My hope is that this post will be about discussion and not "Wby is shit" or something else is shit etc.

Lug set back has often been mentioned on this forum with respect to large diameter cartridges and with CZs and Mausers etc. Mentioned just as often is Wby Mark V only having a few lugs contacting.

Let me say that I believe that 2 lug actions set back and I also believe that a Mark V is doing well to have contact (partial contact) with 3 lugs of the 9.

In my opinion we must also consider bearing area Vs shear area. I think most would agree that if we made the locking lugs a foot long that would not prevent set back on the 2 lug action.

So.....if the 2 lug action sets back and the Wby Mark V only bears on a couple of lugs...could that mean that a Mark V is on the way to a "blow up". Given the number of 30/378s out there that will be lucky to bear on (in my opinion) 3 lugs at the most, then that must mean the there is setback BUT spring back. Will continual Setback/Springback fuck the action.

I mention the 30/378 because it is a major seller for Wby and is quite cheap in the Synthetic. A couple of years ago on this site I saw a member ask if the 4895 he used in his 30/06 would be OK to use in his new 30/378. In short there a plenty of Wbys getting a hammering ....but are they gradually on their way to completely letting go because of Setback/Springback. We all know what happend if you bend a piece of wire backwards and forwards.

So is lack of lug bearing with the Mark V a case of "spring back" and if so is that a lead up to failure...........Mike

As a side note, I have seen a 378 loaded with Varget and the powder measure set for 108 grains of IMR 4350 and 270 grain bullets. The powder measure setting threw a 110 grains of Varget. This was several years ago and before Hodgdon was selling the Australian powders but the 2208 was still the same basic burn rate.

I was the shooter and did not see any difference until I went to open the bolt.Frozen. Mallet and ramrod to get case out. Case head held.

As near as we could figure there had been about a thou or so set back. That was based on chambering cases that had been fired earlier in the day (with firing in removed)and the movement we could feel in the bolt. As you know a thou or two headspace is easy to feel.

Chamber dimensions appeared all OK and that proved to be the case with reloads using the neck sized cases.

Don't know. But I'm wondering if Weatherby make any attempt to get most lugs bearing, and why you think only 2 or three usually are. Can you see rub marks on only a few?

But if these few are going to wear or set back, wouldn't that just bring the others to bear?

I got the impression here on AR the 2 lug ones that set back may be real old clunkers, overloaded, not hardned properly etc etc.
I mean, some of those mausers they rave about making into big bangers are really ancient and belong in a museum.
John.

quote:

I also believe that a Mark V is doing well to have contact (partial contact) with 3 lugs of the 9.

Carlos Critzer once told me the same thing about the Mark V but amended his statement by saying that there was a point at which all 9 lugs bore and that was about one millesecond after ignition of the powder charge.

Seriously, I have never seen a Weatherby with lug setback or shear. On the other hand, any Mark V I ever re-barreled, I lapped the lugs in first, precluding that stretching of the bolt head to make the lugs contact.

Unless the wby is lapped in, your probably making contact with 3 of the lugs according to some dicom tests I have run and I don't know how accurate that is..

At any rate lots of good two lug rifles out there and I don't have any qualms about the Wbys...Why does it have to be my choice in rifles is better than the other guys on these posts.

I like Mausers, Pre 64 M-70s, I don't like Weatherby rifles, but I have noting against them other than the stock design is not to my liking and the action is bulky IMO, but I believe them to be excellent rifles and they have been around for a long time. I think the 300 Wby caliber is one of the all time great calibers.

I have seen photographs and read the story of a Mark V that sheared all nine of its lugs resulting in the bolt flying back out of the action, so I know it can happen.

I can't remember the circumstances and don't have the photos, but I believe they were posted here on AR a few years ago.

quote:

then that must mean the there is setback BUT spring back. Will continual Setback/Springback fuck the action.

Stuart Ottenson had a very good discussion of the Weatherby action in his first book on Bolt Actions.

I have never conducted a reverse analysis of the stresses on a Weatherby action. I don't know the lug thickness. But I have calculated the stresses on a M14 bolt in a very basic way.

What you call springback is really the bolt lugs flexing below "yield" http://en.wikipedia.org/wiki/Tensile_strength . Steel will give a bit, without deformation. When it deforms, the material has exceeded its "yield".

Steel also has a fatigue life. That is the number of yield cycles it takes to cause the metal to crack. Steel can be designed thick enough so that given a certain load, the fatigue life will be infinite.

By measuring the thickness of M14 bolt lugs and given its load, that bolt was designed for an infinite fatigue life.

I would assume that the Weatherby bolt lugs were designed to give an infinite fatigue life given all lugs were bearing. If there is some sort of a dimensional out of tolerance condition, there is always the possibility that one lug would be stretched more than the others. And you could have a lug crack.

I also assume that there is enough design margin in the bolt that there would not be a catastrophic condition when a lug first cracks. I would not recommend ever continuing to fire a rifle with a cracked lug.

I would assume given the high prices of the Weatherby action, that you are paying for the extra QC that ensures that the action is well built. Don't worry about this.

quote:

I have seen photographs and read the story of a Mark V that sheared all nine of its lugs resulting in the bolt flying back out of the action, so I know it can happen.

MR,

What happened with the bolt handle, as the Mark V bolt is one piece.

Mike

I seem to remember that the bolt handle did not hold the bolt in the action. I don't know if it sheared off, but IIRC the bolt somehow managed to fly backward out of the action.

MrLexma,
According to Jack Belk if one does not close the Wby action completely closed it can blow the bolt back into your face, I suspect that is what you are talking about..

Just passing it on for what its worth, have no personal knowledge of this.

The tolerances on a rifle's lugs and action seats are very small, generally less than 1/2 thousanth of an inch. I can assure you that all 9 Weatherby lugs are in full contact before the bullet begins to leave the case.