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joeb33050
11-24-2005, 11:57 AM
Need som opinion here-any left? Happy T-day.
Thanks;
joe b.
On Chronographs
I'm starting to write the chapter on chronographs for the CBA cast bullet book. I've had a Pact chronograph for 15 or more years. I've used it to estimate BC by measuring velocity at 2 ranges, and used that estimate to calculate sight settings for 600 to 1000 yards before going to those long
ranges.
That is about the only use I've ever had for a chronograph.
If there are any things I know about my chronograph and shooting, they are: (normal range of velocities)

Variations in velocity have nothing to do with group size

Individual velocities have nothing to do with where the bullet hits.
Higher velocity than average bullets can hiot higher or lower or eastor west of the center of the group.

Standard deviations of velocity calculated to 2 decimals with n = 5 are statistically meaningless.
n must >/= 30, like it or not.

I've chronographed thousands of bullets, written down the velocities, done some statistics to these sets of velocities, and learned nothing.
I think a chronograph is a waste of money and time.
Comments welcome.
joe b.

From John Bischoff (he must be wrong!)
I only acquired my first Chrony a couple years ago. It gave me a window into what was really happening with my handloads. The various handbooks list x grains of y powder and a z grain bullet for w fps - but one never knows if one is actually GETTING what the books say. Then too, if one wants to use a non-standard powder (H4831 in 222 Rem with a 60 grain cast bullet) to achieve a gentler smoother acceleration, the Chrony lets one know how well the stuff is working (2375 fps, a small SD, and 2 MOA).
One can use a chronograph judiciously to develop a load that is close to max with a powder for which there is minimal data, such as the surplus stuff available from GIBRASS and others. Or, one can verify that a moderate load with such powders really IS moderate.
I love chronographs.
John

felix
11-24-2005, 12:22 PM
JoeB, it's too bad chrono machines we have won't measure acceleration of the boolit in the barrel. That is what we need to be really effective in determining accuracy, or group size. Or, we can get the same information by measuring the vibration pattern at the muzzle. ES is important only for those really long traditional shots, to make sure we can reach out there and touch something. But, John does have a point when he implies that a well behaved powder is reaching its intended burning rate, by observing the smoothing-out of the velocity-weight curve at those series of points. ... felix

Maven
11-24-2005, 12:41 PM
joeb, I question your categorical statements re: SD's (to 2 decimal places) are meaningless with sample sizes of 30 and under and that variations in velocity have nothing to do with group size. Mind you, I don't doubt the main thrust of your comments, just how they're stated. To wit, why not say that with SD measurements with small samples (<30), you can forget about 2 decimal places and the margin of error increases enough to make generalizations risky/riskier. With respect to variations in fps and group size, you're substantially correct: They have less (but not "nothing") to do with grouping than we think. If one has a Ransom-type rifle rest, if there is such a thing, one can easily test both points/hypotheses.

Newboy
11-24-2005, 12:51 PM
It sounds like you don't need a chronograph, Joe.

I use one, because, due to variations in chambers, bore size, bullet hardness, bullet bearing length, powder lots, etc., you can't really know how much pressure you are dealing with.

But, if I am getting 3200 fps with lot A of IMR 4350, and only 3100 with lot B of the same powder, I will increase the powder charge of lot B, until the velocities match, and assume I am getting the same pressures.

Bullshop
11-24-2005, 01:06 PM
*****Variations in velocity have nothing to do with group size*****
Wo down now,not true. Perhaps not everything to do with group size but certanly not nothing. We have all seen wide es that group good but not always. I think we are more likely to see this from heavy barrels and properly bedded barrels/actions than from whippy factory bedded sporters especialy wood stocks.
There will be times when a wide ES will have the bullet/boolit exiting the muzzle at oposite peaks in the vibrational pattern, at the points of nodes but opposite ends.
This most certanly does have an affect on grouping, and is why you will see changes in POI as you go up or down in velocity while working a load.
From starting loads to max loads note the widest,(not largest) groups from the average center of all groups and tweak those velocities for best grouping.
The idea as I see it is to get the boolit/bullit to exit consistantly at a peak where the barrel is slowing to a stop just before it returns in the oposite direction. This I believe is what we call the sweet spot.
Never say always and never say never, sombody (like me) will check you on it for shure.
BIC/**

PatMarlin
11-24-2005, 02:16 PM
But, John does have a point when he implies that a well behaved powder is reaching its intended burning rate, by observing the smoothing-out of the velocity-weight curve at those series of points. ... felix

Felix-

I believe it would be extremely valuable to myself, and many members of this group, if you could explain this process in the simplest terms using a chronograph.

Using an example that begins with a starting load, hypothetical reading on a chrono, then the progression of working up the load, and what signs we need to look for using the chronograph to find the smoothing-out of the velocity-weight curve. When to keep going. When to stop in order to find that "sweet" spot, and recognise the series of points.

David R
11-24-2005, 02:26 PM
ES does have something to do with accuracy in some guns.

See this post. http://www.castboolits.gunloads.com/showthread.php?t=3384 High ES and SD = bigger groups.

This is not always true by far, but in this example, I could tell the high V just by where the boolit hit the target at 50 yards. This is a heavy barrel and laminated Stock.

Crony helps me. I went with out one for a few years and am glad to have it back. It really helps with the unknown.

David

Junior1942
11-24-2005, 03:18 PM
Just because a load in a manual says 1500 fps, for example, doesn't mean the exact same load in your gun gets 1500 fps. A Chrony tells you what you're getting.

mike in co
11-24-2005, 03:22 PM
joe stirred the pot..i think that was the only thing he was trying to do.
he is not sincere in his post or his topic....he owns a chrony!
sorta like saying i dont need a porsche cause my pinto didn't get me to work on time!

off the top of my head( as a prior of an inferior chrono) i suspect your data is of poor guality which is why you canot tell whats going on.

es...you be true.....but smaller is typically better even in small lots of data.

its just a tool , if you have a poor quality tool and/or do not know how to use/apply the data, then you are right...YOU dont need one.

grumble
11-24-2005, 03:35 PM
"its just a tool , if you have a poor quality tool and/or do not know how to use/apply the data, then you are right...YOU dont need one."

You're talking to me with that statement, Mike. I have a chrony and use it occasionally. But, since I've seen no particular correlation between velocity, ES or SD and group size, I really don't know what it's telling me. So, now, I mostly just use it to satisfy my curiosity about how fast my selected load is really going.

How are they supposed to be used?

NVcurmudgeon
11-24-2005, 08:56 PM
I have had an Oehler M33 chronograph for +/- twenty years. I have had trouble with it twice. The first time was when I killed both skyscreens with a single shot, (my fault) Oehler provided replacement screens for $10. The second occasion was when I left the batteries in the chronograph too long and they corroded and ruined the chronograph, (my fault again) Everready/Energizer bought me a new chronograph. I don't use my chronograph for the esoteric purposes Joe refers to, nor do I even fully understand all that he said. I am very interested in the actual muzzle velocity my loads are delivering, as well as their uniformity. Having my chronograph has taught me a lot, and I would not be without it.

mike in co
11-24-2005, 09:04 PM
grumble: it was not aimed at you sir...just joe.

as one example, i was shooting reduced rifle loads, cast, and tilting the bbl up to position the powder. two of the shoots were way outside of the velocity of the others.....i had forgot to tilt. it was easy to see the error on the chrono, which inturned explained why two shoots were out of the group. without the chron data, i might never know what had happened.

its just a tool

mike in co
11-24-2005, 09:27 PM
[QUOTE=grumble]"its just a tool ....."

if you shoot short strings...3-5 vs 10-20 chrono data can be hard to use as the data set is too small.

when i shoot, i know the velocity of each shot, and i know which shot is which on the target. i can then look at the data and hopefully be able to explain each shot and which load is better.

i may have two loads that are close and try to pick one. shape of the group is important, but if its to be a long range load, the velocity change may be an issue too.
i shoot from 7 yds to 600 yds.......
not all things require a chrono and i do not use a chrono on everything i do.
for an nra action pistol i have i worked DOWN a load. its a 9mm only doing 1050 fps...but it is very consistant.
two weeks ago three of us went to shoot pistols, but the range was in use. we went to the 200/300 yd rifle range and did some mil rifle plinking-223-308 and 8mm.
when we were done, i took out my 9mm and started shooting at the nearest target. 175 yds...... aim a little high and hit it consistanly, then to the 200 turkey..again hits...getting brave, i move out to the 300yd gong....two shots and on target....who knows what a 9 mm would do at 300yds...but the consistancy of my ammo allowed me to have fun that day.and neither of the guys i was with could believe the shots...but they were there.....seeing them with thier own eyes and hearing the steel ring.
i keep seeing guys want to get consistant loads in thier 44 rem mags. anyoen can assemble a load, but having chrono data sure makes the job easier.
my old load of a 265 ww with or with out a gc shot 5/8-3/4" groups at 25 yds. was it al luck or did i use the chrono data to my advantage..
i ofeten shoot loads that are only 1 to 3 tenths different. it here where a chrono adds to the data and helps in the selection process...
its just a tool , just like picking the right sizing die....308, 309 310 ??

Frank46
11-25-2005, 04:34 AM
Joe, I use the ohler 35P with third screen and printer. While developing loads for a rem 700 VS in 308. I found I was getting two distinct velocity ranges with IMR4064 this was not expected. The swings were on the order of 100fps. And grouping was lousy. Without the chrono I'd never know what was going on. Do they help, yes. I have a load for my sako 75 in 30-06 with the nosler 165gr ballistic tip that chrono's at 2800 fps. Shoots better than I can, I had my buddy shoot the same loads out of my rifle
(younger eyes) and he got groups of 3/4" or less. Factory ammo (federal) groups with my handloads. I have let other shooters chrono their loads ( ones that I can trust not to shoot the screens) and one shooter who is another buddy that shoots the 30x47 ctg really got an education when he found out how consistent his loads were. So yes I believe that they have their uses. Frank

Bass Ackward
11-25-2005, 08:15 AM
I think a chronograph is a waste of money and time.




I used to use a chronograph pretty extensively. And at that time I felt that it was a pretty important piece of the puzzle. When I started shooting cast, I thought it was invaluable for telling me if I was getting consistent ignition. And I used it alot to play and learn about crimp, neck tightness, bullet seating positions.

All of this was very educational. And looking back, an education that I was glad to have experienced as it made me a better .... reloader. As all education costs something in this life, my chrony was a cheap investment.

But since I have Quickload now, all I need a chronograph to do is adjust the program to each gun .... once. This is just to ensure that the predicted velocity correlates to the actual velocity of the real world gun variables. Now the chrony stays at home.

If you asked me about the "value" of a chronograph while I was in the midst of my educational process, I would have told you that it was invaluable. Now, it is just another tool. When you need it, it's there.

grumble
11-25-2005, 11:56 AM
I wasn't taking offense, Mike. Just wondering what some better use would be for the machine than what I'm using it for, which is only to find an average speed for my developed loads.

I'm learning from this thread.

MTWeatherman
11-25-2005, 12:39 PM
A chronograph is a useful tool...not an essential tool...but still nice to have.

I do believe that loads with a low ES hold the potential for the best accuracy...not a guarantee as others have already pointed out. Barrel harmonics being what they are...I would certainly want to tweak a load with a low ES even if the particular load may not be within my accuracy standards. Consistency is the great contributer to accuracy. Same rifle, same bullet, same lube, same primer, same load, same case...and therefore hopefully about the same velocity...which means a low ES. With cast shooting there are many more variables (alloys, size, lube, etc.) than in condoms so suspect there's more potential for that low ES not to show up as the more accurate as compared to a condom..more things to affect those harmonics. Just a guess but the effect of a low ES may have less of an individual contribution there. It happens that my best loads have a relatively low ES and that wasn't the deciding factor in developing them. That tells me something.

...and along that same line of thinking, A Chrony helps maintain consistency in your own individual load (low ES or not). Powder lots vary. I maintain chrony records of "starting loads" for each load I use. When I switch powder lots, I run those loads over the Chrony. Its a quick reference to tell me if the lot is "hotter" or "cooler" than the previous. From that point, I have a good reference to use in developing the powder weight to equal the performance (velocity) of my desired load. It keeps my loads more consistent from lot to lot.

A chronograph also helps keep your loads safe. All else being equal...powder, bullet, primer, etc, there is a direct relationship between pressure and velocity. If your load is below the maximum listed in the manual, but the Chrony says your velocity has just hit the maximum...its a safe bet that that is a maximum load for your rifle...ie you're at maxiumum pressure.

The effect of different temperatures on lubes, powder burning rates, etc. also may well show up in the velocity data (as well as temperature on your individual load as well).

In general, most cast shooting is not done at long range. However, some certainly is. A Chrony can give you the B.C. for your bullet...plug that in to a ballistics calculator and you have your trajectory, and wind drift data. Thats useful for the long range shooter. Even if you're using condoms, your actual velocity may differ significantly from the loading data (they love long barrels when determining it). The Chrony can provide you with the information to determine that trajectory.

And...of course, it can certainly satisfy your curiosity and enlighten many who are using commercial ammunition (pretty rare for velocity to be as high as advertised).

In deference to those with Oehlers, Pacts, etc. I used Chrony rather than chronograph...easier to type.

The Nyack Kid
11-25-2005, 09:43 PM
i would have to say that a cronograph is an essential tool when one is working with a (chose one ) odd caliber , boolit and/or powder not found in a manual . if velocities are very erradic or way out of the ball park then something isnt right and needs be corrected. it also help to biuld confadance in a load if one Knows exactly what it is doing verses what one Thinks it is doing.

Blackwater
11-26-2005, 10:06 PM
I value my Pact I because it gives me a better "picture" of what my loads are doing. With load data in the manuals varying so much, this can be a MAJOR help. Working with my .35 Whelen Ackley, for which no data is directly available, I feel a lot more comfortable knowing my velocity, since that CAN be a good indicator of if and when I may be loading too much of a given powder. Could be useful in working with small charges of the fast powders, too. Just another piece of equipment to keep me out'a trouble .... or at least TRY to do so.

Everything a man can learn about his loads can be valuable, if only to perplex him with the results. Still, it's really nice to know the velocity when we can't know the pressure. It's not the same thing, but it's better than NOT knowing the velocity, at least.

Loads with very small ES's and SD's point to that load being very consistent, which should mean that SOMETHING's going right with that load - a very nice sign when you get it.

It's just another tool to help us know what our loads are really doing, or at least a bit more about them. I'm keepin' mine.

I DID learn to buy the ones with the remote sky screens, though. Shot my initial Chrony, and went with the Pact I because of the remote sky screens. I make SURE there's plenty of clearance NOW, and friends don't shoot over it casually until I look over their setup - not a problem, since I always answer "Sure," when asked to use it, "As long as you'll get me another if you shoot it."

onefunzr2
12-19-2005, 01:36 PM
I use my Oehler 35 or 43PBL to work up loads all the time.

I can't believe no one has mentioned this feature of chronograph ownership.

It kinda goes like this:

get your average fps reading with, as an example, 50 grains of powder equals 1,000fps

at 51, 52, 53, and 54 grains the average was 1,100, 1,200, 1,300 and 1,400fps.

A 100fps increase for each 1 grain of additional powder.

Then at 55 grains the average suddenly only is 1,450fps. Same increase in

powder weight but only half the speed increase. That tells me something I

wouldn't know without a chronograph. What if I added yet another grain of

powder to 56 grains and still only got 1,450fps? What if I added still one more

grain to 57 and actually lost speed to 1,400fps?

Just an example of getting your money's worth from this piece of high tech

equipment. And if your chrono's instructions didn't point this out...well you got

screwed.

felix
12-19-2005, 01:47 PM
Finding out the top of the curve is the major asset of a chrono, but only after that load has proven to shoot accurately at that area of the curve. When at the top of the curve, the ES should be stable, and the powder amount adjusted in that area until the ES is minimized. This whole affair should be duplicated in each weather condition the gun is intended to be used. If the accuracy and ES match with different ambient conditions, then you know that load is the one meant for that gun. Hopefully, you have a drawer full of the same primer, and same powder lot, and the same lead composition. ... felix

fourarmed
12-20-2005, 03:38 PM
Part of the reason we all have seen loads that grouped well in spite of a large ES is that at certain distances guns can "compensate" for velocity variations. A higher velocity bullet will be out the barrel faster and at a lower angle, while a slower bullet will have longer barrel time and emerge at a higher angle. Both will strike in the same group AT A PARTICULAR DISTANCE. At longer ranges, vertical stringing becomes evident as an unavoidable consequence of large velocity variation.

Testing loads at the 50 to 100 yard range as most of us must can lead you to think everything is OK when maybe it isn't at 200 or farther.

Junior1942
12-20-2005, 03:51 PM
Yesterday morning I put a 220 gr #323471 through my Chrony. Through, not over. http://castboolits.gunloads.com/images/icons/icon9.gif

Scrounger
12-20-2005, 04:08 PM
Yesterday morning I put a 220 gr #323471 through my Chrony. Through, not over. http://castboolits.gunloads.com/images/icons/icon9.gif

Been there, done that...

Poygan
12-20-2005, 05:41 PM
Junior,

I have two on my trophy wall....

Poygan

grumble
12-20-2005, 07:16 PM
What size group did you get, Junior? <GGG>

NVcurmudgeon
12-20-2005, 07:43 PM
Junior, I dropped both Skyscreens with a single .35 cal. 255 gr. Hoch. This event taught me to set up the screens for a scope sighted rifle FIRST, and all will be well when shooting the iron sighted rifle. The reverse procedure may leave the screens too high when shooting a scoped rifle.

waksupi
12-20-2005, 08:53 PM
Yesterday morning I put a 220 gr #323471 through my Chrony. Through, not over. http://castboolits.gunloads.com/images/icons/icon9.gif

Junior, was it well centered, or did you have any wind drift? I like a good, clean, kill on chronys. Mine is only slightly wounded.

Junior1942
12-20-2005, 08:59 PM
I had a little wind drift. The bullet hit at about 2 o'clock and about 3/4" down from the edge. You know, I still ain't figured out how it happened. I thought I was shooting about 6" above the dang thang. Guess what? I wasn't!!!