Berger 6.5 MM 140 gr Hybrid Target - Required Freebore?

[RonAKA]

Posted this in the Gunsmithing section but not getting any responses. All suggestions welcome.

I am waiting for a new barrel chambered with a Match SAAMI reamer in 6.5 MM Remington Magnum. Since it is going into a long action 700 Remington, I thought I was free and clear on any issues with seating long bullets like the Berger Hybrid. Now, I have come to the realization that the 6.5 RM SAAMI was designed for a short action, and SAAMI has potentially set the Freebore for the standard 2.800" COAL in a short action. Ouch! I may not be able to seat those long bullets as far out as I think.

And so we don't go down a semantics rabbit hole, can we assume Freebore is the distance from the end of the chamber neck to the start of the taper into the lands. So it includes the short angled taper from the neck end to what I would call the throat which is typically just over bullet nominal caliber.

I've done a search here, and I find this require Freebore dimension is all over the map. Most discussion seems to end up with. "Just make a dummy cartridge with the bullet you want to shoot, and make it the gunsmith's problem!". I unfortunately don't have that choice. It is a REMAGE barrel and should come ready to use.

I have checked the 6.5 RM SAAMI, and with the definition above, I make Freebore to be 2.389" minus 2.194" = 0.195". I then check the 6.5x284 Norma CIP drawing to see what it has, as this cartridge was designed for a long action. I make the Freebore on this one to be dimension "s", or 8.02 mm, which is 0.3157". Ouch again!

So, now I am panicked, thinking I'm going to have to get this Freebore lengthened with a throating reamer, until I find a few posts here saying that Savage F Class 6.5x284 Norma owners were disappointed in their gun because the Freebore was way too long... It is likely built to CIP standards. And there are other posts which suggest that around 0.200" is fine??

I have tried in the past to calculate required Freebore theoretically using Berger's bullet dimensions, but that seems to result in a Freebore that is way to long compared to what custom guns are actually using. A quick calculation based on Berger dimensions suggests a required Freebore of 0.419"!

So what is the consensus on Freebore for this 140 grain Hybrid? Is the 0.195" in the ballpark? Or should I be panicked?

 

[Geno C]

I have a few fclass buddies that use .160" for that bullet in a 260ai single feeding so I'd say that's close

 

[Auto-X Fil]

I responded in Gubsmithing - 0.195" is on the long side. You'll be fine. I agree that 0.160" sounds about right, but I don't have specs in front of me.

I know my 6.5 Creedmoor doesn't have a lot of neck gripping the bullet with a 0.200" Fb that's eroded about 0.050". I'll go shorter next time. Maybe 0.160".

 

[Terry Altom]

With that freebore, you might want to take a look at the Hornady ELD-M. Those are some very long bullets and most say they're very good. They're too long for my .160 freebore 260AI.

 

[RonAKA]

I have a few fclass buddies that use .160" for that bullet in a 260ai single feeding so I'd say that's close

It sounds like the more common definition of Freebore is just the straight section after the end of the neck, not including the taper down from the end of the neck. With that definition, the standard SAAMI dimension is 0.1643". Is that sounding better?

 

[RonAKA]

With that freebore, you might want to take a look at the Hornady ELD-M. Those are some very long bullets and most say they're very good. They're too long for my .160 freebore 260AI.

Yes, I will look at that. Those ELD-M bullets sure claim a high G7 BC at 0.351 for the 147 grain. It also looks like the 8.5 twist in my barrel should handle them. So far I have not been able to find the Berger Hybrids in stock. Perhaps I will have better luck finding the ELD's...

 

[22BRGUY]

Would suggest you not be afraid to look at the Berger 140 LRBT's either.

 

[RonAKA]

Would suggest you not be afraid to look at the Berger 140 LRBT's either.

I will look into that. Having trouble locating any Hybrids, and I think the LRBT's are in stock at a nearby gun store. I now have some 135 grain Classic Hunters on order. They have pretty good ballistics too, with a .303 BC and .913 Form Factor. Hopefully they won't be too short...

 

[ShootDots]

I will look into that. Having trouble locating any Hybrids, and I think the LRBT's are in stock at a nearby gun store. I now have some 135 grain Classic Hunters on order. They have pretty good ballistics too, with a .303 BC and .913 Form Factor. Hopefully they won't be too short...

RonAKA, if you can get hold of those 140 LRBT's at the gun store, you're in for a treat. I have shot them for several years now and in my opinion they are the finest 6.5mm target bullet made. They have a short bearing surface so can be driven to higher velocities with the same pressures. They have a very high B.C. and their tolerances are much tighter than the Hybrids. They are excellent indeed!

 

[RonAKA]

RonAKA, if you can get hold of those 140 LRBT's at the gun store, you're in for a treat. I have shot them for several years now and in my opinion they are the finest 6.5mm target bullet made. They have a short bearing surface so can be driven to higher velocities with the same pressures. They have a very high B.C. and their tolerances are much tighter than the Hybrids. They are excellent indeed!

Thanks, I'll have to check and see if they are still there. Stock of Berger is real hit and miss up here.