Off-center flash holes

  • 3.1K Views
  • Last Post 16 October 2009
LWesthoff posted this 11 October 2009

Was digging around in the attic today and discovered a 2 lb. coffee can almost plumb full of '06 brass, all headstamped WCC52, still with the crimped-in military primers in place.  After digging out my Wilson decapping punch and decapping them, I noticed that some of the cases have noticeably off-center flash holes.  My first reaction, of course, was to go through them and trash everything with a flash hole that was obviously not in the center of the primer pocket, but then I got to wondering:

With a reduced charge spread evenly in the bottom of the case (I roll every case on the follower before I run it into the chamber), does an off-center flash hole have any measurable effect on accuracy?  I go through a lot of trimming and weighing excercises to acheive as much uniformity as I can, and obviously a couple of off-center flash holes in a string of ten rounds introduces some theoretical non-uniformity, but has anyone ever actually done some real honest-to-God testing to see if it Does make a difference?

Wes 

Attached Files

Order By: Standard | Newest | Votes
corerf posted this 11 October 2009

I have MOST of my brass showing off-center flash holes. I assumed it was just my luck with recent production brass. I have not seen it in older brass. I will keep an eye on the data produced by my loads with both off and on center holes. Thanks for bringing it to the table.

Mike

Attached Files

CB posted this 11 October 2009

Off center flasholes are not an item in brass performance. I bought a box of 100 Lapua in .222. All the brass are off center the same. Load em and Shoot em.

Stephen Perry

Angeles BR:fire

Attached Files

LWesthoff posted this 12 October 2009

No offense, but somehow the fact that Lapua - or any other outfit - managed to let at least 100 pieces of brass get past their Q.C. with off-center flash holes doesn't reassure me that off-center flash holes won't affect accuracy. I was kind of hoping that maybe someone had actually run some tests. I never had much faith in somebody's opinion unless it was backed up by a documented fact or two. It's a problem I have.

Wes

Attached Files

CB posted this 12 October 2009

West

I'll send you some benchrest pictures if you want. I have a Hart .222 barrel I can spin on my HV, jacketed of coarse.

Stephen Perry

Angeles BR:fire

Attached Files

LWesthoff posted this 12 October 2009

Maybe I'm a little dense this morning, but I can't figure out what that last post has to do with my original question: With a low density load (the kind most of us use in cast bullet competition), spread evenly in the bottom of the case, will a couple of rounds with off center flash holes in a ten shot string have any adverse effect on accuracy? Has anyone actually done any testing and come up with any verifiable conclusions?

Wes

Attached Files

CB posted this 12 October 2009

West

Let somebody else have a go at it. I didn't buy the cases to shoot Cast though them maybe later.

Stephen Perry

Angeles BR:fire

Attached Files

CB posted this 12 October 2009

Don't have any first hand knowledge but remember reading an article in the American Rifleman years ago where someone ran a pretty thourough test on off center flash holes and couldn't find a dicernable difference between those with centered and off centered holes on the target.

With the usually small charges of powder used in the military cases you'd think position would have a lot more to do with accuracy than a flash hole a few thousandths off center but even that doesn't seem to be a big concern so I doubt that the flash hole is anything to worry about at all.

Attached Files

cityboy posted this 12 October 2009

I remember the same AR article; it was by Bill Davis. The conclusion was if there is an effect it would take a lot of shooting with a very accurate rifle to determine it

Jim

Attached Files

JSH posted this 12 October 2009

I had some Lapua or Norma 223 cases the flash holes were off center on. Used them to make 6x45 for my XP, shooting FLGC stuff. I had been using a lot I had of LC brass. It would shoot under 1” at 100M, on a regular basis. The L or N cases I had were just sized an loaded, as I did most of my prep work after fireforming. They were allover the place on paper, Shot some over the chrono, numbers were up and down. That explained that, to me any way. Checking for off center flash holse is one of the first things I do on bottle neck cases any more. I don't care if it is going to shoot jacketed or cast. I expect the same from both projectiles. Accuracy the most, speed is a second. I don't need another problem thrown in to the mix on any of my projects. BTW ran across the same thing when Federal, FGM, turned loose of their brass again a few years back, same gun. I found some pull down LC 223 cases and bought a bunch after that. jeff

Attached Files

CB posted this 12 October 2009

Jim

I more than agree Jim and none of us are good enough shots to even try and I do mean all the shooters on this Forum me included.

Stephen Perry

Angeles BR:fire

Attached Files

JetMech posted this 13 October 2009

Wes, no testing on my part, just another opinion. I think that while it may have some effect, primer pocket depth uniformity and deburring the inside will have more of an effect on consistant ignition.

One way to check might be to index the cases and shoot some groups, one indexed one way, one 180 degrees out, and a group where you shoot purposely indexing rounds differently.

It's a good question and while most here seem to think it will have little effect, Jeff (JSH) seems to be the only one who has actually documented experience with off-center holes and had an adverse result.

I'll be looking for the same thing to see if I can document the effects, as far as my loads go.

Attached Files

LWesthoff posted this 15 October 2009

I'm re-opening this thread because I now have a little bit of actual data to report:

First, I figured that trying to test for accuracy was beyond the capabilities of my equipment; neither of the two rifles I have in 30-06 caliber (my cut-down and lightened hunting rifle with a 3X Leupold and my Issue Class 03A3) can be considered sufficiently accurate. However, I do have a recently acquired chronograph and figured if the off-centered flash holes were going to affect accuracy, it would probably show up in velocity/standard deviation. So I loaded 10 rounds of the newly discovered WCC52 brass with centered flash holes and 10 rounds with badly off-centered flash holes, both sets loaded with my favorite 100 yard Military Rifle competition load of Lyman 311284 bullets all from the same casting session, same mold cavity, and weight segregated to +/- 0.15 gr., ahead of 28.0 gr. Varget.

Results: The 10 rounds with centered flash holes gave me an extreme spread of 117.0 fps; S.D. 30.3. The ten with badly off-centered flash holes had an extreme spread of 41.5 fps and an S.D. of 14.6. Incidentally, even though I had decided I was not trying to check for accuracy I did put up a couple of 100 yd. targets to aim at. The off-center flash holes gave me a significantly smaller 10 round group, too????

Although it would take a lot more testing to establish that flash hole location actually had no effect whatsoever on velocity and/or accuracy, I'm satisfied. Mr. Perry, your opinion - in this case at least - seems to have been quite correct (even though you did seem to have a little trouble with which end of the bullet the gas check goes on)!

Wes

Attached Files

billwnr posted this 15 October 2009

Wes,

Those are interesting results and I wonder if it's similar to using a primer with less ignition, resulting in a more uniform ES.

My thinking is the primer hole is off center to the ignition flame, resulting in less flame hitting the powder.

Attached Files

LWesthoff posted this 15 October 2009

billwnr: Actually, I think the fact that the off-center flash holes seemed to give more uniform results and be a little more accurate was just an anomaly. If I repeated the test (which I probably won't do until and unless primers become more available again) I figure the results could just as easily be reversed. One thing I didn't mention in the previous post was that the off-center primer string also had a higher average velocity - by about 20 fps. To me, the only way any of those details make sense is to consider them anomalies: the only valid conclusion I can draw is that off-center primers - for low density cast bullet loadings at least - just don't make any difference.

Eventually I may get comfortable with that idea. In the meantime, I've got quite a few “new” pieces of '06 brass I don't have to throw away.

Wes

Attached Files

JetMech posted this 16 October 2009

Wes,

At this point, you have the first set of reference points. Don't throw out the results just because they don't agree with the “conventional wisdom". Continue with your testing. This is very interesting.

Attached Files

Ed Harris posted this 16 October 2009

Stephen Perry wrote: Off center flasholes are not an item in brass performance. I bought a box of 100 Lapua in .222. All the brass are off center the same. Load em and Shoot em.

I agree.  However, if you know anybody REALLY anal retentive, I would ask them if they had ever marked the off center flash holes and tried orienting them in different directions, to see if it made any difference.  Know anyone like that?

:)  

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

Attached Files

CB posted this 16 October 2009

Ed

Since I haven't left yet I think you indicted yourself on the off center look. First thing I thought of when I saw your Mr Green Jeans look I thought this could be a Rush Limbaugh cousin. So Ed I would say not knowing you, thank God, personally that you have tried all the positions at least you are inferring that way.

You really got excited on this off center discussion. Hope it made your day or night. Remember you made the anal remarks and responded in capitol bold letters.

Stephen Perry

Angeles BR:fire

Attached Files

CB posted this 16 October 2009

Come on guys play nice! Life is way too short to argue about silly nonsense and make cracks about what people look like or whom they may or may not be cousins with. So knock this crap off okay?

Attached Files

Close