In 1975 I was stationed in San Diego. We had finished a cruse and I had lots of free "down time" and was working part time at a local gun shop. The owner had just returned from Mexico where that country had dissolved citizen gun rights and returned with a case of Krag rifles.
Most were in very good shape with bright bores. I got one for 75 bucks and grabbed a hand full of original cartridges and went to the range.
I had been collecting US military firearms for tens yeas by then and was really looking for a nice shooting rifle.
I loaded up the rifle and pulled the trigger. The bullet missed the target by several yards and I noticed "silver confetti' fluttering to the ground. What the heck?
I removed the cartridge which looked fine and the bolt. The rifling was gone! As in blown out of the barrel. The Mexican military had fired mercury primed ammo out of the rifle and never really cleaned them before putting them in storage. The rifling had amalgamated and had become soft/brittle over the decades.
I told the owner what had happened to the rifle and he checked the others as well. Some were worse,others were a little better.
I got 25 bucks back as I wanted to keep the rifle as a type in my collection. I'd find a new barrel and replace it.
That took 40 years! All I ever found was Bubba'd barrels or the wrong year type barrel. I wanted to find an original barrel.
In 2016 I did. It was like new on the inside with a nice patina on the outside that matched the rest of the rifle and it was the same year! Wahoo.
I had my local gunsmith mount the barrel. I went to the range and with 220 grain RNFB FMJ's the rifle shot very well at 100 yards. I set my target to 500 yards and had no problem using the peep sight and hitting the target. The rifle has shot very well at 800 yards as well.
But, there is a problem. The chamber is long. Head space is within "field" but the fired cases stretch in front of the web. They fail if reloaded. Crap. Oh well.

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500 yard target and a couple more photos.
I run NM Military Rifle Pistol Shooters and we shoot out to 1,000 yards with old surplus firearms. Forgotten Weapons on Youtube did an episode on us. 

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'Rapidrob' - Welcome to the KCA Forum!

You can purchase a 'New-Old Stock' model 1898 Bolt from 'Movieman 630' (on ebay), aka - 'Grandpa's Gun Parts' (in KCA Classifieds), for $55. This would likely reduce your head-space. But, that might not be the problem.

With the .30-40 being a rimmed cartridge, 'Head-Space' on a U. S. Krag is measured from the bolt-face to the rear face of the barrel, where the cartridge rim stops.
IIRC - This runs about .064" minimum ('Go') to .074" ('Field').

Many Krag Shooters 'partially' Neck-Size their fired cases and 'excessive' Head-Space is never an issue.

Other excessive dimensions can cause case problems:

1. Excessive chamber diameter (which would leave a case poorly supported and likely to expand and split length-wise). 

2. Overly long chamber (which can allow the case-shoulder to move excessively forward, causing case-head separations).

Photos of some of your fired cases, might better reveal the problem and facilitate solutions.

FWIW - I once had a (.303 cal.) Short Magazine Lee-Enfield - Mark III. Its 'brand new' barrel produced complete head-separations, with new commercial Brass, after one reloading.
The rifle had been 'Factory Thorough Repaired' by B.S.A. in 1953 and was like new.
But, the Chamber dimensions were 'sloppy' and not intended for reloading! The case shoulder was blown forward and the stretch thinned the brass above the case 'Web'.
(Even Neck-Sizing did not help. I have never had this occur with a Krag).

It is probably unknown, what your 'new' barrel has been subjected to?
A 'chamber-cast' would reveal if dimensions are 'out of whack'.

I did a search here several times to find the fellow with the Krag bolts. Can you provide a direct ling to him?
Thanks

If a new bolt fixes it everything is good. If not a suggestion I have seen here on this forum may work.
Putting a wrap or two of dental floss ahead of the rim will hold the case back against the bolt face on the first firing, then neck sizing only after that as suggested by Butlersrangers. Your future reloads will actually be head spacing off the front shoulder like a rimless cartridge afterwards.

Welcome to the forum!

Here is a solution if all else fails.  And you don't have to wait forty years.

CMP E-Store

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'Rapidrob' - A new bolt may be the fix, but, if the barrel chamber is 'messed up', it won't fix that.

A chamber cast may be warranted.

Granpa's Gun Parts can be reached by searching 'Classifieds' at the top of the Board Index Page. There is a Thread, (so labeled). 'Culpepers' response in that thread has a Link, that goes right to 'Granpa's Gun Parts'.

The proprietor of G.G.P. is David Stewart - P.O. Box 92 - Dublin, PA. - 18917 - (mark: Attn: GGP).

Email is: DBS3@GRANPASGUNPARTS.com

(David is the grandson of the late-Joe DeChristopher, who was a noted U.S. Military parts dealer and authority).

David carries on the business. On ebay, he sells Krag parts, as Movieman630, with free shipping.

Try this:

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I found Culpepers. Thank you.
I tried a new load today to see if perhaps the powder/brass was a problem as headspace is not excessive.
I loaded up IMR-7383 under a 200 grain bullet. I lightly lubed the brass to allow the brass to form to the chamber walls. The fired case is identical to a new virgin case other than the shoulder angle. No case stretching.
I'm beginning to think the brass is at fault.
I reloaded the same case five times ( neck sizing only) with no splits.
This powder is slower burning than IMR-4350 and IMR-4895. This may be the powder to use to save the brass.
I will try the load tomorrow at 385 meters and see how it holds up and how accurate it may be. They are calling for winds up to 40 mph. 

What powder charges were you using with the reloads that were stretching brass and "causing cases to fail"? (Full head separations)?

IMR-4895 is too fast of a propellant to use in .30-40 rounds with 220 grain projectiles.

Maximum loads for IMR-4350 and 220 grain bullets is around 40 grains.

IMHO lubricating cartridge cases is courting disaster and likely ups pressures unpredictably.

I went back and looked at your first post. What "RNFB", Full Metal Jacketed, 220 grain bullet were you using?

With lubed cases I would worry more about bolt thrust than pressure. Back in the early 03 Springfield days lubing the bullets was necessary to prevent the stripping of the copper nickel alloy bullets from lining the bore. Sloppy application of the Mobil lube would coat the chambers and cause bolt thrust to destroy the rifle and sometimes injure the shooter.
Be sure to wipe the chamber dry before doing any more shooting of full power loads.
Be careful of forming the brass with reduced loads as some reduced loads can cause a process called detonation. I think pistol powders are preferred for reduced loads. I would try a recommended load from a manual to be safe with reduced loads.

I tried the new load today at the range and the wind was 25-40 MPH.
Once I found the zero at 385 meters, the load shot very well bucking the wind. ( 200 grain RNFB FMJ's) Velocity seemed to be normal and I will try them over the chronograph to see what they are really doing. No unburnt powder in the barrel. Recoil was what you'd expect. The brass did not grow,nor does it show signs of incipient case head separation.
One of the rounds had been reloaded five times by me so I think I may have solved the problem.
In previous loads I had tried IMR-4895 with 150 grain bullets, IMR4350 with 200 and 220 grain bullets and Reloader-15 with 175 grain bullets.
I may have bought a bad lot of brass. Today's brass is much newer than the bulk brass I bought years ago that fails.

Which lot # of IMR7383 are you using?

I have 50 pounds left. There is no lot number on this last batch of powder from G.I. Brass.

I got mine years ago, lot #48000, it's very slow and hard to light.

I have never had to use a magnum primer. It is not a .50 BMG powder and would be very dangerous to use it as such.
Any load over 75 grains in my magnum rifles really changes how it burns.
But in cases from .223 to .300 Win Mag, the powder has worked very well for me. It is close to IMR-4350, just slightly slower, Not 7828 slow.
In cases up to .30-06 and 7.62x54R, a load up to the shoulder of the case is just about right. You can go more but it is really not needed. Just never tightly compress the powder. It will spike like mad if too compressed.
I have many,many loads that work well.

Hi all!

FWIW, IMR-4350 is about as close as you can get to the old Laflin & Rand .30 WRA powder that was used in the original .30 Army ammo.  40.0 grains with a 220 RN bullet is the standard load, and I've been shooting this load in matches for years.  Graf and Sons sells new GRAF headstamped brass... and Hornady also offers brass (you can get this from some of the other online places).  Both are excellent quality!  As others said, neck size only after the initial sizing.

Which ship were you stationed aboard?  I did 4 years and 3 deployments on the USS Ranger CV-61 based at NAS North Island during my Naval Career!

I was a plank owner and served 5 years on USS Joseph Hewes DE-1078,
Plank owner on USS Hewitt DD-966 three years
Served on USS Paul F. Foster DD-964, USS KinKaid DD-965 and USS Stump DD-978.
I did TAD's on the USS Guam LPH-9 and a couple of old Fram cans later on.
I did the Tonkin Gulf Yacht Club a couple of times.
We sailed with the Ranger,Kitty Hawk, Roosevelt,Midway and the Big E.
I was a Gunnersmate,Guns.

As it turns out,the brass is at fault. The Remington brass fails on the 1ST or 2ND loading every time. Winchester brass has been loaded since I first posted this topic five times with no problems at all. I will contact Remington to see if I can get replacement brass or my money back. Since the brass is failing right at the web,I cannot safely anneal the brass cases.
At least now I know it is not my rifles fault.

Well... you certainly did chew some ocean! 

By the way, I use a magnum primer with my Krag loads (Hornady 220 gr RN, 40.0 grains of IMR-4350, and a CCI 250 or CCI #34 (mil spec) primer). 

The load I'm using this weekend is 40 grains of 7383 and a Remington magnum primer to see if the load shoots to the same spot.
With 40 grains the powder is slightly compressed. I tried 41 grains,which was more tightly compressed and the primer took on the face of the bolt and was almost completely flat. This is the characteristics of this powder when compressed more that just slightly the pressure will climb sharply in some bottleneck cartridges.
The rule of thumb with IMR-7383 is that you work up the load and keep checking the bore for unburnt powder grains. Once you find none, stop, and go no farther,you found the ideal charge with a given bullet.
As I posted earlier,  I bought the powder to load my magnum rifles. In particular I wanted the powder for my "mile rifle", a custom 8 MM Remington Magnum  with a 32" barrel firing a 220 grain Match King over 3,200 FPS . With today's triple based powders the charge weights were between 100 - 110 grains. No signs of pressure problems as the cartridge operates at 65-68,000 PSI.
With IMR-7383 I had to stop at 89 grains. The case was only 3/4 full but the pressures were getting excessive with the 220 grain bullets. Accuracy was good ,not great because of the low case density.
However, in the smaller over-bore cartridges,the powders works very well indeed. In the 6.5 Swede and the 7.5 Swiss with 160 and 175 grain bullets respectively accuracy is first rate in these rifles.( '91 Swede and M1911 Swiss)
The Dwell time for semi-auto rifles using gas pistons is a little long and I don't use it in them. Gas impingement as in the French 49/56, Swede AG42B, AR-10, AR-15 seem to like this powder and the brass last a long time.
For night time Hog Hunting or the like, this powder is ideal as there is no muzzle flash. A small,dull red glow is seen from a bystander.

Rapidrob wrote on Nov 4^th, 2018 at 12:28am:

I have never had to use a magnum primer. It is not a .50 BMG powder and would be very dangerous to use it as such. Any load over 75 grains in my magnum rifles really changes how it burns. But in cases from .223 to .300 Win Mag, the powder has worked very well for me. It is close to IMR-4350, just slightly slower, Not 7828 slow. In cases up to .30-06 and 7.62x54R, a load up to the shoulder of the case is just about right. You can go more but it is really not needed. Just never tightly compress the powder. It will spike like mad if too compressed. I have many,many loads that work well.

You must have the faster lot.  This slow lot only goes good with a booster that I put in the middle of the charge of 7383.  I've been using it in my K31 more than my Krags.  There were three loadings used in the spotter rifle, thus the three lots.  The slower stuff was for the tracer round that had a flashtube, plus a non-standard (hotter) 50BMG primer.  I haven't worked with any of the faster lots.  Thing is, the nitroguanidine coating needs to explode first.  That explosion consumes all the oxygen, then the remaining nitrocellulose burns without a flame making it flashless.

Sorry to hear you have to use an igniter charge, but with powders such as 5744 as the initiator , you'd be fine.you'd only need to use 3-6 grains. A so called "duplex load"
I had to do that using the surplus .50 BMG powders.

I use a slightly faster powder.  Big flakes, 10B101 (surplus Vihtavuori powder for 50BMG plastic training ammo).  The flakes pretty much stay in place in the middle of the big logs of 7383.  Very little to no compression, but a caseful with the bullet weights I've so far worked with.  The loads I've worked up are very accurate.  Sorta odd to be able to grab a case as soon as it comes out of the rifle and not get burned by it.  It is a real pain to weigh out three charges per case though!