Load Development

[Jud96]

I have been doing some load development on my .308 Norma with 215 Berger’s using RL26, Norma brass, and Federal 215s. This is a long range hunting rifle. I initially worked up in 0.2gr increments firing one round each at each charge weight until maxing out pressure. Then I went back and loaded ammo in a flat spot. It should have been in the 2950fps ballpark, but 5 shots averaged 2978 with an ES of 32. I understand this could be a scatter node, but why’s the velocity so much higher now? This was using the same lot of brass, powder, primers and bullets. All the brass was also 1x or 2x fired and it was all prepped and loaded the same. I’ll post pictures of my data working up to pressure and my shots I tested today. It also shot pretty well for no seating depth work or anything. I’m going to try the low and wide node at 2900 and see how it does next. I just wanted to see what you guys thought of this.

 

[rsmithsr50]

how are you weighing powder ?
are the bullets seated below the shoulder/neck junction ?
how is neck tension controlled.
I shoot 230s at 2912 or so with rl26 in a 300 win mag

 

[Clcustom1911]

I've found the same thing when shooting a velocity/pressure ladder to doing a load development. I did Reloder 26 in my 7mm RemMag with 168 Berger Hybrid Hunters. The pressure ladder indicated 68, 68.3, 68.6, 68.9 were 2960, 2968, 2964, 2967, respectively, no signs of excessive/unsafe pressures. I could have gone higher, but stopped at 68.9 because I dont like going higher than book max's especially if it's shooting as fast as I want it to and accuracy is there. I loaded 10 at 68.5 just to see where it was going to settle. It ended up being an average of 2995 with a SD of 8, ES of 25.

I didn't think much about it. The load shoots between 0.75 and 1 MOA and the velocity stats are to my liking (6.6 mil elevation at 1000 and supersonic past 1500).

 

[Jud96]

how are you weighing powder ?
are the bullets seated below the shoulder/neck junction ?
how is neck tension controlled.
I shoot 230s at 2912 or so with rl26 in a 300 win mag

I’m using a Bald Eagle digital scale. I’ve never had a problem in the past achieving single digit SDs and even ES with other rifles and cartridges. Bullets are seated just at or just below the neck shoulder junction. There’s not a donut in the necks. I control neck tension with a Redding FL die and then running a mandrel through the necks.

 

[Jud96]

Temperature when working up in powder was mid 50s and today it was low 70s. I could see 10fps difference in velocity, but this is 30fps. I just don’t know if this is just a bad node or what. I also had a couple ejector marks and previously I didn’t see any pressure until 71.8 and now I am seeing it at 71.4 grains. Everything was the same in my reloading and shooting. I used a Magnetospeed for all of my testing as well. So I’m just sure what’s up.

 

[INTJ]

I don't think that 30 FPS variation in velocity for a given load from one day to the next is abnormal. My 300 WSM LR BR rifle shooting Berger 215s with RL-23 gave me these velocity averages for five-shot groups on four different days, same load:

1. 2908 (ES 8) OAT 50 deg
2. 2894 (ES 10) OAT 44 deg
3. 2901 (ES 11) OAT 52 deg
4. 2920 (ES 11) OAT 60 deg

As you can see, there was a 26 fps change in velocity from the slowest to the fastest. I can promise you these rounds were loaded as identically as possible. Case shoulders were sized to within .001", bullets were seated to within .001", seating pressure was within 10 PSI, powder was weighed to the kernel, and primers were weight sorted and seated to within .001" of each other. The average group size of those four five-shot groups at 200 yds was under 5/8", so I consider this load pretty well tuned.

The slowest and fastest also corresponded to the highest and lowest temperatures, though the middle two velocities were reversed based on temp. Realize that it's propellant temp that determines the change in velocity, and propellant temp roughly corresponds to OAT. Even though RL-23 is considered temperature resistant it's not totally immune to temperature changes, and a tuned LR BR rifle is a good place to see that.

RL-26 is not advertised as being temperature resistant. http://bulletin.accurateshooter.com/2017/09/advanced-rl-23-and-rl-26-powders-for-magnum-cartridges/

Add to that you are in initial load development on a hunting rifle, a 30 FPS change from one day to the next is not surprising. That said, I think you have some more tuning to do on that load. While extreme spread isn't as critical as we once thought--positive compensation does seem to be a real thing, 32 FPS would bother me in a long range hunting rifle. I would like to see that under 20 FPS. The fact that you can normally get single digit ES tells me your loading practices are sound so you'll just have to keep at it.

It took me almost 400 rounds (which included a match) to get my 300 WSM LR BR load tuned. I am hoping to have my other LR BR rifle--a 6mm BRA--tuned in less than 300 rounds. I might get there by then............

 

[Bindi2]

72.0 to 72.8 is your node, it is wide and single digit ES.

 

[CharlieNC]

First of all I do not believe it is a valid approach to rely on velocity vs the target to identify a node. But anyway.... The ES of 32 based of five shots is actually higher if more were shot. The single shot at each charge weight has this type of variability as well; so how can you expect what shows up as a node is not just random noise, and you would get a different answer if you repeated the exercise? More shots per charge are needed to have any confidence in the answer. Interestingly single shot ladder testing on targets provides the desired results unless you are a terrible shot.

 

[Bindi2]

Velocity tells you when the barrel is happy. The wider the single digit increase the better with the projectile just off touch select a middle load this gives you wriggle room for elevation and temperature then dial in the tuner. You use far less rounds and have the info for going up or down in loads for elevation and temperature as needed. The chronny is a very important tool.

 

[Jud96]

Thank you all for the replies. The 32 ES is too high for me and I do like to keep it under 20 for 5 shots. The 72.0-72.8 node all has ejector marks so that’s why I’m not shooting it. I should have said that early on. It looks like my next best node is 70.2-70.8 and I have some rounds loaded at 70.4 that I’m going to test today.

I have used this approach to finding a node in the past, and this is the second time i have had similar issues. In the past I would shoot groups of 3 over the chronograph with each powder charge. This would give me a larger sample at each charge weight and show what charges had low ES. Even though 3 shots is small, if one charge has an ES of 20 and the next is an ES of 5, I can tell right there which one is more consistent. This approach just takes longer and takes more shots, but it has always worked. Now I’m stuck scratching my head. I’m not lost, I’m just wondering if this has happened to others. Like I said, my next step is to drop down a grain and be in a he middle of that low node. Hopefully that goes better haha

 

[INTJ]

I have never had much luck with the single round per load ladder that so many like to use. I use three-shot groups for a hunting rifle and five-shot groups for a competition rifle. I have been burned many times by using three shot groups when tuning a load for a competition rifle.

 

[Jud96]

The only thing that I question with shooting groups with each powder charge is what if your seating depth isn’t tuned. Or do you just pick what powder charge shoots the best, even if none of them are exceptional? Or do you pick the groups that shoot to the closest POI of each other like OCW?

 

[Beiruty]

Did you try to load 71.6gr?

 

[Jud96]

Did you try to load 71.6gr?

No I didn’t. I hit pressure at 71.8 and 71.8 broke out of the “node” so I didn’t want to shoot that close to pressure or get erratic results being at the upper end of the node. I believe this is a scatter node though and just isn’t going to work for me.

 

[Jud96]

I just got back from testing 70.4 grains. That was in the middle of the 2900 node I previously found. Well this has gotten more confusing. My average was 2942 with an ES of 29. I also shot 3 shots for group and it opened up. No clue what’s going on. Today’s weather is the same as it was when I did my load work up and found this node. I have 250+ shots on this barrel and it has about 40 shots on it since I cleaned it last. I’m really confused on what’s going on here. Again this is 2x fired brass and I’ve prepped it the same every time and all components are from the same lot.

 

[INTJ]

I would guess that it just doesn't like the load. The nodes haven't repeated, which happens to me all the time, and is why I like to have 3-4 groups shot on different days before settling on a load.

What kind of accuracy do you normally get from this barrel?

 

[Jud96]

Typically I get sub 1/2 MOA without issues. I’m thinking I might just have to try a different powder or something. I’ve had this same thing happen to me with my 284 when working up loads. Found what looked like a great node with RL26 and 180 ELDs but couldn’t get repetitive results with consistency or velocity. So I switched to 175 Elite Hunters and RL23 and it was pretty easy to find a solid node and get it shooting. Maybe this powder and bullet just isn’t going to work.

 

[CharlieNC]

Jud the next time you do your workup I would encourage you to shoot a target with the same shots, and see what it tells you. As I mentioned earlier I do not have any confidence relying on this chrono method, particularly because I cannot see any reason why it would reflect the harmonic vibration behavior of the barrel which leads to minimizing the effect of velocity variation on vertical.

 

[Jud96]

This was 10 shots at 100 yards when I was chronographing from 71.2-73.0 grains when I was first starting load development. It wants to shoot. I just don’t why now I’m having 30-40fps change in velocity when everything has been the same throughout my process.

 

[Bindi2]

poor ignition