When comparing the small Berdan dual flash holes to the rather large boxer flash hole it has always made me wonder what difference there is in ignition and performance when varying the hole's cross sectional area.This curiosity sparked the following test.

Four 5 round groups of LC74 ,.308 cases had theier flash holes opened up to .086" dia., .096" dia., .106" dia. and .120" dia.

All were identically loaded with a 150gr. BTSP bulk bullets. 42 gr. of WCC844, #34 primers, and crimped. The rifle had an A&B barrel with a proven so-so performance.

.086 dia. 2583 to 2676 fps. avg.= 2629 fps., 5 shot 1 1/2" group @ 50 yds. no pressure signs in any group all had a little soot.

.096" dia. 2581 to 2635 fps. avg.= 2608 fps., % shot 1 3/8" group @ 50 yds.

.106 dia. 2609 to 2671 fps. avg.= 2632 fps., 5 shot 1 1/4" group @50 yds.

.120"dia. 2635 to 2683 fps. avg.= 2660fps., 5 shot 3/4" group @ 50yds.

Note; All primers had an identical appearance. Each group in the progression had a warmer barrel than the group before it. The barrel was not cleaned during the test. No noticeable effect jumped out and grabed me.The increase in accuracy could have been due to barrel condition or some other happenstance.

Conclusion; The evidence from this test appears to be almost non existant. To find any profound results a much more stringently controlled designed test need be performed.

Thought I'd share this with you non the less. roger

Roger,

Yup, an interesting topic, at least for us two.....

I load and shoot about 1,000 rounds of .222 Remington anually for a fairly specialized shooting dicsipline (German DJV Shooting, at 3 different 100 meter targets & 40 or 50 meter Running Boar). A pretty keen level of accuracy is required and therefore some attention to detail for amunition requirements. Good case prep, solid load development and shot in heavy-barreled target rifles, too - so there is considerable bench time involved prior to moving off to the off-hand, supported and prone shooting pistions required.

Currently, I've two batches of brass, 200 R-P Nickeled cases and 300 RWS brass.

Initial case prep for me includes inside flash hole de-burring using the Sinclair tool. The RWS cases are obtained from a friend as factory fodder; shot once by him and then given to me in batches. His accuracy from the factory ammo and my reloads are almost the same although my reloads shoot better but the JND isn't worth writing home about. I'm probably averaging an overall 1/2" 5 shot groups depending on the day, some much better and most NEVER larger.

The flash holes from the RWS brass are initially noticably smaller and then opened up as the inside is beveled with the Sinclair Tool. I haven't tried to measure anything (yet) other than eye-balling but the difference is easily seen. The R-P nickeled cases are purchased separately as a component and there is also an initial difference from unfired cases but much less so than with the RWS cases so obviously I'm working with a set of brass with different size flash holes and then they are "standardized" as they are prepped.

Currently, I'm saving a batch of 50 RWS cases with the holes NOT opend up so I can attempt to compare the factory small-holed cases to my open-up "prepped" cases. I'd like to determine (like you said; in a semi-controlled environment) if I'm doing myself a dis-service by opening them up. The current one ragged hole load of Speer 50 gr. TNT HP, 21.5 grs. VV N-130 with a CCI-450 primer with flash holes opened-up would appear from both grouping & chronograph results to indicate that everything is "standard"; therefore, good "standard" results.

Also I want to check other variables like CCI-400 primers vs. the CCI-450's with both small & opened up flash holes.

Did you notice any increase in primer pocket size with the larger holes?
I read an article some where, maybe handloader some few years back and the writter thought this might be a problem ?
Thanks Dave

Roger -


There have been various warnings published in the past about opening primer pockets much beyond .082", claiming that to do so can cause erratic severely high pressures. (Maybe just with some loads?)

Those warnings were in various esteemed source publications so presumably had bases in empirical observation, but who knows?



The "BR Boys" claim the smaller flashholes have a positive influence on group size, when combined with all the other match tweaks which each provide improvements too small to really notice individually, but when put together, work well. On that a couple of thoughts:

1. Would that not be proportionally appropriate when working with the small BR cases and small powder capacities? But maybe it would be INAPPROPRIATE when working with large quantities of slower burning powder, which might require faster and more certain ignition?

2. My own .30-BR rifles DO seem to be demonstrably more accurate using small flash-hole cases such as the Lapua, but one of my shooting friends who also shoots a "sorta-30 BR" (a .30-06 AI reamer run into the barrel the depth of a 6 PPC headspace gauge) uses reformed GI 7.62 brass with its large flash-holes, and still sets national records.....


I guess a final question would boil down to "Does it really matter for the fellow who actually does work up his loads for a specific rifle? It surely might matter for the fellow who just loads to "recipes" he finds in books and on the internet (God forbid!!), but if he is using factory size flash-holes opened a couple of thousandths as a uniforming operation and DOES work up his loads, is there a potential problem, or benefit?"

What do you think, partner?

How about running the test in reverse order, .120 being shot first and see if the grouping follows the first test?

quote:

Originally posted by Alberta Canuck:
Roger -



I guess a final question would boil down to "Does it really matter for the fellow who actually does work up his loads for a specific rifle? It surely might matter for the fellow who just loads to "recipes" he finds in books and on the internet (God forbid!!), but if he is using factory size flash-holes opened a couple of thousandths as a uniforming operation and DOES work up his loads, is there a potential problem, or benefit?"
what do you think, partner?

For the type of person you are speaking, of Ac, .002" dia. difference will not be noticeable either as a plus or minus IMHO. roger