Gentlemen,
Query, I took my new Sterling Davenport 416 Rigby out today for the first time to sight it in. I was shooting factory A-Square Monolithic Solids at 2400 FPS. It has a pre-64 Winchester action with the action modified to accomodate the length of the longer case of the 416. The rounds fed fine. Bolt closed fine. After firing the round however, the extraction was difficult. The bolt would come up halfway and then considerable pressure would be needed to get it the rest of the way up. The case could then be ejected. No primers were raised and I've always been told the Rigby is a low pressure round. Any ideas before I send the rifle back to be worked on? I'd like to use this rifle on an elephant hunt in July of this year but can't do it with the problems it has now. Don't fancy myself as hairy jam under some elephants toenails!

Nitroman,

I am afraid we cannot ban anyone - despite the fact that it is the best thing to do sometimes!

We have a lot of people on these forums with a world of experience, and we have a few who pretend to know what they are talking about.

It does not take long to pick these out of the crowd. Once that is done, just do not pay any attention to them.

If the Ruger's thread is indeed 1 1/8" I stand corrected. I apologize for any hurt feelings. I was told that the Ruger RSM had a 1" X 16 TPI, by a well known gunsmith, no less! He supposedly has reworked several into over 50 cal rifles, I figured he knew of what he spoke.

Again, I am sorry. I should have verified by erroneous information.

Scott

FYI

The Ruger magnum has a 1 1/8" barrel shank not 1" as mentioned above. Also the exterior of the action is almost .100" larger at the receiver ring than a M70.

Either way, the brass should tell the story one way or the other. If it shows a bright polished scuff type of mark in any portion of the chamber more than any other part, then I would look in that direction. If no odd marks are apparent, then try the Federal ammo. It may be that simple.

Gabe

DArcy_Echols_Co,

Believe it or not, I agree with everything you have said. Actually I think the Ultra mags may in fact be over the top for the M70. I think it is at it's practical limit with the belted H&H magnum case head.

My first response to you was erroneous, based upon my not knowing the facts about the M77 RSM barrel shank. I apologize if my post seemed insulting, it was not meant to be. My bad!

From my own experience. I have seen a bulged chamber, but it was the result of someone fitting a 1/4 rib by milling a long and deep slot directly over the first 6" of barrel shank. The calculated burst strength of that particular barrel was somewhere around 57,000 psi (would have to look up the actual calculated results, but it was frighteningly low)! Directly above the neck/mouth portion of the barrel, the barrel wall thickness was only ~ 0.100" thick! This was no cheapo deluxe Kmart blue light special rifle either. It was an expensive custom, in the 50 caliber and above class, made by a maker well known in the the world. The problem was discovered when the quarter rib flew off the barrel after firing some "factory" loads. Ammo was not the issue, it was in the 45,000 - 50,000 psi range. The ammo did; however, induce enough hoop deflection in the barrel to rapidly fatigue fracture the solder which held the rib on.

Scary? I thought so. Anyway, this experience has caused me to be somewhat paranoid, I suppose.

Scott

Thanks DArcy,

That was a good post.

I have worked on heavy caliber bolt rifles for a long time, and I have also seen the "idiot factor" come into play more than once. I can't understand what people are trying to do when they make a god out of velocity, and they dammage guns that have worked fine for 80-100 years before they were dammaged.

Case in point. The Magnum Mausers. As you said, they have small ring shanks and threads. Yet all of the early 416 Rigbys and 404s that were made for those Mausers did not bulge the chambers, until some idiot got his hands on them. The modern CZ 416 has a small ring shank! Some of the issue is about the straingth of the barrel steels now, and 80 years ago.
I used to run Cast Performance Bullet Company, and I have fired more rounds than I can count testing guns. To illistrate, I have done LOTS of work with the 454 Casull. It has EXTREAMLY HIGH PRESSURE. Much higher than a lot of rifles. I have fired thousands of rounds through a 454 which ran 64,000 PSI. That's measured pressure, not theory
Look at a cylinder from one of the Freedom Arms revolvers, and measure the wall thickness. It's only .127" But that does not mean the every kind of steel will hold 64,000 PSI with only .127" thickness. These new revolvers are ammazing. I also know that CZ used to use a steel ( and I think they still do, but I'm not sure) called 'electro-poldi" It is also extreamly strong.

To anyone else reading this post, I believe we should discuss these things, and all share our honest knowledge and honest questions, and quit "flaming' each other. Sometimes one man can see a problem and report it, and others call fowl, because they "know something different" but neither knows all the info. Let share.

SZ

I can understand why the thread diameter may be an issue for someone shooting red hot loads, but the 416 rigby operates at 30-30 pressures. I am no gunsmith, but that would seem to be an important fact. Similarly, we do not hesitate to build a 9.3 x 62 on a World War I mauser even though the steel is soft, due to the relatively low pressures that round is designed for, but no one would want to build a 270 weatherby on a World War I mauser.

Scott
I must admit my grasp of theoretical physics could be considered "entry level" at best. I do have an elemental understanding of the primary stretch equation (=PL/AE) as it would apply to this particular subject. 25 years ago I picked up a Peruvian 98 Mauser action while attending a gunsmithing school. I wanted to chamber this action to the 404 Jeffery. Now to my knowledge non of my instructers had ever taken a physics class, however they had been building and destroying rifles out of curiosity for quite some time as military actions came a dime a dozen after the 2nd WW. Three of these guys were pretty sharp. To the man, each instucter told me while the action was plenty strong to handle the 404, the small thread OD (.980) was to small for a case of that size and I might bulge the chamber when trying to drive the 400gr at the speed of light. They based this advise on the chambers that they had bulged with oversized cases on undersized threads.
I has seen 2 Pre-64 barrels with bulged chambers at the location of the necking cut. Both rifles were still within headspace specs. In each case the shooters used dangerously hot loads over long periods of time. I pulled one of these barrels and could measure a distint bulge in the chamber about .640 ahead of the base of the case at the same location of the factory necking cut. Not long ago I blueprinted an FN action (1.100 thread OD with the first thread removed in the action and no necking cut on the barrel threads) for a local hunter prior to being fit and chambered for the 264 Win mag. A few months later he sheared the primary lugs off the bolt on a hot summer afternoon using his polar bear loads. Out of curiosity I pulled the barrel and checked that chamber as I was sure it would be swelled as a result of the overload. The chamber was well within spec as near as I could measure with a .0000 LAST WORD indicator. Now these limited situations hardly amount to any hard HP White Lab data but they have convinced me that the current Ultra mag/404 based case are right at the limit for a 1" thread OD. Sooner or later we all want to see what our rifle will do when really loaded to the edge of the envelope, as you has so aptly stated with your own Ruger Rigby. Why shoot a 410gr bullet at 2375 fps thats worked great for 80 years when you can get 2500 fps. As I stated in my first post I think the Pre-64 Mod-70 action is a poor choice when a 416 Rigby is desired. The 1" thread OD was the least of those concerns I listed. The action is plenty strong enough, however it lacks critical over all length and a properly configured bolt face to handle such a large rim diameter case. Physical theory is great until something happens that is then best described as a non theoretical event.

Just ban the ISP. All that needs to be done.