Accuracy and temperature

[Travelor]

I shot a cast bullet match yesterday with my 308 and pet loads that shot 3/4" groups at 100 yards in the early Spring. The load was 17 grains of 2400 with a NOE 311-175 FN bullet with the bullet seated .040" into the lands. The groups were embarrassingly large.

What is the consensus as to accuracy when temperatures rise?

Do you increase or decrease your load?
Do you change your lube?
?????????????????????

[44man]

I would work one at a time. Lube that gets slippery can do it as well as powder burn changes.
4227's gave me huge changes just with gun heat in the .44 mag. Even in winter as the gun warmed.

[dudel]

If you think temperature is an issue, some powders are more tolerant of temperature change. I use Varget for .223. One of Extreme series from Hodgdon.

http://www.hodgdon.com/extreme.html

However, to avoid chasing your tail, change one thing at a time to minimize variables.

[Wayne Smith]

Ditto. For example, do not change powder and lube at the same time. You may have success, but you have no idea what caused the success.

[Doc Highwall]

How many rounds were fired through the gun when you made up the load of 17 grains that shot great? Did you clean the gun after or has it been cleaned, and what was the bore condition yesterday for the match. Were you nervous or too excited shooting the match?

I just started a round count log book for my Remington 40X chambered in 7.62 NATO using 2400 powder and Lars 2700 lube just to keep track of the rounds shot between cleanings.

[Travelor]

OK, I'll take your suggestions/questions one at a time:

1. I always change only one variable at a time.

2. I have been shooting competitively for 40+ years so no not excited or nervous". I hold High Master classifications in Mid and long range center fire. I was shooting with friends so not even any strangers there.

3. The barrel was cleaned the same way as always before the match. It had exactly 367 rounds fired with the new Krieger .300"-.308" barrel before the match and has never had jacketed bullets shot.

Lube is a red Alox lube that comes in red foil tubes if that helps any.

The only variable that changed from before was temperature. Wind was calm to 2 mph.

[oldcanadice]

and the question is how temp has affected known-good loads as it changed, not a lot of irrelevant stuff. Inquiring minds would like to know about actual experiences regarding the point.

[John Boy]

The groups were embarrassingly large.Whats the definition of 'large' and what did the POI look like on the target. Otherwise, no basis to determine your issue

[Doc Highwall]

A couple of more questions, were the bullets from the same casting session and mould ( I am assuming they are) How many firings are an the cases? Do you anneal your gas checks?

[Artful]

First thing I'd do is load the cooler and put a thermometer and my ammo in and test your theory.
But to answer your question - yes I have run into the problem you have stated.

And the reverse - worked up a great load one , Temp's in the 89-90's and then fall hunting season we had a cold snap and temps were below freezing and the great groups fell apart. And yes I changed lube and worked
up a different load and it was OK when the temp's climed with the new lube.

[243winxb]

Practice and match conditions, very different for most. Try the same loads at the same air temperature with no pressure on you. I know i always shot my best at practice.

[Doc Highwall]

If he holds a high master in long range I don't think he has a problem shooting matches vs practice.

With powders that are temperature sensitive hotter temps will make the powder burn faster more pressure, and colder will make them burn slower with less pressure.

The load that shot great at a colder temperature, did you chronograph it? Does the red alox lube melt at a low temperature, I don't know as I have not used it.

[Geezer in NH]

I shot a cast bullet match yesterday with my 308 and pet loads that shot 3/4" groups at 100 yards in the early Spring. The load was 17 grains of 2400 with a NOE 311-175 FN bullet with the bullet seated .040" into the lands. The groups were embarrassingly large.

What is the consensus as to accuracy when temperatures rise?

Do you increase or decrease your load?
Do you change your lube?
?????????????????????
Practice more??? Shoot good by yourself then crappy in match means more practice needed.

It is called chocking. Sorry not trying to be an AH but in many years of competition I have seen many long time competitors do it.

[country gent]

I have chronographed the same loads same lot powder same lot bullets same cases same lot primer all loaded in the same session both hot humid and higher baromettric pressures and cold dry and lower pressure at the same range. The side cock pellet gun gave very close readings checking the set ups but the ammo displayed higher extreme spreads and higher Standard deviation. Older powders were temp sensitive and could change enough to cause shifts. The old rule for High power shooters was 1 click down for every 10* up in temperature at 600 yds. This was normally with IMR or H 4895 and 168 matchkings or LC M 852. Pressures can move out of the sweet spot with temps atmospheric pressures

[country gent]

other things more shooter related, Did you increase water intake for the heat? Were you feeling up to par? And the big one here Does diabetes run in you family? This greatly affects eye sight. May be time for a trip to family Doc to get checked out. Its just another few things to think about. My MS was diagnosed after wife and I went to a high power match and I got in position to sight in and couldnt see the sights with right eye. Some times these things are trying to tell us something.

[Travelor]

I have never ********************** ********************************* ***************************** address the simple question please.

Doc Highwall and some few others have a good point and I appreciate the straight forward suggestions, thanks. I have not chronographed the load and to get a cold vs hot differential I will have to cool the ammo whihc I can do. As far as the Alox lube, I'll have to do the same to see.

The simple question was what have you done to affect accuracy changes with temperature changes.

[Toymaker]

Travelor, I've found the same issue, but my experience started with IMR 4198. Over the Fall and Winter I played with a beautiful load only to find it group like a shotgun during the Summer match season. I changed to Hodgdon and the issue went away. Since then I've had this happen again and again with IMR powders. Loads developed during cool weather don't shoot well in heat and visa versa. Now I avoid them when at all possible, mostly using Hodgdon. Yes, I know all about IMR and Hodgdon.
I have played with increasing and decreasing the powder up to 2 grains in 0.1 grain increments but couldn't get my pet load back until the environmental temperature got back. It got close, but not close enough.
I have not tried keeping the rounds chilled until needed. Interesting idea. Don't know why I didn't think of it. I once knew a guy who kept his 45/70 black powder rounds in a cooler. But that was because he had a cookie in the load chain that was made of Jello to keep the fouling moist.

[Travelor]

Toymaker, thanks.

Looks like I will need to change powders for the summer.

[44man]

I have never ********************** ********************************* ***************************** address the simple question please.

Doc Highwall and some few others have a good point and I appreciate the straight forward suggestions, thanks. I have not chronographed the load and to get a cold vs hot differential I will have to cool the ammo whihc I can do. As far as the Alox lube, I'll have to do the same to see.

The simple question was what have you done to affect accuracy changes with temperature changes.
You need to vent, I shot better under pressure, I know from years of competition, NEVER tell me I need practice. I hate that myself. Do you know most that dry fire all year lose it with powder in the case.

[Blackwater]

As noted above, if you're a High Master, I trust your results implicitly. I'm thinking it's got to be the powder or the lube. Here in Ga., we have very hot summers and awfully cold winters. It's the humidity here that makes our cold seem so much colder than it is. Cold moist air acts like a heat sink, and just draws any warmth out of you or your ammo. I've never really shot much cast in rifles in the past, but have noted differences in performance due to season in my handguns, so it seems logical it should be magnified in a rifle. More stress (pressure) should be expected to yield broader results in variables (accuracy). I'm betting a High Master will have it worked out soon!

[runfiverun]

I modify the lube.

there is a 200-300 page sticky in the lube section that will tell you why

[crackerjack57]

I am no where near the shooter you are but when loading rounds here in canada the usual temperature fluctuations between hunting trips can easily be 100 deg f. I load 4759 which is close to 2400 and depending on temperature I can load anywhere from 25.5-28 grains. Of powder. A half a grain difference can get me from 1.5" to easily 5 " group so I load a variety and depending on temperature and choose accordingly. I could probably choose a different powder but this really works well for me so don't want to mess with what works. Sorry, I forgot to mention..... this is in my 45-70. for me, temperature makes a difference.

[Travelor]

Went out Monday and did some testing. My old "go to" load of 17 grains of 2400 was shooting around 2" at 100 yards.

I tried reducing the load with no great success, then tried large pistol primers with 17 grains of 2400 and found success - groups were in the 1" range at 100 yards.

So no, it was not some of the other variables suggested, but rather a load adjustment in the hot weather we are experiencing.

[runfiverun]

hmmm I usually have to add more powder when I use a pistol primer.

your load tweak slowed things down enough to make up the difference for the less frictious [yeah I made that word up] lube which was letting things fly faster than the barrel node was tuned at.
pretty much the same thing many have to do when switching from copper to aluminum gas checks.

[Doc Highwall]

Travelor, in my Remington 40X chambered in 7.62 NATO I am testing Alliant 2400 powder with the SAECO #315 bullet, 175 grain TCGC which is what the NOE bullet is designed after. I am using Lapua Palma cases with the small primer pocket and Federal 205M primers with a O.A.L. of 2.800". With 17.0 grains of 2400 powder I am getting 1698 fps / 34.8 E.S., and with 19.5 grains I had 1862 fps. / 6.79 E.S. at 87 degrees.

I just loaded up 50 rounds at 19.5 grains, 20 at 2.800" O.A.L, 15 at 2.750" O.A.L, and 15 at 2.850" O.A.L..

I am waiting to shoot them as the last several days the wind has been too blustery, 10-15 mph. with gusts to 25 mph. today.

[Travelor]

Doc, let me know how they shoot. A good friend and extremely good shot is using the same bullet with 16 grains of 2400 and a large pistol primer with good success. I have a number of National Level cast bullet match equipment lists - if you will PM me with your email address I will forward them to you.

[Doc Highwall]

Travelor, PM sent.