Shot out K31 turned into a tight 308 pipe

jeanlikethis

jeanlikethis

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Once a bore size is larger than 7.64mm, we claim a K31 to be shot out. However, if we look at the .308 spec, we found .308 has the same bullet diameter as 7.5 Swiss (both 7.8mm, same or very close to the groove diameter) but a land diameter of 7.62mm.

This means "shot out" only refers to 7.5 Swiss, the 7.64mm bore of the K31 is actually a nice and tight .308 pipe.

If we use 308 projectile to reload, there is nothing to complain at all !!

Agree? So, keep your "shot out" K31 and it would be a great 308 projectile launcher. You might have to pay a little bit more attention to the .
 
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The 7.5 Swiss uses a .308" bullet already. There's no such thing as a 7.59mm bullet.
And .308" doesn't mathematically convert to 7.62mm or 7.59mm. Converts to 7.82mm.
 
Actually k31 traditionally uses a .307 bullet that's paper patched. Remove the paper patch and .308 bullets work just fine. Not really sure what the op was trying to say though...
 
The BASE of the GP11 bullet measures 0.3075" . It tapers from the tip to that widest part where the boat tail begins.
It is a bore riding bullet. it measures in the 0.306-0.307" range in front of the case mouth.
That is why there is so much erroneous information out there.
Just reload with .308 and you will be fine.

It is the throat of a rifle barrel that gets shot out first.
Unless some really careless barrel cleaning went on.
 
A K31 is considered unsuitable for military use at > 7.58mm. The reason it is unsuitable is that it does not reliably stabilize the bullets and therefore accuracy is atrocious. K31 ammo has never been paper patched.
As far as I know the bullets for 7.5x55mm and 7.62x51mm ammo are the same diameter, however, even if your theory proves out, rechambering/rebarreling a K31 is not an easy matter. It will cost less to simply buy another rifle than convert to 7.62x51mm.
 
Paper patching was only used for the 1889 Schmidt Rubin's 7.5x53.5 ammo(GP90) and given up by early 1920's
Later production in the 1920's was not paper patched.
 
Don't have re-chamber any K31, Only use .308 projectile to reload the GP11 case would be fine?

Would a 7.62mm bore K31 hold the same accuracy to a 7.62x51 rifle? With the same bullet loaded and same PSI?

Would groove diameter (7.8 vs 7.82) play a role ?
 
Don't have re-chamber any K31, Only use .308 projectile to reload the GP11 case would be fine?
That's right

Would a 7.62mm bore K31 hold the same accuracy to a 7.62x51 rifle? With the same bullet loaded and same PSI?
No real difference.The heavier weight of bullet makes the 7.5 more accurate at longer distances with much lower pressure than the .308 Nato.
The Swiss round is closer to a 30-06 in power.

Would groove diameter (7.8 vs 7.82) play a role ?
7.82 is bullet diameter(= .308 inches"
7.62 refers to Bore, size of drill hole in barrel before it was rifled.
Like British .303(bore) is .312" bullet diameter.
7.5mm is the bore size.
Like .308" bullets in so called .30 calibers like .308, 30-06, 30-30 etc......
 
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WIKI said (assume it is right)

7.5 Swiss has the groove sized to be : 7.77mm
7.62 Nato has the groove size as : 7.82mm

in case a 7.62mm bore K31, the land:groove = 7.62:7.77
in case a 7.62 Nato, the land:groove = 7.62:7.82

Would that make any different in terms of accuracy if both use .308 bullet.


diopter said:
Don't have re-chamber any K31, Only use .308 projectile to reload the GP11 case would be fine?
That's right

Would a 7.62mm bore K31 hold the same accuracy to a 7.62x51 rifle? With the same bullet loaded and same PSI?
No real difference.The heavier weight of bullet makes the 7.5 more accurate at longer distances with much lower pressure than the .308 Nato.
The Swiss round is closer to a 30-06 in power.

Would groove diameter (7.8 vs 7.82) play a role ?
7.82 is bullet diameter(= .308 inches"
7.62 refers to Bore, size of drill hole in barrel before it was rifled.
Like British .303(bore) is .312" bullet diameter.
7.5mm is the bore size.
Like .308" bullets in so called .30 calibers like .308, 30-06, 30-30 etc......
Click to expand...
 
7.77mm is .306" converted to metric.
Doubt the Wiki writer(s) actually took the trouble to measured a K31 rifle barrel, never mind a reasonable sample of them to get an average.

With Jacket bullets , no.
In cast bullets, maybe

7.54mm is a good tight/minimum± bore size for K31. That is is o.297".
I have ones with 7.56 and 7.58 that still shoot very well indeed.

http://theswissriflesdotcommessageboard.yuku.com/reply/4935/K31-bore-specs#reply-4935

http://theswissriflesdotcommessageboard.yuku.com/topic/1029/Bore-Specs-for-75-Rifles
 
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