Free Bore - How Much is Too Much

[tnichols]

How much free bore/jump have you seen or had in a barrel that still shot well? New, used, or tired, just curious what others have experienced. And by well, let’s quantify that by saying sub 3/4 MOA.

 

[Steel head]

I’ve jumped 6.5 hybrids and ELDM’s over a tenth of an inch in my long throated 260 barrels with excellent results.


I’m also current jumping 180 eldm’s in my 7 saum about 60 thou and it’s been hammering for me.

 

[tnichols]

All things Weatherby(reamer).

224,257,7mm,300,375 and 378 mainly.

Which yields how much free bore?

 

[mcfred]

I have a .204 Ruger that's more than .100 jump to the lands using a 40gr NBT and it shoots well.. In terms of bullet diameter to jump ratio that's pretty significant. The bullets are barely seated in the case necks too.

 

[Sheldon N]

My 7 SAUM is throated for long action but I run it mag fed short action. Tons of jump but still very accurate.

 

[tnichols]

Thanks for the input fellas. I maybe should have left out the free bore number in my query, and just asked how much jump you’ve gotten away with as a barrel wears. I realize some bullets are more jump tolerant. Mag length dictates OAL, and if the jump starts in the .150 range, you’ll probably be unable to chase the lands. I posed this question because as of tomorrow I’m retiring my 260 barrel. Jump is now .340, velocity is decreasing, and accuracy is suffering at distance. Most notably beyond 800 in very negative DA environments (-2500 and below). Feel free to keep posting numbers.