Reloading for 35/40 Krag

[FredC]

I am within striking distance of finishing my Krag 35/40 sporter. Looking at starting loads for 308 W with heavy bullets sometimes they are right at 40K CUP and the same powder in a Krag at 40K CUP (was PSI) shows the same charges with Varget. My go to powder has been Varget for some time and Hodgdon shows;
46 grains at 42,800 CUP load for the 358W with a 220 bullet
45 Grains at 40700 CUP load for the 358W with a 225 bullet
34 grains at 27800 CUP load for 35Rem with a 220 bullet
38 grains at 33300 CUP load for 35 Rem with a 220 Bullet
Hodgdon does not seem to be worried about detonation with low pressure loads in the 35Rem with Varget.
Lyman's reloading book had very similar data for 30/40 308W and 358W. I will have to borrow my son's Lyman book to verify.
So the question is does 40 grains as a starting load and 45 grains as a maximum load sound reasonable for Varget in a 35/40? One advantage of using loads like this in Varget, there will be no chance of getting an accidental double charge.

[psteinmayer]

I would be very careful of any load that exceeds 40,000 cup!!! If you are using the Lyman book, stick to established loads. A lot of us use 40.0 grains of 4350 with our 220 GR bullets. 4350 is a nice slow burning powder which approximates the original .30 US round very nicely. There is also virtually zero chance of a double charge, as the case is more than 3/4 full with the 40 grain load (a double charge would mean that you're spilling powder all over the bench, LOL).

[reincarnated]

Mr. Steinmayer's advice is correct. The action is a Krag, not something chambered for .308 or .358. 40.0 grains of IMR 4350 pushes a 220 grain jacketed .30 cal bullet at something approaching the velocity of the original Krag cartridge.

If you use the same 40 grain load in a Krag case opened to .35 caliber, and you are pushing a 220 grain bullet, the peak pressure will be about the same, but pressures will drop quicker because the gas is escaping from a tube that has a bore cavity of greater capacity.

[FredC]

Just got the Lyman book and it has 358W starting load for 220 grain bullets and Varget powder:
47 grain 36,200 cup with a velocity of 2278
That makes Hodgon's 45 grains look like a reduced load.
The Hodgdon 225 grain bullet with 45 grains got a velocity of 2254 fps. 2200FPS is what I was hoping for when I started this project. About 1/2 way between 35Rem and 358W.
Lots of interpolation and guess work going on here on my part. Is a 40K CUP load in 358W the equivilant of a 35/40? A definite maybe I guess. Maybe it depends on whose pressure barrel.
I may end up proofing at 47 grains and using whatever between 40 and 45 grains gives the best accuracy.

On another issue, is everyone else having to get a new password every time you log in?

[RichWIS]

If you are necking the 30/40 case to 35 caliber you are making a 1/10 in short 35 Winchester case. Not sure how much 35 Winchester data is still around (let alone pressure tested) but you can use the starting load data as a guide. The 35 Win was used in the 1895 Winchester lever and had a working pressure of about 45K psi vice the 40K psi for a Krag. The case capacity comparison given for 358 Win and the 30/40 makes them seem very similar, but the data I have seen is based on the case filled to the mouth, meaning the actual powder space in the Krag is a lot less than in the 358 and probably a lot closer to 35 Rem. The ballistic of the 35 Win, at a slightly higher pressure level are only slightly better than the 35 Rem. Before betting any body parts it is good to remember that even the newest Krag action is over 110 years old.

[Parashooter]

Extrapolating data from one cartridge to another of the same bore size depends largely on case volume.

Usable capacity (meaning volume with bullet seated to magazine length) of the .30-40 case is some 2 to 4% greater than that of the .308 Win. case. The same, of course, applies after they are necked up to make the ".35-40" and the .358 Win. The .35 Win. has a usable capacity about 25% more than the .358. Consequently, a reasonably high-density load generating a given pressure in the .358 will yield about 2-4% less in the .35 Krag and one developed in the .35 Win. gives ~25%+ higher pressure in the smaller Krag or .358 case.


Note how 46 grains Varget in .358 gives same velocity but significantly higher pressure than 50 grains in relatively large .35 Win. case.

QuickLOAD estimates - NOT LOAD RECOMMENDATIONS!

[psteinmayer]

FWIW, you can take any data or advice Para offers to the bank! And, as Rich stated, regardless of the barrel used, the action is still a Krag action.

[FredC]

Parashooter,
The 35Win is so far off on volume and no current data was the reason I disregarded it. The closeness of data for the 308 starting loads and 30/40 max loads made it seem like a better choice for "extrapolating" data. 2-4% less expected pressure in the Krag sounds good also.
The pressure curve you posted is in PSI not CUP. Would 51K PSI correspond with Hodgdon's 42.8K CUP?
If so, using 45 grains as a max safe load and looking for an accurate load in the 41 to 44 grain range will be the plan.

Rich, Losing body parts does not sound like fun, if I use Lyman's 47 grains as a proof load it will be with the gun wrapped in a towel, tied to an old tire and the trigger pulled with a string.

[reincarnated]

Fred, what will most probably happen is that the bolt lug will crack. That happened (and continues to happen) to many Krags simply by overloading the powder pushing the 220 grain bullet. I did it to my Krag with 41.5 grains of 4350. Someplace on this site is a link leading to Michael Petrov's experiments in blowing up a Krag.

That said, I have seen Krags converted to both .35 Winchester and .405 Winchester. The magazine must be modified to take the slightly longer cartridge.

Ken Water's Pet Loads book has chapters on all 3 cartridges; .30/40 Krag, .35 Winchester and .358 Winchester. Walter's work is well worth reading, especially the part about asking too much of old rifles.

[FredC]

My goal is to stay below the 40K cup, the problem is using the best interpolation as to what is 40K in 35/40.
Here is what happens from Lyman when going from 308W to 358W with varget maximum loads:
308W 42.5 G 2503 FPS, 60.2K PSI 200 grain bullet
358W 51G 2612 FPS 45.5K CUP 200 grain bullet
I wish both were in CUP
Hodgdon's published maximum loads for 308W and 358W
308W 42 G 2441 FPS 50.1K CUP 200 grain bullet 24 in barrel
358W 51 G 2527 FPS 47.7K CUP 200 grain bullet 26 in barrel
Same thing happens with 06 and 35 Whelen charge weights go up and velocity increases with the same weight bullet, while pressure decreases.

Roughly 20% increase in going from 308W to 358W but the powder may act differently at 308 pressure levels.
I expect the same thing when going from 30 caliber Krag to 35 caliber Krag. Just how much though?!?!
When I had this action apart I did a touch up lapping of the locking lugs just to make sure I had near 100% contact and found the guide rib was also in contact.