About 35 years ago I had a pretty well known BR gunsmith fit a Hart barrel to one of Ralph Stolle's early Panda actions. Well, he made a significant error somehow and the barrel tenon ended up so small that when the barrel was broken loose from the action it would hit the bottom of the barrel channel of the stock (which by the way had a bunch of clearance). I was sure the barrel was scrap. After all these are "precision" rifles and something that sloppy could NEVER shoot. Well that barrel turned out to be a hummer and won a bunch of matches both large and small. After doing a fair amount of barrels myself between then and now I would guess that that barrel had at least .010 of clearance on the threads and maybe a bit more. Food for thought.
effects of using a trued action without proper fit std dia barrel shank
- Thread starter AckleymanII
- Start date
Dusty Stevens
Shiner
With thread gages.... if you got enough money to have a collection of them. Or you could take the long way and thread a stub to fit like you like then measure it with a cheapo thread mic
One torqued up normally 2-3 treads actually carry the load. Put enough torque on the barrel for the preload to be more than the firing load and nothing will come loose. If the tread can’t take that torque there is obviously a problem.
Not really a direct answer to your question, but I know some prefit makers that will cut the tenon .010 oversize just for trued actions. They will be doing this for me with two barrels as soon as I can get the action off the barrel, or vice versa.
I assume most are using a nut wouldn’t that have to be oversized also
Threads are not 100% self-centering. If made on close fit and profile, this is reduced to a strict minimum, but, if loose fit, there is very little chance for it to be on-center.
Also, the tenon is the weakest part at reinforce level and it bears the maximum of the pressure on firing.
If well maintained by correct contact in the receiver, this is OK but, if play exist between male and female threads, there can be expansion of the tenon under high pressure firings. This can cause loosening of the barrel and, in extreme cases, inflation of the chamber diameters.
I think gunsmuths here have noticed that thin walls chambers (Magnums or more) need often, after a certain firingd of high-pressure loads need more torque to be removed than the one they were initially fitted ?.
Imagine the situation if there is enough gap between threads to prevent the receiver to contain the pressures ?.
My point, FWIW.
R.G.C
C-g-designs .blog4ever .com
Also, the tenon is the weakest part at reinforce level and it bears the maximum of the pressure on firing.
If well maintained by correct contact in the receiver, this is OK but, if play exist between male and female threads, there can be expansion of the tenon under high pressure firings. This can cause loosening of the barrel and, in extreme cases, inflation of the chamber diameters.
I think gunsmuths here have noticed that thin walls chambers (Magnums or more) need often, after a certain firingd of high-pressure loads need more torque to be removed than the one they were initially fitted ?.
Imagine the situation if there is enough gap between threads to prevent the receiver to contain the pressures ?.
My point, FWIW.
R.G.C
C-g-designs .blog4ever .com
okie
Gold $$ Contributor
WTFreak!!! thats crazy--got pics???I had this happen on a 788 I re-barreled. The threads were a bit loose but it torqued down tight. After about the 5th shot the barrel came off and stuck between the scope objective and the stock. No harm and the last bullet went out the barrel and moved the group from .75 inch to 1.25 inch. We figured the right hand twist unscrewed the barrel.
butchlambert
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A bunch more internet BS!
ratguner
Gold $$ Contributor
JB Weld appears to be the cure all!
hogpatrol
Gold $$ Contributor
I bought a used R700 off of GB at a good price for the stock, action and trigger. Pulled the barrel, a Shilen, cleaned all the gunk off of it and out of it the receiver. Screwed the barrel back in and it wobbled like a worn out cv joint. IIRC, the o.d. was 1.042. I never checked the root diameter. Was glad I never shot it.
Many here don’t know about a cv joint
lol
The receiver to contain the pressure? The barrel does that. The whole length of thread would have to fit perfectly for this to happen. The only way the action would carry pressure (hoop stress) is for the barrel to deform so much as to seat all the treads.
The threads load different by tightening
Like a bolt the they do being pulled Ike a nut
But with 10 thousand clearance
And 65000 psi not for me
Like a bolt the they do being pulled Ike a nut
But with 10 thousand clearance
And 65000 psi not for me
Wasn't there a thread a month or two back where a member described testing barrels with nothing more than the barrel and cartridge with a crude firing mechanism and really nothing to contain the explosion except the chamber and brass? I believe it was in response to an assertion regarding bolt lug stresses during firing.
hogpatrol
Gold $$ Contributor
Yes, but I can't find it. It was a shotgun shell in a piece of pipe, IIRC.
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I think Mike Bellem of TC contender fame did some experiments with this bolt thrust issue
actually fired a cartridge in a contender barrel with a hammer and nail
brass stayed in the barrel like it is supposed to
so much for 65000 psi on the bolt lugs
if their was a lot of back thrust, there would be a lot of dead or injured contender and encore owners
catastrophic case separations are a different matter
I still think you hope for the best and plan for the worst
It could be safe at 65000
But what if it goes to 75000
Like the wrong powder can do or excessive heat on a cartridge
I dam sure wouldn’t but
Have at it
Works. For me
Bolt thrust is easily calculated. First you must know the case ID at the head. In the case of a br/308 this is about .385".
The formula is pi x (radius of the case head id squared) x pressure.
So, .385/2= 0.1925, squared gives you 0.03705625 x 3.1416= .116415915 x say 65,000= 7567.03lbs. Calculate the area of the lugs to figure psi of thrust.
This doesn't factor in the grip of the case on the chamber walls.
The formula is pi x (radius of the case head id squared) x pressure.
So, .385/2= 0.1925, squared gives you 0.03705625 x 3.1416= .116415915 x say 65,000= 7567.03lbs. Calculate the area of the lugs to figure psi of thrust.
This doesn't factor in the grip of the case on the chamber walls.
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