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Old September 21, 2011, 02:07 PM   #1
cracked butt
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weird horizontal stringing

I was doing some load development for a Swedish M41B awhile back and ran into a probllem that's been nagging in the back of my mind since.

I started out with simply trying to rezero my scope after having it zeroed for cast loads for several years.

I used the load I've always been using for jacketd bullets- 140gr SMKs/46.3gr RL-22/Fed 210 primers/ Winchester brass. I substituted some 140gr SGKs for the SMKs at first to get on paper, and found that at 200 yards they actually shot better...hmmm.
The load shot really good, I was getting 5 shot groups under 1.5" at 200 yards with some groups at 1.25". (which considering from a 110 year old rifle with a 70 year old 4x scope mounted on it, I'm absolutely giddy-happy with).

The next time out, I tried to work up a milder load using bulk 140 gr corelokts since I have about 800 or so of those left. I started at 42gr and worked up to 45 gr, and noticed pronounced horizontal stringing- the groups had a height of about 1-1.5" and a horizontal length of 6" or more at 200 yards.
I figured that something was wrong with the bedding, nope, fired my accuracy load and it grouped tight again, wind wasn't a factor as there was no wind that day, and the range has very little wind on most days due to the surroundign woods and high berms.

I always thought that horizontal stringing was caused by wind and possibly bedding problems (this rifle is slightly pressure bedded at the foreend like other swedish mausers), while vertical stringing is due to changes in pressure? I do get some vertical stringing when the barrel gets hot- I usually get about 10 shots before I have to let the barrel cool down.

I'm confounded.

I gave up on trying to make a load with the rem bullets on this rifle, but I might try again later.

Last edited by cracked butt; September 21, 2011 at 02:14 PM.
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Old September 21, 2011, 02:37 PM   #2
steveno
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are the rings and mount screws tight? I'm assuming the scope is known to be good.
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Old September 21, 2011, 02:54 PM   #3
Tim R
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What powder and primer?
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Old September 21, 2011, 03:46 PM   #4
cracked butt
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Scope mount/rings are about as solid as they get- I think they are made out of cast iron if not steel.
I'm using RL-22.
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Old September 21, 2011, 04:01 PM   #5
mehavey
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Quote:
I figured that something was wrong with the bedding, nope, fired my accuracy load and it grouped tight again,...
Think barrel whip and the vibration modes (and nodes) that each particular load generates. When you visuaize things this way you realize that one vibration mode may have a null at a potential stock/bedding interferance point, while the other load may generate max deflection at that same point. Bingo, ...you then have stock interaction.

Multiple discussions and visuals here:
http://www.shootingsoftware.com/barrel.htm
http://www.varmintal.com/atune.htm


.

Last edited by mehavey; September 21, 2011 at 04:21 PM.
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Old September 21, 2011, 10:23 PM   #6
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I've had a few rifles (w/ free-floated barrels) string a bit when I went too hot for the bullet/case/powder/rifle combo. Last few load development projects have involved loading progressively hotter until vertical strings start, then back off to an optimal load for that combo.
I don't like forend pressure but if your rifle does I'd stay with it. Have read a bit about varying forend pressure but so far haven't had to try it.
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Old September 22, 2011, 05:40 AM   #7
Jimro
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Adjust your seating for the Corelokts and see if that helps. The different ogive of the bullet creates a different "jump" into the lands. Also you might consider upping the powder charge just a hair, the flat base Corelokt bullets are taking up less powder space than the SMK or SGKs.

Good luke finding an accuracy load with the Corelokts. I've had good luck with them in 8x57. They may not be sexy but they shot plenty tight for a milsurp Mauser.

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Old September 22, 2011, 06:57 AM   #8
Dave P
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I would expect any issues dealing with seating depth, bullet type, velocity, etc to show on the target vertically, since that is the primary direction of barrel whipping.

Horizontal pattern is usually shooter issues; trigger pull mostly, maybe cheekweld or not holding hard.
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Old September 22, 2011, 08:16 AM   #9
cracked butt
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Quote:
Horizontal pattern is usually shooter issues; trigger pull mostly, maybe cheekweld or not holding hard.
I tried to rule that out too.
The old scope has nasty parallex, and is mounted high, its almost unshootable without a comb raising pad. I added a Beartooth comb raisign kit a long time ago and am very contientious about getting the same cheekweld every time.

Quote:
Good luke finding an accuracy load with the Corelokts. I've had good luck with them in 8x57. They may not be sexy but they shot plenty tight for a milsurp Mauser.
I've had them shoot really well out of other swede mausers, with lighter loads, but this one simply doesn't like them for some reason.

Quote:
I don't like forend pressure but if your rifle does I'd stay with it. Have read a bit about varying forend pressure but so far haven't had to try it.
Most old military rifles have pressure bedded foreends to some extent or another. If it were a new remington, I'd freefloat it in a heartbeat, but I'm not going to alter it.

Quote:
Think barrel whip and the vibration modes (and nodes) that each particular load generates. When you visuaize things this way you realize that one vibration mode may have a null at a potential stock/bedding interferance point, while the other load may generate max deflection at that same point. Bingo, ...you then have stock interaction.
I guess that makes sense. As others said, I guess I have to experiment with seating depth/loads.
I really hope to get the corelokts to shoot well, the 6.5mm Sierra bullets aren't cheap
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Old September 22, 2011, 10:18 AM   #10
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Quote:
I would expect any issues dealing with seating depth, bullet type, velocity, etc to show on the target vertically, since that is the primary direction of barrel whipping.

Horizontal pattern is usually shooter issues; trigger pull mostly, maybe cheekweld or not holding hard.
Barrels vibrate in every direction. Where the muzzle is when the bullet exits is the where accuracy is determined.

The muzzle will "whip" in a figure 8 pattern as the barrel vibrates. Your best accuracy is going to be found on the smaller circle of the figure 8. If you use Dan Newberry's "Optimal Charge Weight" method you can usually find that particulare "accuracy node" in your rifle with a given set of components.

http://optimalchargeweight.embarqspace.com/

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