Need a new chrono. Thoughts on my thought process?
- Thread starter jb1023
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I would never purchase a chrono that hangs on the muzzle. It will disturb barrel vibrations and POI. So when removed and ready for hunting, you need to re-zero. The Oehler M-35 is the only way to go. Yeah, quality comes at a price.
RustyRick
Well-Known Member
Rogmay - be careful, you might be like the guy with 2 watches. He didn't know which one was right LOL
RustyRick
Well-Known Member
3339,3336,3362,3356,3326 ES36 SDVD15 AVG3344
I'm not a professional re-loader. But what's the matter with these numbers biggreen & phorwath?
I'm not a professional re-loader. But what's the matter with these numbers biggreen & phorwath?
Not bad for a 22LR... I presume you own a Shooting Chrony?
How do you know any of those velocities are correct, unless you have at least one additional means of bullet velocity verification. You're simply forced to believe (accept) or disbelieve (reject) the velocity data when using a single velocity measuring instrument. Especially if that instrument is a Shooting Chrony.
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I learned a lot about light sensing chronograph reliability after mounting an Oehler 35P, an Oehler 33, and a PACT PC*2 in triplicate. I receive four velocities for each bullet fired. I learned all three of my chronographs will periodically record a bad velocity. There is a slight difference in reliability in dim light conditions, and in precision as reflected in the magnitude of the value of the extreme spreads between the three chronographs over the long haul. At least I can identify the chronograph that records a faulty velocity (bad data) with this triplicate setup.
Each of the three chronographs fired on all cylinders for all 33 bullets fired yesterday, as demonstrated by the velocity comparisons between the three units (see two spreadsheets below). The largest deviation recorded by the triplicate chronographs for any shot fired was 4fps, which occurred on three separate shots. The three chronographs recorded a 3fps difference in velocity for two separate shots. Twenty three shots were recorded with a 2fps difference in velocity across the chronographs. Four shots were recorded with a 1fps difference in velocity across the chronographs. One shot was recorded with no difference - all three chronographs recorded the same velocity for this single shot.
If you mount some Shooting Chrony or SuperChrono units in duplicate or triplicate and receive velocity data with precision comparable to the following sets of chronographed data, then you'll have a solid basis to document the reliability, accuracy, and precision of those velocity measuring units. If you perform this type of comparison testing/experiment, please let us know how it goes...
Lefty7mmstw
Well-Known Member
You are actually getting better data than you think Phorwath... You should be experiencing a bit of velocity decay even in the short distance between chrono's, and you are getting that. There is a lot of turbulence in the first few feet after the muzzle, and you aren't looking at the exact same space with each chrono...
RustyRick
Well-Known Member
Yep you're bang on. That's why I deliberately didn't give the make of the chrony.
So your BIG problem is, as is mine, without a tool (not a gun) that spits out a projectile at a pre-determined programmable velocity we're frothing at the mouth when we stake our lives on any chrony results.
Statistically your efforts on the 4th need at least 3 more rounds reversing the order of units and a carefully laid out plan to mix them up in order.
So the real issue is how much am I going to budget for chronographs. You invested in 3 major units. I can't do that. I would like to test velocities down range. You might be a good enough shoot to shoot through your 3 units. I can't. And because of the massive variables like out door temperature, powder temperature, seating depth, etc, etc. The biggest factor is, How OCD (or anal) do you want to be.
4PS's I'd like to buy your 22LR that shoots at 3300 fps. from you. And it wasn't a SC. I see some of your data the speed increased on the third shot. Velocity does NOT tell you precision or accuracy of POI. Often slower means more accurate.
L ... but I know exactly what you mean, I worked with quite a few of them. You concept on my chronograph skyscreen setup, and the center spacing locations for the skyscreens isn't correct. My skyscreens aren't mounted in series, one after another extending further downrange from the muzzle. The center point of all 3 sets of skyscreens are located within 6" of each other on the skyscreen rail. Velocity decay was largely removed from the setup, except over the distance of 6".
My skyscreen rail is 6'8" long. The Oehler 35P and Oehler 33 skyscreens are mounted with 6' separations. They couldn't both be mounted at the same exact location on the skyscreen rail, so they're mounted 6" apart at each end of the skyscreen rail. And of course the Proof channel on the Oehler 35P is set dead center on the skyscreen rail in order to obtain the 3.0' spacing from each of the two primary skyscreens for the 35P. The PACT PC*2 skyscreens are mounted with a 56" separation, with their center point matching the Proof skyscreen of the 35P.
I couldn't figure out how to control bullet turbulence or I would have done that too. But it doesn't seem to wreak havoc with my recorded velocities.
And I already knew you were using a SuperChrono, because you sent me a PM several months ago defending it. So I purposely cited a Shooting Chrony. Two can play this game.
If you're unable to conceptualize how four separate velocities recorded on each bullet fired fails to zero in on the true bullet velocity, no amount of froth from my mouth will help you.
You're frothing now. I already explained how your concern over the sequential spacing of the skyscreens is non-existent.
Only you can decide how you spend your money. I find a way to budget for the items I want, as do most other folks. Two of my chronographs were purchased used for a combined price of less than $135. The 35P did cost $540. On the other hand, the last rifle action I purchased cost $1,600, and the last scope I purchased cost $860. Now... the chronograph setup looks like a bargain.
