38 spl and Bullseye. Seems awfully slow FPS?

[Rule3]

I got my replacement Alpha Chrony. Went to the range to test out some snubs that I did trigger work on.
Model 642 1-7/8 barrel. My loads were 158gr lswc with 3.5 grs Bullseye and Wolf sp primers.

I did not record the whole strings as I was mainly testing for reliability of the gun. I also shot the same loads out of 2 other snubs.

They only averaged around 530 to 550 fps. This does not seem right to me??

Speer #14 says it should be 814 fps out of a 6" barrel.

Thanks

Would the FPS be that much less out of a 2" barrel??

 

[Skip Sackett]

My loads with those components average 790fps out of a 6" barrel. Those do seem kind of low.

What most folks do to check their chronographs is get a box of 22LR where the velocity is known and posted on it and use that for reference. Might be a good thing to try.

The difference in my loads from my M686 6" to my M637 1 7/8" isn't that big. 791fps to 706fps (Average velocity).

 

[Treeman]

Those do seem slow. It is possible that your Chrony is off. It is also possible that you have a slow lot of Bullseye. If you peruse enough dat you will note that top loads of Beye have varied from your 3.5 up to 5.0 in 38 special.....even from the same data source. Some of that is undoubtably due to differences in test barrels and ,some perhaps due to changes in max pressure specs (although the feared Speer #8 had 3.5 as max with 158 gr while Speer 10 had 4.2 as a standard pressure lead bullet load and 4.9 for max +P under a 158gr. jacketed bullet) I have come to suspect that lot to lot variation may be a bit greater than we have all imagined in canister powders and I am convinced that obtaining consistent presure data in relatively low pressure cartridges may be more difficult than most of us ever thought.

 

[acl864]

I agree the 530 to 550 fps isn't correct. 3.5 gr. Bullseye, Fed GM100M primer and a TVB 158gr LSWC out of my M642 w/ 1 7/8" barrel averaged 691 fps.

 

[Rule3]

Well I guess I need to calibrate my chrono against something known. Even using 22lr, is that out of rifle, a handgun or what? Think I will load some with HP 38 also and see what's up.

 

[Spotteddog]

Borrow a 6" .38/.357 from someone and run a few through the traps out of it. Although that FPS even out of a 1 7/8" don't sound Kosher?

 

[cowart]

You might want to re-crimp some of the existing rounds with a heavier crimp. Also, mike some of the bullets to see if they are undersized.

 

[smith17]

chronograph adjustment

If the chrono doesn't have a way to adjust it, how do you figure the correction? By figuring the percentage error when comparing a known .22 LR velocity or by adjusting for the difference in FPS?
Ed

 

[Rule3]

I can shoot some out of my 686 but it is 4". As to crimp, they are about as heavy as they can be, I ran them all through a Lee factory crimp. I will also try loading some Gold Dots and Xtps and see what I get.

I think I liked it better without a Chronograph. No news is good news if it went bang and was accurate All was well.

 

[ChuckS1]

I have a Chrony Beta and I have had a dickens of a time getting reliable FPS readings. First I changed the battery, then I monkeyed with the screens and then Chrony tech support said I had to make sure the sun was in the right position. Finally put it away. Lots of times I would get readings that were half to a third of what I knew the velocity should have been. I seriously doubt there's a problem with your powder.

 

[Rule3]

I have a Chrony Beta and I have had a dickens of a time getting reliable FPS readings. First I changed the battery, then I monkeyed with the screens and then Chrony tech support said I had to make sure the sun was in the right position. Finally put it away. Lots of times I would get readings that were half to a third of what I knew the velocity should have been. I seriously doubt there's a problem with your powder.

Not that it's funny, but that is almost exactly what their "tech" support said to me when I called on my first one which was really screwed up. That's why I sent mine back to Midway and exchanged for a new one. I fired some factory 357 mags also and some where 1000fps+ some where 800 fps, Yep, it's looking like another lemon.

 

[oldRoger]

Velocity for 22lr is quoted from a rifle. Standard Velocity ammunition is very consistent. I agree with the recommendation above, check the unit with a few shots of .22lr from a rifle. Barrel length is not too important, max vel is achieved in about 17" then is begins to slow but very gradually.
You will then have some good figures to use with Customer no-service.

 

[MKT]

Just for comparison 158 gr SWC with 3.3 gr BE and Win Small primer produce 763fps in my 6" Model 14 and 3.6 gr BE gives me 914fps.

You might try pulling down a couple rounds and verify your charge weights as well.

 

[bmcgilvray]

The screens on my ancient Oehler are occasionally fooled by sub-sonic rounds, the sound wave tripping the counter before the bullet does, giving the absurdly low readings you are experiencing. I'm guessing that is the issue rather than the powder.

 

[MKT]

The screens on my ancient Oehler are occasionally fooled by sub-sonic rounds, the sound wave tripping the counter before the bullet does, giving the absurdly low readings you are experiencing. I'm guessing that is the issue rather than the powder.

Which brings up another variable...what is your distance to the chrony? IIRC you should be 15 or 16 feet from the sky screens. If you really need to know the velocity at the muzzle there is a program to determine that from your readings and distance to the chrony.

 

[Rule3]

Which brings up another variable...what is your distance to the chrony? IIRC you should be 15 or 16 feet from the sky screens. If you really need to know the velocity at the muzzle there is a program to determine that from your readings and distance to the chrony.

I set it at 5 feet.

USER'S MANUAL

 

[Treeman]

Too close. See note C under "Stop, before you fire that first shot" in the "getting started" section.

 

[Rule3]

Too close. See note C under "Stop, before you fire that first shot" in the "getting started" section.

Could very well be that. I was going by #8 before that. I did not consider the subsonic aspect. Actually the speed of sound is probably even faster here as I am shooting in 90% humidity so it's basically under water. Better use a Glock.

Thanks! I will move it back further

 

[MKT]

If your chrony has the remote display like mine does I don't measure per se. I step off 4 or 5 good paces, leaving the display on the bench. When the coax (actually a phone line I believe) starts to draw tight enough to lift off the ground I am far enough. A couple times a year I check the reading by shooting .22 lr over and comparing to the stated velocity.

The distance I set as outline above works good for everything I shoot...38/.357 mag, .41 mag,. 44 spcl and mag and .45 Colt. Have not yet run my high power rifles over the chrony but fully expect that my distance will work well with them too.

 

[sonny]

I have a Chrony Beta and I have had a dickens of a time getting reliable FPS readings. First I changed the battery, then I monkeyed with the screens and then Chrony tech support said I had to make sure the sun was in the right position. Finally put it away. Lots of times I would get readings that were half to a third of what I knew the velocity should have been. I seriously doubt there's a problem with your powder.

Sorry for your troble. My PACT has been great for many years. The start-stop screens are set at a standard distance, and electronics does the rest. I've been happy with mine.
Sonny