Seating depth - does it even matter?

[bmart2622]

Yep you're right. I just like to see where each one lands. The point is that 3 shot groups arent enough. If you want to shoot a 20 shot group at one target great, I just dont

 

[Harvey_NW]

Help me understand this statement. If you lose impacts, it means the bullet lands inside of the outermost holes, yes? Which tells you that the observation is within the mean, yes? Which increases the confidence that the group size is predictive and not a result of variation, yes? And therefore has value.



P

Yes. The important part is the aggregate, or compilation, like TK did in his posts. If you shoot 10 - 3 shot groups, you can get the same data as shooting a 30, but you have to do an overlay or a calculation of group centers and spreads.

My personal preference is to shoot 10 when I'm trying to prove anything. I also practice bracketing with the subtensions on the reticle in case I lose my POA. Here's a 10 shot group shot on 2 different days, with cold bores included.

 

[Pharmseller]

Yes. The important part is the aggregate, or compilation, like TK did in his posts. If you shoot 10 - 3 shot groups, you can get the same data as shooting a 30, but you have to do an overlay or a calculation of group centers and spreads.

My personal preference is to shoot 10 when I'm trying to prove anything. I also practice bracketing with the subtensions on the reticle in case I lose my POA. Here's a 10 shot group shot on 2 different days, with cold bores included.
View attachment 565265View attachment 565266

I agree. The key point being overlay or shooting the same target on multiple occasions. I think you need to shoot the same style of target if you’re going to overlay for the results to be predictive.

I don’t think group size aggregation is appropriate for overlay unless it’s the same style of target.

And keep in mind, I am content with 4-shot groups for my applications.




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[bmart2622]

4 shot groups are great....if you shoot 5 of them

 

[Pharmseller]

If you are comparing precision of different loads (the topic of this thread), I think the number of rounds is dependent on the purpose of the rifle/ammo as well as the established baseline of the shooter/rifle/optic/etc.

I agree completely.



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[Pharmseller]

4 shot groups are great....if you shoot 5 of them

…at the same target, or at an identical target and overlay them…

I don’t shoot past 600 yards, so a 4-shot group is good enough for me.

Especially when I’m doing load work up.

I’m not a particularly good shot on paper, so much of the time I’m the limiting factor.



P

 

[Harvey_NW]

At that point, you’re really only able to look at the ES of the group, which is only 2 data points, so you’re losing a ton of info. I would disagree with the assertion that ten 3-shot groups is equivalent to one 30-shot group (at 100 yards for a scoped centerfire bolt gun). I would say that ten 3-shot groups is significantly greater in terms of data quality. When I shoot 30+ shot groups, I do it with individual dots and then compile the data, because seeing a big torn hole doesn't do me any good.

What info are you losing by shooting a 30 shot group? Wouldn't all the data from that just be more complicated to calculate the same data you would get from a 30?

Primarily overall round count, but also round count of individual groups should vary depending on what you are trying to accomplish. If you are simply getting a zero (average location of the group) or average muzzle velocity, 5-shots should be plenty.

Don't you think that depends on the precision of the system? Obviously, you've done the extensive data collection to prove your point, but I think it's safe to assume there are a lot of hobbyist reloaders that don't achieve that level of precision or data collection. If their system averaged 1 MOA or more, the variability of a 5 shot group could lead them to be off by quite a bit.

If you are looking to obtain MV SDs, I think you should be looking at about 15+ rounds. If you are comparing precision of different loads (the topic of this thread), I think the number of rounds is dependent on the purpose of the rifle/ammo as well as the established baseline of the shooter/rifle/optic/etc.

I'd agree with that in that context. However, I think there are a lot of situations where that baseline isn't established and the comparisons or conclusions are simply based on small sample sizes that still fall within the overall variability. To conclude that a 4 shot sample size is plenty because you're never going to shoot more than 4 shots in a row in the field leaves a ton of room for error if that test isn't repeated multiple times to confirm it will produce repeatable results.

 

[bmart2622]

…at the same target, or at an identical target and overlay them…

I don’t shoot past 600 yards, so a 4-shot group is good enough for me.

Especially when I’m doing load work up.

I’m not a particularly good shot on paper, so much of the time I’m the limiting factor.



P

So youre telling me how it should be done and then immediately saying you arent going to do it that way?

 

[Pharmseller]

So youre telling me how it should be done and then immediately saying you arent going to do it that way?

Sure.

I don’t need the kind of information that process provides.

I know how to make damn good mac & cheese, too, but I don’t like it.

Skip to :46:

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[bmart2622]

No thanks

 

[Pharmseller]

It’s a great movie.

The clip is particularly appropriate in regards to mac & cheese.




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[Pharmseller]

Thanks for posting, that was fun to read.




P

 

[Harvey_NW]

If you're still following, look at MV as a sort of analogy to groups. Ammo with higher levels of dispersion (ES & SD) are somewhat analogous to group sizes with higher levels of dispersion (ES and radial SD). Below are graphs from several factory ammo in three different cartridges that have SDs ranging from ~10 fps to over 25 fps and ES from below 40 to over 100 (based on 20 shots). Yet the average MV can be found by about 4- or 5-rounds, and SDs need about 3x to 4x the round count. The higher dispersion data does not require more rounds to get an average MV. This should be easy for people to see, understand, and agree with. And if you understand & agree with the below example, you should be able to see that the same principles apply to group sizes.
No argument from me there. Look at the running SD graph above, and it's a perfect example to see that smaller round counts don't work for everything. A 5-shot group could show an SD of 5-fps, but that same ammo normalizes to an SD of about 15-fps. Look at the running MV average graph, and that's a perfect example to see that smaller round counts are sufficient for some things. Some of the worst (maybe THE worst) ammo in that example is Nosler premium, which had high SD, high ES, grouped terrible, and yet the average MV from 5-rounds is only 2-fps difference from the 20-shot MV average.

Definitely following, and appreciate the input with all the data. Honestly I'd have to say my personal observations align with a lot of what you've posted. The rifles I load for usually shoot sub MOA for 5 shots, and they'll float around a little bit but I don't see the drastic differences the statistics say is possible, so I question small sample results that are on the extreme ends.

At this point in my life, I shoot factory ammo exclusively. However, so many of these reloading what-if's should be pretty easy for anyone to prove to themselves. Same with tuners. It takes ammo and time, but the work is very straight forward. Of course there's a world of difference from proving a causation and saying that whatever you are doing is good enough for you.

Agreed.

 

[Packmansion]

I recently watched that Hornady podcast video. I am an engineer and work a lot with data from the real world. Real world data often sucks. Started reloading recently. I talked to my friend about the Hornady video and I was saying how it makes a lot of sense and he basically said what others on here are saying similar in how if it didnt matter why is this amazing long range guy saying it does. I have 3 pounds of powder and a ton of 223 vmax bullets. I told him we should do our own test in the 100s of rounds. I was thinking I would essentially do a typical Overall Charge Weight Length test multiple times over multiple days and record all the data and see how many different "tuned" loads we wind up with. I was also thinking we could take turns doing it so its different shooters. I figure if we keep landing on the same exact load over and over it would make OCWL look good if not than it will clearly demonstrate OCWL is just reloaders wasting time and resources selecting outliers that misrepresent their actual load. It would not necessarily prove that seating depth matters or not, in fact it would just be several OCWL tests in my specific 223 rifle. Either way should be fun and hopefully add to the controversy of it all. It has also recently been my experience that accurate guns are accurate and inaccurate guns are inaccurate. So far I have not owned any guns that have been extremely problematic.

 

[Harvey_NW]

I recently watched that Hornady podcast video. I am an engineer and work a lot with data from the real world. Real world data often sucks. Started reloading recently. I talked to my friend about the Hornady video and I was saying how it makes a lot of sense and he basically said what others on here are saying similar in how if it didnt matter why is this amazing long range guy saying it does. I have 3 pounds of powder and a ton of 223 vmax bullets. I told him we should do our own test in the 100s of rounds. I was thinking I would essentially do a typical Overall Charge Weight Length test multiple times over multiple days and record all the data and see how many different "tuned" loads we wind up with. I was also thinking we could take turns doing it so its different shooters. I figure if we keep landing on the same exact load over and over it would make OCWL look good if not than it will clearly demonstrate OCWL is just reloaders wasting time and resources selecting outliers that misrepresent their actual load. It would not necessarily prove that seating depth matters or not, in fact it would just be several OCWL tests in my specific 223 rifle. Either way should be fun and hopefully add to the controversy of it all. It has also recently been my experience that accurate guns are accurate and inaccurate guns are inaccurate. So far I have not owned any guns that have been extremely problematic.

Do it!! I actually have a similar test planned and half loaded up, it just got put on the back burner because I had some issues with the rifle I planned to do it with. I think sample size is the major killer for most shooters and interpreting their results. I look forward to seeing any data you come up with!

 

[centershot]

I remember hearing in one of the Hornady Podcasts where they said that on bullets with a sharp angle on the ogive it will matter more than on the sleek bullets with a smooth transition at the ogive.

 

[Walmart Greeter]

I like to keep things simple. I still use a duplex reticle and rarely shoot past 200 yards, but occasionally out to 400. For me, a light for caliber TTSX loaded at the length in the manual with the recommended powder will shoot 3 inch group at 300. All i do is a ladder test with 0.3 grain increments and use the load towards the top end a little before the velocity spikes. Load up 5 and shoot them at 300 to verify. Less than 20 rounds and the load is done. Moral of the story is inside of 400 yards with barnes bullets for hunting level precision it doesn’t matter. Oh yeah this has been with 270 win and 300 wsm in remington, ruger, and browning factory rifles, no custom stuff.

 

[Harvey_NW]

I remember hearing in one of the Hornady Podcasts where they said that on bullets with a sharp angle on the ogive it will MIGHT matter more than on the sleek bullets with a smooth transition at the ogive.

Fixed it.

 

[WyoKid]

Reading though the posts and articles makes my head hurt. For most hunting situations at average distances within 200-300 yds, who gets more than 3 shots at an animal out of a cold barrel? Elk don't care about 10 shot groups off a bench in perfect weather conditions. Hunting situations have too many variables to make a difference between a 1 inch and 1/2 inch group off a bench. If you shoot competitively, then it does make a difference.

 

[ddowning]

People get all caught up in small samples. When looking at a 3 shot group that is 1 moa vs a 3 shot group that is .2 moa, both groups can get larger, but neither can get smaller. Make the big group 3" and it becomes even more obvious.

We shouldn't be looking for the BEST. We should be looking for GOOD ENOUGH. If I have a prs gun that shoots a 10 shot group that is .5moa then I am done. I don't care if there is a load out there that will shoot 3/8 moa for 10 shots. By using small samples to eliminate the BAD loads, we land on many that might be okay. If you really need to know what the gun will do for 30 shots then you can do that with the load you think is the good one to confirm. If I get two 10 shot groups <.5 moa, then I know there is a low likelihood that a shot will go outside 3/4 moa. That is good enough for my use case. I'm not going to spend the rest of the barrel life chasing something better. I'm going to go shoot matches. The only exception is benchrest where the point is to shoot the smallest groups.

The same is true for hunting. If you want to hit an 18" target at 600 yards, a 10 shot group that is 1 moa is going to keep your 30 shot group around 1.5 moa or smaller. That's a 9" group inside an 18" target. Mission accomplished.

That aside, I do think there are loads that shoot better than others. The difference depends on the gun. A gun that shoots everything into a quarter minute is going to be hard to see a 50% improvement. A 2 moa gun will make a 50% improvement obvious. The difference is much more likely to be the bedding, barrel, bullets, brass, scope, or selection of a poor primer/powder match than how much powder you load or the bullet seating depth.