doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com What is this.It looks like a Mauser shotgun.

"Do the small bores use the standard Mauser locking lugs or just the safety lug?"

Safety lug only. Remember, the locking lug recesses are removed.

"but in the case of the shotguns where the front lugs weren't useable the headspace was set with the safety lug contacting it's shoulder."

Correct. One of the reasons the clumsy bolthead was made so large in the first place was to ensure the safety lug locked up. As I said earlier, the lug can stand up to repeated batterings of 15,000 PSI. However, keep in mind most rifle cartridges are up over 35,000 PSI-40,000 PSI; hence why it would be a "one-time-use-only" thing in a rifle just to deaden the force of impact, but it'd be a servicible locking lug in a shotgun.

I suspect a lot of why people think the locking lug is in danger of sheering off is because of the huge disparity between rifle and shotgun pressures. Even a perceivedly wimpy round such as the .22 Hornet has a pressure topping off around 40,000 PSI (I could be off by a few thousand, but it's around that). And that .22 Hornet would blow the lug right off if the barrel were somehow sleeved. But a 12 Ga. shotshell that is 2 3/4" inches long maxes out around 12,000 PSI (with 16 Ga. and 20 Ga. decreasing). Since pressures are really the only thing that matters about the gun's structural safety when it comes to the bolt supposedly flying out, it's well within the safe and normal range for a shotgun. I think a lot of people miss that disparity in PSI and either figure the pressures are similar or just look at it after having shot both rifles and shotguns for an entire lifetime and say to themselves "this can't be right." Well, it is right. One of many "strange but true" things about shooting.

D110;
You have made some very good & valid points & have enjoyed this discussion, but am going to stick my neck out & say, you have totally missed the boat with the above statement.
Pressure, as in PSI is not the determining factor, but rather "BackThrust". Several factors work in combo to determine backthrust. Pressure is of course one of them, but area exposed to that pressure is another, and of course the "Grip" that the case itself has upon it's chamber walls has an affect. Now the lowly little .22LR rimfire operates at considerably higher psi than does a 12ga shotshell, but I don't really believe you or anyone else would fear to fire a .22LR depending solely upon the safety lug of a M98 Mauser to contain it. Now these next figures should definitly not be taken as working figures, because I am just going to campare outside dimensions, not internal where actual pressure is applied & take no account for case friction. A 12ga shell has a head dia of about .811" or .516sqin. A .22 hornet has a head dia of about .295" or .068sqin. Now .516 sqin times 12,000psi = 6,192 lbs while .068sqin times 40,000 = 2,720 lbs. Now again I point out these should not be taken as actual working figures as are not actual areas exposed to the pressure nor do they take into account the grip of the case to the chamber walls, which can reduce backthrust (I suspect this is higher in proportion with the Hornet). I do believe though that any bolting mechanism which can contain 12K psi of a 12ga shell will quite adequately contain the thrust of a Hornet round. I personally would have no fear of one utilizing the safety lug of a M98.

Miller is dead on and he saved me getting out my calculator and doing a lot of writing. The force (back thrust) is calculated as the sq" in area times the pressure. This is something that folks need to know when considering making a double rifle out of a shotgun. Also in a rifle (dry) chamber the expanding brass grips the chamber walls and reduces the back thrust. The English at one time calculated chamber pressure in rifles using a greased chamber.

I appreciate your correction. Better to get it wrong here and stand corrected than getting it wrong in a national publication and being ridiculed. I also would like to learn from this. Could you give me some examples with regards to conversions and backthrust (via email or PM...my email addy is stated earlier in the thread)? Also how I'd calculate how much a '98 safety lug could take? I thank you in advance and will change my approach accordingly.

D110;
While I have outlined the basics, to really get down into working figures is somewhat over my head. You would of course need the actual area the pressure works against, in my example I used case OD which would be larger than its interior area. This as stated would then be multiplied by the pressure & would give the maximum potential thrust. Subtracted from this would be the amount absorbed by the case through it's grip & strength. Another factor which I fully believe plays at least some part is the time factor. This can be appreciated when comparing crusher pressures to piezoelectric pressures. A crusher gun will "Almost Never" read as high a pressure as will the PE gun. This is accounted to the fact the PE crystal reacts virtually instantaneous while the crusher takes an "Extremely Short" but definite time to be fully compressed. In reality then the pressure peaks & begins to fall before the crusher is "Fully Crushed", thus the reading is lower than the PE gauge. In the case of the bolting we would be more concerned with elongation than crushing & steel rather than lead or copper, but the same principals would apply.
As to the lug itself you would need to know the shear area of the lug, the shear strength of the metal & the force to be applied. I was a machinist & a pretty good shop mathamatician but not a stress analyst. There are several here who reach up into that area & hopefully some of them will correspond & give you assistance. Meanwhile I sincerely hope you decide to stick around & become a regular part of the board here.

D110; second Miller--this is fun. OT, but fun.

I remember reading an article, I believe that was published before WWI where they sheared off the lugs in a machine to see how much force it took. This was a 1903 Springfield and I don't remember if they did the safety lug as well, I'll try to find the article. I will also, as time permits, look into some of the other books on the subject But offhand I don't remember seeing one on the Mauser lugs.

You need to learn to just ignore the folks with nothing to offer other than just listing to themselfs. You can click on their profile and "Ignore" that helps some but many folks have not learned to take the bait so you end up reading a bunch that.

The whole thing about the nice little Remo 28 gauge started when I nudged MW while we were standing in front of a gun show table and I said "What do you think of that?" If I'd kept my mouth shut, maybe I'd know more about his new gun. Murphy

Miller...believe it or not, I understood that. Unfortunately, I don't have the time to do some of the measurements required (i.e. shear strength of the metal) and lack the resources as well (not sure where I'd get a crusher gun, piezoelectric measuring device, or crusher gauge). Your post was extremely informative, however, and I do know what you're driving at. The whole thing sounds like it's going to be one of those things I have to put on hold due to circumstances beyond my control.

Mike, will do on all counts. Definitely see if you can try and find that for me. While it's far from exact with an '03, it would at least give me an in-the-ballpark estimate if they did indeed test the safety lug.

eightbore...sorry to hear. That's the only 28 gauge Remo I've ever seen or heard of. It was not catalogued in any of the Remo catalogues or fliers I have. I'd love to know what the company serial number is (vs. the Gewehr 98 serial number...the company serial number is under the wood).

General Hatcher did a lot of experimenting with the '03 Springfield, much of which is reported in his book, "Hatcher's Notebook". Will have to get out my copy & see just what all he did do. I do remember he machined the locking lugs very thin as well as the walls over the chambers.