AMMO SPEED CHANGES WITH THIS WEATHER

[dusterdave173]

A while back during the blister part of the summer I was having a hard time while shooting 50 yard ARA
All of my Lapua no matter the speed on the box was running around 1090 --this was with high 90 degree and very high humidity --as high as 98% humidity that we experience here in the South--I could not care less what speed it was running except it was all shooting like crap--It made the summer months very hard .

OK so we have had a few week break--things have cooled off a lot--I have a match coming up this Sat--so I pulled out my three best lots of Center X--68 degrees and 57% humidity Testing this morning all three lots were avg 1050-1060 fps--all 3 lots were back to hammering again--they had been hard to control in the blistering heat and high humidity. I got my ammo "back"
What tested as good lots is now shooting great again--

I am making no claims --I am just watching, observing, and working to learn. Now...will this ammo shoot good in the cold? We have our winter indoor series about to start--I will just have to see. This all makes me wonder about testing--do you need to go several times a year to keep some ammo in tune with the season? Ammo I would have sold cheap this summer is now hammering again so...the next "bad shooting" lots I get I will keep instead of selling in hopes I can find a 'season" it likes.

Makes me wonder about all the discussion about ammo your rifle likes--
I had been thinking great lots were great in several of my rifles--and bad lots were not good but now I wonder if I had just held on to those "bad " lots would they have come around sooner or later?

Just a rookie thinking things over .........I am just reporting what I am seeing with my trusty CZ MTR Factory class

I have not forgot about the rough patch I had at the first of the season--I had it all blamed on barrel cleaning --i got so far in the weeds it was almost funny--I did figure it out and get things rocking through the middle of the season. I have had a very good season and have made a lot of progress --During the season I have seen top shooters falter at a match or two--then rebound a win , win , win, the falter and blow a couple--
It seems to happen to almost every shooter at some point in the year

Rimfire ARA has been a sobering challenge--but that sure makes any success Feel Good!! Ok...Off to the last of the outdoor and get set for the winter indoor.

 

[Williwaw]

IMO and I look forward to see if others agree...

The actual ammo temp is of greater importance than ambient air temp or humidity and it is in our control. Cool your ammo on hot days and warm it up when it is cooler.

Also note that your summer extremes can give rise to VERY tricky mirage conditions which can really derail your show and have you scratching your head. Persevere, if it was easy it wouldn't be as much fun or as rewarding.

 

[dusterdave173]

I appreciate the constructive ideas! Thanks!

 

[CharlieNC]

That is a major change in velocity, which also results in an associated change in barrel exit time. When doing load development in a centerfire, that degree of change is enough to move completely out of or into a node as associated with the muzzle vibration.

 

[dusterdave173]

That is a major change in velocity, which also results in an associated change in barrel exit time. When doing load development in a centerfire, that degree of change is enough to move completely out of or into a node as associated with the muzzle vibration.

That is what I have been thinking--In the tough hot part of the year I was 'tuning" by selecting ammo that was going slower---it seemed to help some.

 

[CharlieNC]

That is what I have been thinking--In the tough hot part of the year I was 'tuning" by selecting ammo that was going slower---it seemed to help some.

And when it is hot the density of the air is also less, in addition to the velocity itself. Centerfire benchrest shooters adjust the powder charge from morning to afternoon to stay in tune. In Fclass it is becoming more common the tweak the tuner based on the tuner. The same internal and external ballistics govern rimfire as well, but it may lag in the ability to be as effective at this time.

 

[WyleWD]

A while back during the blister part of the summer I was having a hard time while shooting 50 yard ARA
All of my Lapua no matter the speed on the box was running around 1090 --this was with high 90 degree and very high humidity --as high as 98% humidity that we experience here in the South--I could not care less what speed it was running except it was all shooting like crap--It made the summer months very hard .

OK so we have had a few week break--things have cooled off a lot--I have a match coming up this Sat--so I pulled out my three best lots of Center X--68 degrees and 57% humidity Testing this morning all three lots were avg 1050-1060 fps--all 3 lots were back to hammering again--they had been hard to control in the blistering heat and high humidity. I got my ammo "back"
What tested as good lots is now shooting great again--

I am making no claims --I am just watching, observing, and working to learn. Now...will this ammo shoot good in the cold? We have our winter indoor series about to start--I will just have to see. This all makes me wonder about testing--do you need to go several times a year to keep some ammo in tune with the season? Ammo I would have sold cheap this summer is now hammering again so...the next "bad shooting" lots I get I will keep instead of selling in hopes I can find a 'season" it likes.

Makes me wonder about all the discussion about ammo your rifle likes--
I had been thinking great lots were great in several of my rifles--and bad lots were not good but now I wonder if I had just held on to those "bad " lots would they have come around sooner or later?

Just a rookie thinking things over .........I am just reporting what I am seeing with my trusty CZ MTR Factory class

I have not forgot about the rough patch I had at the first of the season--I had it all blamed on barrel cleaning --i got so far in the weeds it was almost funny--I did figure it out and get things rocking through the middle of the season. I have had a very good season and have made a lot of progress --During the season I have seen top shooters falter at a match or two--then rebound a win , win , win, the falter and blow a couple--
It seems to happen to almost every shooter at some point in the year

Rimfire ARA has been a sobering challenge--but that sure makes any success Feel Good!! Ok...Off to the last of the outdoor and get set for the winter indoor.

Some very good reading in this thread: https://forum.accurateshooter.com/t...r-questions-discussion.4145299/#post-39150365

Don't worry too much and over think it. Bench set up, set your wind flags, shooter focus (bench manners) are things you can control. Focus on those items and it will help..... if the POI changes maybe a scope adjustment or hold off is all you (might) need. If possible get out and practice before the match. JME. WD

 

[Straightshooter1]

A while back during the blister part of the summer I was having a hard time while shooting 50 yard ARA
All of my Lapua no matter the speed on the box was running around 1090 --this was with high 90 degree and very high humidity --as high as 98% humidity that we experience here in the South--I could not care less what speed it was running except it was all shooting like crap--It made the summer months very hard .

OK so we have had a few week break--things have cooled off a lot--I have a match coming up this Sat--so I pulled out my three best lots of Center X--68 degrees and 57% humidity Testing this morning all three lots were avg 1050-1060 fps--all 3 lots were back to hammering again--they had been hard to control in the blistering heat and high humidity. I got my ammo "back"
What tested as good lots is now shooting great again--

I am making no claims --I am just watching, observing, and working to learn. Now...will this ammo shoot good in the cold? We have our winter indoor series about to start--I will just have to see. This all makes me wonder about testing--do you need to go several times a year to keep some ammo in tune with the season? Ammo I would have sold cheap this summer is now hammering again so...the next "bad shooting" lots I get I will keep instead of selling in hopes I can find a 'season" it likes.

Makes me wonder about all the discussion about ammo your rifle likes--
I had been thinking great lots were great in several of my rifles--and bad lots were not good but now I wonder if I had just held on to those "bad " lots would they have come around sooner or later?

Just a rookie thinking things over .........I am just reporting what I am seeing with my trusty CZ MTR Factory class

I have not forgot about the rough patch I had at the first of the season--I had it all blamed on barrel cleaning --i got so far in the weeds it was almost funny--I did figure it out and get things rocking through the middle of the season. I have had a very good season and have made a lot of progress --During the season I have seen top shooters falter at a match or two--then rebound a win , win , win, the falter and blow a couple--
It seems to happen to almost every shooter at some point in the year

Rimfire ARA has been a sobering challenge--but that sure makes any success Feel Good!! Ok...Off to the last of the outdoor and get set for the winter indoor.

Heat is what's going to effect your MV's as it effects how the powder burns and the viscosity of any lube on the bullets. Once the bullet exits the muzzle, then things like Density Altitude (having to do with humidity) has an effect down range.

 

[grauhanen]

Last season I shot the same lot of Midas in the mornings before the heat really had a chance to develop. When the temps were in the low 70s (F), the ammo was in the mid-1080 fps range.

When it was colder in late October in the low 30s (F), the same ammo with the same rifle had MVs in the mid-1050 to 1060 fps range.

With another rifle and another lot in similar temps the MV differences were very similar.

The ammo was kept at ambient temperature.

Accuracy performance was not affected by the differences in temperature for either lot or rifle.

 

[J.d. Popkes]

“this was with high 90 degree and very high humidity --as high as 98% humidity that we experience here in the South“


First of all, holy crap, are you seriously outdoors, away from your a/c in those conditions? Your ammo is telling you something. It’s trying to save your life. It’s saying “go to a walk in cooler!”

Ain’t no way! You sir are a gladiator.

 

[TRSR8]

IMO and I look forward to see if others agree...

The actual ammo temp is of greater importance than ambient air temp or humidity and it is in our control. Cool your ammo on hot days and warm it up when it is cooler.

Also note that your summer extremes can give rise to VERY tricky mirage conditions which can really derail your show and have you scratching your head. Persevere, if it was easy it wouldn't be as much fun or as rewarding.

From years of match shooting, IMO the only ammo temp consideration is never let it get overheated…..that is a death sentence.
I shoot with a handful of HOF shooters. Nobody cools their ammo. Miss./ Ga. In summer…..maybe.

 

[Hi-NV Shooter]

Maybe not so much weather changes but overall temperature. I shoot high 30"s to low 40's during winter and 100+ during the summer. during the summer ammo does get squirrely because burn rates are very erratic. wintertime slower burn rate so much more stable performance.

I do use tuners so it does help and what I see is mainly higher POI my tune is set for high POI anyway. I just hold lower during the summer if I need to.

Lee

 

[Frankr]

Well my experience is similar to the OP certain temp and humidity combined with wind conditions can make anything not shoot to well or what was shooting well now is not. I think sometimes you just don’t know what you need. I have been at center fire matches where in similar conditions to the OP. Nothing would shoot well. I came in from a relay and asked a super shoot winner, what do we do? His answer was he didn’t know, they were doing worse than I was. In Rimfire we were actually talking about this at recent match where a guy was telling a story how nobody, experts, top HOF shooter’s with their best ammo was shooting terrible. One guy was shooting some odd biathlon ammo and won the match. So yea IDK. Most of us it’s like a box of chocolates.