Chronographing load???

The results are not mysterious at all. The brass varied 10% in weight. That is a HUGE variation! Case weight correlates very closely to case capacity. I would expect that a case that weighs 27 grains vs the rest which weigh 30 grains would result in one much lower velocity reading. Exactly what happened. Norinoco brass = junk IMHO.
 
hometownhero said:
You don't need to spend $100 on 100 cases to get better results. I've had great results with winchester, remington, and hornady brass. Just use one brand at a time. Work up a load with hornady brass then keep using that. If you want to use a different brand then make a new load with that brass.
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This is what I do. Works well.
 
What is more important, accuracy or consistent velocity? Would you be happier if the velocity spread was 5 fps but the group was 4" at 100 yds?

If the load is accurate don't worry about the velocity spread. It is mostly irrelevant. Velocity spread really only makes a difference at long ranges, prob somewhere over 500 yds.

Rescuing velocity spread is not gonna make the load more accurate.
 
I think a few grains difference in weights of cases are greatly exaggerated, when it comes to the effect on the velocity of the bullet. I did the following test with a 243 a couple of years ago.
I took five WW cases, which averaged 168 grains in weight and loaded them with 46 grains of H414, seated 75 grain Sierra bullets and fired them over the chrony. Average speed was 3491.
I had five Federal cases, which had an average weight of 180 grains, loaded with the same load, 46 grains of H414 and the same 75 grain Sierra bullets and fired them over the chrony, just minutes behind the WW cases.
The heavier Federal with less room for powder, should have given higher velocity. But they averaged 3468 fps.
I find it almost impossible to get an accurate measurement of water in a smaller, bottle neck case. So I tested the volume of the cases with varget powder.
The lighter Winchester cases held 52.5 grains of Varget.
The heavier Federal cases held 50.5 grqains of varget.
Thus, it appears to me that variations of at least up to ten grains in weight, of cases in the 243 class, can be ignored, for all normal shooting conditions.
 
scott_r said:
Im using a Caldwell chrony, only one I could find in Regina. Im a newbie with Chronographs,,,if they are very poor I may return it for some better like you have Stubblejumper.

I was out today and it was very bright, no clouds and I did get some error reading come up on the screen.

Machine was placed approx 10 ft from muzzle on a tripod.

Is there a certain time of day that works best or condition?

Cheers!!
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I am not familiar with the make of chrony.

i use a Chrony brand, almost daily. It works very well on a cloudy day. Not so good with a blue sky. It would not work well at 10 feet. 15 is better. 20 even better to get away from any muzzle blast issues.

It helps to aim at something behind the unit, so the bullet takes the same path through the screens each time. Variations in angle will change speeds. Proper technique with a Chrony can make it as accurate as a very expensive unit.
 
Something else that can occur, with range brass------you never know how many times its been loaded. Thin or thick necks will have varying tension. Annealling helps with this, & the Lee factory crimp die can help put consistent tension holding that bullet in place, if using mixed brass. You don't need expensive brass, just the same brand if you can. Velocity never killed the critter-----accuracy did.
 
Scott, powders like Varget, 8208, H###c etc. (Temp stable, low nitro powders) sometimes have deviation in velocity issues. Some batches are worse than others. This paired with maybe a less-than-ideal chrony setup will give mixed results. Take some VV or Norma powders for example as well. Very temp sensitive, but very low deviation in velocity. Pros and cons.
 
Interesting thread. I have been shooting and reloading for a long time, but haven't been worried about pinpoint accuracy or consistent velocity. I finally bought a Caldwell the other day. I liked the idea of being able to hook it to my iPad. The idea is to satisfy my own curiosity about lighter loads.

I'll struggle along with my Caldwell. It looks simple enough that even I could operate it!
 
scott_r said:
So if you are not loading compressed loads why does it matter that one case may hold a tiny bit more powder? How does this relate to velocity of rounds??

Cheers!!
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If the case capacity varies, the resulting pressure will vary, and the end result is that the velocity will vary. This occurs whether the load is compressed or not.
 
Lots of varibles here boys....lol Wow,,

I think first thing is Im gonna keep the range brass for feeding the Tavor and gonna buy new brass something of decent quality. Next gonna keep an eye on the conditions out and place my chronograph approx 15 ft away and shoot at a target to keep the bullet in the same path. I will see if this helps some. I don't really wanna change powder for the sake of consistant velocity when Varget gives me a very good load. This is very interesting in its own right,,,something to keep me busy with this spring and summer.
 
just for comparison, here's my results with Varget under 55gr bullet and 75gr respectively

55grains bullet
223-55-Varget.gif


75grains bullet
223-75-Varget.gif
 
Brass and accuracy.

Range pick up brass is great for short range plinking.

For accuracy, you want brass of the same make and same lot # This means buying a bag of brass, or, maybe, a bag of once fired brass, but only if you can be sure it is all the same lot #.

Brass should be the same weight, same construction,same composition and same neck tension.

Given how long brass lasts, and how much time we invest in loading 10 or 20 times, plus the actual shooting - the cost of the brass is not really a big issue. I used to buy Winchester brass and sort it by weight,with 50 pieces per box.

Recently I have been using Lapua brass, and it is so good it does not need prep or weighting.
 
Just a tidbit that I don't think has been mentioned: If setting up chrony on snow, particularly on sunny days, it helps to lay down a tarp, or something dark, under it. Reflected light from snow can cause errors.
 
I use Chrony Master - the model which has a separate readout/brain box. Excessive light is the biggest issue - not bright light, but stray light which comes to the sensors from a too-wide angle fore and aft. Narrowing up the window of light so that the shadow of the bullet is more briefly over the sensor gives very good dependability.

I put my little green metal sensor box inside an old powertool box, cut holes in the box and siliconed glass over the holes so that it is completely weatherproof. The sensors are much more shaded except for light which comes straight down onto the sensors. The only bullets which it has trouble seeing is .17 Remington Centre Fire - which is very small and going very quickly - anything else is very dependable. It will pick up velocity readings even when a little snow is laying on the glass.

I don't use the shields at all. The little angled rods that they send with the unit from factory are a bad idea - nip one with a bullet and the sensor is smashed - use soda straws or in my case, I use a screw in each end of the plastic box to help me line up the box with the target - no little rods are necessary.

While on the topic, I will mention that the best way to make the Shooting Chrony work in the cold is with more voltage. They come with a 9volt setup, so in the cold, they just don't get enough power to give dependable service. I've set mine up to use 12 volt and it works at any temperature - perfectly. For a few years, I used a plastic pipe with AAs stacked in it to give 12V and one set of these lasted a long long time, but now I just use an old 12volt battery from an ATV. Get another little 9volt type clip/plug out of an old 9volt toy and make an extension cord - remembering that the polarity switches when you put the two clips together.

About the Original Topic - wide SD spreads are very common - the capacity of the case may have less to do with it than distance from the lands or how stuck the bullet is in the neck.

Lube the inside of the necks - uniformly.

A beginning reloader may trust that the COL can be measured from the tip of the bullet for each cartridge - but bullet tips are so fragile that if trusted, each bullet will have a different length of slide in the case mouth before it hits the rifling. The difference between being 15 thou and 12 thou off the lands is negligible but the effect of being 3 thou to sitting on the lands will give a huge SD.

My opinion - for what it is worth, is this : Too many beginning reloaders think that it is good to stretch the COL.
My advice - good for what you paid for it : Use the COL in the book until you have years of experience - and have everything else perfectly consistent. Stretching the COL is nearly the last step to accuracy.
 
scott_r said:
So if you are not loading compressed loads why does it matter that one case may hold a tiny bit more powder? How does this relate to velocity of rounds??

Cheers!!
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As I pointed out above, I don't think it makes a bit of difference, for smaller differences like ten or twelve grains difference in averaged size calibres.
Look at it this way. Peak pressure isn't reached until the bullet is several inches down the barrel, so what would a couple grains of space in the case mean at that point?
I'll try and find five cases with the greatest difference in weight that I can find, with five others, and test those.
 
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