.243win case weights

padd54 · Posted: Tue Jan 06, 2009 9:19 pm Post subject: .243win case weights

So, I had a little time on my hands and decided to weigh the cases out of a new 100ct bag of Winchester cases for my 243win.

Here is how it turned out;

160.9-161.5gn = 19cases
161.6-162.2gn = 33cases
162.3-162.6gn = 27cases
162.7-163.5gn = 22cases

This gave a total of 101cases in a 100case bag. Smile

Is there enough deviation to matter, if so where would you draw the lines?

I have a Howa/Axiom that I want as accurate as possible and youth model for my grandson that just be to able to hit 2" at 100yrds.

Thanks for your help,
Ray

1895ss · Posted: Tue Jan 06, 2009 9:56 pm Post subject: Re: .243win case weights

It likely won't make any difference for a hunting load or for that matter to most shooters/rifles ability.

hunterjoe21 · Posted: Tue Jan 06, 2009 10:11 pm Post subject: Re: .243win case weights

I've never bothered to weigh them, but then again I don't weight sort bullets either.

Define "as accurate as possible" and I'm sure someone with experience in BR shooting (if that's what your lookin for) will weigh in.

Mine shoots .380 (average) 3 shot groups @ 100 yards, which is plenty accurate for my needs....

English Mike · Posted: Tue Jan 06, 2009 10:22 pm Post subject: Re: .243win case weights

Unless you're shooting Benchrest @ 600yds, I don't think a 1.5% variation in case weight will produce noticeable discrepancies in accuracy.
Of course you could always load up ten of each for two five shot groups & post the results so that we don't have to do it. Razz

padd54 · Posted: Tue Jan 06, 2009 10:32 pm Post subject: Re: .243win case weights

Thanks all, I think I will take 10 from each extreme and see what that does.

It will be sometime before I can post any results, it's just too darn cold out for me right now.

twofifty · Posted: Wed Jan 07, 2009 2:04 am Post subject: Re: .243win case weights

It will be interesting to see your results.

Get your wife to randomly number the loaded cases, with a system that will allow you to later know which capacity cases gave you which target outcomes. Then shoot the case groups in any order you want, but keep notes on what's what.

A numbering system could be as simple as 1-1-1-1-1; 2-2-2-2-2; etc. until you have two groups of 5 for each case capacity.

This will prevent you mind from influencing the outcomes.

Vince · Posted: Wed Jan 07, 2009 6:07 am Post subject: Re: .243win case weights

I've never even remotely considered weighing cases. The only time I could see a problem with a case is if the brass is significantly thicker from one to the other...as in ex military 5.56mm cases. Then you can have a pressure rise which will marginally effect the POI.

Load 'em up, and enjoy shootin' 'em Paddy. As Mike Tha Pom says... unless you are shooting Bench Rest and demand single hole groups at 600m, then you will never notice the difference.

However, do the experimenting mate...that's what handloading is all about, and like the others, I'd be interested in seeing your results.

Cheers, Vince

Pumpkinslinger · Posted: Wed Jan 07, 2009 7:55 am Post subject: Re: .243win case weights

I separate the cases by manufacturer but never weigh them. I too will look forward to seeing the results. It would also be interesting to shoot a group of 10 "mixed" cases to compare.

Dawgdad · Posted: Wed Jan 07, 2009 8:58 am Post subject: Re: .243win case weights

I too will await your results but I will predict that the shift in point of impact from heaviest case to lightest case will be hidden within the normal group dispersion you are capable of shooting.

It is not a wasted exercise if it gives you more confidence in a load, You have to be relaxed an confident in you equipment to shoot anything well.

chambered221 · Posted: Wed Jan 07, 2009 11:55 am Post subject: Re: .243win case weights

I put this chart together in attempt at helping reloaders understand the theory and thought behind the idea of weighing cases and bullets.

The data is based upon my Remington Model 7
7MM-08 / 20” barrel
120gr. Nosler Ballistic Tip / ballistic coefficient .417
44.5 gr. Varget
Federal 210 Match primer
Federal cases
AOL 2.8
vel. 2880 @ 10 feet w/ Pact model 1
ES less than 10 fps
In this chart I substituted a ES of 25 fps for comparison only.
It’s not uncommon to see ES as high as 100 fps. In hunting rigs.
Data created using Point Blank online

Vel.@ 2900
yards....... POI.......... vel........... time......... total drop
100.......... 0.............. 2686........ 0.108....... 2.18
200.......... -3.82........ 2482........ 0.224....... 9.19
300.......... -13.28...... 2287........ 0.35......... 21.83
600.......... -86.9........ 1756........ 0.799....... 105.1

Vel.@ 2875
100.......... 0.............. 2662........ 0.109....... 2.22
200.......... -3.9.......... 2459........ 0.226....... 9.34
300.......... -13.56...... 2265........ 0.353....... 22.23
600.......... -88.71...... 1737........ 0.807....... 107.05

difference
100.......... 0.............. 24............ ................0.04
200.......... 0.08......... 23............ ................0.15
300.......... 0.28......... 22............ ................0.4
600.......... 1.81......... 19............ ................1.95

One theory behind weighing cases and bullets is based upon the pressure differences that create a different velocity.
Most will not argue the fact that a thicker case (heavier case) produces higher pressure which translates into higher velocity.
So if your extreme spread measured by a chronograph is 25 fps. As in this example, you can see that the POI changes with that velocity change.
To a hunter with a factory rifle these small changes are not enough to even think about.
To someone shooting a discipline based upon group shooting (measured in thousandth of a inch) these small amounts can mean winning or losing.

My opinion on the subject is, this is one of those things that benchrest shooters have proven and has trickled down to hunters without truly understanding it.

twofifty · Posted: Wed Jan 07, 2009 12:25 pm Post subject: Re: .243win case weights

Thanks chambered.

From what I've gathered through reading here and there, benchrest rifles have tightly spec'd chambers and trued actions, while hunting rifle chambers/actions are notoriously on the sloppy side due to wide manuf tolerances.

This likely means that differences in case weight will have a noticeable impact on long-range benchrest rifle POI, and a negligible impact on hunting rifle POI with a nil impact on the outcome of the hunt.

Trying to get repeatable super-tight groups in an untrued loosely-chambered hunting rifle would likely be a wild goose chase. A guy would burn up lots of powder and bullets, and spend a lot of time behind the bench that could be better spent practicing one's field position shooting.

I can say from first-hand experience that field position shooting has a noticeable impact on accuracy, and is a fun way to burn powder.

My conclusion based on talking with a lot of very experienced reloaders is that when it comes to squeezing benchrest accuracy from a hunting rifle, there are so many variables that it is near impossible to draw reliable cause & effect relationships.

lesterg3 · Posted: Wed Jan 07, 2009 1:40 pm Post subject: Re: .243win case weights

Hey padd54,

From what I have read the case's weight is not as important as the truness of the case necks.

Are you going to true up the necks before loading?

I am not a bench rest shooter but aspire to achieving that level of accuracy from my hunting rifles out too at least 400 yards, I am not comfortable beyond that.

As I am seriously less than a novice everyone else can tell me how ignorant I am. Go fr it guys. I can take it.

Just relaying what I've read Very Happy

chambered221 · Posted: Wed Jan 07, 2009 3:08 pm Post subject: Re: .243win case weights

Les, You may be ignorant to facts about reloading but you get an A+ for effort in trying to get it figured out !!!

The benchrest technique you refer to here is another one of those things that help the group shooter win a match.
I’m not saying it don’t work, it does. The gain in most cases for hunting trim is not worth the effort and time spent doing it.

Some advise is to look at where your info comes from.
A benchrest forum or a magazine like Precision Shooter will give information that says yes it worked. What they don’t tell you is it only turned into a very small gain. They are dealing with splitting hairs !!!

A hunting mag I once read did an article on neck tension. Their outcome in factory chambers was a disappointment at best.
Think about it. When you start neck turning (removing brass) you make a sloppy chamber sloppier.

Now please don’t anyone take me the wrong way here, It’s not that I’m against doing these things, I’ve done most of them from time to time.
The first thing I do though is check the ES (extreme spread) in my velocity.

Morax · Posted: Sun Jan 11, 2009 6:53 pm Post subject: Re: .243win case weights

well if you wanna go a step further, why is there a difference in weight? is there also a corralation to case volume also, if so then accuracy will be defintly affected by the differences..

chambered221 · Posted: Sun Jan 11, 2009 10:08 pm Post subject: Re: .243win case weights

The difference in weight comes about from the manufacturing process.
Cases are drawn from slugs of brass, not machined to a specific tolerance.
A thicker case is heavier. The heavier the case the less volume on the inside.
So your answer is yes. A correlation does apply.

Less volume usually means higher pressure for a given charge.

Most of us have seen the warnings to lower your charge weight with military brass.
That reason is because the brass is thicker ( heavier and stronger) and has less case volume.