Krag Rifle Strength

[4570guy]

I just ran across reference to this post on the Krag Collector's Forum. I found it very interesting and thought I'd share. Weak indeed....:smile: Gotta' love the old Krag.

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=251923&page=2

[Ed in North Texas]

Great experiment. Thanks for posting.

Ed

[Haggway]

Thanks for sharing. I still make sure to have everything checked out on the old ones.

[Multigunner]

Interesting but while it gives an idea of how strong the safety lug is, it does not change the fact that the single locking lugs and seats were often damaged beyond repair by much lower pressures.
A wrecked rifle is still wrecked even if the safety lug holds.

Now there is the fact that many civilian owners of the Krag chose to lapp the locking lug until the safety lug came into full contact, thus making it a two locking lug system like some European Krags.
This was not always possible due to manufacturing variances, the clearance between safety lug and receiver being too great to allow lapping while maintaining a reasonable headspace.

[madsenshooter]

On the other hand, some who lapped the locking lock so that the bolt guide would bear on the receiver have experienced cracks where the receiver in the link broke. Depends on the heat treat, I'd think. I have a receiver, serial #13,000 something, that is brittle and cracked behind the locking recess. Heat treating wasn't much of a science then, get it hot enough to look this color, then quench it. No doubt the color varied with the available light.

Multigunner, they must have made some bolts that could be fitted. Lapping a regular bolt would come close to creating excess headspace. I have a model 92/96 that some armorer who knew what he was doing fitted. Full width guiderib bears on the receiver, but the headspace is minimal.

[Multigunner]

On the other hand, some who lapped the locking lock so that the bolt guide would bear on the receiver have experienced cracks where the receiver in the link broke. Depends on the heat treat, I'd think. I have a receiver, serial #13,000 something that is brittle and cracked behind the locking recess. Heat treating wasn't much of a science then, get it hot enough to look this color, then quench it. No doubt the color varied with the available light.

Inconsistencies in heat treatment can ruin the strongest designs. Another factor is the quality of the machining.
Years ago I read of some FN manufactured Mauser bolts failing at the left hand locking lug where the slot for the ejector was cut.
The problem was traced to a too sharp angle at the cut. Theres suposed to be a very tiny radius rather than a sharp corner.
The same lack of radius caused failures of many SIG auto pistol frames some years back, and failure of the early .40 S&W Glock guide rails.

PS
I can remember seeing custom Krag actioned rifles chambered for less intense cartridge that had been modified much like the action used in the test. The front lug was despensed with and the safety lug used as the sole locking lug. One I remember was a single shot conversion in .22 Hornet.

[madsenshooter]

A good point on the machining too. On the receiver I have that is cracked, one can see that the locking lug of the bolt was only bearing on the outer edge of the recess. Only an 1/8" or so was bearing. A good heavy load, maybe one of the 2200fps loads for example, on that small an area, and crack! I can't say which part was machined wrong, the locking lug of the bolt or the recess in the receiver.

[SquirrelHollow]

I had to sell my 1895 DCM Carbine last year, when the bolt lug cracked, and the only remaining contact at lock-up was the bolt handle. ...and that happened with my hottest load -- a load that should have come in at only 28,000 psi, or so.

The Krag is a beautiful piece of machining, a piece of history, and a buttery-smooth action. ...but they are not strong.

That experiment only showed us one thing: How strong THAT rifle was.

Mine was pretty weak, as it turned out.


As I said, though... a beautiful piece of machine work. Next time you have one in your hands, think about how many machining operations were required for the complex contours in that action, how almost no surface of that action or its parts is left untouched, and the fact that many of those machining operations were done on manual milling machines and lathes, by absolute craftsmen.

[4570guy]

Agree. I think one of the unsung reasons why the Krag was replaced by the '03 was cost of manufacture. (Sorry - my table format got screwed up, but you get the idea...)

Rifle No. Machining Operations
1896 Krag 131 (receiver) + 34 (magazine gate)
1898 Krag 121 (receiver) + 27 (magazine gate)
M1903 92 (receiver) + 3 (magazine floorplate)
1. Krag data from the 1898 Chief of Ordnance report, App 3
2. M1903 data from Our Rifles and Machine Guns

[4570guy]

Regarding heat treatments and strength of individual rifles - all true and good points. The Krag most likely suffers from the same lack of heat treat discipline that the early '03 Springfield did. I think the main reason we don't hear about Krag receivers turning into shattered shrapnel is the fact that it used a rimmed cartridge, fully supported by the chamber and bolt head; whereas on a Mauser based action, the lower portion of the cartridge head is unsupported - a case head failure on a Mauser allows high pressure gas leakage directly into the receiver.

I'll bet if you randomly "whacked" a number of Krag receivers a sharp blow, they would shatter like an low numbered '03. This may also be why some Krag bolt lugs sometimes crack- too much variability in the heat treat process during manufacture.

[KCSO]

It doesn't matter how STRONG the rifle action is as much as how SAFE it is. Just like a 96 Mauser or a 91 the action may hold but where is all the leaking gas from a pierced primer going to go? I have had 91's shoot gas right back in my face from Argentine military amo and it's no fun. Same with a 73 Winchester, the old baloon head ammo breaks just ahead of the primer pocket and your face gets sand blasted. The fact that the whole gun doesn't go to pieces means very little if you lose and eye at the end of the day. I have seen Krags with ruined headspace with as little as 10 moderate overloads so I just don't overload my Krags. As far as that goes I can't think of anything in the USA i couldn't kill with a 220 grain cast bulllet at 2100 fps.

[4570guy]

As far as that goes I can't think of anything in the USA i couldn't kill with a 220 grain cast bulllet at 2100 fps.

Concur - and true for most other continents as well!

[nicholst55]

I once knocked a Krag bolt off my workbench onto a concrete floor, and the bolt handle broke right off! That was rather enlightening, to say the least. The rifle was in very good condition, and had never fired anything but factory ammo up to that point.

[Haggway]

I have an early 1892 Krag. I make sure to load light loads and light boolits to take the old gal out, and just plink. I plan on doing the same thing with my foreign Krags as well. Its always nice to be shooting somthing like this when there are so many people shooting plastic rifles, and very few actually know what kind of fifle it is.

[Multigunner]

The Krag is one action I'd really like to see revived for sporting rifle purposes.
Manufactured of modern high strength alloys with the possible machining errors taken into account and dealt with, and chambered only for those still highly effective classic cartridges that remain within pressure limitations of the design.
The majority of the old Winchester lever action chamberings should work fine in the Krag.

Barring that, since product liability might still scare off manufacturers, adapting the Krag side loading magazine to a stronger lock up bolt would also be cool.
The magazine design should work well with a rear locking bolt such as that of the 788.

The 788 being another action of great promise hampered by short comings in manufacture.
If the locking lugs of a 788 are carefully lapped into their seats for full contact of all lugs that action would lock up like a bank vault. Unfortunately that wasn't possibile in mass production, so while some are stronger than equivalent Mauser type designs, and handled almost all .308 Win loads with no problems, others suffered from lug setback or shearing with any top end .308 long range match grade loading.
The 788 had other durability problems as well, but not across the board. Again variability in the machining processes made for a wide range in the strength and durability of individual examples.


This sort of situation is why I don't much like to see results of testing of a single example or a small selection of actions given as proof of the strength of a particular action type as a whole.
Over estimating the expected strengths of an action type from this sort of result is why the UK NRA had to crack down on the use of converted No.4 rifles with the modern high pressure .308 Long range loads used in modern competitions.
No matter how many detailed tests were done by the British Proof Authority and Radway Green ammunition manufacturers, someone always knew someone who had over amped a No.4 on many occasions and managed not to blow his face off just yet, so they started all sorts of conspiracy theories to try to explain away the facts.


Madsen Shooter.


A good point on the machining too. On the receiver I have that is cracked, one can see that the locking lug of the bolt was only bearing on the outer edge of the recess. Only an 1/8" or so was bearing. A good heavy load, maybe one of the 2200fps loads for example, on that small an area, and crack! I can't say which part was machined wrong, the locking lug of the bolt or the recess in the receiver.
__________________

I suspect that what you are seeing there is a case of the seat having conformed to an earlier bolt through uneven wear or as it deformed under an over load. The metal of each being soft enough that the steel deformed unevenly.
The Bolt in the rifle now is most likely an unfitted replacement.
An old NRA reprint I have has an article on replacement bolts given free of charge to civilian Krag owners whose rifles were damaged by defective surplus Krag ammo. The rifle owner simply sent in the damaged bolt with a description of the failure and a new replacement bolt was sent from the arsenal.
The article made a point of saying that the bolts required no special fitting, but that would only be true if the receiver showed no uneven wear or damage to the seat.

[madsenshooter]

You're right MG, it did have a later bolt in it, the original would have been one with an uncut guide rib, I got a couple fuzzy pics. You can see it didn't bear at all over towards the left in the bottom pic.

http://castboolits.gunloads.com/imagehosting/thum_12364f6cd1444618d.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=4538)

http://castboolits.gunloads.com/imagehosting/thum_12364f6cd15343ac0.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=4539)

[frnkeore]

The Krag has always been underrated on it'd strengh when made with parts heat treated properly. If you read Hatcher reports on the '03, you'll see how haphazardly the heat treatment was done. The Krags and '03's were made with the same Ordinance Steel. A well heat treated Krag should be able to withstand 50,000 CUP. Although a smaller case head (225 Win), the Savage 340 and variants are rated at upto 52,000 CUP with a sigle locking lug.

I too, would like to see a modern steel Krag.

Frank

[Char-Gar]

As already mentioned Krags vary allot in hardness and the ability to stand pressue. However the action design handles gas far better than any Mauser design. The Krag does not trap the gas and when a Krag fails, I have never heard or known of anybody getting hurt.

In the blown up Krag in the pics, the front receiver did not receive the damage. When the bolt lug gave way, it was the rear receiver ring that took the biggest hit.

[Chicken Thief]

20gr Unique, Sierra 2230 200gr, standard length = @72000psi

30gr Unique, Sierra 2230 200gr, standard length = @139200psi

So some slight abuse was involved in the destruction?

[4570guy]

In the blown up Krag in the pics, the front receiver did not receive the damage. When the bolt lug gave way, it was the rear receiver ring that took the biggest hit.


Notice that prior to the test, the tester purposely removed the bolt lug - therefore the receiver ring couldn't take any load. It was a test of the safety lugs and that is all. I'm sure that if the bolt lug had been in place, the lug would have cracked first and the failure mechanism would have better matched what is documented in P.O. Ackley's "Strength of Military Rifles".

[jonk]

Why did he cut the locking lug off? I'm more interested in what a stock rifle will take.

[Multigunner]

The test does increase confidence in the safety factor of the guide rib lug, but does not give any usefull asessment of the action's ability to handle a hot load without doing irreperable damage to the rifle, or posing a danger to the shooter or bystand should an over stressed bolt shater at the front.
I've tried to impress upon Lee Enfield owners that the bolt blowing straight back in your face is not the only danger during an action failure. In almost all of the reports of injury or death involving a blown up Lee Enfield injuries were from fragments of the bolt head which shattered after gases from a ruptured cartridge case were directed into the opening for the extractor and its V spring.
I found one case where the bolt did blow back at the shooter, the guide rib lug didn't stop it because a large chunk of the rear receiver wall broke away, the lug had nothing to act against.
The left hand lug is position over the hollowed out portion of the bolt body. I've seen a photo of a photo of a blown SMLE bolt showing the lug broken away along with a chunk of the bolt body.

When a bolt lug that is part of the more solid front section of a Mauser or Krag bolt does break it normally breaks at a steep angle. In some case the angle will run downwards carrying away part of the bolt body and bolt face, but more commonly the lug shears at an upwards angle, the remaining portion being driven against the seat like a wedge, limiting how far back it can go.

The Low Number Springfields that shattered seem to have kept the bolt body trapped by the rather large Springfield safety lug. No deaths and few serious injuries could be traced to Springfield failures.
The "Hatcher Hole" the MSMC used to divert gases from a ruptured case or pierced primer seems to have done the trick for them. If any of those rifles blew there doesn't seem to be a record of it.

BTW
Much has been made of the possibility of the two piece firing pin of the Springfield breaking and being propelled at the shooter.
On another board I visit a SMLE owner had the same sitituation with his Enfield, the one piece firing pin breaking at the collar.
One piece firing pin conversion have been available for the Springfield, so it sounds like a good investment.
The main thing is to always use a snapper cap of some sort to avoid weaking the firing pin. A good idea for any firearm.

[frnkeore]

"Why did he cut the locking lug off?"

I believe the purpose of the test was to see what the bolt would do if the front locking lug were to fail. Brought on by the story's of the cracked locking lugs (single lug, multiple guns).

Frank

[frnkeore]

Regarding 03 blow up's. If you will look in the back of Hatchers Note Book, on page 442, you'll find 68 reports of action failures. Resulting in 3 lost eyes, 3 serious injury's, 3 severe injury's and 27 slight injury's. Many more injury's were reported for barrel failures.

Frank

[bydand]

I still wonder what the point was in destroying the rifle?:evil:

[smkummer]

My 1896 Krag rifle is one heck of a cast bullet shooter with a 190 grain bullet and 1800 FPS with 2400 powder. I bet I can shoot this reduced load forever and have no reason to increase pressure or velocity. I don't even want to fire the 2 boxes of both factory remington and winchester 180 grain loads at the claimed 2400 FPS and may trade them off.

[Clark]

When I was in college in 1976, I was forced to take engineering ethics, that was taught by a mechanical engineer.

The old guy said that when a rocket blows up on the launch pad, you don't learn much.

In the following decades I designed gear for a fixed price. I slowly work up to over stressed levels and blew my prototypes up. Then I made improvements on the part that was the primary cause of failure.
I was able to get designs done faster and get more reliable designs than my competitors.
These days it is called highly accelerated stress testing [HAST].

Now I have hundreds of guns for my hobby of over stressing guns.
I have not worked on a Krag, only read Ackley's account.

I feel there would be more learned in the OP if the work up from 20 to 30 gr Bullseye were to be in 1 gr increments, not a 10 gr increment.

[Multigunner]

When I was in college in 1976, I was forced to take engineering ethics, that was taught by a mechanical engineer.

The old guy said that when a rocket blows up on the launch pad, you don't learn much.



Then theres "the Jesus Factor" when all the numbers are right but it still blows up on the pad or misses Mars by 3,000,000 miles. Everyone sits bolt upright, coffee cups and slide rules flying and says "Jesus Christ on a Pony, what the heck just happened?".

I'd expect the Jesus Factor came into play quite often in the early days of smokeless powder.

I vaguely remember that some Krag blow outs were blamed on cold soldering of the bullet jacket to a tinplating they had used inside the cases of some Milspec ammo. The tin plating was to reduce degradation of powder and case if moisture was a concern.
I have seen tin lined Krag cases mentioned in multiple sources over the years.

[Char-Gar]

I am working on some very old memory, but it tells me that the rifles that blew up with "tin can" ammo were 1903 Springfields and a lot of match ammo plated as you describe. A couple of kabooms and thus ended the maufacture and use of "tin can" ammo.

Addendum: I decided to refresh my memory and found an excellent article on the ODCMP site about the development of the 30-06 round in general and "tin can" ammo in particular. Here is the link is anybody would like to take a gander. It is very good and informative.

http://www.odcmp.org/1101/can.pdf