Flash hole reamer question

C

Charles

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Hi guys

Hi have somes lapua brass in 6br that i wont to check in a sinclair case neck tighness.

The problem is that the retainer pin in the tool have .0600 and the flash hole of the lapua brass probably .0590.

I know that i can take a flash hole reamer to make the flash hole at .0625 so i would be able to check the case.

I would like to know if this procedure can affect accuracy.

Thanks
Charles
 
My opinion is yes, it can affect accuracy/performance, and I would not ream out the flash hole. Lapua did not put that tight flash hole and small rifle primer in there by mistake. It was part of the design by Norma from the original 6BR Remington to improve accuracy. Have a read of the Norma info on the cartridge.

6BR Norma
 
I would adjust the tool before I adjusted the brass. Talk to Sinclair and see if they make a pin for the Lapua brass, if not just skinny this one down.
 
Ron AKA said:
My opinion is yes, it can affect accuracy/performance, and I would not ream out the flash hole. Lapua did not put that tight flash hole and small rifle primer in there by mistake. It was part of the design by Norma from the original 6BR Remington to improve accuracy.
Click to expand...


Ganderite said:
Pressure SD is inversely proporionate to the flash hole diameter. Ever see how small the flash holes are in a Berdan case?

Don't drill them out.
Click to expand...

OP, as I stated, changing the size of the flash hole should not change the accuracy of the loaded round, since you will be working up a round anyway. Also since you have not worked up a load, I canot see how it will cause performance problems.
However, if you have already loaded these rounds and were satisfied with the accuracy/performance you received, and THEN you decided to ream out the flash hole and reload using the EXACT SAME recipe, then I can see where you may very well get into trouble. Your pressures will be vastly higher and that will change internal performance, which could change POI, velocity, stabilization, throat erosion, and other damage to rifle due to high pressure. You will have to start again.

I will still maintain that if you are starting with everythiing brand new, and you change the flash hole, you can still get execptional results when you work up your loads, you are just going to have a lower max load.

Just my opinion. Walk carefully.
RW
 
Thanks guys for all of your opinion, this is appreciate !

I have done somes research on i'm own and find this is a very controversial subjects.

Somes shooters are hardcore with this and others said that when they ream the flash hole they have bigger ES. When i will have my load i will do somes tests and post the results.

Thanks
 
Actually, pressure drops if you ream the holes, but I said my piece.

The reason the holes are small is to improve ignition and accuracy, but if you want to take a hammer to your Ferrari engine in the hopes that a bash here and there will "improve" it, be my guest.

Internal ballistics 101, settled by emperical test around the turn of the last century. Confirmed on transducer printouts many times since....

The last published test I saw was by ADI in Australia. They changed from Berdan to Boxer primers in the 223 ammo and everyone wondered why velocity and pressure ES and SD got worse. They ran tests on flash hole size and found (once again) that small holes were best. And the Berdan brass had the smaller flash holes.

I was provided samples of both and asked to confirm the findings. I did.
 
Thanks Ganderite, i will leave the flash hole like they are, less work and better accuracy so the choice is simple...

I have learn something new today thanks for your help to guys.
 
flash holes

One thing you may want to do is debur the inside of the case where the flash hole is. I don't know if it really helps or not but it won't hurt anything either. Theoretically, it will direct the flame from the primer directly to the center of the powder column and provide more consistent ignition.
 
this was just recently posted and thought it was very relevent to the topic at hand.


From the voice of Tom Whitaker

This was one of the discussion points with Lapua when I first proposed the possiblity of producing a SP 308 case. Since they already were setup with small flashhole capabilities with the BR cases it was decided to go that way initially as we could drill out the hole to 0.080 during testing to compare. When I received the first test cases I ran some tests doing just this. The velocity differences between the large (0.080") and small (0.059") flashhole was statistically insignificant. However, I did notice that there were differences in the pressure signs on the primers. To further explore this I loaded both style cases with Wolf SMR primers (i.e. soft cup) rather than magnum or BR primers. Results: The small flashhole casess showed significant cratering but held the pressure (10 shots). With all 10 of the large flashhole cases the primers blew (pierced). This basically tells me that using the small flashhole creates a better pressure vessel in comparison to the large flashhole version. This is inline with accepted BR practices.




Trevor
 
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