The actual problem with this particular M70 barrel had nothing to do with any superficial similarity to a beagle's hind leg. No, in this particular example the chamber was oval. Looked at from the rear the chamber was larger by about .0025" horizontally than it was vertically. This was actually no problem when firing factory loads but was certainly a problem to the owner when he tried to reload the oval brass. Full length sizing would not quite restore the brass to factory dimensions.
I removed the barrel and set it up in the lathe to (a) measure and (b)correct the defect. Removing the barrel was a bit of a challenge in that it was very tight. Strangely, when I got it set up in the lathe the dial indicator only showed about a .001" differential in the two measurements. Odd. Nonetheless I went ahead and set the barrel back and rechambered. It just barely cleaned up all around but looked good. The indicator showed .0005 total runout so everything seemed fine. I had set the barrel back 2 turns removing exactly .123 from the shoulder to do this. I had also faced .002 off the front of the receiver giving me a .125 total. This meant the barrel was torqued up just as tightly as the factory fit. Pretty damn tight (advanced tech term). I tried a factory case in the chamber and it went just fine. I tried a sized case oriented so that the wide spot was horizontal and it went fine. Oriented the same case vertically and.. It wouldn't go! "What the heck gives", I said cheerfully. I retrieved the piece of brass from where I'd thrown it and look at it. No question, it was dragging on the high spots.
I pulled the barrel off and stuck it in the vice to recheck the thing and the brass dropped right in! It not only dropped in but could be spun 360 degrees with no problem. Suddenly the problem became clear and even made sense once I thought of the contributing factors.
First; The WSM is a fat cartridge. New brass measures right at .550" at the solid head. The rifle chamber measures .555" at the rear. ( I could equate it's shape to that of the somewhat rotund Beagle Bailley but she's already bummed out over her crooked hind legs!)
2nd; The winchester has a threaded tenon which is nominally 1 inch in diameter. The minor diameter of the threads is, at the most, about .935. In the case of this particular rifle the major diameter was only .990 and the minor diameter was .920". So the thickness over the chamber at the threaded portion of the barrel is only about .185"
3rd; Anyone who has looked inside a post 64 receiver has probably noticed the threads are not continuous around the receiver ring. Instead, they are very nearly removed by the cutting of the locking lug raceways. This means that the threads are unsupported at 3 and 9 o'clock for about .8" total (about 26% of the circumference of the thread).
So, when the barrel is torqued up there is a significant lateral load put on the 60 degree threads and the barrel is compressed and distorted top and bottom. The unsupported sides bulge outward.
The cure? Two that I can think of. First would be too simply not torque the barrel up too tight. Second is to finsh ream with the action in place so that the distortion has already occurred (my answer in this case was a combination of the two. I relieved the barrel shoulder an additional .002 then reamed by hand after it was screwed together). The real answer is to enlarge the receiver threads to Remington size (1.062) and rebarrel. Even better would be to also change the thread form to an Acme. I personally think Winchester should address this as it's a serious design flaw IMO. I know of a bunch of guys who have similar problems with out of round chambers on WSMs and would be willing to bet the root of their problems may be the same as this one. Regards, Bill.

Bill, was this a 300 or 270, not that it makes alot of differance. I have a 300 WSM that may be one of a kind as it performs perfect in feeding and grouping. I just dug out a bunch of fired brass and all of mine looks fine to my eyes, even with my glasses On

This was a 300. I don't think the problem is by any means universal but I do think it may be relatively common. I don't think a lot of the WSMs anyway and really think the combination of the case and the M70 action shortcomings makes for a potentially flawed outfit. Regards, Bill.

Bill, NOW I know why Savage increased the barrel shank diameter and opened up the receiver of their rifles for the WSM chamberings. I heard that the first run of Savages were standard diameter, then a sudden change to the enlarged barrel tenon for WSM chamberings.

From what you posted, is this distortion exclusive to Winchester and thier incomplete thread contact, or will other receivers lend themselves to this same situation?

Good for you uncovering what was happening!

I suspect the distortion as experienced in this case would be common only to new M70s. However, the Savage, with it's finer threads and barrel nut has the potential to compress the chamber since the lateral force with the finer threads is greater. Also keep in mind that the Savge barrel has no shoulder so is the same size even ahead of the receiver so enlarging the thread makes sense from that standpoint alone. Regards, Bill.

The chamber on my cira 2002 SS M 70 Classic yields round fired cases. But mine may be assembled the best way.

--------------------------------------------------------

Edited.



See update below.

Bill



Please enlighten me and others. Is what you are talking about concerning the threads a common characteristic of all Model 70 actions, or just those made specifically for the WSM line of cartridges.



Additionally, how difficult and costly is the "answer" that you mention.



Blue

Blue,
The "interrupted" threads are common to all post-64 M70s. The enlarging of the receiver thread is not that big a deal and is easily done by using the same setup as one uses to true the threads and locking lug seats. Once the threads are opened up to 1 1/16 you have a full thread. I charge 200.00Cdn to recut threads and true up the face and seats on a M70. I can't say what others might charge. This is work that used to be done only for target rifles but many now want it done on hunting rifles as well. Sometimes the work is justified, sometimes not. In a case such as this I think it is since it is a functional, and to a certain extent, a safety related issue. Regards, Bill.

Bill, have you examined any Browning WSMs? I ask this because, since they both came out, it seemed that Browning had done it "right" and Winchester had some inconsistent results, primarily with feeding. I have a Browning A-Bolt II Hunter which feeds and extracts perfectly (from the magazine!) and has shot several 3-shot 1/2 inch groups. It is without a doubt the most accurate box stock hunting rifle I've ever seen. I know that logic has nothing to do with it, but wouldn't you think these two branches of the same company would have shared some notes along the way, especially with the HUGE gamble on the line with a new, proprietary cartridge? Could you give me any feedback on your experiences working with Browning actions?

Thanks, Bill.....

MKane160 aka BigDogMK

I put a Lufkin bore gage into the chamber of my 2002 SS M 70 Classics chamber. In the back of the chamber there is an out of round condition. I did not measure it as it's easier to measure fired cases.



The average of three 7mm WSM cases measured at the expansion web was .0019" out of round.



My Redding FL die sizes the cases for easy cambering.



I measured just one belted magnum rifle and my pre 64 M70 in 264WM cases measured .0006" out of round done the same way.

Those interupted receiver are about my only complaint with the M70. Maybe Dave Manson will read this & decide to manufacture a tool for rethreading the M70 to M700 specs.

MKane,
I've not looked at an A-Bolt WSM but would expect this particular problem to not exist on these since the design is different. I see very few A-Bolts here. Can't say why.
Sav 99,
If the ovalness(?)you measure is in the horizontal plane then I would suspect the same cause. Keep in mind that chambers are frequently out of round for other reasons as well (e.g. poor set up when reaming). I would expect this to be the case with your pre-64.

Bill,

I marked each of three fired cases by marking them in one spot and miking them at 12, 1, 2, 3, 4 and 5 o'clock. Measurements were taken at the expansion web in about the same place.

I tried to chamber one fired case and it stuck in the chamber. I have been a FL type of loader anyway for hunting rifles but this chamber will not take neck sized reloads.

This rifle is very accurate and has fired numerous one hole two shot groups at 200 yds. This has taken some of the fun out of it however.

Bill,
What you may be seeing is out of roundness caused by the extractor holding the cartridge to one side. There can be as much as .011" clearence between the cartridge and chamber. The extractor holds the cartridge to the left on a right hand rifle. At firing, the cartridge expands to the chamber size while the rim (base) remains to the left creating the out of roundness of the case many people are seeing.

Because of this, the early M/70's bolt faces were a little tight and had to be opened up to allow for better extraction and feeding.

Good shooting,
Headache

Headache,

My chamber is out of round. Come on over to the BCRC in Southington and I will bring my rifle, cases, gages and mic.

Bill, just wondering if you have had a chance to look and inspect many other makers for this problem in say non WSM calibers?

I have a bunch of Winchester once fired brass and some of same in unfired that I am going to have checked to see how it all compares.

I do believe that the current 70's have non-interupted threads. They did make a change, maybe the out of round chambers are only on the older guns.

The M70 "Classic" has interrupted threads on the right side (extractor side) of the reciever.



A thought to ponder: Since these WSM's are higher pressure could it by possible that the barrel (at the chamber) is springing / enlarging when fired in the old m70s at the juncture where the threads are not supported due to the relief cuts on both sides ( 3 O'clock & 9 O'clock ) then springing back? As Bill has stated the chamber walls are not that thick at that point.

Hey Bill, Thanks for the information. This looks like one of those "issues" that a lot of folks will begin checking to see if their rifle has the same characteristics.

For all the WSM fans - Best of luck with yours!

To clarify,
The out of roundness of this particular chamber was most definitely cause by distortion of the threaded portion of the barrel by the lateral pressure generated when the barrel was tightened. When the barrel was removed, the distortion all but disappeared. I have not seen this on any other rifle or caliber. If the threads were complete I suspect the compression might still have occurred but to a lesser extent. Also it would be all around rather than just top and bottom. I also suspect the stainless barrels are perhaps more prone to this sort of distortion than chromoly would be.
As to whether or not the new M70s no longer have this thread I can't honestly say. I can say that this one was bought last summer. Another bought later than that had the same thread (I say had since it now has Remington sized threads). A stainless classic I just rebarreled in 300 Win Mag, ditto.
At this point I believe I would be tempted to rethread any new M70 I build in any magnum caliber and most defintely will rethread all for target work. This is obviously a problem which has not been previously documented perhaps because it simply never showed up until the advent of the WSM cartridges. There is little doubt that the larger diameter of these cartridges is a contributing factor. Further trials will show the amount of distortion one can expect with a full thread of 1 inch diameter as opposed to the incomplete Winchester thread. I must say I have never noted any such thing but I've not looked for it either. If you had asked me last week what I thought of the incomplete thread on the M70s, I would have said I didn't really like it but it was no big deal. This week I have changed my tune. Regards, Bill

I am just curious, but doesn't Darcy Echols, David Miller, Mark Penrod, and others, as a matter of course recut the threads in any rifle that they build, including these model 70 classics?

blue, recutting the threads in and of itself will not necessarily make them "complete". It depends on how crooked they are to begin with. The Model 70, Bill refered to that now has 700 size threads is a LH CM Model 70 action that I sent him. It was so crooked that opening the threads to that size was necessary to get them straight with the rest of the world. I can still remember Bill calling to congratulate me on discovering the crookedest (word?) model 70 he had ever had the pleasure of working on. I was humbled .



Bill and I discussed this over his steak dinner last night (sorry Bill) and came to the conclusion that that crooked action might have been a slight blessing in disguise.



Chuck



P.S. On an unrelated note, but referring to another thread, Bill does a heck of a job building up and checkering the bolt release on a model 70. I inspected one that he had done on my 70, a couple of weeks ago, while checking out my new threads, so to speak . Impressive!

For lack of any other way to measure the chamber, I used a mic to measure some fired cases from a Mod. 70 Supershadow in 270 WSM. This rifle has only been fired 18 times, but the cases all showed to be round (within about .0001 or so), at least as well as I can measure. From what I understand of Bill's explanation of the problem, the distortion is generated when the barrel is tightened in the action and is not related to pressure from the rifle being fired. Is this correct? If so, I would suspect that the chamber on this rifle is OK and that the chamber will not distort in the future as more rounds are fired through it. Would this be a correct assumption, or should I junk the ugly gun before I really start working on it?

Chuck

I think its great that Bill was able to find these problems for you, and I also think that it was real nice of him to come on here and explain all of this to us.

But, it would seem to me that such a defect should have been replaced by Winchester, as especially if there is foreseeable harm which they knew or should have known about.
What I am getting at is this. Can the problem that you had in any way be translated into a safety problem such that somebody could get hurt. If not, then I will shut up. But if so, then definitely Winchester should know about it and do something about it.

On another note, how difficult is it to send gun parts from the U.S. to Canada. I would like to have Bill build up a model 70 bolt release for me, but I don't want to have to go through a billion procedures to get the part up there and back.

Blue

I don't think the rifle I sent Bill was unsafe, and was most likely within "spec".

Chuck

Blue~
Why don't you just pull out the bolt release yourself and send that to him? That way it's just a stamping and I doubt anyone would care. It's flat and would just go in a regular envelope. It's Bill's problem getting it back to you as I'm sure it won't be flat when he gets done with it. If it works, I'll send him one of mine. Bill, do you do stainless too?