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temperature stable load ?

cjmac

Silver $$ Contributor
So what's the easiest or (best way) to find the most temperature stable load ? It's for a 223 rem . I'll be trying 77 grain sierra matchkings . In a 1 in 7 twist . I'm trying to find the load that I can use most or all year to get at least 1/2 moa . Our local range only goes out to 200yards
 
So what's the easiest or (best way) to find the most temperature stable load ? It's for a 223 rem . I'll be trying 77 grain sierra matchkings . In a 1 in 7 twist . I'm trying to find the load that I can use most or all year to get at least 1/2 moa . Our local range only goes out to 200yards

I think it makes most sense to use a Hodgdon Extreme powder. A survey of the top 100 placing Precision Rifle Series shooters found all but 5 used Hodgdon Extreme powder. IMR has come out with the Enduron series of powder which are claimed to be less temperature sensitive, but the testing I have seen does not indicate they have caught up to the Hodgdon Extreme powders.

Within the Extreme powder line you have a choice of Benchmark, H322, H4895, and Varget, in order from fastest to slowest. Surprisingly with the 77 grain according to Hodgdon, Benchmark, the fastest of the bunch produces the most velocity, with Varget second, H4896 third, and H322 last. Generally the slowest powder with a full case that gives you the velocity you want, tends to shoot the best. Kind of suggests Varget, if the velocity is OK... Sierra found Varget to be the most accurate.
 
FWIW, all Hodgen Extreme powders are manufactured by Thales ADI. IMR 8208 is also ADI, called Benchmark 8208. As for Sierra, they haven't updated the manual in 13 years!
 
As far as finding the (stable) load for good year around use what would be best approach for this ?
 
The best approach is to test it yourself.

When i find an accurate load i test it year around in different temp over the chrony. Ive found that most hogdon extreame powders vary 1fps per tempature degree.

There is no perfectly stable powder imo..
 
I would suggest using Dan Newberry's OCW method, especially if you are working with the 100-200 yd range.

http://optimalchargeweight.embarqspace.com/
Also go to
http://practicalrifler.fr.yuku.com/

I haven't worked with 4166 but those that have found it to be very close to Varget in terms temperature sensitivity.
The optimal charge weight site is very interesting. The Brits used to espouse the theory of "compensating whip" where a light-barreled rifle would vibrate in such a way that it would compensate for variations of muzzle velocity. This makes more sense to me.
 
As far as finding the (stable) load for good year around use what would be best approach for this ?

Here is a solid basic approach based on the true Ladder Test method. For clarity I like to use a computer scatter graph to plot vertical POI vs velocity. But, in the example the blog author used, it is pretty obvious without a graph.

The only slight issue I have with this blog is that the author does not include seating depths with a jump. He is focused on a jam, which I also find works well. But, it depends on your gun and bullet. Load development should always include both jump and jam seating depths to see what works best. And the issue not to forget with a jam load, is that depending on your neck tension the bullet may stay in the barrel if you try to extract a loaded cartridge. For some purposes that is not an acceptable risk.
 
So what's the easiest or (best way) to find the most temperature stable load ? It's for a 223 rem . I'll be trying 77 grain sierra matchkings . In a 1 in 7 twist . I'm trying to find the load that I can use most or all year to get at least 1/2 moa . Our local range only goes out to 200yards

Specific to your question, look for Hodgdon extreme powder as per RonAKA suggestion, find your accuracy node and evaluate MV variation (since you only have 200 yard range) over significant temperature i.e. 50-60 degree F and see which one gives you a consistent least MV variation. Keep in mind that the difference is not likely going to be significant between the better powders and so to get meaningful numbers, you are going to need a quality chronograph because one of the cheap ones will have enough noise in their data to make the test meaningless. I would recommend a LabRadar.
 
Put some rounds in a freezer then shoot them. Then lay some on the dash of your truck and shoot them.
exactly what Fred said, my POI changed enough to miss crows at 300 with ball powder, so i started using varget, dont know about 8208?
 
Put some rounds in a freezer then shoot them. Then lay some on the dash of your truck and shoot them.
Just keep in mind that if you put rounds in the freezer and take them outside to shoot on a warm and humid day, you are going to get condensations on the outside of the case. That will be like shooting wet rounds which will give you potential pressure problems as the case will have a hard time gripping the chamber when fired.
 
There is a limit as to how much you can reduce the "temperature sensitivity" of a load. It's not just the ambient temperature effect on the loaded rounds, it's also the temperature of the barrel/chamber. Brass is a very good conductor and even chilled rounds will warm up very quickly in a warm chamber. Further, a significant amount of the powder burn will take place within the barrel. A hot barrel/chamber can also increase velocity via a temperature-dependent effect. To truly test the effects of temperature, the whole system needs to be equilibrated at some specific temperature, not just the loaded rounds.

If you're looking for some load that will show minimal velocity change over a 50-60 degree ambient temperature range, forget it, it won't happen with any powder ever made. If you're simply looking for a load you can shoot a fair bit of the year with good precision, I would optimize it such that you're not going over pressure during the warmer months, let's say an upper limit of 85-95 degrees. In this case, when the temperature drops you're not going to have to worry about blown primers and/or other pressure issues. This will not be true if optimizing a load for colder average temps, so I'd rather not have to worry about over pressure issues...much better to err on the side of caution. With a load optimized for the warmer months, you might experience some drop off in precision when the temp dips 20-30 degrees (or more), but it shouldn't be huge.

If you really want to optimize a load to normalize temperature effects during the season, you need to record good temperature/velocity data over a range of different temperatures for specific charge weights with a given Lot of powder. A program such as Quickload will give you temperature-specific velocity predictions, but how accurate they will be for your specific setup can only be determined by empirical testing. Once you have some idea of a) how much velocity change you observe per degree F; and b) how much velocity change you observe per 0.1 gr charge weight, you can make some fairly good estimates of how much you need to adjust your charge weight to keep velocity within a certain window, provided you're not rapid firing and heating the barrel up dramatically during a string of fire. It's really not that difficult to make minor changes in charge weight during the course of the seasons, I do it regularly. I don't worry about seating depth for this approach, just minor changes in charge weight. But you have to have solid velocity data as the basis for making the correct changes. For your specific purpose, Varget or H4895 might be good choices; both are fairly resistant to temperature-dependent change in burn rate as compared to some other powder choices. However, even these two will show temp-dependent effects; i.e they're not totally resistant, which is why adjustment of charge weight is the easiest approach.
 
What range of temperature are you talking about ? What gstaylorg had to say is good advice. I live out west where it gets HOT but not very cold(you can still wear shorts most of the winter). It seems when you get above ~84F the velocity increase is not so linear and can get over pressure pretty quick. I have a couple hunting loads that I can't shoot in the summer 90F+ when pig hunting is good. When I get time I will rework them.
 

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