Vertical stringing

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Clark500

New member
I finally got all the components to reload 8X56R, so I decided to load up some test rounds. I couldn't find any other reliable reloading data, so I had to use the Lee data that came with the dies. Unfortunately, the most commonly available bullets are in the 205-208 grain range (mine are 208 grain Prvi's) while Lee only lists loads for 200 & 220 grain bullets. I decided to split the difference between the 200 & 220 loads and ended up with a min charge of 40 grains and a max charge of 43 grains of AA4350. I started with the 40 grain loads and was quite pleased with the minimal recoil. However, the accuracy was VERY poor. My shots ended up in a vertical string about 18-24 inches long. This continued through mid-41 grain loads, and I was quickly becoming disheartened. I then tried my 42-grain loads, and like magic I was shooting respectable (for me) 100-yard groups of 2-3 inches using a high-dollar rest (an old GI ammo can with a towel thrown over it). :rolleyes: I am happy enough with the final results, but I am a little confused about the huge change in group size. Can any of you old salts shed any light on this?
 
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Unclenick

Staff
Clark500,

There are two 8×56R cartridges. The Portugese Kropatschek M89 round, and the Hungarian Mannlicher M30S round. The former use 0.323" bullets, and the latter have been chambered in barrels anywhere from 0.323 to 0.330", according to QuickLOAD, which puts 0.329" as the default diameter. If you used the smaller bullet in a barrel intended for the larger bullet, that would sure make for a mess, accuracy-wise. It could also require you get to a minimum pressure that bumps the bullet up enough to fill the bore, which would improve accuracy rather abruptly. You should probably slug the bore to learn its diameter?

Nick
 
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briandg

New member
two things come to mind with vertical stringing.

Is the bedding of the rifle bad?

Second, how hard was that rest? How many layers of towel did you have over the can? You need a firm, but resilient rest. a hard rest will cause bounce.
 
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Nomadicone

New member
I have seen a few examples over the years where too light a powder charge can cause vertical stringing. It sounds like your last charge improved the stringing. You might try a few loads at 42.5 gr or even 43 gr if you have no signs of excessive pressure at 42 gr. It may just improve the group over 42 gr.
 
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Clark500

New member
Nomadicone,

Thanks for the tips. 42 showed no pressure signs, so I will try a heavier charge next time. I'm sure my shoulder will thank you! :D

Could the smaller charges be causing erratic ignition (or something along those lines)?

I didn't mention it before, but the string was an almost perfect vertical line (no flyers left or right) and pretty much equally divided between above and below desired POI.
 
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