Secrets Of The Houston Warehouse

Bob Kingsbury said:
If the typical threaded and shouldered barrel joint is really flawed, why haven't barrel blocks shown a clear superiority ?
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If you're talking about point blank br, the reason is simple. The barrel lengths and weights are not great enough to show this as the most significant error. If you look at 1KBR Heavy guns on the other hand, now you might have a barrel that weighs more than your HV. Building that into a barrelhanger and attempting to send 20 rounds down it, the last 10 for record, well, that ain't gonna work so well.

Now, you might say, well than I guess this isn't a problem in short range. No, it just hasn't become the biggest error yet.
 
dang this thing just died, and i thought we were working towards some good stuff...

someone want to section a case head and see if they can figure out surface areas ?...6ppc....308 win....300 win mag....

look at the exterior of a case and note the rim..it is a large amount of the total surface area but has no push...nothing behind it, so at the most, if one counts that surface area, it REDUCES force on the bolt as it spreads the internal total force over a larger area.......
look at the primer pocket as a reducer also...the primer produces pressure on the primer surface dia, not based on the pocket dia....well unless you flaten primers on a regular basis.

i'd guess that there is less than half the surface area on the inside base of a case as there is surface area on the external base............

mike in co
 
Mike, the primer has nothing to do with it. The only change would be to take the wall thickness of the brass and reduce by that. Otherwise, pressure is pressure, it pushes back either on the case thence the bolt face, or on the primer, thence the bolt face. But one way or another, it pushes on the boltface. Now, if the case head is .473 with .020 wall thickness near the case head, then you can say the effective diameter is .433 and calculate from there.
 
4Mesh said:
Mike, the primer has nothing to do with it.
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Thanks, you are correct. It is the pressure pushing forward (toward the muzzle) that is important. This is what stretches the barrel and loosens the joint. The case has little to do with it either. The brass in the case walls is thin compared to the barrel, and has about half the strength of steel, so it doesn't make much difference. You could argue that the difference between loosening and not loosening is small according to the calculations. But the main point is that what we would ideally like to have is a joint that never even comes close to loosening, say, that would take twice the usual chamber pressure without loosening. At least according to the calculations, we don't have that now.

Cheers,
Keith
 
Keith, according to Vaughn's calculations, I think the PPC is safe in a bench rifle, as long as the barrel is tighten along the lines Jackie gave. It isn't a "problem in search of a solution," but for short-range BR, likely isn't a problem.

It would be nice to have that 50% cushion, and esp. nice to have a solution where it is a problem. What's wrong with Vaughn's redesigned joint on p 119-120?
 
i disagree, but have no way to prove my point.
we have pressure, but a peak pressure for only a short time period. the flash hole METERS the pressure into the primer pocket. i think it sees less total pressure due to this time issue.
it is a small area, so not a big issue in total pressure on the bolt face.
its not just case wall thick ness but the inside of the case does not have a full dia flat surface. there is a bigger reduction than 0.xxx case wall thickness.
was hopping someone would sacrifice a case and get us some numbers.
we have case pressing on the bolt face and the bullet trying to pull the bbl forward.......
now the bullet pull forward is a number i have never heard.
mike in co

4Mesh said:
Mike, the primer has nothing to do with it. The only change would be to take the wall thickness of the brass and reduce by that. Otherwise, pressure is pressure, it pushes back either on the case thence the bolt face, or on the primer, thence the bolt face. But one way or another, it pushes on the boltface. Now, if the case head is .473 with .020 wall thickness near the case head, then you can say the effective diameter is .433 and calculate from there.
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what about reducing the case head area by the "rim" area ? there is no pressure behind it just air ? or reduce the force due to increased area ?...
does the question make sense ?

mike in co

4Mesh said:
Mike, the primer has nothing to do with it. The only change would be to take the wall thickness of the brass and reduce by that. Otherwise, pressure is pressure, it pushes back either on the case thence the bolt face, or on the primer, thence the bolt face. But one way or another, it pushes on the boltface. Now, if the case head is .473 with .020 wall thickness near the case head, then you can say the effective diameter is .433 and calculate from there.
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I tightenned the barrel of my 721 project 30-06 in exactly the same manner as I do my 6PPC's, and if there is any barrel shift, (it's 27 inches), it sure doesn't show on the target........jackie
 
ok you made me do it..i sectioned a 220 russian lapua case.
wall thickness at internal case head .040, actual case dia is .438....minus .040*2 is .358 /2 is 0.179 for r pirsq is 0.179 x 0.179 x 3.1417 is 0.100 sqin x 60kpsi is 6000 lbs...well under the listed 8500 axial load.
someone check my math.
someone else co section a 6br case

mike in co
mks said:
http://www.engineersedge.com/calculators/torque_calc.htm

This calculator gives 8500 lb of axial force in the threads of a 1.0625 barrel torqued to 150 ft lb. Compare this to 10500 lb force from 60 kpsi chamber pressure on a 0.473" BR chamber and 9100 lb on a 0.44" PPC chamber. This suggests both are momentarily "loose" during firing. The calculator assumes dry threads.

For lubed threads, the K factor decreases from 0.2 to 0.18, so the thread force becomes 9400 lb. Then the BR comes loose and the PPC doesn't.

Jackie, I don't mean to argue with your experience, just reporting what the math says.

Cheers,
Keith
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if we ASSUME similar numbers for the 6br case, then we have a case dia of.471, with .04 walls for an internal dia of .391, /2 for .1955 then to pirsq we get .1955 x .1955 x 3.1417 for an area of 0.12 with the same 60kpsi we have 7200 lbs...again under the 8500.....

now torque your bbl to less than 150....you may have an issue......
at
125ftlbs the clamp is 7062 lbs

100ftlbs the clam is 5600 lbs

75ftlbs the clamp is 4260 lbs

you can see where UNDER TORQUE maybe an issue
my math says jackie is right on for 6ppc with his 125 ftlbs number.....

mike in co
 
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quickload is only a tool but it says in a 6ppc with n133 powder and a 65gr bullet......

3200 fps is 55kpsi
3300 fps is 60kpsi
3400 fps is 67kpsi......

it aint perfect, but stick those in above and see what torque you need in your rifle....

mike in co
 
mike in co said:
what about reducing the case head area by the "rim" area ? there is no pressure behind it just air ? or reduce the force due to increased area ?...
does the question make sense ?

mike in co
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I'm far too tired to check the math in the post following this one, if its wrong, you're still on the right track. It looks ok at a glance. But, as to this question, no, it doesn't make sense. Think about it like this. If you have a hydraulic rod that has 10 sq inches of surface inside its diameter, it makes no difference what the shape of the rod is inside. It can be checkerboard'd with high spots, but the real surface area is the area inside the diameter of the tube. If there's 10KPsi in there, there's 100KP of force. 10k x 10 sq in. That hydraulic rod only needs one requirement. It has to be round where it seals, and it has to seal. The shape can be as uneven as it likes. Same for the inside of your case. Makes no diff if there's a flat inside the case or not. If there's a radius (like a case has inside at the base) then there is more force. Yes, some of the force is pushing kinda outward because of the radius inside there. BUT, there's more square inches of area to push on, thus, there's more "force". But ultimately the force in the axial direction is the PSI times the SI's. That shape of what it pushes on is irrelevant.

As to the rim analogy, that's fails too. If you were to use my hydraulic rod example, it would be like saying there is 100K pounds of force on the rod, but if you turn down the rod end to a 1" diameter, thread it and attach it, now somehow the force there is reduced because the diameter is smaller. Wrong, just now the pressure per square inch is greater on less square inches, same force.
 
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yes i just could not convince myself...so i asked....
mike in co
 
If the clamping force we use is so marginal, The barrels on ultra-mags and short mags should still be rattling in the barrel channels
long after the deer falls over. There must be something else going on in that threaded joint.
 
Charles E said:
Keith, according to Vaughn's calculations, I think the PPC is safe in a bench rifle, as long as the barrel is tighten along the lines Jackie gave. It isn't a "problem in search of a solution," but for short-range BR, likely isn't a problem.

It would be nice to have that 50% cushion, and esp. nice to have a solution where it is a problem. What's wrong with Vaughn's redesigned joint on p 119-120?
Click to expand...

Charles, I think you are probably right about the PPC.

Thanks for referencing Vaughn. We are rehashing here what he actually did experiments on. His redesigned joint solves the problem of thermal expansion, because as the barrel heats, it only makes the joint tighter. It doesn't solve the chamber pressure problem, though. High chamber pressure pushes the barrel forward and loosens the back end of the barrel stub, potentially allowing it to walk around. A taper on that stub would tend to force it back to the same location, even if it did loosen.

If the shoulder of a 1" tenon moves radially by just 0.0001", while the rear of the tenon remains stationary (or vice versa), the effect on the target is 0.36". The way this might show up is in otherwise unexplainable flyers, as the shoulder occasionally jumps to a different position for a shot or two and then returns. I think Vaughn says the same thing about his 270.

Cheers,
Keith
 
This past season, I had a chance to see a centerfire BR action in use that had been modified so the barrel tenon was a slip fit into the action. No threads on either the barrel tenon or in the action....like a 10-22 Ruger. The clamping arrangement allowed it's owner to 'clock' the barrel to any position he wished as a tuning aid.

The gun shot well and over the course of the two day event, I'm pretty sure the barrel never fell off.......;) -Al
 
Barrel and action alignment

If you follow all the various threads on chambering, type of thread, torque, etc. you notice a range of opinions.... and all of the methods can produce good results. I don't think aligning the action and tenon is a problem. The problem is how close to that alignment can you get the chamber since everyone seems to be in agreement that the bore is not perfectly straight and some barrels are going to be better than others. Your set up is limited to the tolerances of your equipment, indicators, and the ability to use them more than the method itself. It's all about concentricity and tolerances. - nhk
 
mks said:
Charles, I think you are probably right about the PPC.

Thanks for referencing Vaughn. We are rehashing here what he actually did experiments on. His redesigned joint solves the problem of thermal expansion, because as the barrel heats, it only makes the joint tighter. It doesn't solve the chamber pressure problem, though. High chamber pressure pushes the barrel forward and loosens the back end of the barrel stub, potentially allowing it to walk around. A taper on that stub would tend to force it back to the same location, even if it did loosen.

If the shoulder of a 1" tenon moves radially by just 0.0001", while the rear of the tenon remains stationary (or vice versa), the effect on the target is 0.36". The way this might show up is in otherwise unexplainable flyers, as the shoulder occasionally jumps to a different position for a shot or two and then returns. I think Vaughn says the same thing about his 270.

Cheers,
Keith
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So, The conclusion I took from Vaughn was that the real problem with flyers isn't that that barrel can move around a little, but that the scope is on the receiver & doesn't move with the barrel.

I'm back to my solution, barrel block the rifle, have the scope base on the block cantilevered back over the action (for ease of use), and forget about it.

Anything wrong with that?
 
Barrel block

Charles E said:
I'm back to my solution, barrel block the rifle, have the scope base on the block cantilevered back over the action (for ease of use), and forget about it.

Anything wrong with that?
Click to expand...

Sounds logical. Are you using that method? Aren't most(?) rail guns set up that way? - nhk
 
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