Analysing Small Bore Groups for Problems

[Gwion]

While searching for an old chart i seem to have misplaced, i came across this online article about analysing groups to determine equipment and technique issues. The article is relating to small bore shooting but assuming it translates to all shooting, it has helped to identify some reasons behind my pathetic performance at 500yd F-class on Saturday last.

Hope it helps someone else as well.

http://www.rifleman.org.uk/Fuller_group_diagnosis.htm

[brett1868]

Good article which I read some time ago and book marked for future reference. Its more aimed I believe at rim fire target rifles as very little is mentioned about ammunition having a consistent velocity and mass. Applied Ballistics by Bryan Litz can plot the probability of hit by simulating a thousand shots of more taking into account variables in velocity, wind, temp and several others. It's no surprise the probability of a hit decreases as the range of velocity between rounds increases. My main motivation to buy a chronograph was to check how much my hand loads varied in velocity so I could improve my technique and achieve a consistent velocity around +/- 10fps. Might be time to jump into precision reloading as you may be at the limit of accuracy for your current method. Are you neck turning the cases, primer pocket conditioning, flash hole uniforming, pointing / trimming projectiles and sorting my the 3 measurements...Apollo is into the benchrest scene and a good source of knowledge on precision reloading, I've learnt quite a bit from him.

Interesting read as well
http://www.rifleman.org.uk/Hints_on_Rifle_Shooting_SMRC.htm

[Gwion]

Yeah, that article is focused on rimfire but is handy for pointing out some classic errors in technique and were on the target they will throw your fliers. See the little clock chart at the bottom of the article.

Re: my weekend lack of performance, i think it had more to do with shooting technique as this article points out some classic faults (too much preload on bi-pod giving fliers 10-11 o'clk (for lefty), setting up rear bag on shooting mat resulting in 12 o'clk verticle fliers... etc, etc.

Keen to tweak my loads as well, as i haven't addressed them since fireforming with the original load for my rifle. I have just completed the second firing of this brass and am in the process of turning & trimming the necks. I'll then work on tweaking the load for the lowest possible ExtremeSpead of velocity for shooting out further. An older, highly experienced shooter at the club is suggesting that i'm better to have a jump of 20-50thou or a jam of 5-10thou than i am to be sitting on the lands, as the load is currently. His theory being that any variance in bullet tolerances will show up in velocity (pressure) ES when on the lands or very close to them. I have been meaning to experiment with lead and tweak the charge for a while but wanted to get through a full 100 rounds and record results first, before tinkering too much. At some stage i'll have to update my dies to micro seater and bushing neck dies as well but that's going to have to wait.SLowly, slowly working on making my loading more of a precision process.

Thanks for the other link.

[Apollo]

Thanks for the mention Brett but I can't help much with F-Class / Prone or Full Bore type shooting.

My trials and practise is shooting from a Bench even at short range like 100m but more ideally 200m under ideal conditions to test your reloading as best as possible knowing after all these years of practise that I can in fact call a flier as soon as I touch the trigger if it's been my fault. If not it's caused by something not quite right with my reloading practise or I haven't found that sweet load that works time and time again.

I started off testing with bullets seated just off the lands (0.002") but after a long discussion with my Gunsmith who is involved in Full Bore I have tended to agree with his point that starting seating depth there how do you know which way to go, in or out to improve things. So, I now start all my testing / load development with any shape bullet seated at least 0.010" into the lands (jam) and then find the most accurate, best grouping and most consistant of my loads. To tune from there I back away from the lands and in some cases it's been quite some distance for a jump. A few times with not only my own bench rifles I have only ended up worse off and back to a jam into the lands so then play with neck tension.

I use a Chrony during my initial testing only to just see what sort of velocity I am getting as I change loads or tune then when I'm tweaking the best loads I'm not interested in what the chrony says as a lot of times the most consistantly accurate loads are not the same as the chrony figures say is the antz pants.

Consistant precision reloading practise has the biggest bearing on accuracy I have found and the biggest factor in reducing fliers to near zero.

I was trying all this crazy stuff yesterday getting ready for a two day precision short range benchrest shoot when disaster happened. Got some very nice 0.1" 5 shot groups at 100 yards but the cases that came supplied with the secondhand 6mmPPC started to be very tight to chamber then even more so extract and needed a little tap with the palm of my hand on the bolt to get anything to move...that all came to a halt when the bolt handle broke off the bolt. Examination shows that someone looks to have been giving it a little more help that the palm of a hand. So the competition is cancelled and now I'm facing quite an expense in time and money to get a bolt repaired.

So now I'm back to just 500 Metre Fly Shoots (300m & 200 yard Rimfire tossed in) but all is not lost. I can swap bolts to practise but not ideal for a competition.

Gwion, even if you don't shoot Benchrest normally it might be worth a try if you have someone that will load the gear just to test / prove your loads. It gives a good consistant basis to control other factors. I'm lucky being able to test at home so if I really want to fine tune then I can wait for a day that is ideal or even part of a day when everything is perfect and do the fine tuning. My idea there is that I know what a load will do under ideal conditions so the rest is my ability to do the same when conditions are far worse.

Boy, I wished I started this precision reloading and shooting 50 years ago.

No matter what the main point is to enjoy the whole experience.

[sandgroperbill]

wow... broken bolt handle, sorry to hear, Apollo. That must have been a devastating feeling, mate

[Apollo]

wow... broken bolt handle, sorry to hear, Apollo. That must have been a devastating feeling, mate

Even more so finding out it might take 6-12 months to repair IF I can get it back to the USA and if I can get through all the permits required.

Anyway, enough of that since it's not on topic.

Merry Xmas

[Gwion]

Oh! What a bugger! Good luck with the repair, Apollo.

I am also fortunate enough to have a few rudimentary benches set up across a small gully in my back paddock, so load development is quite quick and easy. So good to be able to just duck inside and tweak the load when needed.

Unfortunately though, I can only safely shoot out to 100m before I lose the definite back stop of the gully. At this range, vertical dispersion doesn't really show up that well and on club day there is too much else going on that I can't just focus on what the load is re: VD. This is where I hope some chrony data will help.

As you say, once I eliminate the ammo as a cause of vertical fliers, etc., I can then settle into working on my technique. My current load was developed whilst fire forming brass and breaking in the barrel, at which time it was shooting just over 0.5moa at 100m. I haven't tested it for group size since but feel it could use a good tweaking now the barrel is well shot and brass well formed. I also just finished turning all the necks to 0.012", so hopefully my neck tension will now be more uniform.

Any way. Merry Xmas to you all.

[Gwion]

Well, a bit of reading up and applying the info paid off today. My most consistent shoot to date. Still not amazing scores but that was due to missing a few wind calls at 500. My second string was 5 Xs, 3 5s & 2 4s(wind dropped off). Very pleased for a 53.5, first string was 50, a 4 & a 3 let it down from mostly 5s with a couple of 6s.

Don't ask why, but we were shooting 300yd targets out at 500yd.

[Norton]

The section on the marksman factor is interesting what they attribute the different kinds of inaccuracy to.

[RDobber]

12 month repair....whaaaat?

[Gwion]

Well... ammo not the issue now! Went back to a lower node and turned all the necks of my cases down to 12thou. Shooting very tight (for me) at 100yd= 0.306". Gotta be happy with that.

[Rocker]

12 month repair....whaaaat?

Yeah f*** that

[Homer]

G'Day Fella's,

Gwion, before I shoot any group, I already know what the problem is and whats causing this problem!
Me!!!

LOL!
Homer

[Homer]

G'Day Fella's,

Gwion, before I shoot any group, I already know what the problem is and whats causing this problem!
Me!!!

Here is just one example, see lower right group and the single flyer!

CZ 452-2E .22LR.JPG (1.87 MiB) Viewed 5109 times

LOL!
Homer

[Gwion]

Fair enough, Home-boy. But that's a touch over simplified, isn't it. I mean, obviously you are always the problem...

Is it your trigger control? Then what is it about your trigger control....
Is it your hold on the rifle? What about it?
Stance/positiion????

And so on, and so on....

So, what was i doing wrong here???

Both-hands-rear.jpg (71.71 KiB) Viewed 5096 times

And what did i get right on the first group of this trio???

Fore-end-grip-session-02.jpg (70.94 KiB) Viewed 5096 times

Everything was the same, here. Same rifle, same load, same scope, same bipod, same rear bag. The difference was the consistency of my position, grip and pre-load on the bipod. These were my first ever groups shooting from a bi-pod at 100m; 223rem.

[Homer]

G'Day Fella's,

Gwion, no its just me, Jumpin on the trigger,.............................at the wrong time!

Doh!
Homer

[Gregg]

Gwion, no its just me, Jumpin on the trigger,.............................at the wrong time!

You're supposed to do it pull it when it's over the bullseye