Chronograph Findings

[kannonfyre]

Used a Chronograph for the 1st time last week and here are my findings....

Caliber tested: .38 Special
Gun in question: beat up S&W model 67 with 4" barrel
Rounds tested: 1) Magtech 158gr LRN, Magtech +P 125gr SJSP, Winchester 110gr STHP, "blue plastic box" CCI lawman 110gr SJHP and 158gr Fiocchi "made in italy" maroon box LRN-GZN.
Distance of muzzle to chrony: about 9 inches.

The magtech 158gr LRN standard velocity appeared to be underloaded. After firing 12 rounds, the average velocity was 725ft/s. This ties in with what many other shooters have said.

Winchester STHP clocked in at 1140ft/s average velocity. This is somewhat surprising being that their website claims a 900 something ft/s velocity.

The CCI SJHP round averaged 1170ft/s. This is a long discontinued round and since it's significantly more expensive than the silvertip, I'll remove it from my shopping list. (30ft/s improvement not worth the 12% price difference)

The fiocchi maroon box stuff really ought to be labelled as +P. It gave me 850ft/s as an average speed. Only goes to show that the italians really do load their stuff hot!

Lastly, the +P 125gr SJSP magtech really stumped me, I shot 6 rounds and while 2 shots produced an error reading, the other 4 gave me an average speed of 405ft/s! This can't be true! The cartridges are only 1 year old and have been kept in a cool/dry place. Above all, the felt recoil was heavier than the other magtech LRN round tested.

Need some help here....what do you think is going on guys? How in the world can a +P .38 round which has been properly stored deteriorate so much? The magtech website says it supposed to be about 948ft/s and yet all I get is 405ft/s.

 

[3 gun]

None of your figures are to be trusted. Your set up was much, MUCH to close to your muzzle. You might even want to check your equipment for muzzle blast damage before using it again. Also what kind of light were you using? That can also make a big difference. As you use it more you'll find small changes in how you set up can make major changes in the readings.

 

[gfmun]

I go back 10-12 feet minimum to get a good reading. Much closer than that and the readings are all over the place. Also light is important. Are you outdoors....watch for shadows..

thanks, George

 

[brickeyee]

"Distance of muzzle to chrony: about 9 inches."

All you managed to do was measure the speed of sound from the muzzle blast or get useless readings.

 

[Caimlas]

I didn't realize the use of a chronograph is such a complex process...

 

[MCgunner]

Just step off 15 feet, not complicated. You have to get it lined up with the target and the sand bags where you're shooting if you're going to shoot for group and chony figures like I usually do, takes a few trips out to line things up. But, you have to give it some distance. Heck, the first rounds out of my 7 mag over the chrony when I got it, the muzzle blast blew the chrony over off its tripod. LOL! I had to go out to 25 feet with it to keep the thing in place.

 

[Lancel]

Also it's likely that sooner or later a bullet will catch one of the diffuser supports. It's a good idea to use wood dowels (Home Depot or Loews) to hold the diffusers. They'll break instead of your chronometer and are cheap and easy to replace.

Larry

 

[jwr_747]

read your paperwork for distance to chrony.most rifles are 15ft.pistols usually 5 to 7ft. you start shooting at 15ft. YOU GONNA POP A CAP INTO THE CHRONY.been there,done that.unless black powder,5ft.is what both my chrony's paper work suggested. jwr

 

[The Lone Haranguer]

Nine inches? In chronograph data I've seen in magazine articles, the instrument is placed 10-12 feet from the muzzle. I would think that the bullet would need that distance to fully accelerate to "attack speed" anyway.

I really ought to obtain and play with a chronograph, because I've long had a curiosity about the real difference (if any) between .357 Magnum and .38 Special loads fired from a two- or 2 1/4-inch snubnose revolver, and 9mm fired from a three-inch auto. (An autoloader's barrel length includes the chamber, so the length of actual rifled bore is about the same.)

If I clocked Remington .357 SJHP from my Ruger SP101 at nine inches, the blast would probably blow the instrument right off its stand and several feet downrange.

 

[MCgunner]

read your paperwork for distance to chrony.most rifles are 15ft.pistols usually 5 to 7ft. you start shooting at 15ft. YOU GONNA POP A CAP INTO THE CHRONY.been there,done that.unless black powder,5ft.is what both my chrony's paper work suggested. jwr

I shoot 15 feet with pistols and have never hit the Chrony. I've got the old, old Shooting Chrony with the old paper/plastic screens with the little hole to shoot through and it's plenty big enough with a rested gun on sand bags. I've had this thing 20 years or better and it still works fine. I've shot numerous snubbies over it and never hit the thing. I guess if your gun shoots THAT bad, you need a new gun and if YOU shoot that bad, you need to practice.

I've avoided two things with my Chrony. Chronographing shotguns is out of the question and shooting sabot bullets (as I shoot in my black powder rifle sometimes) is not advisable. If the sabot hit the thing, it could do damage.

 

[the naked prophet]

First time I used a chronograph, I was fine at about 20 feet until the 12 gauge with 3 inch magnum slugs came up. I've got a photo somewhere of the giant fireball extending through the chrono tunnel, and blasting the shades into the sky...

 

[jwr_747]

in spite of what I read on the internet,I'm still prone to belive the manufacture on how to operate their product.went back and reread the book for my chrony.it still says pistols 5ft.(1.5m) so that is what I shoot at.I have been shooting competitively for 48 years,so I don't think I'm that BAD a shot.and most of the pistols I shoot are the weapons that have won me many trophys,medals and ribbons,so I'll assume my guns don't shoot that BAD.probably had between 17,000 and 20,000 rounds thru that 1st chrony,without any trouble.was testing a 1895 Nagant pistol,with it's 20# trigger pull and popped a cap in the chrony.had the chrony set at 14ft.for some rifle testing.won't happen again.Mr. instruction book says 5ft. 5ft. it's gonna be. jwr

 

[Erich]

And which manufacturer of chronographs gives such instructions?

 

[Redneck with a 40]

I've been using a chrono to gauge my pistol rounds, I usually fire from about 10-15 feet away. I've also found that factory velocity claims are bunk. My 155 grain Winchester Ranger's are supposed to be at 1200 fps, I got 1100 our of my 4" XD. The 125 grain 357 factory loads claim 1450 fps, I don't buy this either. The best I could do with a max charge of 18.5 grains of 296 was 1400 fps out of my 4" tracker. I'm thinkin' the factory loads would be down around 1350.

My 154 grain Wolf soft points out of my SKS is a different story. They claim 2100 fps, I got 2200 fps.

 

[CB900F]

Fella's;

"I would think that the bullet would need that distance to fully accelerate to "attack speed" anyway" No.

Once the bullet leaves the barrel, gas pressure is dissipated and the bullet goes into ballistic flight. It would be extremely unusual (read Nobel prize I'd think) to find a method by which the bullet would accelerate ex-barrel, given conventional cartridges. Gee, I had you Gyro-Jet guys all wound up there for a sec, didn't I?

In fact, it's possible for a bullet to decelerate in the barrel. Think .22 rimfire in a long barrel. That's a small powder charge that totally burns in around 16.5", after that, friction will have it's way once the gas column stops expanding.

900F

 

[vanilla_gorilla]

I shoot 15 feet with pistols and have never hit the Chrony. I've got the old, old Shooting Chrony with the old paper/plastic screens with the little hole to shoot through and it's plenty big enough with a rested gun on sand bags. I've had this thing 20 years or better and it still works fine. I've shot numerous snubbies over it and never hit the thing. I guess if your gun shoots THAT bad, you need a new gun and if YOU shoot that bad, you need to practice.

That was a 180 grain .44 Magnum bullet at 1600fps from a 4 inch barrel. What many would refer to as a "pre-ignition push" or as my father would say, snatching the hell out of the trigger.

In regards to distance, with my .357s and .44s, I normally have to go out to 15 feet to avoid messed-up readings. Any closer gets me reading of 200-500 fps.