Secrets Of The Houston Warehouse

Charles,
When using quotes around words attributed to someone else, the convention is that they would have actually used those exact words. In reviewing my posts, I did not find them as you have them in post #125, and if you take another look at post #120, I think that you will see that your quote substantially misrepresents the gist of what I said. As a matter of fact, it was Vaughn who said that there are several factors that reduce the probability of barrel movement in a benchrest rifle. I am just agreeing with him. I also engaged in conjecture as to other reasons for what he reported...in my earlier posts. Looking back, the question as to barrel stress may have been off the mark, but I make no claim, nor have no delusions as to my infallibility, so I left it as I wrote it.

Getting back to my reference, in an earlier post to the fixture in which the rifle was held during his tests, if there is a threaded joint between two pieces, an action and barrel, and the action is prevented from moving with the barrel, does this restraint not put more stress on the joint than if the two were free to move together? I think that the answer is obvious. Vaughn was a very bright fellow. I learned a huge amount from reading his book, and will learn more as I go back over it, but he was human, and I do not think that he got every single thing absolutely right. I was lucky enough to have had several phone conversations with him, in which he was engaged and quite cordial. I wish that he was still alive so that we could have more discussions.

Threads on these forums often involve differing opinions, and as long as we are not rude to one another, no harm is done.
 
It does solve the problem of the use of quotes, but I still feel that you have misread my intent (not that big of a deal after all). To be clear, I am of the opinion that his choice of test rifle, and the way that it was fixtured may have increased the probability of movement within the barrel/receiver joint, and for that reason, additional work may be required before his results can be taken to apply to custom actioned benchrest rifles, that are not fired in a machine rest, and that we should satisfy ourselves that a particular rifle actually has the problem before investing time and money in a fix. (Yes, that is a terrible run on sentence.)
 
Boyd the frustration I was -- am -- feeling is that I've been set up. Whenever I (we, including Phil) give one type of answer -- general, math, someone, including you, says (sort of) "what about the real world?" Whenever we turn to that, the reply changes to (sort of) "what about the science?" I ain't going to play that game.
 
Charles,
None of us makes our living off of this board. I suggest that you relax and enjoy a little more, and consider that it is the very nature of discussions that differing opinions are expressed. It has never been my intent to upset anyone, at least within this thread. Engineering problems tend to have multiple variables that may or may not have been taken into account before the calculations were done. That is why there are test pilots, and why this happened. http://www.youtube.com/watch?v=3mclp9QmCGs

Boyd
 
Just thinking AL,. Some years back, it was common to find a white compound on the threads of factory installed Barrels.
As it was kinda tuff stuff, I doub't that it was thread sealer or anti seize. More like the locktite that is made for
fasteners over 1" diameter. I also might note that many of them were pretty good shooters. They were also
kinda tough to disassemble. You gotta wonder.
 
Al, really the only two things to consider are:

1. How much axial (rotational) force does a bullet really impart to the barrel as it travels down the bore in a CF rifle.

2. How much, if any, forward thrust (for lack of a better term) does the barrel 'see' relative to the bolt thrust.


This formula will get you started on #1. You'll want some fresh batteries in the calulator, as you won't believe the end result and will refigure it a few bazillion times. ;)


T = (1.7x10^-9 x W x R^2 x N )/T
T= torque in lb ft
W = bullet wt. in grains
R = radius of bullet dia. in inches
N = bullet r.p.m.
T = time bullet is in barrel in seconds

Good cypherin'. -Al
 
OK, let's keep going on this.

Imagine a non-threaded tenon of 1.062 diameter and a matching non-threaded area in the reciever that has provisions for clamping to the barrel tenon. If the tenon is 1.00" long, there will be 3.336 sq. in. of contact surface between the tenon and the i.d. of the reciever, assuming 100% contact when the front ring of our modified/prototype reciever is clamped. Even if contact is only 80%, we're still looking at over 2.5 sq. in. of contact (2.688 sq. in. to be exact).

If we accept the commonly held premise that only 3-5 threads on a 'conventional' threaded tenon actually hold the load.....how much contact area are we actually talking about in a 'conventional' setup?

We all understand that tightening/torquing the barrel to the face of the reciever loads the threads and gives the 'tightness' to the connection. Using the example of a 1.250 shank dia. barrel, there is roughly .100 of of contact area from the the outer edge of the threads to the outer edge of the shank of the barrel. Basically, a .100 flat area of contact between the barrel and the face of the reciever. This figures out to be less than .4 sq. in. of contact surface (.3926 sq. in. to be exact).

So, here's the quandry:

Is there a point where the increased clamping area of a non-threaded tenon/reciever joint equals, or exceeds, the 'stability' of a conventional threaded connection?

4mesh, Charles, Boyd, Jackie, alinwa, Greg Walley, Jim Borden, Jerry Stiller, Mike Bryant, Butch Lambert, Nate Lambeth, Gene Beggs, anyone and everyone.....your thoughts on this?

Maybe I should have studied Mechanical Engineering instead of Physics and human anatomy???? :D :eek: -Al
 
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I don't have enough engineering background to know for sure and what engineering I had for the most part isn't all that applicable to mechanical engineering. One year of architechtural engineering before I decided it wasn't for me. My thoughts on clamping a barrel is that it might be a recipe for disaster. Is it tight enough, is it not? The barrel shooting down the forend might be the least of the worries. I doubt if the cartridge case would be staying in the barrel and would probably be leaving the chamber as the barrel leaves the receiver. I'll take a mechanical lock over a friction fit anytime.
 
Al,
How does it go? The definition of insanity is doing the same experiment over and over, and expecting different results. If we always knew what was going to happen before we did something, there would be no failed experiments. As long as safety procedures are followed, I am all in favor of trying things that at first thought seem off the wall.

While we are talking unconventional....it seems to me that if you look at the barrel to receiver joint, that one way to look at the generation and control of the lateral forces that are generated, and which must be countered and controlled for barrel stability, that the distance between the threads that carry most of the load (conventional threads) and the action face, could be looked at as one side of a fulcrum, with the action face being the pivot, and the barrel being the other side. If this view applies, wouldn't it be better if the working threads and the action face were farther apart? Also, isn't the leverage of the barrel on the joint radically increased as the barrel gets longer. If we take this to the limit, for purposes of visualization, think about an 18" barrel with a 2" tenon, threaded for the last 3/4" at the chamber end, compared to a 30" barrel with a conventional tenon of about 1" length. Also, when the barrel of a rifle engages in first mode vibration (the whole barrel swing, hinged at the back) doesn't the weight of the rest of the rifle load the joint? Also, what about things that increase or decrease the tendency of the rifle to try and rotate about it's center of mass? It seems to me that many current short range benchrest stocks tend to minimize the distance between CM and the axis of thrust( CL bore). The point of all of this is that there may be things that we can do to modify existing designs to stabilize the joint. Feel free to tear up any of this that you don't like. My only request is that you explain why you disagree...so that I can learn something.
Boyd
 
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Wasn't it Schultz & Larson that used press-fit barrels on some centerfire rifles, including some for "fullbore match"? We need the strength of that -- in all planes -- with the ease of changing barrels given by a threaded joint.

Al (Nyhus), I don't see why JB Weld won't work for you. We use it on barrel blocks, where that is the only means of attaching the barreled action to the stock. Never heard of one coming lose, & the force going rearward has to be roughly the same as the force going forward, right? According to the guy that juggled apples . . .

It's late, what an I missing?
 
Boyd: I think you bring up some valid ideas for 'stabilizing' the barrel/reciever joint. Perhaps all that's needed to measurably increase the stability is a larger flat interface between the barrel shank and the reciever face? Another .100 of 'flat' would huge. But we have these pesky rules on barrel shank diameter.....

Charles: It was alinwa, not me, that is going to JB a barrel into a reciever. ;) You're right on some of the S&L's having pressed in barrels. In his book 'Bolt Action Rifles' 3rd. edition, Frank de Haas talkes about several S&L actions. He doesn't mention pressed in barrels, but does mention that the Super Magnum action was a threaded barrel. Other production cf rifles that had pressed in barrels were the Krico 300 (22 Hornet) and the Anschutz Classic (22 Hornet).

alinwa: Current S&L rifles have the lugs machined into the barrel. However, not all S&L's were like this. Several models had rear locking lugs (ala' the Rem. 788) and press fit barrels. I'm not a S&L historian, but here's a pic of one of the bolts:

photo6.jpg


As far as chamber pressure, during firing the majority of load is axial...outward. That's how chamber pressure is measured using pizeo-electric strain guages. If anything, firing should make the joint tighter as the barrel tenon exerts outward force on the reciever.

So, the only area of mystery seems to be whatever forward force the barrel may see during firing. Bolt thrust is easy to figure, but is there a direct correlation to what a chamber 'sees' in the opposite direction? I'm not sure how to figure that, but my guess is there's not as much as we think. Think about it this way: if there was all sorts of forward thrust...how can barrel blocks work? Since the action floats on barrel block rigs, wouldn't this Z axis force loosen the barreled action in the block(s)? But yet, this doesn't happen.

A couple/few things to think about:

1. This is all predicated by the 'fact' that there are issues in a conventional threaded tenon/reciver setup. Which, quite honestly, I don't completely buy. Nonetheless...

2. Rifles with similar setups that I've described (clamped tenon/reciever) have been made and used in the commercial market (S&L)

3. There is at least one BR rig out there with the setup I've described. I've seen it and it shoots well. The latest issue of the NBRSA news bears that out. ;)

4. A clamped tenon/reciever setup would offer 360 degree indexability of the barrel for tuning.

Good shootin'. -Al
 
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Sorry Al (Nyhus).

There are a few people who posts I try to always read, usually no matter what the topic. Al Nyhus and alinwa are on that short list. While they approach things from a quite different perspective, they're both pretty sharp, and the things they approach are usually things I find interesting. Both their insights and perspectives are helpful.

That's my excuse for my confusion, & I'm sticking to it. The other option has to do with age & other places better not gone.
 
alinwa said:
I'm seeing this as the difference between a screw and a nail.
Click to expand...

Exactly, the press fit simply has to slip for the barrel to come out. The threaded joint has to shear threads off.

I did a little figurin' with this calculator for Lame's equation: http://www.meadinfo.org/2009/07/press-fit-pressure-calculator-optimize.html

Just some quick checks, so don't anyone go out and build a rifle based on this (and get killed). With 60 ksi chamber pressure (which is what pushes forward and tends to shoot the barrel out of the action) in a BR case (0.473" diameter), with dry steel on steel joint (friction coefficient 0.8), you need 0.006" of interference fit. A lot, but doable.

With lubed steel on steel (friction coefficient 0.16), you need 0.016" of interference. And this would exceed the yield stress of steel (by about 50%), so this much press won't work.

Could we insure that lube would never get into the joint? I wouldn't want to bet on it. And these figures include no safety factor. One should increase the interference by a healthy factor to make sure the joint held in overpressure situations. My conclusion is that this is not a safe design for BR cartridges. Maybe just fine for small cartridges.

Vaughn's joint has a threaded nut to hold a slip fit barrel stub in. You could add some interference on the stub to prevent radial movement of the barrel, and the nut would prevent axial movement. The only other thing I might add would be a shallow taper on the stub so that it is easier to press in and out.

Cheers,
Keith
 
Al,
Going back to Jackie's earlier post, we may not have a problem. I think that Vaughn's test rifle was significantly different from long and short range benchrest rifles, and it may be that the fixture in which it was held increased stress on the barrel receiver joint. Given the cost of fixing the "problem" don't you think that it is prudent to verify that it exists for a specific rifle/rest configuration?
Boyd
 
German,
Lacking any restraint, the barrel will go down range. A fellow that I knew years ago put multiple charges in a '06 cast bullet load. When the case ruptured, it blew the top of the receiver ring, and the barrel went down range. I think that the maximum, greased chamber force that is trying to push the barrel out of the front of the receiver ( case intact) would have to equal the bolt thrust, and we have figures for that.
Boyd
 
German,
Even without friction, the bullet's inertia would contribute significantly, and the shoulder of the chamber is also an area where some percentage of the outward pressure of combustion is parallel to the bore, depending on shoulder angle.
Boyd
 
Boyd Allen said:
Al,
Going back to Jackie's earlier post, we may not have a problem. I think that Vaughn's test rifle was significantly different from long and short range benchrest rifles, and it may be that the fixture in which it was held increased stress on the barrel receiver joint. Given the cost of fixing the "problem" don't you think that it is prudent to verify that it exists for a specific rifle/rest configuration?
Boyd
Click to expand...

Boyd, I agree completely. Like I said in my earlier post (# 143), I don't completely buy the idea that a problem exists....given good machining and fit up, of course.

Like German, I look at the clamped tenon as a potential tuning aid (360 degree barrel indexing).

As for the barrels zingin' forward, the Krico and Anschutz rifles I mentioned earlier use lightly pressed in barrels with either a single (Krico) or double (Anschultz) roll pin to hold the barrel in place. The 22 Hornet cartridge these are chambered for is a small case by centerfire BR standards, but top loads for the Hornet are still a smidge over 50,000 psi. ;) So, if we accept that a barrel will launch forward from the reciever of our not-so-theoretical action...we must also accept that these itty bitty roll pins on the Krico and Anschutz are all that keeps the barrel in place and that these roll pins are actually capable of doing that if the barrel really 'sees' 50,000 psi of 'forward push', for lack of a better term. Is 50,000 psi from a Hornet different from 50,000 psi from a 222? Or a BR? :confused:

Bolt thrust differences due to case head diameter notwithstanding, if only obviously..... -Al
 
I think that it is better to talk of bolt thrust in actual pounds of thrust, rather than PSI because is seems that there are those who say/know that it means pounds per square inch, but somehow fail to make the connection that we no nothing of the actual force exerted on the bolt until we multiply the unit pressure (PSI) times the effective area that it acts upon, in this case, the internal diameter of the case at its head.

If we take a look at the Hornet and the .308, since I don't happen to have the internal diameters at their heads, using the Hornets OD above the rim, and the .308s above the extractor groove, with the applicable pressure limits 25,000 and 62,000, using rough numbers, the bolt thrust of the Hornet is around 16% of the .308, ignoring reduction for case cling to chambers....so they are a LOT different.
 
I'm reading this on the iPad and haven't caught every detail...so take this for what it's worth.

If one is interested in using the barrel clamping for barrel indexing, might not straight threads solve the issue of clamping force?
 
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