After reading cleanining the Bore 7.5x55.

[Beak50]

After reading that thread it makes me wonder if shooting .308 bullets I plan on reloading are to big for the bore.I have heard conflicting accounts.Is 7.5 = 7.62? Will I somehow wear out the rifling?Should I just stick with the GP-11 ammo since all I do is target shoot for fun anymore?

 

[Canuck-IL]

Have you measured the diameter of a GP-11 bullet?
/Bryan

 

[barnbwt]

Measuring the diameter of the GP11 pulled bullets is one way to know, slugging the barrel would be even better (in case it's tighter than typical). I've heard (numerous sources, namely SwissRilfes.com) that the reason for the numerical difference from 7.62/.308 is due to the Swiss measuring from the groove, as opposed to the lands, when naming the chambering. Bore brushes are more flexible than bullets, so I'd guess you have more latitude in choosing a size.

I've not heard of any problems with folks reloading .308 bullets, I believe there are 175gr slugs out there that would pretty much duplicate the GP11 174gr bullet load. Slug the barrel to be sure.

Maybe someone will chime in and suggest how much larger/smaller than the bore diameter a bullet size can safely be used?

TCB

 

[Slamfire]

I have shot hundreds, getting close to a thousand 308 diameter 174 FMJBT's. These are hard military bullets. Not a problem in my K31's.

As long as the case neck can expand and release the bullet you won't have pressures issues when going from 0.307 bullets to 0.308.

Anytime the case neck is pinched, or the bullet is soldered into the case neck, then pressures can climb to extreme levels and blow the action.

This is what happened with the 1921 Tin Can ammunition. The bullets were coated with tin, the tin coating migrated into the brass case necks creating a “cold solder joint” between the bullet and case neck. This raised pressures disastrously and apparently caused blown rifles.

Instead of “fessing up”, the Army created a coverup, blamed civilian shooters and the grease they were putting on their bullets, and Hatcher supported the coverup 100% in his book.

However, if you have been shooting Swiss surplus, you might have noticed the grease ring around the bullet and the case neck:





I guess Hatcher lied!

 

[Beak50]

Yes the ammo I've been shooting has the wax/grease ring around it.I noticed Hornady use's .308 cal for their 7.5x55,so I'll use them.I haven't pulled a bullet from the GP-11 Ammo I have.I just got my Swiss Magazine Loading Rifles 1869 to 1958 yesterday and am gonna start reading.Thanks for your input everyone.Next step is to find a load comparable in performance with the GP-11 using a target bullet.

 

[T Bran]

I agree with barn.
Slug the bore just to be on the safe, side could be a little tight could be a little loose. This would be a big help if you start getting pressure signs early in your load developement or or the opposite if you reach max and still show no signs of pressure.
T

 

[lonniemike]

.308 bullets are correct. Actually W-FBern, the Swiss gov assembly factory, says the correct dia should be .3087". But what does a few thousands matter when you are working up loads, right? 7.5 is the nominal bore dia. Swiss lands are about .006" not like US lands which are typically about .004". Groove dia is 7.84(.308) like most(7.62 is a bore dia for most US) 30 cals. Slam is giving some good heads up. 2560fps is what GP-11 is typically reported as by the Swiss in the K-31.Best

 

[Caliper_Mi]

I've slugged mine... .308 groove, .297 lands.

How people measure bores differs everywhere. I think the split is that in Europe they tend to measure the lands and the US measured the grooves. 7.62 in the USA = 7.5 in Switzerland = .308 bullet. But, in Russia, 7.62 = .311 bullet

 

[skidooman603]

Hundreds of .309 casts down the pipe of my K-31 and 1896/11 Swiss

 

[lonniemike]

This is my last post in this thread. 30 caliber is .300" bore diameter,as US is 7.62mm, as Russia is 7,62mm. Swiss is 7.5, French is 7.5, these are bore diameters closer to .2956 to .297" And to say 7.62mm bullets are .308" in diameter is an oxymoron. Most 30 caliber bullets are 7.82mm in diameter and will fill the groove diameter of most 30 cal guns. The Russian .311" groove diameter is not 7.62mm or 7.82mm but is supposed to be closer to 7.8994 or about 7.9mm in diameter.Best All