.338x.284 Win* Load Workup

[gitano]

I've been doing a lot of analyzing and paper-whipping. (Always happens after a range session. Especially when I'm working up a load.) As a result, I've decided to combine the "change-the-charge" method with the "change the seating depth" method.

Since I have at least a preliminary idea about this rifle's 'native' harmonic timing, and mostly because that preliminary data fits well with almost all of my previous timing data for precise loads, I decided that I could use both timing and seating depth to get where I wanted to get with regard to precision and delivered energy.


To reiterate my personal ballistic standards:
1) Precision of one minute of an angle or better at 100 yd.
2) For calibers .308 and smaller, deliver at least 1500 ft-lb to 300 yd; and for calibers larger than .308, deliver at least 2000 ft-lb to 300 yd.
3) Total vertical deflection of the trajectory 12" or less over 300yd.
4) Ideally have muzzle energy of less than 3500 ft-lb. This can go up to 4000 ft-lb if necessary to meet #s 2 & 3 above.  (This criterion is more flexible than the others because perceived recoil depends on the weight and stock shape of the rifle almost as much as muzzle energy.)

I was also looking at my stock of powders and .338 bullets and found some red-plastic-tipped 225-grain boat-tails I bought from MidWayUSA when I was still patronizing MidWayUSA. (They were sold under the MidWayUSA brand, but I'm positive they're Hornady's.) I have 100 of those. I also found, again from MidWayUSA, some flat-based 250s that look like Partitions with a graphite coating. (I'll post a picture later.)

Now consider the myriad possibilities if you're gonna fiddle with charge and seat depth. However, things get at least a little simpler when you start to put constraints like those above (1-4), and you constrain the bullet's barrel exit timing to one or two.



To spare you lots of the gory details, I settled on two powders: I3031, and Bl-C2. The timing node I want to hit is 1.320 msec, which corresponds to the timing of the smallest group I shot the other day at the range. It's seat depth, (hereafter, SD), was 0.250", but I'm not concerned about a specific SD. I'm concerned about "hitting" a specific exit time. 1.320msec is 3% slower than the theoretical 4th node on a 28" barrel. Moving "up" to the next slower node 5, and dropping 3% down from it, yields an exit time of 1.474msec.




The reason I dropped down to the next slowest node is that I can't stay below max chamber pressure with the 225 bullet, (Accubond or other), at an exit time of 1.320msec at any seating depth. However, I can hit the 1.474msec mark with the 225s and keep the muzzle velocity up enough to meet the necessary criteria.


As it turns out, I'm using the I3031 at 1.320msec for the 200-grainers, and Bl-C2 at 1.474msec, for the 225s. About this time you may be saying, "I thought you were going to change charge too." Right. So for each powder I'm loading three different charges for three different seating depths, all of which yield exit timings of either 1.320msec for the 200-grainers using I3031, or 1.474msec for the 225s and Bl-C2.

The three SDs are: .34" (a caliber deep), .30", and .24" (minimum SD). Each of those SDs would yield a different exit time if the charge wasn't adjusted just a little. So there is the "change the  charge" component.

I'm loading 5 cartridges at each SD for each bullet, (3x5x2=30). Since I have 50 cases fire-formed, I'll load 3 each for each SD and each bullet weight, (3x3x2=18) to get statistically better MV data. Therefore, I'll be putting another 48 bullets down the bore for a total of 70, (last range session's 22 plus the 48 of the next one). That, (plus fire-forming 50 cases), should help get the bbl 'shot in', and hopefully, I'll find "The Load" amidst all of that.

News at ll.



Paul

[gitano]

Those that know me will know that I don't always "have a good day at the range". There have been some real disasters. Kinda goes with wildcat territory. However, yesterday was not 'one of those days'. It was great!

As I explained in the previous post, I had loaded 18 rounds of 6 different loads: 3 different seating depths, three charges for each seating depth for 2 bullets using 2 powders. These 18 for getting good muzzle velocity data. 'Caught' all 18. I also loaded 5 each for the same 6 different loads, (for a total of 30), for group size.


The six loads were:
1) Seating Depth - 0.24"; Bullet - 200g Nosler E-Tip; 50.4g I3031;
2) Seating Depth - 0.24"; Bullet - 225g MidWayUSA/Hornady; 56.6g BL-C2;


3) Seating Depth - 0.30"; Bullet - 200g Nosler E-Tip; 49.7g I3031;
4 )Seating Depth - 0.30"; Bullet - 225g MidWayUSA/Hornady; 55.8g BL-C2;


5) Seating Depth - 0.34"; Bullet - 200g Nosler E-Tip; 49.3g I3031;
6) Seating Depth - 0.34"; Bullet - 225g MidWayUSA/Hornady; 55.25g BL-C2;

Here are the MVs in f/s in seat depth pairs:
Load 1 - 2705, 2712, 2762. Average - 2726, (2780/+54*) Standard Deviation - 31
Load 2 - 2785, 2783, 2820. Average - 2796, (2741/-55*) Standard Deviation - 20


Load 3 - 2695, 2730, 2721. Average - 2715, (2771/+56*) Standard Deviation - 18
Load 4 - 2739, 2765, 2707. Average - 2737, (2732/-5*) Standard Deviation - 29


Load 5 - 2688, 2712, 2714. Average - 2704, (2768/+63*) Standard Deviation - 14
Load 6 - 2747, 2726, 2768. Average - 2726, (2725/-22*) Standard Deviation - 21
* - Quickload predicted/Difference.


Here are the MVs in f/s in bullet weight triplets:
Load 1 - 2705, 2712, 2762. Average - 2726, (2780/+54*) Standard Deviation - 31
Load 3 - 2695, 2730, 2721. Average - 2715, (2771/+56*) Standard Deviation - 18
Load 5 - 2688, 2712, 2714. Average - 2704, (2768/+63*) Standard Deviation - 14


Load 2 - 2785, 2783, 2820. Average - 2796, (2741/-55*) Standard Deviation - 20
 Load 4 - 2739, 2765, 2707. Average - 2737, (2732/-5*) Standard Deviation - 29
Load 6 - 2747, 2726, 2768. Average - 2726, (2725/-22*) Standard Deviation - 21
* - Quickload predicted/Difference.


Here's a screenshot of the part of the analysis spreadsheet with the MV data:

In the MV column, the background color denotes the case manufacturer.

As you can see, there were only two batches of three bullets with the same case: The 225 Hornady with 0.24" seating depth, and the 200 E-Tip with the 0.30" seating depth. There were some differences, clearly, but I wasn't after 'perfection', I was just after "what's the general MV". I didn't even shoot paper with these shots. On the other hand, all 5 of the cartridges for each load for "group" were the same manufacturer. Precision matters. MV, not so much.


Also note that QuickLOAD consistently overestimated the MV for the 200g/I3031 loads, and conversely, underestimated the MV for the 225g/BL-C2 loads. Although, it was essentially "right on", (missed by 5 f/s),  for the 225g, .030 seat depth load.


The next picture is the actual target shot for group size. The first one is the 200g E-Tip with 0.24" seat depth.

This one looks like it's all over the place, but in fact, I was adjusting the scope between shots. Since I noted the exact adjustments, I could later put a digital target together with the adjustments taken out. The digital target is below.

The max spread is 2.97". Nothing to write home about. A little disappointing to tell the truth, but I couldn't see how bad it was at the range because of moving the point of aim around. However, things were about to get much better.

Here's the next target I shot.

You can see the shot sequence. When I shot the second shot, I couldn't see the hole. Hmm... I was pretty sure I didn't miss the paper! Upon closer inspection, I saw that the two holes were almost one! Yeehaa! Next shot, #3. ALL RIGHT! Looking good! Took shot #4, and while 'away' from the first three, it was still inside MoA. Took the 5th and last shot of that load. Right as the trigger released, I saw that PoA was low. :frown @#$%^&*! However, I saw exactly where the crosshairs were, and knew I could adjust later. Even so, it still wasn't bad.

Here's the digital target. The red dot is the adjusted PoI for that 5th shot. You may choose the one you want, but I know what happened, so I'll take the smaller group as representative. Max spread for the unadjusted 5-shot group is 1.38". Adjusted max spread is 0.98".


Given the strategy of my loading, AND the "precious" nature of bullets and powder, as far as I was concerned, I had found my load. What I will do now, is load some 225 Accubonds, and tweak the charge to fine tune it. No need to fiddle with the seating depth unless the AB groups go completely south.

I packed up and went home. I'll pull the bullets and put the powders back in their respective canisters.

By the way, note the average MV for that 1 MoA load: 2796 f/s - for a 225g bullet! Assuming the 225 Accubond's speed is the same, it will deliver over 2850 ft-lbs to 300 yd, , and is 8.5" flat over that same 300 yd. (1.5" high at 120, and 7" low at 300.) Impact velocity at 300 is 2386 f/s. That 'beats' the .338 MAI by about 850 ft-lb and almost 400 f/s. (Frankly, it's equivalent to my .338 Win Mag loads. Of course I don't load my WM loads as 'hot' as this because they're not for a No.1 action.) The predicted max pressure is 'right up there' at 60835 PSI, but in the No. 1 action, that's no sweat. Theoretical rules of thumb aside, the reality is that the cases swelled only 0.006" max, and the primers were still "rounded".

Some days chickens, some days feathers. Yesterday was definitely a "chicken" day.

I'll be hunting with this rifle this fall.


Paul

[gitano]

I got to the range to check out the load that worked with the 225 Hornady on the 225 AccuBond. Same charge: 56.6g of BL-C2. Same seat depth: 0.24" of shank. Same case: Frontier 7.5x55 Swiss. Same primer: CCI 200, Large Rifle.  


No called fliers. Max spread 1.76 inches. :frown

You can see from the target that the rifle is stringing them vertically. This is the classic problem with the No. 1, and is a function of that blasted "hanger" in the forearm. I'll have to fix that if I want the groups to tighten up. Group size for first four was just over 1 MoA at 1.14", and first-and-second, and third-and-fourth, were very close pairs. I'll work on the forearm/hanger issue, and try again.

Muzzle velocity was a little slower at 2747 f/s, than the Hornady (2796 f/s). Standard deviation was a little worse at 33 f/s vs 21 for the Hornady. However, I think this is a function of neck tension. The bullets were not very tight in the necks of the five I used for MV measurement. I suspect MV will go up and std dev will go down when the neck tension is tighter and more uniform.

Were it not for the amazing terminal performance of the AB, AND the high (TRUE) BC of the AB, I'd be using the Hornadys. They're cheaper, and for the moment at least, they shoot straighter. Probably.

Paul

[gitano]

I didn't have the QuickLOAD-predicted muzzle velocity when I made the above picture. It is 2744 for the 225 Accubond. That's only 3f/s slower than the observed of 2747.

Paul

[gitano]

Just ordered 8 lb of BL-C2 at a cost if $248.50 delivered (to Missouri). That's $31.06/lb. Not a smokin deal, but $32.50 of that was shipping and PayPal fees.:frown

Such is the 'way of the world' these days.


Paul

PS - Used to be, you could transport small amounts of smokeless powder in your checked baggage. The fascist sons-of-bachelors at Homeland Security now say NO "gunpowder" of any  sort. So... I'm trying to cancel the above order as there is now NO WAY for me to get ANY amount of BL-C2 to Alaska.

Many of "us" are sitting quietly. Seething. It's going to be bad for politicians and other fascist sons-of-bachelors when the silent majority decides that enough is enough. I suspect it will make the aftermath of the French revolution look like a walk in the park.


Paul