Case Fill

[joelkdouglas]

Do you consider case fill an important part of a load for hunting? What case fill do you hope for?

Really this: I have a Partition load that shoots a bit better with a powder that fills up 85-90% of the case instead of another load where the powder is at 100%. Opinions? They both shoot acceptably, just one a touch better. Velocities are close enough the difference doesn't matter.

Thanks gents.

 

[DrMike]

I've never given serious consideration to case fill with hunting rounds. Usually, my case fill will be ~100% to ~110%, depending on the powder. However, I have a few loads in which the case fill is as low as 80%.

 

[Oldtrader3]

One of the first articles that I ever read was about the separation and setting up of conditions for powder detonation based on density, fill percentage and and primer separation of powder granules leading to ideal conditions for a detonation. This would have been about 50 years ago.

As a result, I have always tried to keep powder loading densities in bottle necked rifle cases, especially with high expansion ratios, to 90% of more. In retrospect, after firing tens-of-thousands of loads in the past 50 years, I think this set of possible detonation conditions is very rare and should be largely ignored.

All of my preferred loads shot accurately and deliver optimal downrange ballistics for that particular caliber. I think that this is the preferred outcome and should be the goal for loader. Being careful about my loading has not hurt anything and has made me more aware of the methods to create optimal loads, in any case.

 

[tjen]

I would look to the best ST.DEV. and it usualy corisponds to be best accuracy most of the time. Barrel harmonics can differ but have not been an issue in my loading. Dencity will differ between powders but I just watch the ST DEV go up as the dencity does. As long as the velocity is enough I pick the the charge with the best accuracy and than play with the OCL to further fine tune the accucacy.

I have some comperssed loads and some around 90%. I would rather have very little room left in the case than a lot. Say 90-98%. Also stix powders have more space between grains than a ball would even if 100%.

 

[Oldtrader3]

For most shooters, Standard Deviation is not a good indicator of accuracy. The reason for this is simple: there are serious "degrees of freedom" issues with applying data sets which are extracted from small sample sizes (3 shots, 5 shots, 10 shot groups) and generalizing to make a statistical comparison of variance numbers which have a low correlation percentage because larger errors are driven by smaller sample sizes.

You can do the math yourself but, in order to derive a confidence level in your numbers based on sufficient sample size (or fewer degrees of freedom problems), a shooter can use a look up table to find the sample size necessary to drive even a 95% confidence level indicating the data set is statistically accurate for a particular lot of bullets or load of powder. Suffice to say, that 3 shot or 5 shot groups will not give you a data set which is more than basically directionally accurate.

This is why most match shooters do not rely on sd for predicting groups size. It is only partially accurate without extensive sampling.

 

[SJB358]

I tend to shoot mostly slightly compressed charges. Not really shooting for it, but they work for me with the chosen powders. My 264 load isn't compressed in the least, but shoots fine? I find out more and more, there may be some science, but most of it is magic!

 

[338winmag]

Oldtrader3, I see you took "just a little bit of statistics" :wink:

Yeah, I know alot of people jump on the StdDev train but I agree with your comments on the topic. I too know the voodoo math, as one of my friends use to call it, and unless I am going to at the least perform decent lattitudinal studies with the numbers, I think StdDev might be a liitle too time and "barrel life" consuming to be that beneficial. TJEN does have an offerable approach so I am not saying it doesn't work but rather the true amount of work needed might diminsh the benefits of the returns.

Performing all the brass prep, rifle prep and care, reloading prep and action, knowing how to shoot one's rifle, testing patiently component combination and keeping results recorded, and reloading competency will get you pretty darn close to clovers and bullet hole on bullet hole at 200.

One of the best tools I have found for reloading is ""right here"". :mrgreen: :mrgreen:

Just my teenie bit of sense.
338winmag

 

[nvbroncrider]

Charlie is right in order to get a good sample for testing for SD and ES a guy really needs to shoot 40rounds to find out exactly where he is at. Shooting that many will give you an accurate feedback on what your dealing with. It will take any outliers out of the equations and will give you the best feedback data. If I guy really needed to know the ins and outs of his load he would really need a string of 200 rounds to make a accurate prediction of what he has.

 

[338winmag]

If I guy really needed to know the ins and outs of his load he would really need a string of 200 rounds to make a accurate prediction of what he has.

Yup, relying on the StdDev and high confidence levels, 200 might be a ball park number. :mrgreen: :mrgreen:

 

[Oldtrader3]

As .338WinMag and NVbroncrider said, there are external forces, ballistic axis yaw, pitch and the phase of the moon influences which may have more effect than standard deviation does on grouping in real time at least with me shooting these groups. Anyhow, I am basically lazy and have no wish to shoot $200 worth of .338 Partitions to predict my "s" accurately when the wind vector is changing 90 degrees every 5 seconds out there at 300 yards regardless.

After 40 years of being an engineer, I realize that empirical and real life seldom intersect and I would rather be outside at the range wondering why I pulled that last shot than running calculations anyhow. Thanks guys.

 

[tjen]

For most shooters, Standard Deviation is not a good indicator of accuracy. The reason for this is simple: there are serious "degrees of freedom" issues with applying data sets which are extracted from small sample sizes (3 shots, 5 shots, 10 shot groups) and generalizing to make a statistical comparison of variance numbers which have a low correlation percentage because larger errors are driven by smaller sample sizes.

You can do the math yourself but, in order to derive a confidence level in your numbers based on sufficient sample size (or fewer degrees of freedom problems), a shooter can use a look up table to find the sample size necessary to drive even a 95% confidence level indicating the data set is statistically accurate for a particular lot of bullets or load of powder. Suffice to say, that 3 shot or 5 shot groups will not give you a data set which is more than basically directionally accurate.

This is why most match shooters do not rely on sd for predicting groups size. It is only partially accurate without extensive sampling.

I do not rely on standard devation for accuracy it simply corrilates to the best loads in any cartridge I have loaded to date. As my charge goes up from the starting load you can watch the st-dev and in my reloading it finds its sweet spot goes for a few loads and then start to get worse. This is usualy close to peak pressure and my actual groups are better a few grains less than the max charge where the st-dev is at its lowest. Depending on the powder/cartidge combination this could be any where from 90% to 100%. If I did not use a chrony I would have no data to compare. I then would just load to listed max or till I saw signs of pressure. And with that load tune the OCL to the best group.

Finding where the powder burns the most consistant is surely just one more tolerance in the game of tolerances which is reloading. Getting consistant pressures means consistant velocities which means consistantly keeping the bullet exiting in the barrels vibration node thus accuracy.

I used up all my words for the day miss spelled or not.

 

[Oldtrader3]

Tjen, use whatever works for you on ballistic deviation analysis. If it it happens to closely match the s for 5-shot group velocity variation or that number will get you in the ballpark, use it. I just think that a larger sample size for later ANOVA is better.

Especially with premium bullets, you may not want to shoot a really large sample size considering cost anyhow.

 

[tjen]

I am saying that I use group size to determine the best charge for accuracy. But it is alway with in the "range" where I have the the better st-dev measurements. And its relation to dencer powder charges.

With my 221rem I was spitting out 40gr HPV bullet at 3470fps and was at the max charge with Lilgun. This load had low dencity and poor st-dev. I loaded some longer deeper setted BK 40gr bullets and and the accuracy and st-dev improved. I have loaded up some loads with longer deeper yet setted b-tips with Lilgun and hope to see better yet st-dev and accuracy. these are at max OCL of 1.830". Once they prove promise I will tune the OCL to this rifles vib node.

A bullets exit from the barrel needs to be timed when its moving the least and not whipping around. So nothing will circomvent that. But do not ignore the ST-DEV. A short string of data needs lots strings to get good handle on it but You only need few strings of data if their very long strings. Statisticly it just comes out in the wash. Sometimes you need to look at the cement wall to see how it works not the grains of sand that its made of.

My solution to the ambiguous direction to graft a bluk pack of M&Ms was a smiley face and an empty jar. Problem solved may be I should be a judge.

 

[Oldtrader3]

When will I learn?

 

[Gm weatherby man]

Oldtrader3, you slay me, being on this site is like being on a high school debate team :lol: , but not having this site would be more unfortunate than dealing with any conversation hear. :wink: Here we learn something, be it technical,culture, opinions or how the world is effecting others around the world. :idea: Never the less it is never boring on the nosler forum, great people for most part. :roll: :lol:

 

[Oldtrader3]

GM Weatherby Man, It is the only shooting forum site that I regularly visit any more. For one thing, the information posted here is better thought out and there is a lot of experience in many facets of shooting here. Plus, I can express myself without anyone taking offense to it (or me) which is nice.

Most other sites do not have much optical device expertise (except for recommending Leupold). So I will keep coming here and take what this site has to offer.