Chrony accuracy in the snow . . .

[longwinters]

It was up to the high 40's today so I took my new chrony out to test some loads.  One of the loads I tried out of my 280 was 57 gns of H-4831 (temperature insensative) with a 140 gn Nosler accubond.  This has been a very accurate load for me and from what I have read and deciphered from several reloading manuals should have given me close to 3000fps.  I set the chrony up about 10ft from my muzzle and shot about 8 shots.  The velocities averaged between 2730 and 2757.  Ok, so I know my loads are pretty consistent but those velocities  :eek: .  My question is, would a bluebird sky and snow covered ground effect the chrony's reads?  Or maybe the load really does shoot that fps.  Velocity typically is not that important to me but I am working up loads for Wyoming antelope next year.

Long

[ricciardelli]

The first rule drilled into any new pilot's brains is, "Always trust your instruments!"

I suggest the same...

[longwinters]

I was taught that about using a compass.  But now I live in an area with iron ore deposits and learned that you cannot always trust the compass, so I also use a GPS. But your point is well taken.

 I just did a search on the internet about chrony problems.  Seems that a common problem with correct readings is clear sunny days and snow cover. But I understand that just because the chrony does not give me readings that I might expect does not mean that the chrony is off.  So for now I will "trust my instrument".  However,  when the snow melts I will try again  

Long

[ricciardelli]

Just remember that when the snow melts, it will probably be about 50 degrees warmer...

[Jerry Lester]

Considering that most load data in the books is worked up in test barrels(nearly always higher velocities), and at room temperature or higher, I'd say your chrono is likely spot on the money.

Most times if your chrono is reading wrong, it'll be doing it erratically. If it's not right, you'll usually get all sorts of readings, instead of fairly close ones like you're getting.

[longwinters]

I realize that there can be several reasons why velocities might differ . . . but thought with using "temperature insensative" powder the results would be alot closer between published velocities and the real world.  Now this whole thing is starting to bug me  :?

Long

[jhalcott]

long,my Hornady book(3rd edition) shows 57.9 gr /H4831 getting 2900 fps from a 22" barrel with a 139 gr bullet.Considering the temperature ,this could be your problem. How close to other published loads does your gun track? Some guns are "fast" and some are slow. Try some other loads and see how well they compare to the "BOOK" speeds.
  Oh and just so you know a 2700 fps 139 gr ,7mm bullet WILL kill an Antelope at 350 yards! The trajectory difference is only about 2-3 inches if zeroed at 200 yards,for a 2700 and 3000 fps load. I'd check the load in the kind of heat I expect to hunt with before I up the powder charge.  I did have a can of powder that was close to 150 fps slower than the previous can of same brand/type some years ago . Factory response was "different lots CAN give slightly different results.ALWAYS work up when using a different lot of powder!"

[Questor]

First, I think 10 feet may be too close. I get quite a bit of blast from cartridges of that power and I like to be more like 15 feet away. So try again but farther away.  PACT warns that a shock wave can affect results if the chronograph is too close.

The times my chronograph had problems to related to the environment the results were way, way off. Like 3500fps for a 45ACP.  The problems were not because of the sky, but because of the low angle of the sun during winter.  

As for trusting instruments, I don't trust my chronograph much because it does rely on the quality of ambient light to work properly.  

I think your velocities are accurate because they're plausible. Just try shooting from farther away to see if there's a difference.

My experience with the Nosler data has been that their published velocities are always quite a bit higher than what I actually get in my guns. For example, they say that the load I'm using for .270 Win 130 grain Ballistic tip should be about 3150fps, but I get just over 3000fps.  Likewise for .223 and 6.5 loads.

[Mac11700]

It was up to the high 40's today so I took my new chrony out to test some loads.  One of the loads I tried out of my 280 was 57 gns of H-4831 (temperature insensative) with a 140 gn Nosler accubond.  This has been a very accurate load for me and from what I have read and deciphered from several reloading manuals should have given me close to 3000fps.  I set the chrony up about 10ft from my muzzle and shot about 8 shots.  The velocities averaged between 2730 and 2757.  Ok, so I know my loads are pretty consistent but those velocities  :eek: .  My question is, would a bluebird sky and snow covered ground effect the chrony's reads?  Or maybe the load really does shoot that fps.  Velocity typically is not that important to me but I am working up loads for Wyoming antelope next year.

Long

Longwinters:

I don't think anything is wrong with your chrony...but perhaps your interpitation of your loading data.....Noslers 5th edition...doesn't list using H-4831 or the newer accubond bullet but does list  their other 140 grainers...and the list with IMR-4831.not  H-4831..they show a  max charge of 56.0grains of IMR-4831 at 3070fps..and the 2 additional powders they show clocking @3000fps or better is RL-19 at 57 grains...3152fps....and W760 @52 grains at 3056fps....checking further in my Hodgdons annual manual(latest edition)...they show the range of H-4831 for the Nosler 140 grain partition as ...54.0 grains...2732fps.up to...58.5grains...2927fps....the Nosler data uses Remington cases and Federal 210 primers...and the Hodgdons uses Remington cases and Remington 9-1/2 primers.....and I've always found Noslers and Hodgdons data to be pretty much on the money when using the exact components and data..where you run into problems is when you start trying to exstrapolate data and switching one component for another...you results can vary greatly.....I have the Beta Master Chrony...and set up 15' away from the muzzel...and super bright days will play havock with your readings with them...especially if you are using the sky screens on these type days...


Mac

[longwinters]

I appreciate the advice.  I did realize that nosler's data (powder, bullet and barrel length 26") is different than mine 22 7/8".  They say on their website that the Accubond can be used with any of their same weight bullets but do not note any velocity changes.  They rarely site H-4831 as one of their powders for anything.  Usually go with the IMR 4831.  I asked them about that, on their website,  but never got an answer  :? .But I did look at other reloading sites as well as Hodgons reloading guide and a couple of other manuals.  Obviously my extrapolation skills need some work :lol:

Thanks again for a lot of good advice.  I am definitely listening.

Long

[Seedsntrees]

Long,

I think your results sound about right. Try putting a tarp beneath the Chrony if you question the output.

I would say the Chrony is reading correctly.

[tony212]

Two things I can share with you:
            1. I have never been able to match reloading manual speeds Sometimes I come close, but I never match them.  
            2. My chrony reads 100- 150 FPS slower on bright sunny days than on overcast days.  I have actually tried the same loads on both sunny and cloudy days and noticed this difference.
Hope this helps;
Tony212

[longwinters]

:lol:  :lol: I think I would have been happier just seeing my bullets shoot MOA and not have been curious about velocities.  I should just have lived with my illusion of higher velocity and not worried about the real world tests.  :lol:

Long

[Racepres]

But... a chrony is a very good way to assure yourself that you are not "on the edge" pressure-wise. If you showed More velocity, then I would be suspect in regards to pressure in your particular firearm.. IMHO.... Marty

[longwinters]

Well, I went and shot thru the Chrony today.  Temp in the low 60's with slight variable breeze.  This was out of my 280 with a 22 7/8" barrel. Tried a warmer load of 58gns  H4831 with 140 gn Accubonds.  Average FPS was 2800.  Shot the same thing with 57gns of H4831 with average FPS of 2750.  So it looks like the snow had no effect on the readings of the Chrony.  Granted it was a clear day with the sun at an angle (since it was still morning).  I just gotta wonder how some of the reloading books and writers like Forker and Barsness can get/quote over 3000fps with a 24" barrel.

Long

[Chainsaw]

Hey Long, I think it is all in the rifles chamber and barrel. All that I currently have left to whitetail hunt with are two 30-30 single shots, one being a pre-bancruptcy (1984) H&R and a newer NEF Handi-rifle. To get the same velocity in both rifles, one needs 3 grains more of the same identical powder while still using the same cases, primers, and seating the same make and weight of bullet for optimum results. Each rifle that I ever owned was a story in itself.

I have not had anything close to the Barnes data that is printed in their loading manuals, but they are just a reference to me. Fact is my scale may not be in correct adjustment all the time (even though it is close) and my 50 grains may be their 51 grains. If I work up a load for a rifle I am somewhat reluctant to reference it as your scale or rifle along with your particular lot of powder, primer and case maybe slightly different. As for my Chrony, mine may read somewhat different than yours. Good luck with your further testing. All we seem to actually know is that we always don't know..............Chainsaw