load testing

Swiss K31

I built test loads for a couple of rifles. Monday’s weather was as suitable for testing as I was going to see for a while. It wasn’t real cold and very light winds grew into pretty light winds by the time I’d finished. I probably did my testing upside-down as the notch-sight rifle results are questionable anyway, while the scoped rifle would likely perform noticeably better with no wind.k31-sight-picture-gray

The Swiss K31 will spend its entire life with challenging-to-shoot-well notch-and-post sights. Especially with older eyes, the rear sight is a vague flat top and fuzzy groove in which I try to place a crisp, clear front post with protective ears, then line the whole thing up with a blurry 8.5″x11.0″ piece of paper upon which I affixed an indistinct chunk of black duct tape.

The sight picture you see is slightly off of desired alignment as it was the only way I could photograph it with my cheap snapshot camera so you can see the notch and post.

I had previously massaged some new brass, then carefully made up ten loads of three each with hand-weighed charges going from 40.0 to 44.5 grains of IMR4064 powder in 0.5-grain increments, pushing a 125-grain bullet.

When the shooting started I became quite skeptical that I would learn a thing. My ability to aim anywhere near the same spot for three shots in a row at a target 100 yards away is questionable even to the most generous observer. Doing that times ten … well … What the heck. I was there. I had the ammo. Might as well complete the exercise.

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On the first three targets I just used blank sheets of paper. When I planned this exercise, I didn’t figure I would see much more than that from 100 yards away anyway.

The next three targets received the diagonal stripe of duct tape which helped me line up a little better. Then I switched to a simple rectangle of tape which worked better still …
none of it being really trustworthy, as I said.

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The holes in the last four targets were spread out far enough that I didn’t even bother bringing them home. Suffice it to say, those loads are not good in this rifle.

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However, this one load has me shaking my head.

Do I even believe it?

I really want to, but my test procedure is no good.

How can I trust the results?

The string of three ran off the target, so I cheated with a pencil and drew the third hole in the same relative pattern of the actual holes.

This certainly looks like a good load, and seems to say the rifle and rifleman can work well together.
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I will be re-testing this particular load along with a couple below and above in tenth-grain increments.

It is tempting to accept that group as the best this rifle can be expected to do with those sights (and this shooter), but I really can’t trust them, and might as well shoot a couple groups a grain or two on either side of this as well.

I’ll be trying to conjure up a target that minimizes the challenges of getting a consistent sight picture with notch-and-post sights. I’m looking forward to it.

My Swiss K31 to the left. Adopted by the Swiss army in 1933, it is a mechanical jewel. The bolt handle is slapped straight to the rear, then straight forward, rotating the bolt as it unlocks and re-locks the action.

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Armalite AR-10

Oh yeah, then there was this other rifle. Eight groups of three in 0.3 grain increments running from 42.5 through 44.6 grains of Varget pushing 168 grain Hornady SSTs. As I mentioned, the breeze was growing, but still pretty light and mostly from my back, I think. Not great, but I was just trying to narrow down the area for further 0.1-grain testing.

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These tests are a whole lot more legitimate. I can hold the scope cross-hairs pretty-much on the center of the target while I squeeze off the rounds. There are undoubtedly better bench-rest shooters all over the place, but for my purposes, I am good enough. Most importantly, I can SEE what I’m doing.

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Now THIS ONE below is getting into the realm I want to be working. I’ll re-do with a pair of 0.1 grain 5-shot groups below, at and above this 43.7 grain load. And I’ll make darn sure there is NO wind.

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And now I’ll earn a heap of abuse from my good friend

who is an actual rifleman …

Since I really want to know which ones behave well out at 200 yards and beyond,

I did my testing at 200 yards.

Adjusted to a more normal (he’ll say “intelligent” or something like that) rifle testing distance of 100 yards, this group would be under an inch … particularly if I test with NO wind.