Bump up charge weight for winter loads

[SPAK]

Just curious if anyone bumps up their charge weight for their loads in the winter. I'm using RL 22 which is pretty temp sensitive. I can bump the charge weight .3 gr and get back into the velocity and accuracy window. Just wondering if anyone else does the same.

I know the better solution would be to find a powder more temp stable, but I'm also wondering how much of the velocity loss is a factor of the powder burn characteristics vs the muzzle velocity loss as a factor of the air temperature's effect on the bullet.

 

[Tripwire]

Re: Bump up charge weight for winter loads

Isn't one of my main concerns.....

 

[Victor N TN]

Re: Bump up charge weight for winter loads

That's why I make note on the weather and conditions when I'm shooting. Especially across a chronograph. Make notes at different temps and loads and use the notes...

Good luck.

 

[SPAK]

Re: Bump up charge weight for winter loads

thanks Victor. I noticed that I started to get slight vertical stringing when I started shooting close to 0 degrees and below. This is with a load developed at 60-65 deg F. Velocity dropped about 70fps or so. If I bump up my charge a small .3gr I get back into the velocity at which I developed the load at originally and the accuracy returns.

obviously I wouldn't shoot the winter load when it gets warmer. just interesting, makes me wonder if I properly identified my optimal charge weight or not. Or maybe it's just that the temp sensitive RL 22 rears it's ugly head again.

 

[Victor N TN]

Re: Bump up charge weight for winter loads

My HUNTING loads are loaded either with Nosler Partitions or Barnes X bullets. All the loads for them are worked up below 50*F. Usually if I'm hunting it's between 40 and 20*F If it gets much colder my old bones start to request me to stay in where it's warmer. I'm not as young as I once was.

I believe that if you bump up the load and make a note on the box for cooler weather, you'll probably be fine.

 

[Tripwire]

Re: Bump up charge weight for winter loads

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body"> just interesting, makes me wonder if I properly identified my optimal charge weight or not.</div></div>

Usually, IME, a proper OCW will negate enough "temp sensitive" stuff to the point that I don't buy into the arguement that some powders are sensitive to the point that I need to worry it. The whole purpose of OCW is to work out a consecutive range of powder weights that work; this by default also equals a consecutive range of operating pressures that work. If you are in the middle of that range, the +/- margin is large enough in most seasonal change situations. Here, we can easily have a temp swing of 90 or more degrees between August and December. Nothing I've done after a proper OCW leads me to believe I have to adjust charges for warm or cold weather.

But I'm not a bench rest shooter either, so......

 

[SPAK]

Re: Bump up charge weight for winter loads

I agree that a proper OCW should buffer the changes in temperature. But I wonder to what degree??? I have found very few shooters who claim RL 22 as NON temp sensitive, but many shooters with experience that say that it IS temp sensitive. The load I worked up in 60-65 deg weather, I can shoot .2 grains +/- sub .5 MOA. Temperatures in the 40's -80's I haven't seen a whole lot of difference. However, since the weather has changed to sub zero, velocity has dropped and some vertical stringing has been induced. Bumping my charge a few tenths returns my previously accuracy.

If the burn characteristics of a particular powder do change enough with temperature, then I can't imagine that same consecutive powder charges are producing the same amounts of pressure when the load was originally developed at said temperature.

I'm not a powder specialist so I can't say for sure what happens to different powders with temperature extremes. But I can only go by what my targets show. It's not really enough for me to cry about except I still like to shoot long range in the winter as cold as it is

 

[kombayotch]

Re: Bump up charge weight for winter loads

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body">I agree that a proper OCW should buffer the changes in temperature. But I wonder to what degree???</div></div>

You are correct in assuming that OCW will only counter to a certain degree. It is not a substitute for temperature insensitivity.

With testing, you can derive the relationship between charge weight and velocity for a fixed temperature (usually done when working up a load). By running a temperature test (3 points), you can derive the relationship between change in temperature and change in velocity for a given charge weight.

If you know how much you can deviate your charge weight from your OCW before it goes off of the node, you can correlate that back to temperature change using velocity.

 

[Fred_C_Dobbs]

Re: Bump up charge weight for winter loads

This is another reason I tend to always shoot over a chrono (if I'm not hunting). Over time, I've built up a very valuable database on bullets and powders and weather.

My .204 Ruger varmint loads (RL-10x) vary more than 100 fps from winter to summer. The load was worked up in winter (I use OBT to select my starting OCW charge weight) and the groups definitely blossom when temps are high. To make matter worse, that rifle shoots 0.25 MOA on a typical (low wind) day so even a minor disturbance is very noticeable. So I download by a few tenths for summer shooting. I should probably look into switching to 8208 XBR ...or maybe Benchmark, but I don't do a lot of whistle pig hunting when it's hot as blazes anyway.

I don't shoot such a temperature-sensitive powder in anything else, and nothing else I have groups so tightly, so that's my only rifle that gets such special treatment.

 

[Tripwire]

Re: Bump up charge weight for winter loads

Are we fretting over a little bit of "group size", or completely blowing a shot?

Wonder if they do a Summer Blend with Gold Match......

In the real world, the wind will fuck you worse than any minute difference in pressure due to amibient temps.

Of course, this wise ass wisdom comes from a thing hitter....not a group shooter.

 

[rweaver00geo]

Re: Bump up charge weight for winter loads

what about changing your primer? ive been told by an old timer to go from a standard to a magnum primer for winter loads? ive never tried it though.

 

[SPAK]

Re: Bump up charge weight for winter loads

It's not the group size, it's the vertical dispersion. I absolutely agree with the wind being a greater factor. But it's even more difficult if I have to deal with vertical dispersion at distance. Combine that with muzzle velocity variance then in my opinion it could mean blowing a shot. If I can keep the vertcial stringing to a minimum then at least that's a little less that I have to worry about.

I don't know what powder they use in FGMM ammo but it's probably something thats a bit more stable than the Alliant RL series. Unfortunately, right now the load combination that I've chosen uses such a powder.

As far as primers go, if I change to magnum primers the safer thing to do would be to rework the load completely as I'm on the upper end of the charge. I've seen magnum primers make as much as 1 grains worth of powder charge difference in velocity.

 

[coldboremiracle]

Re: Bump up charge weight for winter loads

I was gonna come in here tonight and ask this very same question, I just finished loading a box of .223's with 75 Amax's and 24 gr of RL-15. My single feed accuracy load for my RRA/LAR 15 with a 20" 8 twist and I shoot it with my can on it too. I'm just wondering if I may have to back these loads off a bit before the summer heat gets here. I also have just a little conscern about the op pressure when using the can, it works just fine but with the heat of the summer I dont know how much increase to expect.

So I guess my question is, for anyone who may know, How much does one need to back off?

 

[SPAK]

Re: Bump up charge weight for winter loads

Personally, I would work up the load with the can on and find out where your rifles usable max is with that combination of components. Once you start seeing pressure signs, I would back it down a grain or so and consider that my usable max load. Whether or not you choose to load there is up to you depending on how the accuracy is.

Once the summer comes, I would back it down 10% from where your found your max load in the colder temps and work back up slowly to find your max load in the summer. This way you know how much room for error you have on the upper end of the charges.

Shooting with my can, I hit pressure signs earlier than without the can on.

 

[coldboremiracle]

Re: Bump up charge weight for winter loads

Yes, frog, that is my plan (since I got the can I haven't shot anything without it

) The load as it is now doesn't show any signs of pressure, so i think it will be fine. I'm just wondering if there is some kind of formula or something that can help a guy figure out how much he needs to back off but maintain the same velocity/accuracy. I fear that the formula is simply test test and more testing year round until you figure it out.

 

[Fred_C_Dobbs]

Re: Bump up charge weight for winter loads

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: coldboremiracle</div><div class="ubbcode-body">...I'm just wondering if there is some kind of formula or something that can help a guy figure out how much he needs to back off but maintain the same velocity/accuracy. I fear that the formula is simply test test and more testing year round until you figure it out. </div></div>
QuickLoad software can do it but my guess is that there's too many variables involved -- QL has eight variables just related to the properties of the powder itself -- to do it in a simple formula.

Even QL has to be tweaked to match the particulars of your rifle and cartridge before its predictions are meaningful.

 

[jbailey]

Re: Bump up charge weight for winter loads

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: coldboremiracle</div><div class="ubbcode-body">I was gonna come in here tonight and ask this very same question, I just finished loading a box of .223's with 75 Amax's and 24 gr of RL-15. </div></div>

24.0 gr of RL-15 + 75gr AMax is not a particularly hot load for 223Rem. I would think you are fine from a pressure standpoint and probably pretty consistently accurate too. I have loaded up to 24.5gr of RL-15 and the 80gr AMax jammed a little bit into the lands with no pressure signs in 90+ degrees.

Of course, always practice safe loading and work up to loads

 

[coldboremiracle]

Re: Bump up charge weight for winter loads

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JamesBailey</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: coldboremiracle</div><div class="ubbcode-body">I was gonna come in here tonight and ask this very same question, I just finished loading a box of .223's with 75 Amax's and 24 gr of RL-15. </div></div>

24.0 gr of RL-15 + 75gr AMax is not a particularly hot load for 223Rem. I would think you are fine from a pressure standpoint and probably pretty consistently accurate too. I have loaded up to 24.5gr of RL-15 and the 80gr AMax jammed a little bit into the lands with no pressure signs in 90+ degrees.


</div></div>

Yeah, thats kinda why I plan on staying where I'm at, I do shoot 24.5 with the same pill in my boltgun though. On that one its starting to get a little close.