Grouo size and weather change

[cjmac]

Sooo, went to the range sat. Had a great load i made back when it was about 70 or 75 deg out. Was getting groups less than half inch .And when i went saturday it was 50 deg out .. my group was ALL over the place. Like one and half inch.. same primers , same everything .... WTF ? The powder is benchmark and im shooting a 223

 

[Greyfox]

Wind flags? The tune will change about every 5º. If you had a lot of vertical you might blame it on that.

Rick

 

[Tim Singleton]

It's hard to find a load to shoot the same day in and day out.
You know what it doesn't like in that condition now.
I've shot great one day and think my barrel is bent the very next day starting with the same load.

 

[jlow]

This is the reason when you run an OCW for load development and you find that cluster of loads that all have similar POI you choose the center one so that when temps change, you are not sliding out of your accuracy node. On that topic, I have always found .223 to have narrow accuracy nodes because of the relatively thin barrels, so not a big surprise…

 

[LHSmith]

There-in lies the reason Benchrest is so challenging......it is extremely rare to win with simply quartering the mothball or X and just pulling the trigger. You have to learn to make adjustments to compensate for mother natures effect on bullet flight.

 

[cjmac]

How would i run a OCW test ? Or the easy i should say .. i load at home so im sure it will be a pain . Guess i could gear up for loading at the range

 

[cjmac]

This is no thin barrel

 

[JamesnTN]

How would i run a OCW test ? Or the easy i should say .. i load at home so im sure it will be a pain . Guess i could gear up for loading at the range

Load up several charges in .2 grain increments and go to the range on a nice calm day.

Also I've found in most cases for every 15* in drop you can add .1 grain of powder.

 

[LHSmith]

How would i run a OCW test ? Or the easy i should say .. i load at home so im sure it will be a pain . Guess i could gear up for loading at the range

FWIW.....most shortrange BR competitors load at the range....those that use a powder measure monitor the temp (and humidity depending on type of powder) and adjust to maintain the same weight ....Powder is typically denser in the AM.
Beware of "nice calm days" ....any mirage (which most people can't read without high magnification) will render the testing meaningless.
There is a reason the best BR targets are shot when fired in ONE condition preferably a steady head, tail or true crosswind......you can see what the wind is doing......not so much in "calm" . Always test over flags (simple survey tape is fine), or, as someone on here recently said 'you are just plinking" getting no useful target feedback.

 

[LHSmith]

Also, did you reload that brass that shot well? If so, check your sizing die adjustment.

 

[savagedasher]

That is a common problem ! That is the reason I have tuners on all my guns.
Larry

 

[Travelor]

Get a chronograph and load the cold temperature rounds to the same velocity you had in the warmer temperatures. This should solve your problem.

 

[Cold Bore]

How would i run a OCW test ? Or the easy i should say .. i load at home so im sure it will be a pain . Guess i could gear up for loading at the range

Load up several charges in .2 grain increments and go to the range on a nice calm day.

When doing load development, I load small batches and toss them in Ziploc baggies with a slip of paper that has the load data written on it.

Easy to toss half a dozen or so little baggies in the range bag and head out.

It eliminates the possibility of confusion, and takes up much less space than an equal number of boxes.

 

[jlow]

How would i run a OCW test ? Or the easy i should say .. i load at home so im sure it will be a pain . Guess i could gear up for loading at the range

If you want to learn OCW, you've come to the right place. Go to Eric's thread here and read it:

http://forum.accurateshooter.com/index.php?topic=3814361.0

"thin" barrel is all relative. Even regular non-pencil barrels on ARs are thin unless you got one of those heavy barrels.

 

[Brians356]

There's the effect on exterior ballistics (bullet flight) of colder air, and the effect on interior ballistics of colder rounds.

WRT the latter: Some newer powders are supposed to be temperature insensitive - Hodgdon Extreme and IMR Enduron. Is there a general consensus forming on whether they really are insensitive? Are the popular accuracy powders in BR still the old standbys?

FWIW when I go out to shoot groups on a cold day, I stage groups in shirt pockets, under my outer coat, and let them come up to body temperature before shooting. I chamber and shoot the first 3- or 5-shot group out of one pocket, then put the 3rd group in that pocket before switching to the 2nd group in the other pocket. Alternating this way between two pockets, I'm always shooting groups which have come up to body temperature. I'm never chambering rounds which are at outdoor temperature. And, after a few sighters, the chamber will be warm as well (an ice cold chamber will suck heat out of the chambered round quickly.)

 

[Dusty Stevens]

Didnt barney keep his bullet in his shirt pocket too? Maybe he was smarter than andy gave him credit for

 

[cjmac]

I just realized that ot was NOT the same brass .... i made the load in lake city match brass , and shot it in hornady match brass . Man, cant believe that I didn't even think about that

 

[cjmac]

Might try that load again with LC match brass