Unexplained flyers....

[TrapperT]

Unexplained flyers....I recently had this occur again during a match this weekend. First a little background - I'm shooting f-open using the 7/300WSM. I push the 180 gr Hybrids Bergers at around 3080fps using H4831SC. The barrel is new (I now have 280 rounds down it) - BTW its the third barrel on this gun. I have shot 180 Berger VLD's, 180 SMK, and now the 180gr Hybrid. The barrel's have been the same length, twist and manufacturer. I have also used the same action and stock. I neck turn, weigh brass, bullets, sort bullets by length, etc. My vertical was great for the match thsi entire weekend - except for these occasional shots that would go low. Do they all go as low as the 8 ring? No, but it has become a common theme that I have noticed over the past two shooting seasons.

I also do initial load testing at 300yards and verify at 1000 yards. My vertical at 1000 during load development for this load has been under 2.375" for all of the bullets/loads and has actually been well under that multiple times.

What I have noticed is that for some reason during a string, I'll get a round or two that will go low. This past weekend I had a round drop straight down into the 8 ring at 1000. When the target came up, I was bewildered to say the least. My next shot I held exactly the same and scored a ten. The next shot was an X and I didn't have any issues after (BTW - the 8 happened on my 10th shot). The conditions were such that I was on pace to shoot in the high 190's. I have had this happen with every bullet I have tried. It is also not predictable. I have also used the same manufacturer for the brass and primers with all of the bullets above. In speaking to a few people at the match, they mentioned that the firing pin may be to blame.

So, has anyone had this happen and could it be the firing pin, spring or something else?

Thanks in advance for the help. Sorry for the long winded note.

Tony

 

[Alex Wheeler]

I cured one of my rifles of this by bushing the spring on the firing pin. Would throw one to 10 o clock. Does that low shot also have a lower velocity?

 

[Leaddog]

If, on a mainly sunny day, a cloud rolls over and throws a shadow over the range and you take the shot, it's going to go low. Something to think about.

Neck tension. Annealing cures many unexplained shots. My vertical has tightened considerably since I went to annealing after every firing.

 

[hoverp]

+1 for annealing after every shot on the brass. Neck tension, must, repeat must be controlled. If I'm seating for a long range event any case that gets a bullet seated that doesn't have the same force to seat, gets culled out for practice. Now annealing after every event has certainly helped with that. As you know, at 1000 every thing counts. How are you cleaning your cases and controlling neck tension? Powder load accuracy? What is your brass prep scenario? Lots and lots to analyze . Vertical shots can and will drive a person crazy, especially when you are holding x ring for the shot and you end up with a 9.

Vertical mirage can on some ranges push enough to go high and a change in conditions can go low if you don't take correction off during a change.

 

[TrapperT]

My brass prep includes FL size using a Warner die, anneal and ultrasonic cleaning of the cases after every firing. I have a Wilson seater which is cut to my chamber and I monitor force required to seat the bullets. Using a digital scale to weigh powder and I also re-weigh each powder charge. I then weigh the loaded rounds to ensure that I haven't missed anything. I feel fairly confident of my reloading techniques and since I have done the same thing for each barrel, I feel that it is leading me to something going on with the gun.

Charlie - It was a clear day...no clouds

Malibu - No idea on the velocity since I was in a match

I do appreciate everyone bringing up anything they can think of as it just might bring to light something I overlooked or have been overlooking.

Tony

 

[lpreddick]

tony boyer, in his book on benchrest shooting, call such shots "stupid shots". he feels the carbon ring that forms just in front of the case mouth, end of the chamber, can be pushed into by a case that is a little bit longer than ones fired previously. this can actually have a crimping effect on the case and increase pressure, etc. if you monitor and trim precisely all cases fired then this is not the problem. i'v had this exact problem and now that i have a hawkeye borescope, i check my carbon ring at each cleaning and it is always there. getting it out is not easy. nylon brushes don't touch it...brass will. trimming cases is now a ritual..a pita but having less flyers. fire several cases of same length, then one that is .005 longer and that .005 hits the carbon ring and can "crimp" the case slightly...?results. my $.04, inflation, you know.

 

[Preacher]

Sometimes it's just one case in a batch that won't behave like the others.
I like to keep track of where each case is in the loading block after it's fired, so if there is a problem it will show up for each case and be easy to find and toss..

 

[TrapperT]

lpreddick - I trim all my cases after sizing, which means I trim then every time. Also, increased pressure, should translate into higher velocity. But, I will measure my cases to verify length as my cases are only .010" shorter than my chamber length.

Preacher - I have thought about the brass. I actually weight sort cases after each firing to make sure nothing has changed. Not that this necessarily will catch the issue, but rather to make sure cases are grouped together correctly. I have been meaning to do what you stated and never have.

Again, I would like to thanks everyone for their feedback.

Tony

 

[jcampbellsmith]

Sometimes it's just one case in a batch that won't behave like the others.....

That's an excellent comment. I used to work in a factory that made batteries and occasionally the press that made the zinc battery cases would stop. When it was running, it would go thump, thump, thump.. for days on end.

Given that it takes 6 or 7 steps to make a brass case, there are bound to be cases that were first off or last off a machine as it started up or stopped. These cases are bound to be a little bit different. Within manufacturing tolerances, but not quite the same as the rest.
Thanks JCS

 

[Preacher]

I have one 284 case for my XP-100 that weighs with in .02 tenth of a grain of all the others, same length, same everything, except for when I put it on my old bullet spinner (Vern Juenke's mass metal spectrometer) then it would drive the indicator crazy, seems like it was thicker on one side of the case..
Every once in a while I'll load it up and shoot it right out of the group again....
Probably should have kept that old machine, but I let it slip away..... Now if one case acts weird for no reason, in the junk pile it goes..........

 

[GLC]

Hi Tony/gentlemen

I have also experienced this problem recently in two rifles, both shooting a very similar load to you with the same calibre and bullet, I cannot say for sure what the problem is, my feeling is the bullet, however I need to do more testing before casting any dispersion on the hybrids, (they group very well at short range And perform well at long apart from the odd "blip" I am going to shoot them over a chrono for at least 10 shots at distance and see if I have any low velocity cases, i did not experience this problem with the vld with the same cases.
This post is not really a lot of help, but you are not alone!
Regards
Gary

 

[TrapperT]

Preacher - I know of a person who has a Juenke machine. If I can figure out approximately which case it is, maybe I'll have him spin it for me.

I was thinking of something else today...I use BR2 primers. Have worked fairly well, but...could this be a potential cause? I know of some very good F-Class shooters who use magnum primers in their 6.5-284's. Although I am shooting a 7mm, the amount of powder that I am burning is significantly more than a 6.5-284. Could it be that the variation in BR2 primers causes a less then optimal burn? Whereas the magnum primer, even though it too may have variation, would help with optimal burn even if they very slightly because of the overall hotter flame? Hmmmm.......

 

[hoverp]

Are you putting the weighed loaded rounds in the order of firing sequence for the match?

I sort all mine from low to high in weight of the finished loaded round. I only do this by the grain. for me I start out shooting with the 314grain till those are out then the 315 then 316...so on. I set those up in my box so i shoot the lightest first as the barrel heats up the higher weight cases if i go from one grain set to another mid string due to the number of loaded rounds I get from my reloading session in that weight category" SHOULD " help me keep a consistant velocity relative to the barrel heating up .... ***but more importantly than that shooting all the loaded round by same weight "should" help with less shot to shot variation in the string I am shooting like going from a 314 to a 317 and back to 314 g.

Now after all this Im not saying that my unexplained shots in the vertical have stopped but they have been reduced.

 

[TrapperT]

MT - I do not sort my loaded rounds and put them in either descending or ascending order. The reason being is my finished rounds all weight within less then a grain of each other. I sort so that each round within a 20 round string are all within a grain if not much less, relative to each other. So lets say the loaded round weighs 277gr, all of the rounds in that string will be approximately equal. The next 20 rounds will be 228 grains and all grouped together. It obviously takes more brass to achieve this. Yes, call me anal....