Let’s talk load development

[stagpanther]

50% group diameter 1.88" or 0.76moa
90% group diameter 3.44" or 1.38moa.

Excellent!

Interpretation. If you fire a lot of shots, half of them falls inside circle of 1.88" diameter. 90% falls inside circles of 3.44" diameter.

Thank you--that means at this particular distance? And how would the radial SD compare to the mean radius?

[tangolima]

Originally Posted by stagpanther

Thank you--that means at this particular distance? And how would the radial SD compare to the mean radius?

Sigma= 0.8". This is the characteristic parameter of the underlying Rayleigh distribution.

Mean radius= 1.253*sigma =1"

The standard deviation of radius

0.655*sigma = 0.524"

-TL




Sent from my SM-N960U using Tapatalk

[tangolima]

To summarize procedure to calculate different parameters based on mean radius (mu).

To compare different groups at same distance, direct comparing mu suffices. Smaller mu is a better group.

For a given group with mu, the characteristic parameter of the underlying Rayleigh distribution

sigma=mu/1.253

50% group size

D50_inch=2*1.18*sigma

D50_moa=D50_inch/R*0.95

R is target distance in hundreds of yards.

90% group size

D90_inch=2*2.15*sigma

D90_moa=D90_inch/R*0.95

-TL

Sent from my SM-N960U using Tapatalk

[Metal god]

I think that’s pretty nice group stag , especially since you’re trying to time your shots . IMHO that might be more impressive than calling the wind. I personally would rather try calling the wind and use my reticle to hold off whatever I think it needed .

Very nice !

I forget if you mentioned what position you were in . Are you on a bench , prone , shooting behind you with a mirror?

[stagpanther]

I forget if you mentioned what position you were in . Are you on a bench , prone , shooting behind you with a mirror?

This is a pic while shooting the group. I took it because there was a 4 point buck (his velvet rack already coming in even though the does are just now dropping their fawns) just inside the tree line munching away on grass and watching me the entire time I was there, just over an hour. Unfortunately the iphone camera didn't resolve him out. Whenever I shoot longer distances than 100 yards generally this is the way I have to do it because I have to be able to monitor traffic and move on a moment's notice. The wind gusts enter the slot in the tree line where the road goes through at the far end and where I'm parked and roll down the road, sorta like bowling balls in a gutter at a bowling alley.

[Metal god]

Wow I’m even more impressed with that group . All the ways I thought you might be shooting , that wasn’t one of them. Haha just throw some bricks up on the hood no big deal.

[stagpanther]

Do one thing often enough--and you're bound to get pretty good at it. Drawback, of course, is that sitting and prone skills atrophy. Also it's quite hard to get a good level (sloping hood) so it has occurred to me that what works on the hood of a vehicle probably won't hit the same POA when shooting other positions.

Forgot to mention--this was my .257 Weatherby build shooting 134 eldm's.

[tangolima]

This is one of the best >10-shot groups I have shot with my silly .243 ar-10.

11 shots. 150yd. Target is a 2"x3" stamp.

Mean radius 0.84”
50% group 1moa
90% group 1.9moa
Hit rate 82%

Shot to the left of the target was cold bore. The one below target had higher than average MV. All shots are included for calculating the mean radius.

-TL

Sent from my SM-N960U using Tapatalk

[stagpanther]

link doesn't seem to work, at least on my browser.

[pete2]

I'm a deer hunter. Case prep, tumble, size, clean primer pockets, trim and chamfer if necessary. Do segregate brass. Load. .05 grain increments (.270 .243 etc.). I would prolly go .02 for tiny rounds like .223. Use book overall lengths. Shoot at 100 yards for best group. Used to want 1" max. but that isn't necessary for my style hunting. Farthest I ever shot a deer was 400 yards,.
My 2 cents for what it's worth. I have shot competition precision pistol but no long range or benchrest rifle. Have won a few club matches in the old days. Now 80 and don't get to shoot much.

[tangolima]

Originally Posted by stagpanther

link doesn't seem to work, at least on my browser.

Fixed.

-TL

Sent from my SM-N960U using Tapatalk

[tangolima]

Originally Posted by pete2

I'm a deer hunter. Case prep, tumble, size, clean primer pockets, trim and chamfer if necessary. Do segregate brass. Load. .05 grain increments (.270 .243 etc.). I would prolly go .02 for tiny rounds like .223. Use book overall lengths. Shoot at 100 yards for best group. Used to want 1" max. but that isn't necessary for my style hunting. Farthest I ever shot a deer was 400 yards,.

My 2 cents for what it's worth. I have shot competition precision pistol but no long range or benchrest rifle. Have won a few club matches in the old days. Now 80 and don't get to shoot much.

With scales available to most of us, 0.05gr is a struggle, and 0.02gr is very hard.

I do 1% steps. .243 load is around 35gr, so 0.4gr step. 5.56 load is around 25gr, so 0.2gr step. That basically gives me 10 ish steps between min and max. Good enough for my need.

-TL

Sent from my SM-N960U using Tapatalk

[stagpanther]

That's impressive tango--especially when considering your POA. I use high power FFP scopes that can zero in on very small POA targets at a low magnification setting--one of the key tools for accuracy/consistency for me personally.

[tangolima]

Originally Posted by stagpanther

That's impressive tango--especially when considering your POA. I use high power FFP scopes that can zero in on very small POA targets at a low magnification setting--one of the key tools for accuracy/consistency for me personally.

Thanks! I had 10x SFP mrad scope for this one. I will keep going till I have similar hit rate on a 1.5"x2" stamp.

-TL

Sent from my SM-N960U using Tapatalk

[Metal god]

What do we make of this group at 300yds . I shot this yesterday and Might be my best group ever based on wind calls but not on size . Winds were gusty at anything from 3 to 6 mph . I had a ribbon on the target at 300yds . POA’s were 2” left to 1” right and several in between those aim points . I’m very happy with my wind calls but this vertical stringing I keep getting is starting to frustrate me FWIW all shots being high is just a scope adjustment issue .

I should add this is a new 308 build I’m actually having a hard time getting to shoot . Savage action , Criterion barrel . New stock ( forget name ) , Vortex 6x24 strike eagle FFP scope .

[tangolima]

I think it is excellent. It should be submoa if we measure mean radius and calculate 90% group.

Windage is good. Wind is +/-2mph. The bullet should be doing no more than 0.75moa per 10mph per 100yd. So +/-0.5moa ish. Your group has less than that, so your wind hold had helped. It is only my take. People fixate too much on the wind at the target. It is actually the wind at firing line that matters the most. I have been practicing feeling the wind on my face while observing signs (flag, grass, mirage) mid-range.

For vertical dispersion, it would help if you have mv. Fast bullet hits high, slow bullet hits low. You have the undesirable negative compensation. Vertical despersion will deteriorate with extended distance. The other way around is positive compensation, that the vertical dispersion (in moa) could actually improve with extended distance. That can be fine tuned with seating depth in small (0.003" to 0.005") steps.

Top-notch shooting!

-TL

Sent from my SM-N960U using Tapatalk

[Metal god]

What kind of velocities variancescould change point of impact 2 inches at 300 yards . I’m thinking like 100 mph maybe 150 . I asked because I’m pretty meticulous on my charging process. Check weighted then weighed to the kernel . Based on my previous loadings over the years and testing muzzle velocity. If I had to guess I would say my extreme spread is no worse than 40. Maybe 50 on a bad day.

[tangolima]

Originally Posted by Metal god

What kind of velocities variancescould change point of impact 2 inches at 300 yards . I’m thinking like 100 mph maybe 150 . I asked because I’m pretty meticulous on my charging process. Check weighted then weighed to the kernel . Based on my previous loadings over the years and testing muzzle velocity. If I had to guess I would say my extreme spread is no worse than 40. Maybe 50 on a bad day.

I suppose you are talking mv, not speed of cross wind.

MV affects flight time. Longer flight time has more drop. But it also changes the instance the bullet exists the muzzle, relative to barrel vibrations, so that the bullet has different angle of departure. The latter can easily move poi by 1 moa if not more.

Absolute mv variation in fps doesn't mean much to me. I like to use sigma/mean, or coefficient of variance. I have tried to make <0.5%, but so far 1% is something I can regularly do. I have seen cold bore shot with 2% higher MV than the average, and the poi shifts as much as 2moa.

-TL

Sent from my SM-N960U using Tapatalk