Freebore Question

[Thunder]

Howdy -
I'm a long time 'browser' and first time 'poster', and I could sure use a little barrel freebore advice.

I'm about to order a new Savage 'pre-fit' 6MM BR barrel for my Model 12 target/varmint rifle. I believe that I have everything figured out except for the proper amount of freebore.

I plan to get a Shilen or McGowen barrel,or maybe Douglas) in a 10 twist and 'no-turn' neck.
I will be handloading with Lapua brass and using Hornady V-max 58, 65, 75, & 87 gr. bullets, along with Nosler Ballistic Tip 55 & 70 gr.
Will be shooting at distances out to around 400 yds.

I have read all of the threads that I could find here about freebore, and I confess,I'm still a little uncertain about what would work the best with this barrel and bullet combination.

Would any of you guys like to offer some advice or opinions on this so I do this right the first time? : )

Thanks much!
Ron

 

[Thunder]

Hey gunamonth -
Actually, I hadn't read that!
I just searched the forum for 'freebore' & read the various post there.

From what Dave says, I conclude that a freebore of .80" would work for bullets up into the 80 gr. area.

Now I'm off to search for a barrel with that spec.

Thank you for the'quick & easy' answer! : )

Ron

 

[CatShooter]

Hey gunamonth -
Actually, I hadn't read that!
I just searched the forum for 'freebore' & read the various post there.

From what Dave says, I conclude that a freebore of .80" would work for bullets up into the 80 gr. area.

Now I'm off to search for a barrel with that spec.

Thank you for the'quick & easy' answer! : )

Ron

that a freebore of .80" would work for bullets up into the 80 gr. area.

With a freebore of 0.80", you could launch MK-48 torpedoes

Be careful when you order a reamer - you WILL GET what you ask for!


.

.

 

[tightneck]

I'd probably limit the freebore to .060". If you planned on shooting only 80's, that would be another story. You won't lose too much case capacity with the .060" freebore and the 80 grain FB bullets, but you may be jumping lighter weight bullets with the .080" freebore. Oh, and BTW, go with either a Shilen or PacNor prefit, there's just no reason to take chances. JMHO

 

[Thunder]

CatShooter -
You caught my typo before I did!
I of course meant .080"

tightneck - Thanks for the advice. The .060" does make more sense. And I will check out the PacNor also.

Ron

 

[Williamb]

Ron -

Take a look at Gun of the Month #36 -

http://www.6mmbr.com/gunweek036.html

Very interesting discussion about developing a reamer for a Pac-Nor barrel with various bullet weights to be mounted on a Savage. Good chance that the reamer print for this still exist.

 

[Ackman]

My shooting is strictly varmints and mostly with lighter bullets going fast. Seated just shy of the lands I want them as far into the neck as possible. So my reamers have 0 freebore. Here are some measurements for this kind of setup. You should be able to figure how much freebore you want.

The 6BR case is 1.555" and has a fairly long neck. My chamber length is 1.565" with 0 freebore. So bullets seat about as far down as possible with this cartridge. If the chamber is longer, bullets will seat that much further up the neck.
With bullet just kissing the lands, the distance from base of neck to base of bullet is:

55 BlKing - .175"up - has lowest bc for light bullet
--------
55 Bal Tip - .150"up -high bc .275
70 Bal Tip - .030"up
--------
58 VMax -- .120"up - bc .250
65 VMax -- .060"up
75 VMax -- I don't have any. My guess is about at base of neck.
87 VMax -- goes into the case, start of boattail taper is at base of neck

This is easy to measure with a split neck case, you can see exactly where the bullet is.

The 55 and 58's will be very accurate up to about 3900 depending on powder/bullet combination. Also I've had real good accuracy with a couple 65's at up to 3700. Never shot anything heavier than that. It's an awesome cartridge.

 

[SmokinJoe]

FWIW, I just received a 6X47Lapua reamer from Dave Kiff yesterday, and I had sent dummies with an 87 V-Max and a 66 gr BR bullet. He made the reamer with .065 freebore, so that is probably in the ballpark. Also, I have used the 1-10 twist for 87 V-Max with excellent acuracy. Good luck with your project. Be sure to let us know how it turns out.