new/old chrono

[tedbeau]

I was looking on Ebay and found a Pact model one that was about 20 years old but apparently new in the box, never used. The auction started out at $5.00 so I decided to take a chance on it. I ended getting it for $47 dollars plus shipping, so about half the price of anything else available.

This model has the two sensors that are connected to the electronics/display by two cables with stereo type plugs. I had to make a frame to mount the sensors 24 inches apart.

I took it to the range Saturday. I set it up and plugged the cables into the display and fired my first round thru it: no reading, after several failed attempts I rechecked the cables and of course while tracing them from sensors to display they had crossed and I had them plugged in wrong. After fixing that the chrono worked fine for a 10 shot group. I had grabbed the ammo out of box of mixed loads that were all about the same powder charge, however they did have two different bullets, (same weight, just different manufacturers) and several different primers. they were loaded on different days and the powder charge may have not been exactly the same. Since I am loading for IDPA and only looking to make the minimum power factor of 125 I was only concerned about being to low, and knew I was well below the listed max for the powder I was using.

I had estimated the charge based on the lowest listed charges for the powder. Since It's 40 caliber using a 180 grain bullet I need to be just at 700 fps to make the 125 PF. Also since I am shooting a glock 27 in the CCP class I am giving up about an inch in barrel length so I knew I would be a little slower than published data.

Of the 10 shots, two or three fell blow 700, my average was 707 and my SD was 25. The extreme spread was 77.7.

Based on this I am going to bump up my loads a little even though they would probably all pass if I shot them thru a longer barreled gun, which IDPA will allow if you fail to make the PF with your gun. My goal is to get them all up over 750 FPS so the PF would be 135. I have match ammo loaded already that will probably make that.= I just didn't take any to the range with me.

I did however then try to chrono some of my SD ammo. I was carrying Hornady XTP 180 grains. For some reason every one I tried got an error message.

I wish I would have switched back to the hand loads to see if they would read or not.

The only possibilities I can think of for the hornady's not reading were that the battery was getting low, or the hollowpoints were causing more muzzle blast and the chrono was reading that. I had the near sensor about 10 feet from the gun. maybe I need to move it back more. Next time I'll take a second battery too.

oops just looked at the manual and I may have still been in review mode, apparently you need to press edit and review buttons at the same time to start a new string, but I think I actually turned the unit off when I was getting error messages so I would think that would have cleared it,

Anyone else ever had issues with hollowpoints instead of round nose?

[Hi-Power Jack]

Anyone had issues with hollowpoints instead of round nose?

I can't imagine that would present any kind of problem - but I may be

surprised by other people's experiences.

How far was the muzzle from the chrono?

[rhett45acp]

I have a Pact IV and it's a love hate relationship. It is very very important the cables and control box stay away from the muzzle blast as much as possible. If you set the control box conveniently to the right of your shooting platform, like I like, the results will be less than satisfactory. I find I have to put my control box underneath the bench or way to the right or left.

I bet the muzzled blast from the Hornady loads are just enough to make the difference.

[Steve RA]

You may have to build a sunshade, if it didn't come with anything of the sort, as some of the really shiny bullets will reflect sunlight in all directions and not provide a shadow for the sceens/sensors to react to successfully.

[tedbeau]

as far as distance from the muzzle to the sensors, I paced it off as three paces so that should be about 8 feet, It might be just a little to close. In retrospect as I said, I had reviewed the data for the first string and then tried to check the hornady. maybe I needed to reset the unit. The manual says to push the edit and review buttons at the same time which I did not do, but I thought I did power it off and back on so I would think that would reset it.

Ill play with it some more in the spring unless our weird warm weather continues.

[rishii]

just to get this out of the way, the early pact chronos didn't have a diffuser screen over the sensors, the V shaped thing that every chrono has today

if it doesn't, you'll need to order new sensor housing and diffuers from pact.

if it does, then the various thing I've done

put up a blast shield, which is putting up a cardboard target in front of the sensors, and cutting a hole in it for the bullets to pass thru

clean the contacts on the plugs

block sunlight from hitting the sensor by taping cardboard to the side of the diffuser bracket

and if all else fails, call pact, evertime I've called someone answers the phone

[tedbeau]

Mine has the diffusers (pact calls them skyscreens I guess). That's how I knew the unit was never used, the plastic diffuser panels are attached to the metal frame with tape and the tape still had the protective paper backing that needs to be peeled off to attach.

I had read a tip from someone else about putting a cardboard target in front. Question though, why cut a hole in it, the cardboard shouldn't slow the bullet down, of course I guess it would be harder to see the relationship of the target and the skyscreens and sensor without a hole, so more chance of shooting the unit if shooting blind. one other interesting thing, I took the battery out and noticed that the wiring harness for the battery connector appears to be spliced. It had electrical tape in the middle of it. I unwrapped the tape and each wire was joined with heat shrink tubing. I'm not sure if it's a factor joint, or if someone replaced the battery connection. IF it's a solder joint it should be ok, if' its not it might be causing power supply issues. If I continue to have trouble I can replace the connector, I have one and I can solder it on to make sure its a good connection.