Chronographing

[Jim White]

In the past I've chronographed and for optimun results (I believe), I always try to place the CHRONY where the bullet passes directly over the sensors and centered between the upper end of the screen and the CHRONY. I've noticed that if the bullet is to far left/right and to high/low the readings will vary some what. What I'm curious is;

1. When you folks chronograph your loads how far do you place the chronograph from the muzzle of the rifle? I believe I'm limited to about 14 feet MAX. It would seem to me that there would be a difference if the muzzle was 10 ft vs 14 ft from the CHRONY.

2. Have you ever noticed a difference in readings whether its sunny or overcast?

3. Have you ever noticed a difference in readings whether or not the screens are used? I have a CHRONY and using the screens are optional.

Thanks!

[Silverfox]

I have a Chrony Beta Master and ALWAYS use the screens. I place the chronograph on a camera tripod so that the first screen is 12 feet from the muzzle of my rifle. I am limited in the distance I can get the Chrony away from the muzzle by the length of the cord between the electronic eyes and the digital readout device that sits on the shooting bench with me.

I have had no problems getting readings on days that are cloudy, bright sunshine or anything in between. The only time I have missed readings has been when the sun goes down so far that the shade from the roof over the shooting benches is over my chronograph. I have black electrician's tape on the metal rods that hold the screens over the chronograph and the tape is at 3" and 6" from the top of the front electronic eye. If memory servers me right, that is the distance the directions tell you to try to have the bullet travel above the electronic eyes. I always level the chronograph so it is perfectly level from front to back and sideways as well. Before I take any shots, I always make sure that the center of the chronograph and the center of the space between the rods that hold the screens is pointing right at my target box at the 100 yard distance at the range. I set my rifle in the front rest or use my bipod and in the rear rabbit ear bag and get the crosshairs holding steady on my target. Then, I stand behind my rifle, I also sight down the side of the barrel to make sure the barrel is aimed so it is between the 3" and 6" pieces of black tape and pointing down the center of the rods so my bullets will be going over the center of the electronic eyes, or as close to the center as I can get it.

You want the first electronic eye far enough away from your muzzle so muzzle blast does not cause erroneous readings. There is a difference in the velocity readings if you have the chronograph placed at 10 feet or 14 feet. I use the online ballistics calculation Web site: http://www.eskimo.com/~jbm/ballistics/traj/traj.html and there is a place in there where you type in the distance your chronograph is placed from the end of your muzzle and that software calculates what the velocity of your bullet is at the muzzle.

[Bunnybuster]

I got an inexpensive laser bore sighter at WalMart, that goes in the front of the barrel for about $20. I had forgotten to take my bore sighter with me, when I bought the sorta stepson a 10/22 for his birthday, and needed to get a scope on it.

I use it to line up the rifle on the chrony. Unfortunately it doesn't go small enough for the 204, but it does work well with the rest of the rifles.

[Jim White]

I have a Chrony Beta Master and ALWAYS use the screens. I place the chronograph on a camera tripod so that the first screen is 12 feet from the muzzle of my rifle. I am limited in the distance I can get the Chrony away from the muzzle by the length of the cord between the electronic eyes and the digital readout device that sits on the shooting bench with me.

I have had no problems getting readings on days that are cloudy, bright sunshine or anything in between. The only time I have missed readings has been when the sun goes down so far that the shade from the roof over the shooting benches is over my chronograph. I have black electrician's tape on the metal rods that hold the screens over the chronograph and the tape is at 3" and 6" from the top of the front electronic eye. If memory servers me right, that is the distance the directions tell you to try to have the bullet travel above the electronic eyes. I always level the chronograph so it is perfectly level from front to back and sideways as well. Before I take any shots, I always make sure that the center of the chronograph and the center of the space between the rods that hold the screens is pointing right at my target box at the 100 yard distance at the range. I set my rifle in the front rest or use my bipod and in the rear rabbit ear bag and get the crosshairs holding steady on my target. Then, I stand behind my rifle, I also sight down the side of the barrel to make sure the barrel is aimed so it is between the 3" and 6" pieces of black tape and pointing down the center of the rods so my bullets will be going over the center of the electronic eyes, or as close to the center as I can get it.

You want the first electronic eye far enough away from your muzzle so muzzle blast does not cause erroneous readings. There is a difference in the velocity readings if you have the chronograph placed at 10 feet or 14 feet. I use the online ballistics calculation Web site: http://www.eskimo.com/~jbm/ballistics/traj/traj.html and there is a place in there where you type in the distance your chronograph is placed from the end of your muzzle and that software calculates what the velocity of your bullet is at the muzzle.

Silverfox,

I appreciate the info and I'll plug info into the ballistic calculator when I chronograph this round. I've often wondered when I see all the various velocities that are listed on the web what the distance was between the muzzle and the chronograph.

Several years back I was checking some M14 target rounds and with the same load within a few days (3-4) the velocity was quite different. The only conclusion I could come up with was the distance from the CHRONY to the end of the muzzle. Like you, I always try shooting down the center between the rods and I've found the results are pretty consistent.

In recent years I haven't chronographed anything and the club has added baffles that restricts the light somewhat. One thing I need to figure out is why the 1st shot out the barrel is always a little bit off from the others.

Thanks for the info.


Jim

[scootertrash]

If you just subtract 1 foot a second for every foot your chrono is from the muzzle, you will be very close to actual muzzle velocity. In other words, unless you are putting your chrono waaaay down range, it ain't enough to worry about.

As far as the velocity of the first shot being way off, it is my experience that the first shot from a clean barrel is slower. I've seen almost 100 fps slower. The last thing in my barrel during the cleaning process is Wipeout, and even though my bore is dry patched, I believe the remnants of the Wipeout leave a film. For lack of a better term, I think this causes the first shot to "lose a bit of traction." Point of impact remains the same with this shot, just a lower speed.

I also did testing and found almost every rifle I own will hit close to point of aim on the first shot from a cold clean bore.......if I store it muzzle up. If they are stored muzzle down, the first shots are almost always errant. Again, I attribute this to remnants of cleaning products working their way down the barrel. Some folks have concerns about the cleaning products eventually gumming up trigger mechanisms when stored muzzle up, and rightly so. But a little preventive maintenance once a year or so will keep this from happening. Also, there are bore plugs available to plug your barrel during storage.

These are just my observations, yours may differ. But try it sometime, it would be intersting to see if others get similiar results.

Mike

[JD11]

Thanks from me too, Silverfox. Never had one, but I just ordered one and it should be here Tuesday and your setup advice is more helpful than the manual I read a couple days ago on the Chrony website. I really don't care to blast a hole through it the first time I put it to use.

For what it's worth, the Chrony manual states that the shields are needed to shield the sensors from direct sunlight, but for best operation they should be removed on cloudy, overcast days.

[Jim White]

Mike,

I just picked up this rifle (CZ-527 American) and was just checking to see how good/bad 39 and 40-grain bullets would perform. From what I’ve read both here and elsewhere, some rifles like them, some don’t. When I got the rifle (NIB) I shot 40 rounds to break the barrel in. The barrel was-not free floated and the over all accuracy was around 1 to 1.5” at 100 yards. I had it free floated and bedded and decided to check on any improvement. I also decided to settle on Remington cases and primers (7 ½ ) and H-4895. The scope is a 6.6-20x44 Nikon Monarch UCC with FCH/Dot reticle.

I remember from my target shooting days, (especially the .223) some powders just don’t follow others very well often taking several shots to settle down. Since I had an abundance of H-4895, I figured I would start with that. With the 223, I found the following powders provided excellent accuracy in varying conditions (temperature), H4895, Reloader-15, Varget and Vihtavouri N-135, N-140 and N-540. There are others I tested and used but for the most part mostly H-4895 and the Vihtavouri powders. I found that ball powders, AA2520, AA2230, Win 748 were good but tended to be temperature sensitive.

Anyway, I loaded three 5-shot groups (26.5, 27.0 and 27.5 grains) for each bullet, seated them to a COAL of 2.250” and went to the range. Where I sold myself short was I didn’t make enough fouling rounds (I only made 1). In between each 5-shot group I let the barrel cool for 20 minutes since it heats pretty quick. I started off with the Sierra’s.

Sierra 39gr with 26.5gr H 4895:
- 5 shots: Horz: .471 / Vert: .974.
- 4 shots: Horz: .148 / Vert: .534 (minus the cold bore shot).
- No Pressure signs.

Sierra 39gr with 27.0gr H-4895:
- 5 shots: Horz: .389 / Vert: .509.
- 4 shots: Horz: .290 / Vert: .291 (minus the cold bore shot).
- No Pressure signs.

Sierra 39gr with 27.5gr H-4895:
- 5 shots: Horz: .450 / Vert: .335. This group was in two different groups (cluster of 2 shots & a cluster of 3 shots with about .15 seperating the two groups).
- No Pressure signs.

Hornady 40gr with 26.5gr H 4895:
- 4 shots: Horz: .295 / Vert: .598. (On the last shot I blinked as the round was launched and struck about .250 inches low. Since I couldn’t call the shot I discarded it). The cold bore shot is included.
- 3 shots: Horz: .154 / Vert: .004 (minus the cold bore shot and the low shot mentioned above).
- No Pressure signs.

Hornady 40gr with 27.0gr H-4895:
- 5 shots: Horz: .622 / Vert: .624.
- 4 shots: Horz: .389 / Vert: .450 (No cold bore flier with this group. However, on the last shot the scope was a tad blurred (don’t know why) and the shot went just slightly high and right).
- No Pressure signs.

Hornady 40gr with 27.5gr H-4895:
- 5 shots: Horz: .779 / Vert: .576. The group was round but is defiantly starting to open up.
- No Pressure signs.

All-in-all, I was quite pleased and with both bullets. I believe the BC of both bullets is pretty even. I don’t have any unknowns with the Sierra’s from this test and they seem to group better at the higher velocities. The Hornady’s doesn’t group well at the higher velocity. While the 27.0gr load shot well, the 26.5gr load has a question mark as to whether I was the cause of the low shot or not. From this test it seems both bullets fly fairly true with 27.0gr of H4895 and the Sierra flies true at higher velocities.

Thanks for the feedback.

Jim

[Silverfox]

Jim White--If you haven't already decided on one of those loads as your keeper, I'd like to suggest increasing your powder charge only .2 of a grain instead of going up a full .5 grain on your next trip to the rifle. So with the 39 gr. Sierra maybe start at 26.5 gr., then 26.7 gr., then 26.9 gr., then 27.1 gr, etc. and do the same with the 40 gr. Hornady.

This is just my opinion, but I think .5 grain increments is too big a jump in charge weight for this caliber. You could be missing an absolute perfect load somewhere in between your 26.5 and 27.0 gr. loads and likewise for the 27.0 gr. and 27.5 gr. loads.

Some of the groups you listed look good enough to me to just load up 5 or 10 casings with 26.5 gr. of H4895 and the 40 gr. Hornady and do the same for the 27.0 gr. and 27.5 gr. loads of H4895 and the 39 gr. Sierra and see if you can duplicate the accuracy. You don't have many rounds down the barrel, so one can only hope accuracy will improve. If it does improve, you will have a KILLER barrel there!!!!

[Jim White]

Silverfox; I will. These loads were just a test for 39 and 40 gr. Right now Sierra's are more abundant here so I'll go with them for now but I believe I would be just as happy with the VMAX's.

When I first took this rifle to the range with the Remington 40gr factory loads I was disappointed that 1.5" groups was all I could get. My hope was that at least one of these load test would be .75" or better and then go from there. As it turns out just about everyone could be a good starting point. Total rounds down range is 75. I might try moly coating to cut down on the fouling but thats a dirty process plus getting it on your hands in the field because the moly sure-doesn't come off very easy, not to mention, "completely" removing moly from the barrel is a small chore.

Thanks,

Jim

[Silverfox]

If you are really interested in shooting coated bullets, I'd suggest going with either Danzac or HBN (hexagonal boron nitride). Here's a link to a discussion on moly, Danzac, and HBN.

http://www.websitetoolbox.com/tool/post ... on+nitride

I have used Danzac and am just getting into using HBN. HBN is white and while there is some dust, there's nowhere near the dust you get with moly.

[Jim White]

If you are really interested in shooting coated bullets, I'd suggest going with either Danzac or HBN (hexagonal boron nitride). Here's a link to a discussion on moly, Danzac, and HBN.

http://www.websitetoolbox.com/tool/post ... on+nitride

I have used Danzac and am just getting into using HBN. HBN is white and while there is some dust, there's nowhere near the dust you get with moly.

Hmmm,

I'll take a look. I used moly bullets in Highpower Rifle competition when I was more active and I really liked them. If for nothing else, they made cleaning a lot easier. As time went by there were some things that came out about moly that didnt sound too appealing, especially if you weren't shooting that often as the sulfur in moly and the moisture in the air (may) cause corrosion in the barrel. I never experienced this but at the end of the season or, if I wasnt going to be shooting for any length of time, I would scrub the moly out.

I always moly coated my bullets and it could get messy but no more than changing the oil in my rig. The stuff doesn't clean off very well and it can take a little bit of efforet to get it completly out of the barrel. Whether or not it increases/decreases barrel life is unknown to me.

Jim