30-40 Krag brass to 303 British

[303carbine]

I picked some loaded 30-40 Krag ammo and pulled a few of the bullets so I could try the brass in my 303 British.
The bullets were pulled and the Krag brass was run through the full length 303 die, I trimmed with a 303 case length gauge and chamfered and deburred the cases.
I used a bit lighter powder charge and seated 150 Hornady 303 bullets into the cases.
Upon firing they fire formed perfectly and were accurate as well. I am going to anneal the cases because of the fire forming.
I am going to see how many reloads I get from the Krag brass compared to 303 brass. The Krag brass is slightly bigger at the head and should help with case seperation common with 303 brass.
The Krag brass is Winchester and shows no sign of case bulging like the Winchester 303 brass does that I have....interesting.:-o

[EDG]

The best brass to start with is probably the PPU aka Prvi Partisan.
It is larger at the head than US brass and the shoulder is a closer fit to the chamber.
The shoulder in Lee Enfield chambers seems to have little relationship to the location of the shoulder on loaded ammo.
Older US Krag bras was larger at the head. I think more recent Krag brass may be the same size as .303 brass.

[littlejack]

303:
If you can still chamber your reloaded rounds, after ONLY neck sizing or partial sizing your cases, your brass will last longer.
Regards
Jack

[303carbine]

303:
If you can still chamber your reloaded rounds, after ONLY neck sizing or partial sizing your cases, your brass will last longer.
Regards
Jack

I measured a fired case and compared it to the loaded factory round, the head of the case didn't expand like the Brit cases do, and it fits back intot he rifle and neck sizing is all that will be needed now.

[303carbine]

I neck sized the brass and annealed it, it looks nice too.
The Krag brass is 2 thou bigger at the head than the Brit, there was no head expansion at all at all after firing. When firing 303 of any kind in my No1Mk111, I get the tell tale sign of case head bulge like most of them do, the Krag brass is perfect and stays the same size without any distortion of the case.
Whoo hoo...:bigsmyl2:

[madsenshooter]

It's a little harder to come by than the 303, so if you see some, get it.

[N4AUD]

I'm glad I saw this. I've got a bunch of 30-40 Krag brass and no rifle to shoot it in but I do have a Mk4 No1 and very little brass. Thanks!!!

[303carbine]

I'm glad I saw this. I've got a bunch of 30-40 Krag brass and no rifle to shoot it in but I do have a Mk4 No1 and very little brass. Thanks!!!


Before you load it be sure to use a 303 full length die or neck sizer die to expand the case mouth, trim to length with a 303 case length gauge and chamfer and deburr the case.
I prefer the neck sizer die because it only touches the neck, the full length die can be used as well as the Krag brass is shorter and the die won't touch the shoulder anyways.
Use a starting load for the 303, load your projectile and shoot in your No4, it will fireform to fit your rifle perfectly.
After firing, I would anneal the cases and neck size only after that for the rest of the life of the cases.
As usual we have the obligatory thing to say be careful, this works in my rifle blah, blah blah.....it works perfectly and the brass will last longer because it's bigger to start with.
In my old Hodgdon manual, I checked the case drawings for the Krag brass, it's 2 thou bigger at the case head. This is exactly how much bigger the 303 chamber is bigger than most of the 303 brass!!

[N4AUD]

I just meant that I had forgotten I had the 30-40 brass, not that I didn't know what to do with it. :razz:
Before you load it be sure to use a 303 full length die or neck sizer die to expand the case mouth, trim to length with a 303 case length gauge and chamfer and deburr the case.
I prefer the neck sizer die because it only touches the neck, the full length die can be used as well as the Krag brass is shorter and the die won't touch the shoulder anyways.
Use a starting load for the 303, load your projectile and shoot in your No4, it will fireform to fit your rifle perfectly.
After firing, I would anneal the cases and neck size only after that for the rest of the life of the cases.
As usual we have the obligatory thing to say be careful, this works in my rifle blah, blah blah.....it works perfectly and the brass will last longer because it's bigger to start with.
In my old Hodgdon manual, I checked the case drawings for the Krag brass, it's 2 thou bigger at the case head. This is exactly how much bigger the 303 chamber is bigger than most of the 303 brass!!

[longbow]

Here is another vote for neck sizing only. Not only that, most lee Enfields have grossly oversize chambers (likely military spec) and dies are made to SAAMI spec so I found that my RCBS dies were sizing the necks to about 0.311" and I am loading 0.315" boolits! that's a lot of neck tension and brass stretching!

First I made a new expander button to open the necks up to 0.313" which helped accuracy bunches as the brass no long sized the boolits at seating. The brass was still getting worked lots though. Next to save the brass I picked up a set of Lee Collet Dies and set that up to give 0.313" neck diameter. Now I neck size only and to suit the boolits.

Good brass life and good accuracy doing it this way.

I have heard that .304-40 Krag brass makes good .303 brass for just the reasons you state but full length sizing will still result in short life if you have a gun with an oversize military chamber. Case head separation is due to stretch lengthwise not in diameter.

Longbow

[303carbine]

Here is another vote for neck sizing only. Not only that, most lee Enfields have grossly oversize chambers (likely military spec) and dies are made to SAAMI spec so I found that my RCBS dies were sizing the necks to about 0.311" and I am loading 0.315" boolits! that's a lot of neck tension and brass stretching!

First I made a new expander button to open the necks up to 0.313" which helped accuracy bunches as the brass no long sized the boolits at seating. The brass was still getting worked lots though. Next to save the brass I picked up a set of Lee Collet Dies and set that up to give 0.313" neck diameter. Now I neck size only and to suit the boolits.

Good brass life and good accuracy doing it this way.

I have heard that .304-40 Krag brass makes good .303 brass for just the reasons you state but full length sizing will still result in short life if you have a gun with an oversize military chamber. Case head separation is due to stretch lengthwise not in diameter.

Longbow

Longbow, that's true, but having 303 brass that is 2 thou smaller at the casehead doesn't help either. I like the fit of the Krag brass in the chamber, no case bulging like the Brit stuff.

[longbow]

No argument there. That seems to be a common complaint. Not sure if that is also a military thing to make the whole cartridge undersize to accommodate dirt but certainly the Lee Enfields I have all have large sloppy chambers. Apparently the .30-40 Krag brass is a little larger in the head so makes a nicer looking cartridge.

I was planning to try them myself but found that .30-40 Krag bras is considerably more expensive than .303 brass at least where I live. So... I live with bulgey brass.

I found I was getting rapid case stretching when I full length sized but then the shoulder moves forward about 1/16" every time it is fired! That has to be hard on brass!

Even the stock dies didn't swage down that bulge at the head though. Does kinda make you wonder.

Longbow

[303carbine]

No argument there. That seems to be a common complaint. Not sure if that is also a military thing to make the whole cartridge undersize to accommodate dirt but certainly the Lee Enfields I have all have large sloppy chambers. Apparently the .30-40 Krag brass is a little larger in the head so makes a nicer looking cartridge.

I was planning to try them myself but found that .30-40 Krag bras is considerably more expensive than .303 brass at least where I live. So... I live with bulgey brass.

I found I was getting rapid case stretching when I full length sized but then the shoulder moves forward about 1/16" every time it is fired! That has to be hard on brass!

Even the stock dies didn't swage down that bulge at the head though. Does kinda make you wonder.

Longbow


303 brass has a memory, I believe it remembers that it likes the bulge and stays that way just to spite the shooter.
But, I always neck size 303 or any other cartridge I'm loading for, I just want to see if the Krag brass will outlast the Brit stuff doing the same neck size procedures on each. I am going to use the same loads and see which one lasts longer.
I looked at the drawings of each case, the Krag is 2 thou bigger at the casehead, I believe this small difference is enough to stop the expansion at the casehead and will extend the brass life. The brass may not be thicker, it's bigger in circumference and that is what will fill the chamber of the 303 and will extend brass life.

[nanuk]

does anyone use an O-ring on first firing in the 303?

[303carbine]

Even if you do the o ring method, it will still bulge the case on whatever shot you don't use it.
I like the bigger 30-40 brass to fit the larger chamber of the Brit, it's a fit thing without the brass slopping around in the chamber.

[303Guy]

Ooooh!:violin: Better not post such dangerous practices lest a newbe reads it and blows himself up!:bigsmyl2: (Just something 303 and I have shared).
I don't see any chance of my finding 30-40 cases in my parts or I'd get some too. I see a benefit in being able to trim the cases to fit the chamber length to minimise the neck to throat gap.

[screwcutter]

Another vote for the Prvi brass.
If you want a nice tight fitting 303 brass, form them out of Hornady 405 Win brass. It is a lot more work you also get a thicker rim, and there are feeding issues because of this. It works fine for single shot target shooting, am still working on the feed issue.

[N4AUD]

I have 20 rounds of Privi, but a friend gave me a bunch of his grandfather's reloading stuff that included a few hundred 30-40 cases or I wouldn't be trying this. I don't see a Krag in my future any time soon but I've got the Enfield in hand.

[EDG]

I made a few .303 cases from .405 brass.
The necks were so thick I had to turn about .002 off. The rims were so thick that half of the cases caused the bolt to close with some effort. My #4 has a #2 bolt head. I suppose if I substituted a #1 or 0 bolt head I could use the .405 brass. It is about .458 in dia at the rim and my chamber is .460 so there is very little clearance.
Not only that but when you form the brass you can set the shoulder to be a close fit to the chamber.

I know everyone is on the 30-40 Krag band wagon but I have read that late model Krag brass is the same diameter as .303. Check it before you buy a large quantity of it.


Another vote for the Prvi brass.
If you want a nice tight fitting 303 brass, form them out of Hornady 405 Win brass. It is a lot more work you also get a thicker rim, and there are feeding issues because of this. It works fine for single shot target shooting, am still working on the feed issue.

[303carbine]

I have several different brands of commercial and military brass, the outside dimensions of the Krag brass is 2 thou bigger than any other brass.
I believe the difference makes the Krag brass fit better to the Enfield's oversize chamber. The Enfield chamber is well designed for battle conditions and they never reloaded their ammo so the brass seperation wasn't a problem.
But for the shooter/reloader a better brass to chamber fit is better, being the Krag is larger in diameter at the head makes for a tighter fit in the chamber. I am on my third reload with the test Krag brass and it still measures the same as a new Winchester 30-40 at the head.
The brass was annealed after the second firing and will be done again after about the fifth reload. I am using Canadian IVI brass in comparison to the Krag stuff, both are good brass, but the Krag still fits better, I think that will be the tale of the tape so to speak.
To get an accurate brass life test, both the 303 and the Krag brass will be loaded with the same bullet and powder combination.

[EDG]

It is my experience that if you load full power loads equally factory ballistics you will get somewhat poor life with any kind of brass. The Lee Enfield especially the #1 Mark 111 was a transitional design created about the time black powder became obsolete. Being rear locking with a thin right receiver rail results in a springy action. Combined with the huge chambers relative to brass you get poor case life with full power loads.
The chambers I have checked measure .460 and US made brass usually measures .450. Ten thousandths is way too much clearance. I know there are a zillion Brits that will claim the LE was the best battle rifle but the rest did not require a huge oversize chamber to function. The fact was the Brits were so poorly funded they could not even design their own bolt guns so they used James Paris Lee's design. They once investigated changing directions but decided against that. They probably did that because they already had rifles and did not want to pay for replacements using a new design or manufacture new ammo that would not be common to all types. So they wound up stuck with the LE until the 1950s before they adopted another foreign design. It seems the Brits have some aversion to designing anything that is not derived from the traditional double barreled shotgun. For example the excellent Bren gun was ripped off from the Czech ZB 26.



I have several different brands of commercial and military brass, the outside dimensions of the Krag brass is 2 thou bigger than any other brass.
I believe the difference makes the Krag brass fit better to the Enfield's oversize chamber. The Enfield chamber is well designed for battle conditions and they never reloaded their ammo so the brass seperation wasn't a problem.
But for the shooter/reloader a better brass to chamber fit is better, being the Krag is larger in diameter at the head makes for a tighter fit in the chamber. I am on my third reload with the test Krag brass and it still measures the same as a new Winchester 30-40 at the head.
The brass was annealed after the second firing and will be done again after about the fifth reload. I am using Canadian IVI brass in comparison to the Krag stuff, both are good brass, but the Krag still fits better, I think that will be the tale of the tape so to speak.
To get an accurate brass life test, both the 303 and the Krag brass will be loaded with the same bullet and powder combination.

[303carbine]

I am not going to do full power loads, I am going to test with the same load data and find out which brass lasts longer, 303 or 30-40.
The Krag brass didn't expand at all at the case head while the 303 did using the same load data.
This is a brass test, not fullhouse load testing.

[Multigunner]

It is my experience that if you load full power loads equally factory ballistics you will get somewhat poor life with any kind of brass. The Lee Enfield especially the #1 Mark 111 was a transitional design created about the time black powder became obsolete. Being rear locking with a thin right receiver rail results in a springy action. Combined with the huge chambers relative to brass you get poor case life with full power loads.
The chambers I have checked measure .460 and US made brass usually measures .450. Ten thousandths is way too much clearance. I know there are a zillion Brits that will claim the LE was the best battle rifle but the rest did not require a huge oversize chamber to function. The fact was the Brits were so poorly funded they could not even design their own bolt guns so they used James Paris Lee's design. They once investigated changing directions but decided against that. They probably did that because they already had rifles and did not want to pay for replacements using a new design or manufacture new ammo that would not be common to all types. So they wound up stuck with the LE until the 1950s before they adopted another foreign design. It seems the Brits have some aversion to designing anything that is not derived from the traditional double barreled shotgun. For example the excellent Bren gun was ripped off from the Czech ZB 26.

To be fair there were a lot of very innovative inventors involved in British firearms design and especially manufacturing. Brits invented Nickel Steel and the earliest Stainless steels, the later came from a failed experiment on producing a .303 barrel that would not corrode or erode from use of cordite.

They produced very few homegrown autoloader designs, but did a great job of working out the bugs in non British designs they bought the rights to.

Practically all their firearms related mass production technology was bought from Colt, Robbins and Lawrence, and Pratt and Whitney, which is no suprise since most of the civilized world used this same technology.

All old article on hand loading the .30-40 has a list of rim thickness of the various brands of .30-40 brass available in the 1960's. Some of this brass had rims as thick as .068, which would be really handy for making .303 cases for a loose head spaced Enfield.

The original reason for forming .303 cases from .30-40 cases was not the size of body or rim thickness, it was because boxer primed .303 ammo was scarce and expensive, but out dated milsurp .30-40 ammo was being sold off dirt cheap to be broken down for components. Reforming the Krag cases gave you a cheap reloadable case for your .303.

[303carbine]

To be fair there were a lot of very innovative inventors involved in British firearms design and especially manufacturing. Brits invented Nickel Steel and the earliest Stainless steels, the later came from a failed experiment on producing a .303 barrel that would not corrode or erode from use of cordite.

They produced very few homegrown autoloader designs, but did a great job of working out the bugs in non British designs they bought the rights to.

Practically all their firearms related mass production technology was bought from Colt, Robbins and Lawrence, and Pratt and Whitney, which is no suprise since most of the civilized world used this same technology.

All old article on hand loading the .30-40 has a list of rim thickness of the various brands of .30-40 brass available in the 1960's. Some of this brass had rims as thick as .068, which would be really handy for making .303 cases for a loose head spaced Enfield.

The original reason for forming .303 cases from .30-40 cases was not the size of body or rim thickness, it was because boxer primed .303 ammo was scarce and expensive, but out dated milsurp .30-40 ammo was being sold off dirt cheap to be broken down for components. Reforming the Krag cases gave you a cheap reloadable case for your .303.


That's a good piece of knowledge and history I didn't know about why the 30-40 brass was used for the 303 Brit. The headspace on my No1Mk111 is real good and the bore is very decent and shiny. The chamber is a bit large like most 303's that I have owned and shot, the 30-40 brass takes up that extra space in the chamber and works very well. I picked up 50 new 30-40 plus 30 loaded rounds for $75 Canadian. The pulled bullets will be loaded into my 30-06 and the brass will be fireformed into 303. With having the brass fit better and the bedding that I did on the No1Mk111, I already shrunk the groups on the rifle.
At least this site has a bunch of knowledgeable and open minded people who know their stuff. It's nice sharing ideas and not having old nervous nellies telling me that something is dangerous when it's been done for ages.

[N4AUD]

Here's the finished product after sizing, trimming and fire forming. All I can say is that I need to get the power attachment for my Lyman trimmer, it's quite a job trimming dozens of these manually. :bigsmyl2: 83850

[clearwater]

Here's the finished product after sizing, trimming and fire forming. All I can say is that I need to get the power attachment for my Lyman trimmer, it's quite a job trimming dozens of these manually. :bigsmyl2: 83850

Might be able to use one of these first to trim.

http://www.harborfreight.com/1-8-eighth-inch-to-1-1-8-eighth-inch-tubing-cutter-92878.html

I use one when converting 06 to 7x57ai brass.

[N4AUD]

Might be able to use one of these first to trim.

http://www.harborfreight.com/1-8-eighth-inch-to-1-1-8-eighth-inch-tubing-cutter-92878.html

I use one when converting 06 to 7x57ai brass.
Thanks, I've got one I bought to cut down .223 to make 7.62x25. They are less work for a first rough cut but I didn't think it would work in this case (no pun intended). Maybe I should take another look at it. I've got quite a few left to trim.

[KCSO]

A freind clued me into 30-40 in the 303 in about 1972 and this is what I use for hunting loads all the time. Brass life was tripled or better.

[303carbine]

I just got back from the range, I fireformed 10 more 30-40 Krag brass into 303 British, they sure look nice and make perfect 303 brass.
I have a Lee case length gauge that attaches to a drill, it sure speeds up the trimming part of the process.
I am going to use commercial 303 brass for range work, heavier military and 30-40 Krag brass will be used for hunting.
I have about 100 once fired IVI for the 303, they should last for at least 4 reloads or more, the next gunshow I am going to grab all the Krag brass I can get my hands on.

[N4AUD]

I've finished about 60, I have another 50 or so to trim and fire form. The fire forming was fun, I used 85 grain Hornady XTP .32 cal JHP's. Nice groups but low at 25 yards. I suspect these will last me a long time since I don't do "hot" loads.

[303carbine]

I am shooting two grains below max loads, 42 grains of H380 under a 150 Hornady fireforms them perfectly.
The hunting load is the same but a 180 grain RN Hornady is seated instead of the 150 grain SP.

[303carbine]

Here's the finished product after sizing, trimming and fire forming. All I can say is that I need to get the power attachment for my Lyman trimmer, it's quite a job trimming dozens of these manually. :bigsmyl2: 83850


Those look just like the ones I fireformed, how many firings before I should anneal the cases?

[Multigunner]

Here's the finished product after sizing, trimming and fire forming. All I can say is that I need to get the power attachment for my Lyman trimmer, it's quite a job trimming dozens of these manually
When trimming some found .32 H&R mag cases to .32 S&W length I used a dowel rod wrapped with tape inserted in the case and chucked in my drill press. I set the table to a height where I could hold a needle file against the neck at the proper length. I left the cases a tad long then used my home made neck trimmer to finish them up.

My home made trimmer is a flat countersink used to countersink wooden furniture parts for large diameter washers, I found it laying on the road years ago, with a partly threaded rod run through the center and secured by a nut. The rod is turned to the ID of a .303 case neck which is close to that of the .32 S&W.

[brassrat]

It's a little harder to come by than the 303, so if you see some, get it.

Well I again came across 2 bags of 50. I bought 1. They are new and look like they may have been 1 bag of 100... $ 33 for 50. Gonna try em as .303 and ignore the headstamp if my reloading ocd will let me :razz:

[303carbine]

Well I again came across 2 bags of 50. I bought 1. They are new and look like they may have been 1 bag of 100... $ 33 for 50. Gonna try em as .303 and ignore the headstamp if my reloading ocd will let me :razz:

I usually start by running the Krag brass through a 303 neck sizer, trim it with a 303 Lee case length gauge. I don't bother with small charges of pistol powder or fillers.
I go two grains below max with any appropriate data and shoot as I would for 303 brass.
After the first firing, I anneal with a torch, I hold the brass in my fingers and work the brass around till it turns color.
When it gets too hot to handle, I place it on the bench (outside of course) and let air cool.
After they cool, I take a bit of 0000 steel wool and clean the brass....done.
PS, your OCD will be happy. [smilie=s: mine is...:bigsmyl2:

[Multigunner]

I usually start by running the Krag brass through a 303 neck sizer, trim it with a 303 Lee case length gauge. I don't bother with small charges of pistol powder or fillers.
I go two grains below max with any appropriate data and shoot as I would for 303 brass.
After the first firing, I anneal with a torch, I hold the brass in my fingers and work the brass around till it turns color.
When it gets too hot to handle, I place it on the bench (outside of course) and let air cool.
After they cool, I take a bit of 0000 steel wool and clean the brass....done.
PS, your OCD will be happy. [smilie=s: mine is...:bigsmyl2:

I've used a similar method, only before starting I fill each case, still with expended primer in place, about 1/3 with water.
I turn the case with my fingers, when it gets uncomfortably hot I drop it into a bowl of water.

I've used a very fine polishing compound to shine up a case, but most often I leave the exterior of the case as is unless its really badly stained.
After cleaning I wipe each case down with a cloth moistened with a light oil or WD40, then after a few minutes I wipe the cases again with a dry cloth. Otherwise finger prints form on the polished brass.

To clean the inside I just wrap oooo steel wool around a Q-tip and break loose any powder residue. I don't brother trying to get the inside of the case perfectly clean.

I sometimes polish the inside of a once fired case neck using 1000 grit silicon carbide paper wrapped on a dowel rod turned to the exact diameter.
Most case necks are very rough inside. Since I re size the neck undersized and don't crimp, a smoothly polished neck makes pull strength more consistent.

[303carbine]

I've used a similar method, only before starting I fill each case, still with expended primer in place, about 1/3 with water.
I turn the case with my fingers, when it gets uncomfortably hot I drop it into a bowl of water.

I've used a very fine polishing compound to shine up a case, but most often I leave the exterior of the case as is unless its really badly stained.
After cleaning I wipe each case down with a cloth moistened with a light oil or WD40, then after a few minutes I wipe the cases again with a dry cloth. Otherwise finger prints form on the polished brass.

To clean the inside I just wrap oooo steel wool around a Q-tip and break loose any powder residue. I don't brother trying to get the inside of the case perfectly clean.

I sometimes polish the inside of a once fired case neck using 1000 grit silicon carbide paper wrapped on a dowel rod turned to the exact diameter.
Most case necks are very rough inside. Since I re size the neck undersized and don't crimp, a smoothly polished neck makes pull strength more consistent.

I think I will give the 1/3 of a case full of water a try for my next annealing session, good idea, thanks Multigunner. I'm always open to good ideas.

[303Guy]

I have about 100 once fired IVI for the 303, ...I have a number of IVI 303-25 cases! They look pretty new, probably factory loads once fired.

I annealed a number of 303 and 25-303 head stamped cases by standing them in a small basket in water then applying a gas torch until I could see the dull red glow inside the dark necks. Still with fired primers - the idea being to keep the interior dry. Well, it might have been a great idea if it didn't fully anneal them. Not sure it's a bad thing, full annealing but it does reduce neck tension. The first time I experienced a bullet being dislodged from the neck by a primer alone. Also, the following round chambered (having thought I hadn't chambered a fresh round) had the bullet pushed back onto the powder - good thing it was a case filling powder or I might have had a double bullet firing! To me that's what's wrong with over-annealing. I'll use the finger hold next time.

Someone came up with a automatic case annealing method. I forget who or where - somewhere in these hallowed pages I think.

You know, if 30-40 cases are still available it makes re-barrelling a Lee Enfield to 30-40 a viable option, specially far casters, with the long neck.

[Multigunner]

You know, if 30-40 cases are still available it makes re-barrelling a Lee Enfield to 30-40 a viable option, specially far casters, with the long neck.

I've heard this has been done occasionally in Alaska.
The neck deepened to take an unaltered .30-40 case then fireformed to match the .303 body and shoulder.
This would serve to clean out an eroded .303 throat and give new life to an old barrel.
One should stamp the alteration boldly on the barrel and or receiver.
Check the thread on Kortnek Mauser blow up for why it might not be safe to fire a .303 in the altered chamber.

[303Guy]

That's the first problem that comes to mind. Can a 303 Brit round be chambered in a 30-40 Krag chamber? And 30-40 Krag in a 303 Brit chamber?

[303carbine]

That's the first problem that comes to mind. Can a 303 Brit round be chambered in a 30-40 Krag chamber? And 30-40 Krag in a 303 Brit chamber?

I have tried 30-40 brass in the 303 chamber, it is a bit long and you can see where the case mouth deforms in the shorter chamber of the Brit.
I have heard of old timers using loaded Krag ammo in the 303, I'm not about to try that or put 303 in the Krag. Seeing that 303 has larger diameter bullets, this would create a very high pressure situation.
Reforming brass is one thing, removing digits by explosives isn't something I am willing to try.

[303Guy]

It could be disastrous if the 30-40 round headspaced on the leade of an oversized bore Brit! The 308 Win being chambered and fired in a 270 is not unheard of (headspaces on the bullet). Sometimes the action breaks, sometimes not. The one instance my uncle told me of the receiver ring split, releasing the barrel downrange (test rifle fired remotely - the technician mixed up the ammo).

[Multigunner]

A collector of the Arisaka rifles, specializing in the rare sniper rifles apparently, posted on another board of somehow chambering a 7.92X57 in a Jap 7.7 rifle. Luckily he was remote test firing with a shielded booth. Apparently even the Arisaka has its limits, the rifle was destroyed. I wish I'd asked for more information on how it came apart.
Julian Hatcher wrote of two teenagers firing .35 Remington cartridges in a 7.7 Jap rifle. The action held together for the first two shots then went to pieces driving steel splinters into the shooter's brain. The boy survived after delicate brain surgery, probably made more difficult by the effort to find what must have been the smallest brain in history.

A member of another board wrote of finding a shattered Krag rifle left laying at a range. He took a look and found the head of an 8mm case stuck in the chamber.
I have a feeling this was a case of trying to force an oversize cartridge in the chamber and somehow causing the cartridge to fire while the action was unlocked.

People do downright stupid things some times.
If a cartridge doesn't chamber fairly easily something is bound to be amiss.

I have also heard of a case neck becoming separated and left in the chamber neck, the neck of the following round being squeezed down tightly and the whole shebang going up.

[dtknowles]

I have also heard of a case neck becoming separated and left in the chamber neck, the neck of the following round being squeezed down tightly and the whole shebang going up.

I found a .223 cartridge at the range with a ring of brass jammed on the bullet. I think that a neck separated and when the next round chambered it jammed the gun and the operator ejected the jammed round and left it lie.

Tim