6BR Barrel with .050 more freebore

[JBattles]

I started shooting 6BR on an MPA chambered barrel a couple years ago and it shoots Hornady 108s great with .035 jump. I just got an AI AT-XC and put a Mile High Factory WinTac 6BR barrel on it. When I measured the AI barrel, it has .050 more freebore to the lands that the MPA barrel. I haven't seen this with other calibers when getting different barrels, they are all pretty close, but .050 seems like a big difference. I used the standard OAL tool to find the lands on both barrels with the same bullet.

Anyone run into this before - these are both very high quality barrels and smiths? Is there a 6BR variant that is shorter and longer? I am planning to load for the 2 rifles differently and run the AI rounds longer to make up the difference.

Hornady 108 ELDM
MPA - 2.350 OAL to Lands
AI - 2.400 OAL to Lands

 

[Mike Casselton]

I've seen 6-BR barrels from 0 freebore all the way to .200.
It just depends on what reamer was used, and the purpose of the barrel.

Personally, if I'm never going to shoot short, light bullets, I'll take as much freebore as I can get in the BR.

They feed better and you can add a bit more powder to help with velocity. Just don't go crazy trying to get speed out of it.

I have a barrel with 5290 rounds on it. To reach the lands, the 112 Barnes won't fit in my MDT BR mag.
The 105s will though.
It does feed extremely well in the 5 round plastic Magpul mag.



From a rickety-assed wooden bench, it'll still do this, so I'm gonna keep using it until it completely dies off.

I should probably try it from a concrete bench or prone to see what it is still capable of.

Edited to remove duplicate image.

 

[JBattles]

Thanks Mike - I figured as much, seems to be lots of variation... guess I am running two wildly different sets of ammo for these barrels.

 

[Mike Casselton]

Thanks Mike - I figured as much, seems to be lots of variation... guess I am running two wildly different sets of ammo for these barrels.

On the two fast twist barrels, I can load for both using the 0 freebore OAL and they shoot very well.
If I shoot the 104 FB ammo in the 0 FB barrel, I just don't try and remove a chambered round. The bullet is jammed in there pretty hard.

Just understand, I don't load for maximum velocity. I load for consistent, day-to-day accuracy.

If I chose to make life simpler, I'd load both barrels for the 0FB and rock on.
Thankfully, I have a few seating dies and use the one that matches the barrel's preferred OAL.

 

[Mike Casselton]

One other thing I forgot to mention is the leade angle on the reamer.
If the angle is shallower, your bullet ogive contact point will be longer

 

[JBattles]

I've only shot the short freebore rounds though it and at .070 jump is shoots very well - interested to see what happens when I load them out .035 longer, maybe it's not required... love being able to tweak all kinds of things with handloads.