Home Forums Hunting & Shooting Gunsmithing Barrel Shank Length

Please excuse my ignorance in this matter...But a question occured to me the other day concerning guys putting custom barrels on their builds. Why do some guys prefer a 1" others a 1.5" etc. shank on a given barrel? Is there a performance benifit to a longer or shorter barrel shank?

Thanks in advance,
Erich

Some of it may due to aesthetics.. Some is due to the stock inlet (using original - or custom) and some is due to the chambering (safety/pressure issues)..

The model 70 FWTs in standard chamberings have a shank only about 3/16" long.. Sporters are usually about an inch before taper.. The bigger magnums (like .416 etc) can have a shank length of 1.5" or more..

some guys like longer barrel shanks because they think they'll have the barrel set back and a new chamber cut to get a little more barrel life. i don't see the economy of trying to salvage a toasted tube by sinking money into it, though. if i'm gonna spend the money to have a chamber cut and barrel fitted, it's gonna be on a good tube to start with.

Good question deerhunter - I've been trying to sort this question out myself!!

Any other insight on this??

Would there be any reason not to use a 1" shank for a 30/06 barrel?

Shortening the shank also reduces the overall weight of the barrel. An inch off the shank is probably equivalent to 2" off the muzzle end.

I thinks it's closer to 4 1/2 times as much for a typical #3 contour.

I'd go shorter. 1/2 to 3/4 at most.
No need to add unnecessary weight.

That's really up to the owner.. To some, a 1" shank on an -06 seems to provide an aesthetic balance to the rifle.. But all that needs to be coupled with the stock design, barrel length etc..

There's no performance difference - just all in the eyes of the beholder.

You need to remember to cut enough off to get rid of the slop from lapping.
Butch

A longer shank makes the barrel stiffer for the same overall length. This reduces the amplitude of vibration of the muzzle and may make it more accurate. Target contours are supplied with as much as 5" shank. The only cost is weight. For the barrel maker more shank just means less machining.

Barrel Contours

Most standard shanks on a blank are close to 3" long - to give the smith and customer options re: length.. But even a short shank's lapping abnomalies are taken care of with the introduction of the chambering reamer..

Red Neck you are correct, but I had rather indicate my chamber in a place the lap hasn't stopped and started. Not a biggie probably, just my way.
Butch

???

All shanks I've had in from the various makers have a centering cut at the bore that's independant of the lapp. Don't you use a centering rod during setup?

Maybe I'm way off here..

But the shank's cut to length (tenon+shank) and then mounted and squared in the lathe before bore is indicated with the centering rod.. That removes the 'start/stop' area of the lapp..

Even so, let's assume the barrel ordered was a short-shank.. After mount/square - it's easy to take a boring bar and make a 1/8" indent around the bore.. Then re-install the centering rod and double-check the indicator for zero.. Most times it's going to be off .010-.050.. Another 5 mns of adjusting the 4-jaw and you should be at true zero..


To be clear - I'm not in any way questioning you - I was just trying to understand exactly what you meant.. It took me a while - but then, I'm old..

Sorry Butch..

Hope I'm not hijacking here, but it is sorta realated? What is the smallest, safest, diameter barrel dimensions at muzzle and forward of the shank? I know a Win FWT barrel steps down to approx .980" after the 1/4 in shank and has a .550" muzzle diameter. Remington Mountain contour has similiar muzzle dimension. How much shank/diameter is needed to contain pressures of standard cartridges such as 308/270/30-06?

A rough approximation of stress can be calculated with the thin wall cylinder formula.

Stress = Bore x Pressure)/(OD-Bore)

Or in your muzzle example

Stress = .308 x 60,000/(.550-.308)
Stress = 76,363 psi

That is quite a lot, and normally you would double that for a factor of safety of two. Suspect most barrel material is not good for 150,000 yield. So in that case they must be counting on the presure to be much less than 60,000 when the bullet gets to the muzzle. And it is.

For the cartridge end, you probably should use a thick wall cylinder calculation, and I can't remember what it is. Your chamber really does see 60,000, so obviously it has to be thicker. And to really answer your question you need to have good information on the yield strength of the barrel material in its final condition after stress relieving.

I cut the shank to length before installing it in the lathe. The centers in the barrel when I receive it are useless to me. I chamber in the headstock. I indicate the leade area in the grooves and at the muzzle. This is just a simple way to tell you. I am visiting my youngest Son in Kalif. We are here for his retirement ceremony tomorrow[Air Force]. Can't get on the computer much. I can treat you with my chambering setup when we get home next weekend.
Butch

Pretty much what I do also..

I know there are some guys who chamber using a steady rest.. I just can't see that.. To me, it invites sloppy chambers, since no way can you dial in the bore that way...

Maybe I'm just nuts..

I always hated to see guys buying pre threaded/chambered barrels because they tended to have the full shank on them. It kind of destroys the idea of a custom. For a hunting rifle in 30-06 length or shorter calibers I was taught to leave 7/8" of the shank before the taper and then whatever length the threaded tenion beyond that. I was also taught to cut off an inch from both ends of the barrel blank.

ETA: The 7/8" is purely for looks. And I should clarify max 30-06 length. Now a heavier hard kicking caliber can use a longer shank to help add weight as would a target or longer range rifle. But 7/8" looks good on a standard hunting rifle.