Bore sluggin' Saturday

[ben hunchak]

Due to some recent posts regarding the proper bullet dimensions for a .43(11mm) Mauser and others, I thought I would measure some bores at the shop as follows: SMLE .303 Br........312"
Mauser 71 .43 Mauser..... .446"
Vetterli 69 .41 Swiss RF.... .430"
I thought this info may be interesting as some have mentioned using .452" or larger bullets in the .43 and just points out the importance of checking the bore on each ind. rifle.......using even light smokeless loads and a bullet that is very much oversize can jack the pressures way up on the old girl.

 

[david doyle]

Ben right you are. Always best to know exactly what you are playing with! Slugging a bore and having real numbers always makes me enjoy a rifle more and obviously cuts down on the risk of inaccuraccy and higher then desired pressures.
Just out of curiosity do you know off hand what year/factory or manufacture your 71 is?

Thanks.

 

[ben hunchak]

I'll find out next time I'm in the shop.

 

[Andy]

Due to some recent posts regarding the proper bullet dimensions for a .43(11mm) Mauser and others, I thought I would measure some bores at the shop as follows: SMLE .303 Br........312"
Mauser 71 .43 Mauser..... .446"
Vetterli 69 .41 Swiss RF.... .430"
I thought this info may be interesting as some have mentioned using .452" or larger bullets in the .43 and just points out the importance of checking the bore on each ind. rifle.......using even light smokeless loads and a bullet that is very much oversize can jack the pressures way up on the old girl.

Mauser 71/84's tend to slug to about 0.446" groove diameter, and Mauser M71's to about 0.454"

The old adage to go 0.001"-0.002" over groove diameter does not imply that going more is dangerous. Those numbers are recommended minimums, and take into account the usual neck sizes you will encounter. In fact it is suggested that you go as much over groove diameter as your chamber neck will allow, and 0.006"-0.008" over is not uncommon among experienced cast bullet shooters. Pressure does not spike at those levels oversize, to the contrary tests have shown no measurable change (some have shown a drop!). Lead is malleable and easily conforms to the bore. We think nothing of using bullets jacketed with tough gilding material (BHN near 100) that has to cut into the rifling, yet we worry about the swaging of much softer lead.

 

[Win 38-55]

I've found that going too far over the groove diameter can make accuracy go downhill fast, especially with hardcast bullets. .001 is usually fine, but .002 can be better or it can be worse, depending upon the rifle. .003 and up is usually not good for accuracy .... at least in my rifles.

 

[Andy]

I've found that going too far over the groove diameter can make accuracy go downhill fast, especially with hardcast bullets. .001 is usually fine, but .002 can be better or it can be worse, depending upon the rifle. .003 and up is usually not good for accuracy .... at least in my rifles.

Good point - just because it's safe and you can, doesn't mean you should. In one of my Mauser 71/84's, a 400gr bullet, no matter how "fat or thin" did not shoot well. A 500gr on the other hand, at 0.003"-0.005" shot very well, probably due to the longer bearing surface it offered.