Let’s talk load development

[tangolima]

Originally Posted by tangolima

50% group 0.61moa
90% group 1.12moa

Not quite submoa yet, but very good already.

-TL

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If you fire a lot of shots, 50% of them are expected to land inside a circle around the group center with diameter of 0.61moa. 90% of the shots are expected to land inside a circle with diameter of 1.12moa.

The 90% group size is close to the extreme spread group.

-TL


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[tangolima]

Originally Posted by Metal god

Can you explain to me what that means? What’s good or bad about it? I just don’t know what the significance of those numbers are .



I was listening to a podcast of guys talking about why mean radius is good . They were talking about shooting 30 shot groups in 10 shot increments letting the barrel cool in between 10 shot strings. They shot two separate groups of 30 and both groups add statistically the same group size of 1.4 moa . However, the first 10 shots in group A shot .6 moa and the first 10 shots in group B shot 1.4 moa . I thought that was interesting , they said the mean. Radius of group B ultimately ended up being the better group. And is the point of my question. If both group groups ultimately ended up at 1.4 MOA. How is the main radius different?

Mean radius method is better than extreme spread because every shot contributes to the overall statistics. More shots you fire, more accurate the results will be.

I don't care about splitting hair on subgroups. If it is up to me, all shots should be counted as one big group, as long as the load is the same.

For instance, I plan fire 30 rounds. I can fire them in one go, just like the Preston guy on YouTube. If I want to keep barrel from overheating, I could fire 10, take a break, fire another 10 etc. But I will count all 30 as one group.

If I want compare different loads, I fire say 10 rounds of each load, and compare their mean radii.

-TL

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[stagpanther]

Mean radius method is better than extreme spread because every shot contributes to the overall statistics. More shots you fire, more accurate the results will be.

^^^^this^^^^

As opposed to the much more common CTC ES; which really accounts for just the two shots that are furtherest apart. So the mean radius weighs the result more "democratically" by accounting for the contribution of every single shot in the group instead of just the two ES shots.

[Metal god]

Thanks TL that’s helpful

[tangolima]

Originally Posted by Metal god

Thanks TL that’s helpful

No sweat. Neck turn already!

-TL

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[georgehwbush]

Originally Posted by 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 .

doesn't look like velocity stringing to me. looks more like you are just off the node and you need to adjust either the charge or seating to correct it. but all around not bad shooting.

[Metal god]

I think I may have figured it out . I have a rail section on the bottom of my forend of the stock for a bipod . I was using the front rest that day and I think that little rail section is causing inconsistent recoil movement as it hits the the rest during recoil . My plan is to take that rail piece off and maybe not let the rifle recoil back as much as I was letting it .

I hate dealing with this kind of crap because it’s almost certainly just one little thing causing the vertical stringing but it could take me 3,4,5….8 tries to figure out what that one thing is . I did do a seating depth test at 100 yards but only with five shots each. Not sure how valid it is, but I did find a different node at .080 off the lands , I started .020 off the lands . I can always try that as well.

[stagpanther]

Recently I dropped my Mossberg .375 Ruger Patriot action into an MDT Oryx chassis. I know this thread is about shooting lots of cartridges in tests--but that's not easy to do with a big magnum with significant felt recoil; and is going to eat through lots of powder, bullets and even barrel(s) doing the kind of testing we've been talking about here.

The loads that used to work OK in the old Mossberg wood stock (which I modified with pillars and bedding) were fairly light loads in the 250 to 270 gr bullet range, but they did not seem to shoot well in the new chassis. Today I shot a couple of 5-shot groups of 300 gr accubonds driven by RL 15. Here is an upper-end load shot at 128 yards:



I'm still getting used to the balance of the Oryx chassis which is similar to the other MDT all-metal chassis but still seems to shoot a bit differently, I think because of the fixed stock arrangement (not a bad thing, just different). The Oryx balances well enough that I could take shots without holding the fore-end and the rifle sliding back and not muzzle-flipping and giving me a scope-eye tatoo, kinda surprising considering the power and light weight of the rig. The two times I shot not holding the fore-end are the very highest and very lowest impacts. When I switched to holding the fore-end tightly and pulling in to the shoulder--I got the 3 shot splotch in the lower right.

Whaddaya think?

[tangolima]

Originally Posted by stagpanther

Recently I dropped my Mossberg .375 Ruger Patriot action into an MDT Oryx chassis. I know this thread is about shooting lots of cartridges in tests--but that's not easy to do with a big magnum with significant felt recoil; and is going to eat through lots of powder, bullets and even barrel(s) doing the kind of testing we've been talking about here.



The loads that used to work OK in the old Mossberg wood stock (which I modified with pillars and bedding) were fairly light loads in the 250 to 270 gr bullet range, but they did not seem to shoot well in the new chassis. Today I shot a couple of 5-shot groups of 300 gr accubonds driven by RL 15. Here is an upper-end load shot at 128 yards:







I'm still getting used to the balance of the Oryx chassis which is similar to the other MDT all-metal chassis but still seems to shoot a bit differently, I think because of the fixed stock arrangement (not a bad thing, just different). The Oryx balances well enough that I could take shots without holding the fore-end and the rifle sliding back and not muzzle-flipping and giving me a scope-eye tatoo, kinda surprising considering the power and light weight of the rig. The two times I shot not holding the fore-end are the very highest and very lowest impacts. When I switched to holding the fore-end tightly and pulling in to the shoulder--I got the 3 shot splotch in the lower right.



Whaddaya think?

Sounds like a hard kicker. You shoot off bipod or rest? For bipod, do you preload?

-TL

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[Metal god]

He shoots off bricks and Chryslers lmao

[tangolima]

Bipod works well on truck hood. He can adjust the legs to compensate for the slope. Just need some contraption, magnet blocks for instance, for preloading.

-TL

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[georgehwbush]

just a word of caution, i know this guy that shot off his truck hood a lot, until the windshild fell out.

[stagpanther]

just a word of caution, i know this guy that shot off his truck hood a lot, until the windshild fell out.

Yeah, I expect that could happen at any moment. The truck is a 2002 Tundra about to be retired--nothing can resist Maine's neutron bomb grade road salt for very long.

[stagpanther]

After raining most of the day it finally stopped though fog hung around. But there was virtually no wind--so I decided to shoot the next 375 ruger load which QL said was flirting with max pressure--though I didn't have any bolt lift issues or see any pressure signs on the brass.

I loaded 6 cartridges of 300 gr accubonds driven by RL15--intending that the first shot be the fouler for the first cold clean bore shot. Once again, it smacked almost dead on the point of aim, so I include it in the overall group.

The velocities fell short of what QL predicted by about 50 fps--and by about 100 fps for some of the hotter commercial/custom loads I've seen; maybe the patriot's 22" barrel has something to do with it. At 100 yards I suspect anything it hits is going to take a walloping.

The shot numbers are in the actual order I took them in for once. One thing that seemed a little unusual compared to my "stand-up and shoot off the hood technique" was that I had harder time keeping the barrel from muzzle-flipping. I didn't even notice any tendency to do that when standing up; but shots 4 and 6 I didn't pull down and back hard enough and the fore end jumped out of the caldwell rock front rest on those shots.

[tangolima]

Panther. Ran numbers on your group real quick.

50% group size 1.08moa
90% group size 1.98moa

Vertical dispersion slightly positive compensated, almost perfect.

Horizontal dispersion shows trend that higher MV hits right. Was the first shot real cold bore? Was the gun fired more than 12 hours prior? Its MV is right on average. So not much of cold bore shift.

Sample size is small, and a couple of shots recoiled irregularly. I wouldn't trust the "analysis results" a whole lot just yet.

-TL

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[stagpanther]

These big bangers are hard to shoot in large groups--but thanks for the feedback.

Don't know what you mean by "real cold"--it was in the 50's outside, but I shot a group yesterday--and 2 groups the day before that. I always clean the bore after shooting, so the first shot is out of a clean, cold bore.

To be honest, my impression is that for a big bullet going relatively fast at fairly close range, you're not going to see that much dispersion between clean bore and fouled bore or between moderately different velocities.

[Metal god]

Look at you looking all professional did that window finally fall out of that Toyota lol .

[Metal god]

A couple two or three weeks ago I cleaned my new build after 200 rounds total fireed from the rifle to a squeaky clean bore or as clean as I was willing to get it, which was pretty darn clean . When I went and shot it last week the first clean bore shot was inch and a half to 2 inches high. The second shot was about an inch high and the third shot was basically right at point of aim and it settled in right there for the rest of the day .

I believe there is something to point of impact shift with a clean bore . I don’t however buy into the Cold bore point of impact shift . I mean, it probably happens with some ammo and some rifles for sure. Don’t get me wrong but generally speaking I don’t see it much as long as my rifle is fouled , it pretty much shoots point of aim whether it’s cold bore or not.

[tangolima]

Originally Posted by stagpanther

These big bangers are hard to shoot in large groups--but thanks for the feedback.



Don't know what you mean by "real cold"--it was in the 50's outside, but I shot a group yesterday--and 2 groups the day before that. I always clean the bore after shooting, so the first shot is out of a clean, cold bore.



To be honest, my impression is that for a big bullet going relatively fast at fairly close range, you're not going to see that much dispersion between clean bore and fouled bore or between moderately different velocities.

I did experiments on cold bore. It was my AR-10 in .243 that consistently shots up to 2 moa to the left cold bore. The first cold bore shot always has 2% higher mv. I concluded the shift was related to this MV deviation.

After firing a group, I waited an hour to let the rifle completely cool down. Then I fired another "cold bore" shot. Surprisingly there was no higher MV, nor poi shifting to the left.

I repeated this on different days with similar observations. The first shot of the day, real cold bore, always had higher mv and shifted to the left. Other "non-real cold bore" shots during the same trip didn't do it.

Cold bore doesn't seem to have much to do with temperature, but the condition of the bore. After resting for long period of time, say over night, the carbon deposit in the bore hardens and changes the MV. Some said it was the loss of water content (humidity). One military sniper wrote he would fire one fouling shot at the beginning of the day, and the gun would stay good for rest of the day.

That's what I meant real cold bore. If you had fired the gun some time prior on the same day, the bore is not cold. You said it was from clean bore without any fouling shots prior, then you have an excellent rifle. Mine takes up to 10 shots from clean bore to settle.

Good shooting as always.

Regarding muzzle flip/rise, I have found preloading bipod helps.

-TL

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[stagpanther]

I almost always completely clean my bores after each shooting session. Barrel makers stay happier that way. I think the residual cleaning fluids in the bore probably contribute in some way to initial variation in shots. Inconsistent bores probably play a role in "fouling in" accuracy.

The rifle above is not likely to be embraced in the competitive shooting community and is made for big game hunting. The argument could be made that consistency over a large group of shots is less important than just the first shot--and perhaps the next one or two.

Look at you looking all professional did that window finally fall out of that Toyota lol .

I know, I have a Rube Goldberg reputation to uphold.

[tangolima]

Originally Posted by stagpanther

I almost always completely clean my bores after each shooting session. Barrel makers stay happier that way. I think the residual cleaning fluids in the bore probably contribute in some way to initial variation in shots. Inconsistent bores probably play a role in "fouling in" accuracy.



The rifle above is not likely to be embraced in the competitive shooting community and is made for big game hunting. The argument could be made that consistency over a large group of shots is less important than just the first shot--and perhaps the next one or two.



I know, I have a Rube Goldberg reputation to uphold.

For that, I would shoot the rifle in a different way.

For hunting, first shot hit is king, probably no
more than 2 follow-up shots. For each trip I would fire 3 shots. Same distance, same POA, same settings. All shots from different sessions are to be grouped into a super group to calculate the statistics.

-TL

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