Eccentric flash holes? BIG DEAL!

19 January 2002, 07:00

R Flowers

A few months ago I posted the question as to whether or not eccentric or off centered flash holes made a difference in ammo performance. I have seen a couple of other shooters post the same question. No really good answers were posted.

So, being bored I decided to do a little study with my .223 Remington. I searched through several hundred (like six or seven hundred) military cases that I bought from Midway some time back and finally found 30 that had obviously eccentric or off center flash holes. I loaded those 30 and another 30 that had nicely centered flash holes and went to the range.

The cases were all treated the same. They were all military cases with LC 75 stampings.
They were all full length resized, trimmed to 1.75 inches, deburred and chamfered, the primer pockets were uniformed, and the primer flash holes were chamfered from the inside. All powder charges were had weighed on an electronic scale. All shells utilized Remington 7 1/2 primers seated with a Lee hand tool.

Now this test was done with some components I wanted to use up and the rifle is a standard weight barreled Remington 700 BDL that is strictly stock except for a nice trigger job by a local gunsmith. It wears a 4.5 X 14 Leupold scope.

The results are interesting, I found that there is darned little difference. I used two powder types to see if that had any influence.

Loads tested with 25 grains of XMR 2015 powder behind a 50 grain Sierra bullet seated to an OAL of 2.25 inches gave the following results:

Centered flash holes: 0.90 inches average for three five shot groups.

Off Centered flash holes: 1.07 inches average for three five shot groups.

The difference a whopping 0.17 inches. Oddly enough, though, the off centered flash hole groups did show more vertical stringing than the others.

Then I tested a load of 28 grains of 748 behind the same 50 grain Sierra bullets seated to the same 2.25 inch OAL.

The results:

Centered flash holes: 1.07 inches average group size for three five shot groups.

Off Centered flash holes: 1.12 inches average groups for three five shot groups.

The difference: an even smaller 0.05 inches!

So, for my uses of a .223 Remington as a "walk around" varminter I can see little reason to worry about eccentric flash holes.
I feel that these small differences in groups sizes are insignificant.

For what its worth, there it is.

Randy Flowers

19 January 2002, 07:56

dan belisle

Thanks Randy. - Dan

19 January 2002, 08:21

<500 AHR>

Randy,

The next myth you can help dispell is the one regarding squareness of the action. In my experience the barrel more than any other component of the rifle itself affects accuracy.

Thanks for the interesting data.

Todd E

19 January 2002, 11:21

JerryO

quote:
Originally posted by R Flowers:
So, for my uses of a .223 Remington as a "walk around" varminter I can see little reason to worry about eccentric flash holes.
Randy Flowers

Yep, and your mighty convinceing that it DOES matter if the smallest group wins.

Thanks, JerryO

19 January 2002, 12:42

<500 AHR>

JerryO,

Do you really expect us to belive that you can hold a hunting rifle to within 0.05" shot to shot?

Randy,

Did you measure the velocities of these loads with the concentric and eccentric flash holes?

Todd E

[This message has been edited by Todd E (edited 01-19-2002).]

19 January 2002, 14:57

<vssf>

What's the point in preping brass if you are going to acept an obviouse defect that could degrade your groups by more than 10%? If you are interested in accurate reloading put them in the bin.

Regards

Ray

19 January 2002, 22:09

<2ndaryexplosioneffect>

When you start loading calibers with slow burning powders in cartirges that hold 50-90 grains of powder, ignition makes a big differance. Non-uniform flash holes will become apparent then.

20 January 2002, 02:45

<heavy varmint>

In my view MR. Flowers resultes were apparant, when hunting game there is most likely no reason to get uptight about the flashhole but if hunting paper.....

20 January 2002, 03:04

<500 AHR>

Everything I load for holds well over 100 grains of powder. That said my experience is very close to Randy's. I find very little difference in groupings. Actually, I have tried found that often the primer pocket is not concentric to the outside diameter of the case and that the flash hole in reality is concentric to the case diameter. I determined this by deburring operation carried out on a lathe. To verify I swept in the primer pocket.

Now in the above scenario the flash hole is concentric, but the pocket primer is not. I still noticed no significant opening up of groups.

For hunting critters bigger than flies I see no reason to worry.

Randy,

Are you sure the flash hole are eccentric? It could be an illusion due to an eccentric primer pocket.

Todd E

20 January 2002, 05:02

R Flowers

Well, as usually happens, a post on this forum brings out more questions. I will try to respond to them briefly.

Todd, I did indeed chronograph these loads, I just left that data out because the post was so long already. The average velocities were nearly identical. HOWEVER, on odd thing showed up; the off centered flash hole cases actually had a smaller Standard Deviation on average than the centered flash holes. Actually, all these loads showed pretty high SD's.

25 grains XMR 2105 loads:

centered = 3293 fps ave 42 ave SD/5shots
Off center= 3286 fps ave 31 ave SD/5shots

28 grains 748 loads:

centered = 3211 fps ave 59 ave SD/5shots
off center= 3238 fps ave 38 ave SD/5shots

I am not sure why the SD's are so large for these loads. I was shooting in 50 degree weather with lousy light condiditions, I do not know if that effected the chronograph.
However, my "pet" load of 28 grains of H 335 behind a 40 grain V-max gave an average speed of 3577 fps and only had a SD of 11.
And a load of 26 grains of N 133 with the same 40 grain V-Max gave 3617 fps and an SD of 14. Go figure. (The groups for these loads were 0.85 and 0.79 inches.)

Ray, you are right, I probably should just throw the off center batch away. But, this was just a test to see if I could tell any difference. I did a similar test recently comparing military cases to Remington cases, maybe I will bore you with that one some day.

Back to Todd, I do believe that the flash holes are eccentric. The primer pockets appear well centered and man those flash holes are WAY off center.

Thanks for the responses.

Randy Flowers