velocity fluctuations ???

[irold]

I finally got a chronagraph....a F-1 Chrony .  Seems more than adequate for me.  I tried it out the other day, ( cloudy, 53 degrees ) On most of my loads , I was getting around 25 FPS difference between my Hi and Lo........however as an example: my Encore with a 12" 44 mag gave me readings of 1660, 1655, 1618 , 1612 , and 1648.......does that sound right ?  I'm refering to the spread in velocity.  Or do ya throw out the Hi and the Lo then average the remaining three ??  I use a RCBS powder measure with 296  ( in this example ).  I'm aware it doesen't throw exactly with every turn of the handle....never worried about it.  Would this throw the velocities off this much??   I'm "new" to using a chronagraph..........maybe I'm splitting hairs........remember I'm a hunter, not a bench rest shooter.  I was just curious as to if these reading seem normal.    As always , thanks 

Regards  irold

[huntswithdogs]

Sometimes we can get too much technology. Heck, a bumblebee ain't supposed to be able to get his butt off the ground but he does. Reckon somebody forgot to tell him...

Has this particular load been shooting okay for ya? If it has, then I'd not worry too much about it.


Just my opinion...

HWD

[wncchester]

"I was getting around 25 FPS difference between my Hi and Lo........however as an example: my Encore with a 12" 44 mag gave me readings of 1660, 1655, 1618 , 1612 , and 1648.......does that sound right ?   "I'm refering to the spread in velocity.  "

Just my opinion, but there is no way in the world any of us can tell you if that is "right", but a 25 fps spread isn't bad at all.


"Or do ya throw out the Hi and the Lo then average the remaining three ??"

If we toss the ones we don't like, it sorta destroys the validity of an "average" of anything.   Average, by definition, includes all the applicable data points.

[Darrell Davis]

Seems in line to me.

And a 25fps spread is not at all bad.

Keep looking and reading and you will find that at times, tests with a much broader range of velicities will shoot very well.

Why ?? Seems that just shouldn't happen.

With that being said, it is always good to get that spead as close as possible, but that doesn't mean the load with the smallest devation will also provide the smallest groups.

Isn't this loading/shooting/load development fun!

In the years before the Crony and other affordable units, we still got great groups and many times according to the books, great velocities.

Well now, a bit more truth comes out and I personnaly find that many times I will find a rifle to be "slow" according to the books.  Sometimes equal to and once in awhile a touch faster, but as many times as not, slower then what I would expect from my reloading manuals.

Many are the factors coming to play here, brass, barrel - length and quality, chamber, powder - slow or fast lot, and on and on.

Such fun!  Just be safe, load, shoot, learn but most of all, have fun!

Keep em coming!

CDOC

[irold]

OK ,  then a 50 fps deviation is not out of the norm ??   How big a shot string do ya use for averaging your velocity.  As mentioned before a friend of mine shoots 5 , then throws out the hi and lo then averages the remnaining 3.  Does that sound reasonable ??  thanks for your thoughts ,  irold

[Darrell Davis]

Just IMHO, but 50fps is not great, but while doing test loads it is not unusual to see that and more.

About throwing out the high and low, ?? well, that is one way to do it I guess, but that is a three shot average out of a five shot group, so what is the point?

Just IMHO.

Where I personaly find the chronograph to be very usefull is during the testing of a series of test loads.

For example, let us say I want to try to develop a load for my new .302 1/2 maxi thumper, using the new external bonded 237gr reverse expansion bullet from one of the custom bullet makers.

Looking in my stash of reloading manuals, I find info for a 240gr slug along with a dozen or so usable powders.

One of the powders is shown to give the best groups with the test barrel in use and a couple of others show better velocies by as much as 200fps.

Well, I would chose one or more of the listed powders, which I also happen to have in stock and then plan my test series something like the following -------

Powder #IMBB 741 shows a starting load of 97gr. at a vel of 3495 and a top recommended load of 102gr. giving a vel of 3589.

I would probably do three shot test groups - in the intrest of conserving expensive bullets - of 97, 98, 99, 99.5, 100, 100.5 and 102grains.

Now this is where I find the chronograph to be really handy, as shooting for group and velocity at the same time makes it possible to watch the consistancy or lack there of, for both of these factors.

Sometimes the groups will start bad or so so and get better, sometimes start good and go bad, maybe start bad and go good and back to bad.


Using the velocities of these groups, the normal is to see each group average a bit - 25 to 50fps+/-  - faster then the one before.

If at any point I start to see signs of excessive pressure, possibly wild groups or velocity, and/or any other sign of excess, it is time to stop, go home and pull the bullets on the remaining test loads.

However, this has for me. seldom happened, allowing me to complete the tests after which I can sit down with my targets and chronograph figures to determine, what if anything I have learned from the test series.

It is nice to know what velocity I am getting, but the most usefull info is what I get along with the groups produced by that load.

Be safe, shoot and enjoy!

Keep em coming!

CDOC

[buck460XVR]

I use a RCBS powder measure with 296  ( in this example ).  I'm aware it doesen't throw exactly with every turn of the handle....never worried about it.  Would this throw the velocities off this much??

296 meters quite well outta most measures. I've found that from my Uniflow load deviations are very small. I've also found with W296/H110, that a consistent crimp is as important as anything to get consistent velocity and accuracy. Only way to get this no matter how you load, is to keep all cases the same exact length. Many claim this is not that critical for accuracy at handgun ranges for anything but competition.  I trim my Handgun brass once for hunting loads, but don't for plinking. IMHO, with your relatively small SDs, I wouldn't worry about it. Crono's are fun to play with and a good tool to make sure you are not pushin' the envelope, but the proof of a good load is with it's accuracy.

[irold]

Appreciate the info and the opinions..........thanks.    You mentioned case length,  I realize it does make a difference.  My goal is to have all the same length......however in the real world, I can't keep them perfect.  What is acceptable ??  Most of mine are within .003 to .004,,,,,,, Even after trimming I end up a couple of thousands differnce......this excessive??    thanks, irold

[Graybeard]

No that's not excessive. I've been reloading for something around or perhaps over 40 years initially for shotshells and straight wall handgun rounds. To date I don't recall ever trimming a straight wall handgun case. I've always used them as they come and had no problem. They just don't seem to grow like bottleneck cases do.

I still have and use .44 mag cases I've been reloading for close to 25 years and no doubt they've been loaded over a hundred times and they are still fine and have never been trimmed and haven't failed me yet.

[irold]

Sounds good !   Thanks for all the info........regards, irold