K31 / GP11 consistency for long range marksmanship course

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woodcr24

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Hello All,
I came across this forum a few months back, and have learned a tremendous amount about my milsurps from you all. I have a question that I didn't see referenced in the forum, pertaining to repeated firing and long range consistency. Later this year, I'm taking a three-day course on long range marksmanship, ultimately firing at targets at ranges of 800 - 1,200 yds. I expect to fire ~250 - 300 rounds over the three days. I intend to use GP11, all from the same case.

The specific K31 (1950) that I will be using is one that I picked up from a shop, and had been "bubbafied". The top stock forend and band had been removed, the lower stock was cut back behind the band and was coated in what appears to be olive green truck bed liner, and a pair of Weaver mounts were attached to the carrier (the different height of the receiver makes the mounts sit at different heights, so they will be removed shortly). The barrel is original, and has had the front sight removed. I picked this up as a project gun. My intention is to replace the stock, either with one from Bluegrass or McGuinness (likely the latter, but the action will be pillar-bedded in either case), and then to use either a Rocksolid K31 scope mount or the St. Marie mount that I use with my intact K31 (1942). I'll likely add a muzzle brake to this improved sporter, as well.

I have two questions, if you please:

Would you expect the accuracy to hold over the course of the three days, firing that many rounds at the ranges that I have mentioned?

I am left-eye dominant and shoot left-handed. To date, I have not used the St. Marie scope mount with my other K31; I purchased one of these during a search to adapt the rifle for use with a scope, but the fact that the scope sits on the right side of the action makes it impossible for me to get a good cheek weld while getting lined up with the scope. Does someone know of a fix for this, or am I better off selling that mount and just going with the Rocksolid for the sporter?

Many thanks for your time.

Best,

Chris

6.5x55; 7.5x55; 7.62x54r
 
If you are allowed to clean the bore, I don't see why not. They are consistently accurate across decades, after all. Why would they be worse than any other full stocked rifle? Worth noting their barrel is less tied to that wood than most service rifles, as a sort of free float. Just keep the gun clean and wear more than a T shirt to shoot it, and multiday adventure should be a cakewalk for the old horse. I'd be more worried by the scope staying zeroed, considering the great distances (better be real certain about your mounting job being solid, mainly)

TCB
 
Olive green truck bed liner? Pics needed...

I'm a lefty with a K31, i'm of the opinion that scope & mount is not the way to go. There's other rifles out there for that.

As to the three day event; i think a K31 & GP11 is a very solid choice.... can't think of a better one really.
 
Don't have ballistic tables handy, where does the 7.5x55 swiss go through the trans-sonic threshold? Just wondering because 1200 yards seems a stretch for it. Long range shooting is tough enough without the complication of a round that is going to near mach 1 line during it's flight - things tend to get pretty damn unpredictable when that happens.
 
At 5,400' ASL (which is the elevation of the range that the course is being conducted on), the round doesn't drop below the sound barrier until it reaches ~1,350 yards. Mach 1.2 at ~1,050. This is data compiled from 'Shooters Calculator', based on a BC of 0.505, and the stated MV for GP11.
 
Here's another ballistic calculation that indicates that it might not:

http://forums.gunboards.com/showthread.php?223452-GP-11-Bullet-Drop

Parashooter is the Swiss Rifle Message boards version of rc. I wouldn't argue with him. He used a BC of 0.496 and a MV of 2580 fps. The MV is pretty well documented for GP11; the .496 BC might be a little underestimated. As near as I can tell that is a good number for a 175 SMK and I'd guess the GP11 is more aerodynamic.

Just curious, how do you lefties handle the bolt? I figure its nearly impossible with a Swiss Products mount.

Laphroaig

Just noticed Parashooters calculation is at sea level.
 
Thanks. I've seen the BC for the GP11 projectile listed as being between 0.505 - 0.514; I used the lower value to obtain those velocity numbers. I'm not concerned that the round is capable of maintaining adequate velocity over the distance that I will be firing; I've seen it used at much greater distances than I will be attempting. Rather, the question is whether or not the factory barrel will be able to maintain accuracy with that many shots over the course of 2.5 days. I expect to be able to clean the barrel each day, at least once.

Re: left-handed firing, it's really the same for me as with any other bolt-action made for right-handed shooters. I support the rifle with my left hand and cycle the bolt with my right. When shooting from prone or bench, my right hand is always free to cycle the bolt.
 
"the round doesn't drop below the sound barrier until it reaches ~1,350 yards."

Man, them bullets sure are long, ain't they? :D

I thought there's a Swiss Products left-handed op-rod conversion for the K31's? I don't know if it works with the scope mount installed, though.

TCB
 
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