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Enlarging brass flash hole?

I have enlarge primer pockets in 308 cases to take shotgun primers .... for sub sonic loads, but that compromises the strength of the case for high pressure loads.
A slight increase or even a decrease in flash hole will most likely have little effect.
I shoot .059 and .082 sized flash holes in both 308 & 6.5 Creedmoor with SR small dia primer and LR primer the larger dia. flash hole.
Large Rifle primed cases are about 40 fps faster with the same charge..but that is more likely to be the result of more primer mixture in the LR primer rather than the dia of the flash hole.
 
I ream all of my flash holes to 0.0625" for uniformity using the Sinclair tool. I can't quantify the result - it may be too small to matter - but I like my brass to be as uniform as possible. It's a one time operation that I can do in the off-season.
 
John Weigel said:
I’m just wondering if changing flash hole diameter might change the dynamics of the ignition in a favorable or unfavorable manner. Have not heard of anyone actually enlarging them (small amounts) as a test. So I may have a go of it for curiosity’s sake.
Click to expand...
Using the 6br/dasher brass as an example, Alpha brass use an .080 flash hole vs Lapua that uses an .062 flash hole. Both shoot extremely well for me in my rifles. Both shoot basically the same load using H4895, within
.1 to .2 grains of powder. Alpha had done testing on both flash holes and says that there is no difference in performance.
 
I have a couple of .22 Creedmoor rifles I use for predator hunting in the winter. It gets COLD in Montana that time of year, so I have been concerned about ignition with a SRP in that case. I have tuned the firing pin fall, spring rate and firing pin protrusion in both rifles to optimize ignition. I use 6mm Creedmoor Lapua brass necked down and of course it has the small primer pocket. I did a test yesterday morning to try and sort out any issues with that setup. I had some brass to dedicate to the test that I used a K&M .080 flash hole deburring tool on 10 cases and left another 10 with .062 flash holes from another K&M tool. Powder weighed to .02 grains and annealed brass. All other conditions were the same. I used CCI 450 primers for the test. At 4 BELOW ZERO there was essentially no difference between the large flash hole and small as far as chronograph data or accuracy. Furthermore, I have tested LRP brass in .22-250's several times in temperatures as low as -18 degrees and really didn't see a difference on the ES/SD when compared to the SRP .22 Creedmoor. There may be something out there that is of significance but I certainly can't detect it.
 
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John Weigel said:
Wow! I should abide by my intuition more often. Very interesting, and I’ll start the drilling to confirm!
Click to expand...

In my opinion the study was done well from a scientific standpoint.

However, keep in mind unless you use the exact same components under the same conditions, you are introducing variables. I would like to see someone duplicate the test to try to confirm the findings. That, in my opinion would make it valid.

I wouldn't start off by drilling all my brass because of this one test.:)

Jim
 
STS said:
I have a couple of .22 Creedmoor rifles I use for predator hunting in the winter. It gets COLD in Montana that time of year, so I have been concerned about ignition with a SRP in that case. I have tuned the firing pin fall, spring rate and firing pin protrusion in both rifles to optimize ignition. I use 6mm Creedmoor Lapua brass necked down and of course it has the small primer pocket. I did a test yesterday morning to try and sort out any issues with that setup. I had some brass to dedicate to the test that I used a K&M .080 flash hole deburring tool on 10 cases and left another 10 with .062 flash holes from another K&M tool. Powder weighed to .02 grains and annealed brass. All other conditions were the same. I used CCI 450 primers for the test. At 4 BELOW ZERO there was essentially no difference between the large flash hole and small as far as chronograph data or accuracy. Furthermore, I have tested LRP brass in .22-250's several times in temperatures as low as -18 degrees and really didn't see a difference on the ES/SD when compared to the SRP .22 Creedmoor. There may be something out there that is of significance but I certainly can't detect it.
Click to expand...
When I lived in Minnesota and one day went out to the range to test some 260AI loads
that had Lapua SRP flash holes. after the outside temp had dropped quickly over the night before, from about 33 degrees down to 5 degrees, I had enough fail to fire and delayed ignition problems after 6 or 7 times trying, that I decided to load up and go home.
All summer and fall before that I didn't experience those issues.
 
22BRGUY said:
When I lived in Minnesota and one day went out to the range to test some 260AI loads
that had Lapua SRP flash holes. after the outside temp had dropped quickly over the night before, from about 33 degrees down to 5 degrees, I had enough fail to fire and delayed ignition problems after 6 or 7 times trying, that I decided to load up and go home.
All summer and fall before that I didn't experience those issues.
Click to expand...
What primers? I had a .22x47 Lapua several years ago that would have delayed ignition with Federal 205’s in below zero temperatures.
 
Tom and I did test flash holes in Alpha BRA brass. They sent me brass with no flash holes. I drilled and reamed them. We went from .050 to .080. It was a hard choice between. 050 and .080. .060 was good, .070 was not. I didn't expect results like that. Probably why you will hear people say not to open them up. Your much better off at .060 than .070. But if you go past that to .080 it's good. I would not assume the same results in all cartridges or even in the same with different powder or primer combos. We liked .080 enough that Glenn came over here and reamed his Lapua up to .080. I'm not sure if it's better but we are trying it.
 
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