Chronograph worked last time but now???

[deadlyswift]

I have one of the Chrony Master F-1 chrononograph's. I know this is one of the cheaper chronograph's but it has worked well in the past. Last time I used it, I put a new 9v battery in. I was shooting a .308 with a 26" barrel with 44.5 gr. of varget. I was consistently getting a avg. vol. of 2630fps with the 175gr smk. I felt like this was a honest reading. The .308 I am shooting now has a 24" barrel and shooting the 175gr. smk's and 175gr. berger target long range BT with 44.2gr of varget I am getting consistently reading of a avg. 2855fps. I wouldn't call this a hot load. Pressure signs don't show up until 46.2 gr, but that's on a 75* bright sunny day. The day I was using my chronograph it was blue bird skys sun directly above.

To start I had the chrony 10ft from the muzzle. It was giving reading of over 5000fps. Ok so I'm too close to the muzzle and getting interference from muzzle blast. So I moved it out to about 15ft. Then got 20 shots reading an avg. of 2855fps. I done the math with a calculator and ES was 11 SD was 4. I would love to believe that the chrony wasn't lieing to me, but better judgement tells me it is. The only thing I can think of that might be the problem is that the chrony set for about 8 months between use. Maybe I just need a new battery, but thought I would ask if anybody had any idea's as to what have might been the problem?
Thanks
Mark

 

[zullo74]

Do you see any bullet holes in it?

Seriously, are you using the sun shades? You could be getting false readings due to glint off the bullet.

 

[Mikem]

If you have any other ammo that you checked the MV on, run it over it again, and see if the speeds the same. After you put a new battery in it.
That load using a 175g bullet over 44.2g of Varget for 2855 fps does seam a bit fast.
My 24" barreled 308 with 168g SMKs and 44.5g of Varget is 2710 fps on avg.

Like 74 said, it could be the light.
Or you might try someone else's Crony.

 

[deadlyswift]

Put a brand new battery in the Chrony today. No Bullet holes are in the thing! and yes I'm using the sunshades! So here are the velocities that I got today. Same bullet same load same gun. I think I'll throw this thing in the trash and just invest in a good chronograph!
1.2736 11.2753
2.2756 12.2766
3.2763 13.2764
4.2731 14.2763
5.2759 15.2735
6.2758 16.2766
7.2733 17.2743
8.2752 18.2750
9.2752 19.2739
10.2759 20.2749

If anybody has any answers to what might be going on please offer advice. I still think these numbers are way to high for the 175gr. berger from a 24" barrel! last time I was getting an AV of 2855fps. With a new battery none of these are even in the 2800s. To me if these numbers where 100fps slower that would be more believable. Any good explanation will be appreciated!
Thanks!!

 

[zullo74]

Is the spacing BETWEEN the screens correct for your model chrono?

If you send me the COAL I will send you a screen shot of your load from my Quick Load software. BTW, your recorded velocities seem about 100 FPS too high to me too!

 

[deadlyswift]

Joe,
I have not messured the COAL, to the tip yet. Here is the length messuring with my comparator if that will work 3.254. If this want work I'll size one of the cases and seat a bullet to depth then messure to the tip?

On another note I entered the data into my software by Bryan Litz's. The one you get with his book Applied Ballistics for long range shooting. When I done this the inches in drop from 300, 400, to 500yrd was so dang close to the amount of moa that I had to use to get there was scary? I don't know! I'm getting ready to go out to eat with the family and stop worring about it for a cpl of hrs. ;D Thanks for the help! I get back to you!
Thanks!!!!!!

 

[zullo74]

I'll need the COAL (tip to base end).

 

[deadlyswift]

I'll need the COAL (tip to base end).

Joe, My COAL is 2.923"

 

[zullo74]

Mark,
I sent you a PM containing a screen shot from Quick Load.

Here it is for others to see...
http://www.northfloridashooting.com/images/Load_Data.jpg

 

[deadlyswift]

Joe Zullo,
Thanks for the Screen shot from Quick Load. It does seem that the 175gr. berges at 2618fps would be more logical with a 24" barrel.

How ever guys I still have more questions. Due to futher testing? I have ran my 2753fps on my ballistics software that I got with Brian Litz's book (Applied Ballistics For Long Range Shooting). The inches in drop that the software gives me from a 300yrd zero are all but dead on from 4, 5, 6, &, 700yrds. In other words. The amount of MOA I have to come up on my turrets Match the drop in inches that my software is giving me. Not exactly macthing but very close. Off no more than 1/4 MOA.

Also I have ran my 270wsm with the 140gr. Sierra gamekings and 60.8gr of RL-17 I was getting 3176fps with this load and caliber. This rifle also has a 24" barrel. Before I shot the 270wsm over my chronograph I figured I'd probably get numbers between 3150 to 3200fps. Don't know if It was just a lucky guess or not? With getting lucky or not on my guess with MV on the 270wsm, and with the amount of MOA having to come up at different distance, and that it is so close to what my ballistic software is telling me on my 308. I am still in question if I'm actually getting a average of 2753fps with the 175gr bergers and 44.2gr. of varget? I also shot this past weekend with the Berger's and Sierra 175mk. Bergers are still giving me a avg. of 2753fps as well the Sierra's are giving me an avg. of 2726fps.

So could it be that the numbers are right? If so what would make a barrel shoot faster than what most are? Wish I had another Chronograph to run the load over, but I don't so I'm trying to figure this out? The amount of MOA that I am using to get out to different ranges, and my software's drop in inches being so close it still has me in question?

Joe's Screen shot says I should be running at around 2618fps.

Thanks to anyone that can shed some light!
Mark

 

[1000yardstare]

I used a Master Beta Chrony for a number of years. Found it very sensitive to bright light, especially coming in at an angle. Sky screens didn`t make any difference. Would give readings between 5 fps and 5000 fps for what should have been around 2800 fps. Worked best on a cloudy day (light grey). Wouldn`t give a reading at all if the sky was too cloudy (dark grey).

Also battery voltage was very critical. Nominal voltage had to be above 9 volts as in a new battery. Voltage didn`t have to be much below 9 volts to get wonky readings.

I bought the auxilliary printer and it packed it in after a few years. The internal wiring cable started to fray about the same time and I had to be careful of electrical shorts.

The Chrony has a very short distance between photo cells compared to other makes. Because the Chrony folds up for storage and must be unfolded to use, it is very critical that the device be unfolded totally flat. If the slightest "V" shape exists, this shortens the distance between the photo cells which alters the readings.

The plastic sky screens eventually turned to cottage cheese due to UV radiation but this is a problem with most makes.

I only live 2 hours from Markham, Ontario where the Chrony is made and could go in for repairs. But can`t be bothered.

I mail ordered the original PACT chrono from Texas back in the mid 1980`s and it still works. Decided to upgrade to the PACT Pro. Those great guys in Texas mailed again into the boonies of southern Ontario and all is well.

 

[robbin]

Drop tests are the only sure way to tell what your muzzle velocity is, and you know what the Chrony told you it was. So You have the TRUTH, no guess work, and you simply remember the difference. You can't trust any chrony that you buy. When in doubt, drop test. I do like the CED 2K chrony thou.

By the way, I've seen some pretty large differences in MV from the same load in fairly new barrels. If you've got less than 200 rounds thru it, you might want to hold off on a new chrony.

 

[robbin]

Brian Litz's book is awesome....