Help with some weird 44 spcl Chrono results

[typetwelve]

Quick facts:
Loading for 44 special, all using CCI non magnum large primers.
-Ran some Missouri 240g lead over 6g Unique (my control)
-Ran some Hornady 200g XTP over 9g Unique, 13.5g 2400, and 18g 2400
-Ran some Hornady 180g XTP over 8.5g Unique, 14g 2400, and 16g 2400

All rounds were through my S&W 629 4".

I started with my 240g lead "control", chrono was a-ok, showing very predictable results in the high 700 fps range.

I started with the 200g XTP over 9g Unique, not sure what the deal was, the fps was coming in at high 300 fps range, not possible. I moved to 13.5g of 2400, it was reading mid 500 fps range, again, not possible with that load. When I moved to the 18g 2400 load, the wheels fell off, FPS on the first 2 shots was in the 8000 fps range. I immediately stopped, popped in a control round, and it was a-ok, showing fps in the high 700's. I ran 3 more of those 18g loads, 2 of which were again way over and one read 812 fps. With the recoil (and flame) of those 18g loads, there's no way they were moving in the 800 fps range. I know that's a hand-dyno assumption, but I know what a 1000 fps load feel like in that 629.

At this point, I ran another cylinder of my control and once again, A-ok.

I moved on to my 180g loads and all of them chrono'd just like I expected them to; 8.5 unq in the mid 900 fps, 14g 2400 in the mid 700 fps range, 16g 2400 in the mid 900 fps range.

I never moved the chrono during this session.

So, I have two questions:

-For the life of me, every 200g XTP load I made caused problems, I have no idea why.
-Every 2400 load I made thew unburnt powder everywhere.

Any help on this one?

 

[moosedog]

Might be the "glint" of the jacketed bullet in high sunlight throwing off the results? Just taking a guess.
I found it best to chronograph on over cast days

 

[rockquarry]

I've had six chronographs in the last forty years; cheap ones and expensive ones. All have quirks. Try chronographing at a different time of day. I've found from early morning to well before noon often gives best results with the skyscreen-type machines. "Overcast" as someone mentioned is also worth a try. I'm sure I've done this but don't recall results.

 

[njl]

What was your distance to the chronograph?

 

[ken158]

What chrono were you using and put in a fresh battery. Are you sure muzzle blast was not affecting results?

 

[typetwelve]

What was your distance to the chronograph?

I'd say 7-9 feet.

What chrono were you using and put in a fresh battery. Are you sure muzzle blast was not affecting results?

Prochrono DLX.

I'll say this, I'm not 100% sure it was the chrono figuring it was giving solid results the entire time, before and after. It even gave me a solid control eading during that botched set.

 

[Warren Sear]

Overhead tree branches will give unpredictable results.

 

[rwsmith]

Might be a little close.....

...to the chronograph. Your control shots were fairly benign but then you started measuring heavier loads. I'll bet that the shock wave fouled up the readings.

 

[S&WIowegan]

The OP's chrono problems are not unique(pun intended). After 20 yrs. of chronoing my handloads and some factory ammo and trying all brands of chronographs, I decided the answer was to chrono indoors. I use a PACT PC with sky screens illuminated by infrared light. There are drawbacks to my method including what building, bullet trap, no flourescent light and neighbors who may be annoyed. Fortunately, my closest neighbors go to Florida for the winter. Bullet trap is problematic when it gets too full and may cause a ricochet in your shop(don't ask).

The final benefit is chrono in any weather and set-up is easy.

 

[M29since14]

I agree with what others have already said. In particular, I'd recommend you get about 15 feet from your chronograph. Naturally, staying away from trees, clouds, high winds, and direct sunshine is also good.

You're going to get unburnt 2400 with those types of loads. Even with full-charge 44 Magnums and heavy bullets I always get some unburnt powder. Light bullets and reduced pressures compound the phenomenon, but fortunately it doesn't really hurt anything. For the lighter bullets I'd probably be using something other than 2400. Maybe stay with Unique, or something similar like BE 86 or Power Pistol?

 

[texmex]

make sure each time it is on feet per second and not meters per second

 

[fredj338]

I'd say 7-9 feet.



Prochrono DLX.

I'll say this, I'm not 100% sure it was the chrono figuring it was giving solid results the entire time, before and after. It even gave me a solid control eading during that botched set.

Too close IMO. I test pistol @ 10-12ft. As noted, jacketed sometimes will reflect the light that is supposed to cause the shadow. So simply coloring with a black sharpie will help. I find best results early am or late afternoon, regardless of chrono.
Unburned slow powder with light for caliber bullets is pretty normal. Try a mag primer there.

 

[Nevada Ed]

I never had problems with 9mm or 357 magnum loads at 10 feet or more.

I will do 12 Ga. at 4 feet........ and
Large bore Rifle at 15 feet due to muzzle blast.

 

[ArchAngelCD]

...to the chronograph. Your control shots were fairly benign but then you started measuring heavier loads. I'll bet that the shock wave fouled up the readings.

My thoughts exactly. The muzzle blast will throw off the numbers if you are too close.

 

[Beemer-mark]

My thoughts exactly. The muzzle blast will throw off the numbers if you are too close.

Not just the muzzle blast but the unburned powder also. On heavy revolver loads I usually move it to the end of my printer cord. 15' ?

 

[SMSgt]

I can't offer much because I never used a chrony until today. I bought a Magnetospeed Sporter, the bayonet sendor style. It took a few rounds to get it figured out (bore to sensor distance is critical), but it ran like a champ after that except for one round.

That round ran 300+ fps faster that the others (3100 fps versus 3400 fps). Boy, did it ever skew the SD and ES. The case is nearly full in that load, certainly does not have room for 300 fps faster load, and I visually check powder levels for each load.

My opinion is anything that depends of electronics to work can and will do weird things for no apparent reason.

 

[dla]

Sky screens when it is sunny. Stay back 15 ft. Keep your shots 8" or more over the sensors. Always buy a chronograph with a remote display that can remember a 20 shot string and calculate, High, low, average, extreme spread, standard deviation.

 

[kingrj]

Just my guess but I would suspect that your sky screens are retriggering on unburnt power AFTER the bullet has past. My home made chrono has flip-flops that trigger once and will NOT retrigger until complete reset..It could be that your chrono is rolling over and retriggering on the ejecta after the bullet has past..I bet if you use Bullseye or 231 you will NOT see this..Just my guess but you posted it so I ran my mouth..I don't really have any other reason...maybe ******* uncertainty? LOL!

 

[RDub]

Sounds like the chrony is too close. Move it back to 15' and try again. If all is good, move a few feet closer and try. Do this until you start seeing errors again. I'll bet 12 to 15' will be good for what you're doing.

 

[Ivan the Butcher]

I have a question, please don't flame me.
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Did you read the instructions?

Ivan (I'm not telling where I hid my man card!)