greatest weather to be shooting in but as i mentioned it was an ignition test ..

Sometimes we do our predator thinning in these temps and the rifles have to go bang lol. I had also conducted a similar test on a straight 243 win , using palma brass and the results were not great when using ball powder (for onvious reason i suppose) at frigid temps.

I am a fan of the small rifle primer pocket but it has it's limits.. My less than scientific testing has shown it doesn't help opening up the flash hole so I leave them be and worry about other tangible things.. like keeping fingers warm lol.

 

[spclark]

Well I'll leave the sub-zero testing to you my friend... not something I want to take on anytime soon.

I'd think ball powders would be less affected than stick, being generally easier to ignite but then at this temp extreme I can see reasoning behind using a large standard primer, if in fact not a magnum, for no other reason than to get things started more reliably than a small primer is capable of.

I used some multi-times fired Palma brass last year as the basis for a wildcat 7mm (284INCH) and it performed quite nicely for me once I'd wrung out what was the best propellant and charge weight for Berger's 180 Hybrids. But then the coldest day I had THAT out was I think about 60°F, nowhere near your -28°C!!