Trust a chrono :-)

[FishingPilot]

I used to reload with Alliant Reloader 10x for 223. I ran out. None available locally. I was able to pickup 2 one pound jars of IMR 4198 though at Ace Hardware. Here are the details from Hodgdon:

Bullet: 55gr SP
IMR 4198
Bullet diam: .224"
COL 2.200"
Starting Load: Grs. 18.8 / 2885 fps
Maximum Load: Grs. 20.4 / 3122 fps

I loaded 10 of these with 20 grs.
I measured each case before reloading (1.175" +/- .001").
I measured each powder drop (20 grs +/- .1grn).
I expected a velocity of ~3060.
No dice. I only got 2750 fps (deviation was only 20 fps)

The only thing I can think of is that the chrono was not reading these correctly. It actually only measured 8 of the 10 shots.
Shooting to high maybe? The chrono was about 12-15 feet away. The AR was the only thing I took to the range so I was unable to measure against any 'known' loads from my pistols or other AR rounds (those done with Reloader 10x).

Anyway, question: is there anything, economical, available to accurately check a chronograph's calibration? Other than checking it with some 'known' velocity ammo I can't think of anything.

[peterthefish]

What's your barrel length? What's the length of the test barrel for the load?

I would trust a good chrono over published load data that does not use my exact equipment any day.

[venomballistics]

Old school way was a ballistic pendulum.

Shooting into a suspended chunk of log, of known mass with a projectile of known mass sets it swinging a given distance.
From these results, energy can be calculated.
After you have that, E=MVV, to derive velocity.
Can't give you anything cheaper than a chunk of wood.

[Larry from Bend]

I've had Shooting Chronys since they first came out and have learned to "warm up" my Chrony by shooting a 22 handgun over it. Sometimes (though rarely) I'll get errant readings ---- always too slow. Usually it was on my old model that had poor sunscreens. Adjusting the position of the Chrony would fix the problem.

Usually, shooting too high gives no reading at all.

12 feet is as close as I'd test.

I've heard (never experienced it) that a 9V battery on its last legs can cause errant readings, also.

Several years ago a few of us tested several brands of Chronographs and found all of them agreeing with each other. The $80 F1 Shooting Chrony was one of them.

[Waywatcher]

The chrono was probably right.

Don't always trust published velocities.

[Bruce51]

Your chronograph is working great.

In my mini 14 it takes 22 grains of IMR 4198 with a 55 grain fmj to achieve 3000 fps.

At the time I tried this load combo I also shot some PMC 5.56 55 grain fmj.

Velocity of that load was 3200fps.

The mini has an 18" barrel with a one in ten twist.

Hopefully this information will give you a better idea of how IMR 4198 performs. It is a great powder for the mini 14.

Tell us about your 10X loads. I have a pound, but have not tried any loads.

BLM

[Twoboxer]

Just for kicks looked up your combo in Hornady 9. It shows 3100fps for 20.0gr IMR 4198 . . . from a 26" barrel.

Using the same data, Quickload estimates 3093fps for that 26" barrel . . . and 2771fps if using a 16" barrel.

So assuming a 16" barrel and 12' away . . . I'd say 2750fps would be a pretty good report.

ETA: This is about the best "calibration" you can perform on a chrono . . . except using two of them and see if their different measurements at least correlate well.

[Nevada Ed]

I can check my chrony with a Daisy BB gun............

If you have a pellet gun that will do nicely too.

+1 on old batteries that can start to give bad info.
Always carry TWO extras in your case.

[A.O.]

I've always noticed that the reloading books from all manufacturers seem to be very optimistic about their numbers. And yes that length of barrel makes a big difference also.

I'm thinking that chrony is probably spot on.

[jwalts27]

+1 to what A.O. said. I have run some pretty hot loads from my AR and have a hard time hitting some of the speeds they indicate in the books.

[FishingPilot]

Barrel length on Hodgdon is 24", 1:12" twist
Mine is 16", 1:9" twist
I didn't even think about the barrel length. Good point!

Bruce Lee M states: In my mini 14 it takes 22 grains of IMR 4198 with a 55 grain fmj to achieve 3000 fps.

With my loads being a little less than that and with only an 18" barrel, I suspect my readings are probably accurate.

Thanks for all of the tips and comments guys. I need to remember to check the length of the test barrel used in the load workup.

[FishingPilot]

Originally Posted by Bruce Lee M

.......

Tell us about your 10X loads. I have a pound, but have not tried any loads.

BLM

This is from a post a made a while back. I only tried 5 rounds of each in this test period:

Loaded up some .223 rounds using RMR's pulled 55 gr .224 bullets. They shot fairly well compared to some Winchester white box rounds.

Stag Arms AR-15 in 5.56, 1 in 9 twist
Chronograph was positioned 12 feet away

Winchester 55 gr factory loads:
5 rounds
low : 2704 fps
High : 3016 fps
Average : 2812 fps
Max spread : 312 fps

Reloads:
RMR's 55 gr pulled bullets
Reloader 10x, 21 grains
CCI 400
Lake City used brass
5 rounds
low : 2677 fps
High : 2849 fps
Average : 2757 fps
Max spread : 172 fps

The Alliant recipe data called for 23 grains of Reloader 10x for 3159 fps. Since these were my first reloads for this caliber, I decided to start a little lower. It looks safe enough to bump them up a little. Except for that one 3016 fps Winchester factory round, my reloads were within just a few FPS of theirs. I'm proud of these results for my first try at reloading .223 rounds.

[AveragEd]

I check my chronograph with a second one set up right behind the first one. I have a newer digital chronograph and an older analog one - both ProChronos - and if I see suspect readings on the new one, I set the old one up behind it. So far, the chronograph has been right every time.

Ed

[scooter123]

Originally Posted by FishingPilot

Barrel length on Hodgdon is 24", 1:12" twist
Mine is 16", 1:9" twist
I didn't even think about the barrel length. Good point!

Thanks for all of the tips and comments guys. I need to remember to check the length of the test barrel used in the load workup.

Once you start doing that you'll probably come to the same conclusion that I have. That being that the velocities listed should be regarded as exaggerated and in many cases unachievable. Frankly I'm a bit surprised that Hodgdon used a barrel as short as 24 inches, because with their 357 Magnum data they use a barrel 2 1/2 TIMES the length that most 357 Magnum shooters are using.

[MN2944]

As others have said, I'd trust the chrono over load book data any day.

[jepp2]

Some things to keep in mind:

- published load velocity are muzzle speed, your chrono is 12 feet away and the bullet has already slowed down.
- Hodgdon data was on a 24" barrel. Just to give you an idea how much barrel length and different actions can generate. A load of mine will chono 130 fps faster out of an 18" rifle gas system barrel compared with a 16" carbine gas system barrel.
- if you don't set up your chono using a level, you can make the distance between the sky screens to be longer and it will record slower velocity than actual.
- different powder lots can theoretically vary in burn rate by up to 10%. Add to that - difference in chamber size, brass volume, altitude, humidity, temperature, primer, bullet seating depth, distance from lands, barrel condition, etc.
- my chono claims to be 0.5% max error, but that can still be almost 15 fps on your load.

Your chrono is telling the truth.

[WR Moore]

Additional point: data from powder manufacturers is shot in specially made test barrels in universal receivers. These barrels have dead minimum SAAMI spec bore & groove dimensions plus minimum chambers to create a worst possible case with respect to pressure.

It's unlikely that production firearms are going to approach that situation. That will result in lower velocities for the loads.

IMR 4198 was my powder of choice for 55-60 gr .223 loads for decades until the recent shortages. I still have about 1.5 lbs for varmint loads. Never loaded any as low as 20 gr. though. Your results seem reasonable comparted with what my heavier loads clock.

I've still got a ballistic pendulum with a steel impact plate for pistol loads [power meter for IPSC competition waaay back]. After I bought a chronograph, I checked it against the clock and it was surprisingly close.

[arizona98tj]

Probably should rename this thread...."You can usually trust your chrono"

[ironhead7544]

The loading manuals are just a guideline. Your firearm may or may not get close to the quoted velocities. I have had problems with start loads being too hot. So, be careful. Loads have changed over the years. If you look at the older manuals you will see that.

I use IMR4198 for 223 loads as it requires less powder. Your load will probably be very accurate and wont eat cases. Your velocity is close to what I get. Good general purpose load that I have been using since the 70ties. For specific purposes, you can work up a hotter load if necessary.

To check my chrono, I used to use the factory Gold Dot load for the 44 Special. It would only show about 5 fps variation. Too expensive now. It looks like you found the right load to check yours. 20 fps variation is good.

[fredj338]

Originally Posted by FishingPilot

Barrel length on Hodgdon is 24", 1:12" twist
Mine is 16", 1:9" twist
I didn't even think about the barrel length. Good point!

Bruce Lee M states: In my mini 14 it takes 22 grains of IMR 4198 with a 55 grain fmj to achieve 3000 fps.

With my loads being a little less than that and with only an 18" barrel, I suspect my readings are probably accurate.

Thanks for all of the tips and comments guys. I need to remember to check the length of the test barrel used in the load workup.

This is everything. Expect to lose 40-50fps per inch in 223. I had a friend who didn't understand this & kept pushing his 9mm loads, trying to get book vel. Problem, he was shooting a khar!

[rwsmith]

In addition to the good comments here from those that know I have gathered that if a chrono messes up on a shot, it messes up big time and the numbers that it gets won't be repeatable. If it gets reasonable numbers consistently with a load, it's most likely right on even if they seem low or high. A number that is way off from the others can usually be tossed out.

[John357]

Originally Posted by scooter123

... I'm a bit surprised that Hodgdon used a barrel as short as 24 inches, because with their 357 Magnum data they use a barrel 2 1/2 TIMES the length that most 357 Magnum shooters are using.

I like the Lyman (49th ed.) manual's specs for 357 Magnum: 4" barrel (Universal Receiver).

Hornady (9th ed.) uses an 8" barrel, in a real gun (Colt Python).

[shil]

My humble opinion: Published data, as mentioned earlier in the thread, can be considered only a guideline. There are too many variables among individual firearms. I don't own a chronograph. Maybe some day. In working a load up to maximum published, I'll pick the load that yields the best accuracy, whether or not it's the maximum. For me, velocity is secondary. If I had a chronograph, I would trust its readings if there were no wild variations shot to shot.