New 300 weatherby barrel

[Teaman1]

I'm looking into building a 300 weatherby. I was thinking on having the barrel made with no free bore. I'm wondering if this is a good idea, or if I'd be better off with the free bore. What would I lose or gain?

 

[Teaman1]

The main reason I'm asking is I heard they could be more accurate without the free bore, but would it be dangerous and would I lose much velocity?

 

[Laelkhunter]

I think you would see a problem if you tried to use Weatherby Factory ammo. It is probably designed with the freebore in mind, and the pressures would probably be excessive (possibly dangerous) if there was no freebore. I had my .340 rebarreled, but the gunsmith put the freebore in the Lilja barrel.

 

[wind gypsy]

This is a new concept to me so someone correct me if needed. Only way I can see it making sense is if you are are constrained by magazine length and your bullets need to be seated so deep the bearing surface is at the mouth or inside the neck of the case. In that scenario it could improve accuracy by shortening the distance bullets jump to the rifling. There are numerous negatives though.

Basically, no freebore:
-No go on factory ammo unless factory ammo has the bullets seated that deep?
-raise pressure, so should have slightly higher velocity than with freebore all things being equal
-bullets not seated for no freebore could get stuck in rifling if you try to eject an unfired round, dumping powder in your action
-deep seating bullets reduces case powder capacity and the ability to maximize velocity at safe pressures

IMO one of the primary reasons to build a custom is to avoid these compromises. I would have your gunsmith spec freebore based on your magazine length and bullets you intend to use. That and I'd build a 30 nosler instead to get the same performance with less length issues and no belt on the case.