Small primer brass on larger cases

[KMart]

In this discussion, I am talking about the 308 Palma, 6.5 Creedmoor, 6.5 x47L etc. I have read several post here that people have said that one should NEVER increase the size of the flash hole size in these type cases. If you do, all kinds of bad things will happen to accuracy, pressures and other things.
There are other examples of cases using small rifle primers with large flash holes. Examples are the 222 Rem, 222 Rem Mg, 223/5.56 cases, 6x47 Rem and maybe others. Those cases seem to just fine for accuracy, pressures etc.
Other than having to experiment with the larger flash holes in the Palma type brass and being careful with what you do, what would be the downside?

 

[Patch700]

My best guess as to why the larger flash hole works on the latter cases you mentioned is that they do not have as large a powder colum nor the powder capacity as the 308 etc... I have no concrete evidence of this other than my own testing years ago on a 22 cheetah.

To put it crudely I assume it is not unlike the old garden hose theory in that if you put a restriction on the end the flow will travel farther... In this case , the flame would travel further thus enhancing a more uniform ignition.

Good discussion.

 

[bobinpa]

I have often wondered why people want brass that takes small rifle primer, whenever they can get it. What makes it better or more accurate?

 

[johnfred1965]

I have often wondered why people want brass that takes small rifle primer, whenever they can get it. What makes it better or more accurate?

The small primer pocket, thus a smaller hole, leaves more material in the case head. For Palma shooters(palma brass) it allow them to "hotrod" their loads, getting better performance from the limited 308 case. Safety of these loads are up to the shooter, and I don't think Lapua endorses this practice. In the instance of other calibers, Lapua can establish a higher pressure for the cartridge, and still get good case life

For myself, I shoot an autoloader, and I like the stronger head for durability during the extraction cycle, reducing deformation, real or imagined

 

[JRS]

German Salazar conducted a test trying to ascertain the differences.

 

[johnfred1965]

I get distracted easily. To the OP's question, I have to agree with Patch's description of the waterhose.
Also, I am sure the cartridge designers have looked at differing flash holes, and are giving you the optimum for their designs, and modifications would only lower performance.

I do know of wildcatters experimenting with oversize flash holes, most notably, subsonic loads for the 300BLK, to assist ignition in those low pressure loads

 

[JRS]

 

[JRS]

Top picture is a BR case with 0.080 flash hole.
Bottom picture is a Lapua Palma case with 0.062 flash hole.

Draw your own conclusions.

 

[LitLBoy]

JRS one thing to consider --- those are also two different primers. Or, are they?
LitLBoy

 

[JRS]

JRS one thing to consider --- those are also two different primers. Or, are they?
LitLBoy

Both cases were primed with the Remington 7.5 primer

 

[6MMsteve]

what is a 300 blackout good for I don't understand the con con cept, on the primer test I would prefer the top fired primer looks like a nice ignition

 

[Patch700]

Top picture is a BR case with 0.080 flash hole.
Bottom picture is a Lapua Palma case with 0.062 flash hole.

Draw your own conclusions.

I have seen these type of comparisons before and although looking at it from that perspective it seems a no brainer... But I feel as though there are more things at stake here than visually dissecting a flame... I may be way off base here but is an explosion hotter than a properly tuned flame? I don't have that answer but I can say that I have had dismal results trying to ignite 42+ grains of powder in a case with a colum size roughly equivalent to that of a 308 ... The problem never went away when I opened up the flash hole. Not the most scientific i realize lol.

 

[M-61]

To the OP: I have no knowledge of what would happen if one changed the flash hole size. What I do know is that I would be most reluctant to make this type of alteration as I 'assume' the manufacturer did not arbitrarily punch or drill that diameter hole. There would be a reason for it that, that I can't speak to.

Pictures: I have seen these before but is indeed the top picture the one that is the most desirable for accuracy? Is there a definitive test that shows this to be more accurate or is it's use to light off a larger column of powder.

 

[KMart]

I have seen these type of comparisons before and although looking at it from that perspective it seems a no brainer... But I feel as though there are more things at stake here than visually dissecting a flame... I may be way off base here but is an explosion hotter than a properly tuned flame? I don't have that answer but I can say that I have had dismal results trying to ignite 42+ grains of powder in a case with a colum size roughly equivalent to that of a 308 ... The problem never went away when I opened up the flash hole. Not the most scientific i realize lol.

Interesting results that nothing changed when you opened the hole size.

 

[Patch700]

Interesting results that nothing changed when you opened the hole size.

To be clear I didn't notice an improvement in reliable ignition... What did change was the velocity E/S increased by roughly 100% based on a previous E/S of 12-18fps.. These numbers are based on one case , one powder and one primer so take that for what it's worth i guess..

Why I tried enlarging the flash hole was in an effort to achieve more reliable ignition in extreme cold temp situations, as I said no change there by increasing the size.

 

[M-61]

Top picture is a BR case with 0.080 flash hole.
Bottom picture is a Lapua Palma case with 0.062 flash hole.

Draw your own conclusions.

What comes with a .080 flash hole? Or was this done for the test.
I wonder what the pics would be like with .062 vs .057?

 

[JRS]

What comes with a .080 flash hole? Or was this done for the test.
I wonder what the pics would be like with .062 vs .057?

Remington BR brass.

 

[butchlambert]

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.

 

[dkhunt14]

Top picture is a BR case with 0.080 flash hole.
Bottom picture is a Lapua Palma case with 0.062 flash hole.

Draw your own conclusions.

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

 

[redrockranger]

To be clear I didn't notice an improvement in reliable ignition... What did change was the velocity E/S increased by roughly 100% based on a previous E/S of 12-18fps.. These numbers are based on one case , one powder and one primer so take that for what it's worth i guess..

Why I tried enlarging the flash hole was in an effort to achieve more reliable ignition in extreme cold temp situations, as I said no change there by increasing the size.

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