Thread: .243 load development part deux

Originally Posted by Micky Duck

For grins n giggles.get fresh blank bit of paper.stick every target over top of it and draw impact points onto the fresh bit of paper so you now have a twenty plus shot group shot onto same target....THAT will open eyes up. What's good n tight are central,what's not hover around the outside of central cluster.... Just like that sugar pile. It's percentage game. The higher the percentage in the cluster the better.

You mean like this? So now I have a 20 shot group sample...which has reinforced that the 42gr load is performing the best.... what am I missing?

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@Tentman so IF I shoot for the sake of discussion 50 rounds of each load, I have a larger sample size from which I can determine an average or mean radius and the load giving me the smallest radius would be the "optimal" load from the sample sets shot, yes? So what you're saying is I don't have a large enough sample group to be able to declare "this is the optimal load for this gun with this projectile"

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Originally Posted by Zedrex

@Tentman so IF I shoot for the sake of discussion 50 rounds of each load, I have a larger sample size from which I can determine an average or mean radius and the load giving me the smallest radius would be the "optimal" load from the sample sets shot, yes? So what you're saying is I don't have a large enough sample group to be able to declare "this is the optimal load for this gun with this projectile"

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Exactly, if you fire 20 of the 42 gn you'd for sure find the group would be like your dots picture . . . .

The debate is when sighting in or choosing a load, what number of shots is statistically relevant to get enough knowledge so that you feel comfortable using the load in your rifle at your hunting ranges.

I think that any load can statistically shoot a good group once in a while. So was your chosen group an anomaly? or is there something about it that made it shoot better than the other loads?

In my experience a projectile either shoots in your rifle, or it doesn't. Which is What I think Gimp suggested from memory. Changes in powder really only change the velocity And may effect accuracy by small margins if the standard deviation becomes greater?

I think you probably should shoot a few 3 or 5 shot groups with that load to see what it does, and if it starts behaving like the other groups, then try other projectiles before mucking around with those ones more.

And I say 3 or 5 shots because of this.

[QUOTE] I think my consistency may be one of the hurdles to overcome during this load development. /QUOTE]

I suspect you can shoot better than you think. It takes a lot of shooting to be confident in your own abilities. But dont try and shoot big groups, as the mind can play tricks on you or frustration can build up. Shoot small groups often and overlay them. Like many things it takes time to build up the concentration fitness to do things well over a sustained timeframe.

Yeah I recommend collecting more data, whether you want to shoot 10rd on one page or 2 5rd groups and overlay them is up to you, it achieves the same end result, as long as you keep a fixed point of reference and look at the position of each shot

Originally Posted by Zedrex

You mean like this? So now I have a 20 shot group sample...which has reinforced that the 42gr load is performing the best.... what am I missing?

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Everything between red dots is good..... Not terribly bad group....so you have wiggle room around the best that still ok.

There's five that are terrible,rest not too bad ...was my point.its a mixed up larger group. Gives better picture.bigger picture of what's going on.

Originally Posted by Zedrex

You mean like this? So now I have a 20 shot group sample...which has reinforced that the 42gr load is performing the best.... what am I missing?

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You don't know any more than you did previously. What your multiple groups should tell you is that your rifle doesn't like that projectile and your 'good' group is an outlier with zero statistical validity.

Someone has already suggested your next move - try another projectile. If you want a plastic tipped bullet there's Nosler Ballistic Tips in 90 and 95gn, Sierra 90gn Gamchanger or Hornady 90gn Eld-X - these are on the spendier end of the range. For conventional lead soft points at a great price you have Speer 100gn SPBT or 90gn HotCors and Hornady and Sierra also do similar but at higher prices.

Get 15 count sample packs of whichever appeals, load all 15 to the manufacturers recommended overall length at 1 grain of 2209 powder under book max and go shoot each 15 at it's own aiming point (all 15 at one point or 3 x 5 that you can accurately overlay).

The answer to 'what projectile should I use' should be evident at the conclusion.

Originally Posted by Steelisreal

You don't know any more than you did previously. What your multiple groups should tell you is that your rifle doesn't like that projectile and your 'good' group is an outlier with zero statistical validity.

Someone has already suggested your next move - try another projectile. If you want a plastic tipped bullet there's Nosler Ballistic Tips in 90 and 95gn, Sierra 90gn Gamchanger or Hornady 90gn Eld-X - these are on the spendier end of the range. For conventional lead soft points at a great price you have Speer 100gn SPBT or 90gn HotCors and Hornady and Sierra also do similar but at higher prices.

Get 15 count sample packs of whichever appeals, load all 15 to the manufacturers recommended overall length at 1 grain of 2209 powder under book max and go shoot each 15 at it's own aiming point (all 15 at one point or 3 x 5 that you can accurately overlay).

The answer to 'what projectile should I use' should be evident at the conclusion.

This!!!!!

Originally Posted by Zedrex

@Tentman so IF I shoot for the sake of discussion 50 rounds of each load, I have a larger sample size from which I can determine an average or mean radius and the load giving me the smallest radius would be the "optimal" load from the sample sets shot, yes? So what you're saying is I don't have a large enough sample group to be able to declare "this is the optimal load for this gun with this projectile"

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That group is worth a reshoot.

A brief story of a 7x57 I used to have. I couldnt get it to shoot a group better than three inches. This is with reasonable loads that had worked in many other rifles. And then I fired a group that all went into one hole, five shots into a quarter of an inch. Now I am getting somewhere I thought. So I fired another group of the same after cooling the rifle down and had a bit of a rest, and then shot a five round group again. They went 3.5 inches. I kept hammering that load trying to get it to group again but it turned out that rifle had something bent with the barrel and chamber - it was just the sheerest chance they all went into one hole, that one time.

Personally I dont get too crazy about it, if I can shoot two groups of five shots that group the same way and have the same group centre, then I am fairly sure Ive got a decent load. Over time you will shoot more with it and get some more information. I can tell if a rifle will shoot well with a load from sighting it in - if the rifle and scope adjust they way I tell it to, then I can be fairly confident the load is going to be usable by the time I zero'd on paper at a 100m. Rifles that dont shoot are a bitch to sight in.

If I have a rifle and load that I trust, I use three shot groups, or even two, when adjusting zero.

Originally Posted by Zedrex

Ah but I do worry lol, it seems there is a method to measure CBTO without a gauge by mounting a projectile in a case with a medium to light neck tension and then chambering the round which should have the lands push the projectile back into the case to give me a measurable CBTO, that needs verified by repeating that process a number of times to get a consistent CBTO within 0.001" and then I can with reasonable certainty load within the window?

Reference: https://bergerbullets.com/shoot-bett...coal-and-cbto/

https://www.derraco.co.nz/product/de...romo-in-stock/

This is what id buy and your sorted for life. Can be used to compare headspace on cases also for confirming shoulder bump back during sizing.

Also shooter ability at a range is a small contribution. Shooters want to blame themselves and think there gun is better but my partner can come shoot and with about a minute of guidance can often get very close to the precision in getting in said rifle. Often she will outdo me on a couple groups.

Switching projectiles has been my biggest effect also. I have tried with multiple projectiles that rifles (and multiple barrels) didn't like and tried every suitable powder to find changes where very minor (Most extreme cases Was about a 20% improvement for 25 shot groups) but a change of bullet brings instant results. This is annoying if you want a specific bullet to shoot but I am unlikely to chase accuracy in a specific bullet in future.

Originally Posted by Steelisreal

You don't know any more than you did previously. What your multiple groups should tell you is that your rifle doesn't like that projectile and your 'good' group is an outlier with zero statistical validity.

The answer to 'what projectile should I use' should be evident at the conclusion.

Or does the "outlier" group indicate that the barrel harmonics and velocity are converging to the sweet spot? There is plenty of evidence out there where shooters have experienced groups converging and diverging as they move up through load weights in as little as 0.2gr increments with a variance of sub MOA to 1.5MOA over 3 load increments. This might be also shown by the grouping of my shots spreading as load weight increases?

I'm not saying that your theory is wrong but I am saying that no ones addressing barrel harmonics which absolutely will have an impact on grouping.

side note: I chose the SST not because of the plastic tip but for the flatbase and weight, I've already shown that my 1:10 twist in this particular rifle does not like boat tail projectiles AT ALL

Originally Posted by Zedrex

Or does the "outlier" group indicate that the barrel harmonics and velocity are converging to the sweet spot? There is plenty of evidence out there where shooters have experienced groups converging and diverging as they move up through load weights in as little as 0.2gr increments with a variance of sub MOA to 1.5MOA over 3 load increments. This might be also shown by the grouping of my shots spreading as load weight increases?

I'm not saying that your theory is wrong but I am saying that no ones addressing barrel harmonics which absolutely will have an impact on grouping.

side note: I chose the SST not because of the plastic tip but for the flatbase and weight, I've already shown that my 1:10 twist in this particular rifle does not like boat tail projectiles AT ALL

How many shots did these shooters use per group to see these changes in dispersion? If you say 3-5, you’re not understanding what everyone is telling you. If you say 10 - 20, showings the data. Send us the links.