Group Reformation

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  • Last Post 06 February 2013
Lefty posted this 05 February 2013

Each time I think I am finally gaining some expertise an event occurs which reminds me how much there is left to learn. I was reading articles from old issues of TFS tonight. The following sentence appeared in an article authored by Lloyd deVore in Issue #157. This is an article regarding testing pistol powders in a 30 BR. I quote: “All groups showed classic reformation according to linear small increases in powder weight. ie round groups, then vertical groups, then diagonal groups, then horizontal groups, then diagonal again, then round and the whole series repeating as powder charges increased 0.35 grain at a time."

I have shot many diagonal groups in my time and never knew why this would happen. I am really hoping that one of our contributors can explain what Mr deVore is describing and if there are practical implications for our load development. If I am the only one who hasn't heard this before, I do apologize.

Jim

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onondaga posted this 05 February 2013

That is a classic case of vivid imagination being stated as fact. Ive heard it before too, if you duplicate it with 0.35 grain increments, you are a poor shot !!!!!

Gary

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Duane Mellenbruch posted this 05 February 2013

Well since Lloyd is in the match results and was shooting the heavy class, at 100 yards, I might put more stock in what he sees over what some others give as openion.

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onondaga posted this 05 February 2013

http://www.castbulletassoc.org/view_user.php?id=55>Duane Mellenbruch:

I didn't say Lloyd can't shoot, or even that his oscillating patterns from 0.35 grain  incremental charge changes are big oscillations of holes on his targets. They are probably tiny, but enough for him to see and to annoy him.  I can present a reason more likely than his reason, as I have duplicated what he is talking about and corrected it.

There is a host of bench shooting quirks that have come and gone over the decades. One of them produces the patterns Lloyd discusses.  Top bench shooters will do a breathing exercise and have a self hypnosis relaxation method of some sort (some call it ZEN shooting, or getting into their ZONE) to slow down their heart rate and shoot between the beats as they watch their heart blip motion to the cross hairs of their scope or even an iron site shooter can do this.. That is how I learned to shoot from a spectacular marksman when I was in single digit age. It is nothing new at all and I have taught it to my children and grandchildren.

However when It is coupled with a specific “in motion” hold method, the patterns will appear. Most shooters use a rise to the mark and pull the trigger or a drop to the mark and pull. Some of the very best shooters will use a very precise horizontal figure 8 and time the motion of swinging the tiny 8 in rhythm with their heart beat and the  pulse of their arms controlling the horizontal 8 till they shoot in the middle of the cross in the horizontal 8 precisely at a particular point in their heart rhythm. I did this for decades and shot my best with that method in duty. I still do it. Again this is nothing new at all and my grandson does it.

UN-fortunately, there is a problem that arises from the horizontal 8 ZEN shooting. It is mathematically linear to how fatigued the shooter is. The mental delays of fatigue register as geometric patterns of bullet holes because of changes between the relation of heart beat to the arm pulse that swings the horizontal 8. Fatigue changes the relation. At this point the shooter becomes a "bad shot"  with geometric patterning as I said,  as he has lost his ZEN.

I have learned to conquer this dilemma in a couple of ways:

1) Walk away from the bench and take a long break. 2) If I was horizontal 8 ZEN shooting and really want to keep shooting, I slap my self twice on each cheek then change to vertical up, or down ZEN shooting.

P.S. (from the old guy) “If the bulls eye isn't moving on the cross-hairs the way you want it to, you are not holding your rifle correctly and you aren't listening to your heart".

Gary 

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pat i posted this 05 February 2013

onondaga wrote: (from the old guy) “If the bulls eye isn't moving on the cross-hairs the way you want it to, you are not holding your rifle correctly and you aren't listening to your heart".

Gary 

Lloyd's also a national champion. If I remember right Tom Gray wrote soemthing along those lines too at one time.

If the crosshairs are moving on a 14 lb rifle with a 3 inch forend nestled in 30 lbs of rests sitting on a 600 lb cement table with no contact but your trigger finger you better listen to your head instead of your heart and take off for for open ground because you're experiencing an earthquake.

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Chargar posted this 05 February 2013

In spite of my age, I am always in learning mode and would be very interested in learning more about Mr. deVore's observations.

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R Dupraz posted this 05 February 2013

Why does the phrase “INFORMATION OVERLOAD” come to mind?.......... Just slap the trigger as the bull whizzes by,reload and repeat!:D

All the rest is just magical theory.

RD

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Tom Acheson posted this 05 February 2013

There is another forum (Shiloh Rifle) where the question was recently asked..."what's your accuracy?". This is BPCR, people shooting off cross sticks. I'm going to quote one frequent poster below, Dan Theodore. Note how important (his view) that grip pressure is.

Gents,

At 500 yards or meters, IMNSHO, vertical dispersion is most interesting, since our bullets' trajectories are greatly affected by wind, with regard to horizontal dispersion. I wouldn't shoot a load, in matches, that couldn't hold 1 MOA of vertical at either of those ranges in decent wind conditions. And, since the rifles we shoot off of cross-sticks are very grip sensitive, we are really talking about the combined effects of grip and our rifle's load with regards to accuracy. After years of spotting/coaching in our BPCR competition domain, my take is that consistent “grip” is tantamount to getting all the accuracy possible out of one's load/rifle combo. And, the more recoil, the more inconsistent grip opens up a group. Plus, recoil strongly contributes to nasty things like flinching, that further opens up groups.

To get at what I'm trying to say with respect to “grip,” stand behind prone shooters and watch what happens to their barrel/muzzle when they break their shot. It is amazing how barrels move about when some shooters break shoots. And, just as amazing, the top shooters' barrels recoil like they are on a machine rest. Checkout Doc Lay, Klaus Schattleitner and Michael Rix when they break shots. It'll blow your mind how consistently their rifles recoil; their barrels sliding straight back with no bounce off their cross-sticks. Maybe more time and effort should go into figuring out how to do that, then all that load testing. It's been my observation that crappy grip and/or inconsistent grip will put 1 to 2 MOA of vertical into one's group, on top of a load's inherent accuracy.

Another gent said: I've been getting inconsistent results with loads that used to work well so I've been playing around a lot with grip and, in particular, shoulder tension recently. Things are getting better again now that I'm really focusing on it. I find that I need to go through a mental checklist to prevent my bad habits from creeping back in.

True, like Pat said, anchored down the way some of us are at our benches we should be more stable than sitting on the ground, using cross sticks. But the consistency of hold, grip pressure and shoulder interaction can effect the outcome from both shooting positions.

Grip pressure? Try shooting a single action revolver and use different types of grip pressure, etc. Those guns are very difficult to shoot CONSISTENTLY and ACCURATELY AT DISTANCE.

Tom

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R Dupraz posted this 05 February 2013

Tom:

I absolutely agree with what you wrote in your last two paragraphs. Haven't figured out how to cut and paste here yet. While D. Theodore is pretty full of himself most times,and has more trigger time than I ever will have,I do think he's on the mark as well.

Throughout the mid “60's” and into the early “70's", I competed pretty much on a national scale in three gun pistol bullseye, to include Camp Perry. As well as indoor gallery pistol at fifty feet. In pistol shooting, that marksmanship fundamental of consistant grip and grip pressure cannot be ignored.

And the same thing applies to rifle shooting, whether four postion or off of a bench. This has never been more evident to me than when I shoot my Old K-98 Israelie 7.62mm Mauser in the military bench matches. Any inconsistantcey in grip or shoulder pressure,"the hold", has a direct and noticable effect on the group at the target line and contributes to inconsistant recoil as well.

I have found that every rifle likes to be held a little differently but I am a firm believer in first mastering the basic “fundamentals” so that they become second nature.And then one can add these other magical things. After 50+ yrs., I'm still working on the first part.

RD

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pat i posted this 05 February 2013

All true if you're shooting a rifle you have to hold on to off the bench or shooting offhand but Lloyd shot HVY class. I'll say it again if your crosshairs or dot is doing a figure 8 on the target with a gun like Lloyd shot head for some open ground.

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R Dupraz posted this 05 February 2013

No argument here!:D

RD

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onondaga posted this 05 February 2013

Yes, argument here:

Horizontal 8 ZEN shooting with heavy rifles was how I shot my lifetime best with a 26 pound open class rifle. The key to shooting horizontal 8 with a heavy weight is the fit of the rest to the rifle and of course a shooting form with the body allowing the rifle to do that. I have to float the rifle on the rest with a balance of body forces that allow the rifle to drift in horizontal 8s. That means lift and hold with zero canting  forces.  It is a great deal easier with a 14 pound rifle or a sport rifle to readily get the 8s going and I'm sure shooters have individual rifle weight limits that they can accommodate to get the 8s going. I could do it with a 26 pounder in my early 20s. I haven't tried that in a long time as I haven't had a rifle that heavy in a long time, but I certainly do it with my 10 - 12 pound bench rifles I currently shoot. Because some else thinks it is impossible to float a 26 pound rifle on bench rest with shooting form doesn't mean it is impossible. I've certainly done it,  and it is work,  and it is fatiguing,  but, it is how I personally did my best.

Physical fitness is an important part of that kind of shooting form. I am still 6 ft 2 inches, but at 20 something I had the body of a 245 pound body builder with a 34 inch waist, a 19 inch neck and 20 inch biceps. That makes a difference.

Gary

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TRKakaCatWhisperer posted this 05 February 2013

Lefty wrote: Each time I think I am finally gaining some expertise an event occurs which reminds me how much there is left to learn. I was reading articles from old issues of TFS tonight. The following sentence appeared in an article authored by Lloyd deVore in Issue #157. This is an article regarding testing pistol powders in a 30 BR. I quote: “All groups showed classic reformation according to linear small increases in powder weight. ie round groups, then vertical groups, then diagonal groups, then horizontal groups, then diagonal again, then round and the whole series repeating as powder charges increased 0.35 grain at a time."

I have shot many diagonal groups in my time and never knew why this would happen. I am really hoping that one of our contributors can explain what Mr deVore is describing and if there are practical implications for our load development. If I am the only one who hasn't heard this before, I do apologize.

Jim

I see the sequence often. It is most obvious when you put 9 or 12 1” stickers on a 24x24 target and shoot the 5 or 10 shot groups in ascending order of loads.

WHY does it happen? Read up in Franklin Mann's volume about barrel vibration. Increasing the charge slightly changes the timing/intensity of the forces launching the bullet - affecting the vibration. Where the end of the barrel is at the time of the bullet leaving will affect where it hits. When the group is small and round the cause is that the end of the barrel coincides with the node (smallest magnatude of movement) of the vibrations. Different shapes (horizontal/diagonal/vertical) are caused by the harmonics present (the pattern in which the end of the barrel moves).

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pat i posted this 06 February 2013

onondaga wrote: Yes, argument here:

Horizontal 8 ZEN shooting with heavy rifles was how I shot my lifetime best with a 26 pound open class rifle. The key to shooting horizontal 8 with a heavy weight is the fit of the rest to the rifle and of course a shooting form with the body allowing the rifle to do that. I have to float the rifle on the rest with a balance of body forces that allow the rifle to drift in horizontal 8s. That means lift and hold with zero canting  forces.  It is a great deal easier with a 14 pound rifle or a sport rifle to readily get the 8s going and I'm sure shooters have individual rifle weight limits that they can accommodate to get the 8s going. I could do it with a 26 pounder in my early 20s. I haven't tried that in a long time as I haven't had a rifle that heavy in a long time, but I certainly do it with my 10 - 12 pound bench rifles I currently shoot. Because some else thinks it is impossible to float a 26 pound rifle on bench rest with shooting form doesn't mean it is impossible. I've certainly done it,  and it is work,  and it is fatiguing,  but, it is how I personally did my best.

Physical fitness is an important part of that kind of shooting form. I am still 6 ft 2 inches, but at 20 something I had the body of a 245 pound body builder with a 34 inch waist, a 19 inch neck and 20 inch biceps. That makes a difference.

Gary

I should probably leave well enough alone but I have absolutely no idea what you're talking about.

I'm 6 foot even, as round as a basket ball, have a neck that looks like a pack of hot dogs was implanted in the back, and arms that I have to paint blue when I go to an Italian restaurant so the servers can differentiate between them and and the spaghetti they're serving but when I lay my HVY rifle on the bags there's no wandering crosshairs or dot. Maybe we're talking about two different diciplines.

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Tom Acheson posted this 06 February 2013

Going back to the OP......for those of us who don't posses a Greek God's physique, or have grandchildren who can outshoot us or aren't from the biathalon crowd, TRK' s (post #13) explanation finally provided some credible and understandable observation's.

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onondaga posted this 06 February 2013

http://www.castbulletassoc.org/view_user.php?id=5498>pat i.:

Yes, there are a lot of different shooting bench form disciplines. At 62, I'm no where near the musclebound gorilla I was at 20. I weigh 225 now with a 40 inch waist and on Tuesdays I walk with a shillelagh.

The power worked for me when I was a kid and I made the best of it.

Gary

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Ken Campbell Iowa posted this 06 February 2013

first of all, i give mucho credance to whatever crumbs of experience lloyd de vore ....or ...tom grey ....  have to give us.  i believe lloyd dropped out of cba before he ran out of great advice ..  in respect for truth in suck-up, i have a copy of frank de haas'  single shot actions ... signed by the publisher ...lloyd de vore !  trivia r us ...

secondly, i also agree with  ZEN or  ZONE  effects ...in this case, ... affects ...( g ) .. in both my earlier competition racing and shooting , it either worked or i thought it worked ...  which may be the same thing ...

however, i tend to believe that the near-sine-wave graph of bullet group shapes/locations ....,are real, and are due to barrel vibrations.  this from observing hundreds of thousands of very accurate .22 rimfire shots/targets ...all equipped with barrel tuners.

for further inquiry, go to benchrest.com/rimfire  and chat with the ara guys.  when i quit rimfire, 99.9 % were using tuners .  one or two thousands of weight movement could double your group size !

i do stop short of believing in vampires ...  ken

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Lefty posted this 06 February 2013

Harmonics? Now that is making sense to me. Increasing the charge changes the wave length. as a result periodically we have the node of our wave occurring at the muzzle of the barrel. This results in smaller rounder groups. Nice! It seems logical.

Would we typically expect to see on this phenomenon to be apparent with only .25 grain increments in the powder charge? I suppose this was true because Mr deVore was using small charges of fast burning pistol powder. Does it follow that this effect would be apparent at larger charge weight intervals when employing our slower burning propellants?

I have an uneasy feeling my load development has been deficient in the past.

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TRKakaCatWhisperer posted this 06 February 2013

When I develop a load I use 5 shot groups - 1 grain apart. THen 5 shot groups 0.2 grns apart bracketing the potential smallest groups. Then repeat 5 shot groups to verify at the smallest setting. Then I move to changing seating depths.

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onondaga posted this 06 February 2013

http://www.castbulletassoc.org/view_user.php?id=40>Ken Campbell, Iowa: Tuning barrel resonance with adjustable barrel tuners can certainly demonstrate an effect on group size in .22RF, I haven't seen it effect group location significantly with any patterning and repeatable effect. If it could be shown that barrel resonance in .22 RF does effect group center location dispersions (moving groups around), that still has no relation to propellant charges with incremental changes. That is comparing apples to peaches.

Gary

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