Krag bolt interchangeability

U.S. Military Krags
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butlersrangers
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Re: Krag bolt interchangeability

Post by butlersrangers »

'Zac952' has loaned me three of his new Graf .30-40 cartridge cases.

The cases arrived today. A quick comparison shows the shoulder to be farther forward than on my Winchester, Remington and original Frankford Arsenal cases.
The difference was obviously visible and very apparent with a caliper.

I tried a Graf case in a model 1898 Krag rifle, that can almost close on a 'No-Go' gauge. (The bolt was stripped of parts).
The bolt closed with almost normal effort, but, I could feel a slight contact and 'springiness'.
When the bolt was opened the case dropped free. There was a very slight rub mark on the brass shoulder.

I tried that same case in a model 1898 carbine that has tighter head-space. It took greater effort to close the bolt. The case again dropped free, but, now shows marks similar to Zac's. experience.

(Photos & measurements in a day or so).
Last edited by butlersrangers on Wed Jul 07, 2021 3:14 pm, edited 3 times in total.

Zac952
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Joined: Wed Apr 07, 2021 1:37 am

Re: Krag bolt interchangeability

Post by Zac952 »

Fred, yes the case holder is touching the die as it cams over, I have even set it in a full turn past touching and came to a full stop on the shell holder before it cams over to ensure it was in full contact, seems weird the dies seem to be slightly off also, but I'm still waiting on that remington brass, and as soon as it gets here I'll see if it chambers and let you know.
BR thanks again for checking it on your end!

FredC
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Location: Dewees Texas

Re: Krag bolt interchangeability

Post by FredC »

"I tried a Graf case in a model 1898 Krag rifle, that can almost close on a 'No-Go' gauge. (The bolt was stripped of parts).
The bolt closed with almost normal effort, but, I could feel a slight contact and 'springiness'.
When the bolt was opened the case dropped free. There was a very slight rub mark on the brass shoulder.

I tried that same case in a model 1898 carbine that has tighter head-space. It took greater effort to close the bolt. The case now shows marks similar to Zac's. experience." QUOTE
Butlersrangers, just remember that Krag head spaces off the rim and has nothing to do with the shoulder distance.With 3 or us confirming Grafs has a problem all doubt is gone. I think chambers and reloading dies are cut to a theoretical sharp corner where it breaks from the body taper to the shoulder angle (I have only had 3 chamber reamers in my hands to actually check and that is what I remember). I am thinking about making a gauge to check that dimension but it will take some time to draw it up then program it.

For Zac send that shell holder or send it to me for a five minute modification. Once the shell holder contacts the die you can gain nothing by tightening it further. If you have mixed brands on the shell holder and dies that could be the problem. If you have you are not the only one as I have several mixed pairs myself.
Last edited by FredC on Mon Jul 12, 2021 1:27 pm, edited 1 time in total.

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butlersrangers
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Re: Krag bolt interchangeability

Post by butlersrangers »

Being a rimmed cartridge, the head-space for the .30-40 Krag is measured from the barrel breech to the bolt face.

However, IMHO, when a case is 'out of specifications' and, (when chambered), is making contact with the bolt face and at the case-shoulder, this becomes for practical purposes the "head-space".
The front surface of the rim is not in contact with the barrel breech.

In fact, the case rim could be totally removed and the cartridge successfully fired in the chamber. (Extraction becomes trickier, though).

FredC
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Location: Dewees Texas

Re: Krag bolt interchangeability

Post by FredC »

Br, Correct on all counts.
This issue could happen completely independent of any "rim" gauging.

Added a photo of the RP and Grafs cases. RP is on the left with a 308 bullet. Neither has been fired. Pretty obvious difference in the body to shoulder dimension. The points where the angle and neck meet are very close as well as the overall length, both cases are sitting on the comparator table.

Just a little trivia here. The Grafs case does have an angle that measures about 21 degrees it is a little harder to find the RP angle as the radii stretch a long ways. What I can measure looks more like 18 degrees. Pretty easy to see why reloads are potentially better as the new cases so much smaller than the chamber.
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Grafs-RPCasesRS.jpg
Grafs-RPCasesRS.jpg (456.84 KiB) Viewed 1324 times

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butlersrangers
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Re: Krag bolt interchangeability

Post by butlersrangers »

My tools are far more basic than Fred's and this experiment is admittedly faulty, since the .308 Winchester cartridge has a different case shoulder than the .30-40.

For What it is worth, I inserted a variety of empty cartridge cases and loaded .30-40 rounds into a Wilson .308 cartridge case gage.
Then, I measured how far that the base of the cartridge projected out of the gage.

The flaw in this plan is that the different (manufacture) case shoulders may not have contacted the gage at the same point (and it just is not a .30-40 gage or chamber).

However, the GRAF and W-W cases do appear to contact the gage at about the same point on the shoulder. The Graf cases projected approximately .038" further than W-W cases out of the gage.
(This is more than the thickness of a credit card).

BTW - The GRAF case, that I forcefully chambered in two Krags, now projects .005 to .006" less than the other GRAF cases.

In the first photo, an arrow points to a new GRAF case.
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compare W-W.jpg
compare W-W.jpg (177.33 KiB) Viewed 1314 times
compare cart base projection.jpg
compare cart base projection.jpg (172.22 KiB) Viewed 1314 times

FredC
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Re: Krag bolt interchangeability

Post by FredC »

Pretty fair test with results as expected. Remington and Winchester brass are probably very close. I am just surprised that the several members here that used Grafs' brass in the last couple of years did not catch this problem. I wonder how easy it is to contact Grafs with this info. It would be really good to have them as a supplier when these ammo panics happen.

The brass I have on hand was purchased soon after they first produced it. I wonder when Zac got his?

I can see the angle changing when fired, but I have no idea how to predict the change. I could see it getting better or worse depending on unforeseen dynamics during fire forming. Choices are better, worse or stays the same. Anyone got a 3 sided coin?

Zac952
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Re: Krag bolt interchangeability

Post by Zac952 »

I received my Graf brass in April 2021, just a week or so prior to my first post. Fred I actually will take you up on that offer for the shell holder if it still stands, I can send both the shell holder and sizing die so they could be matched if need be, I really appreciate it, and could send them this week if you wouldn't mind pm-ing me the shipping info. I have some pickups in need of repair so reloading on my weekends is a few weeks out.

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butlersrangers
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Re: Krag bolt interchangeability

Post by butlersrangers »

How they ranged:

I measured the length of the case (of new GRAF & W-W brass, and loaded Remington & Frankford Arsenal cartridges) that projected from the Wilson .308 gage:

GRAF - .125" and .127"

W-W - .087" and .089"

Frankford Arsenal Cartridge - .090"

Remington factory cartridge - .095"

I measured two fired Remington cases, they averaged - .124"
(These fired cases could be chambered in the test Krags, but offered resistance similar to the new GRAF brass).

I Full Length Re-Sized one GRAF case and a fired Remington case using an old set of R.C.B.S. Dies.
Afterward, I measured the projection of these cases from the gage:

GRAF .115"

Remington .112"

(These re-sized cases chambered with no unusual effort in a Krag with close head-space).
Last edited by butlersrangers on Thu Jul 08, 2021 12:30 am, edited 2 times in total.

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butlersrangers
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Re: Krag bolt interchangeability

Post by butlersrangers »

In summary, I think the GRAF Brass has a shoulder that has been located longer than usual, or the angle of the shoulder creates that effect.

I suspect Zac's F. L. Re-Sizing Die does not have as tight a tolerance as many. My R.C.B.S. .30-40 F.L. Die moves the GRAF shoulder back, for easy chambering.

Thinning a 'shell-holder' should be a good fix with Zac's Die.

The GRAF Brass is quite nice. If many users run their brass through a full-length re-sizing die, when loading their GRAF Brass for the first time, it is unlikely any problem was noticed.
Last edited by butlersrangers on Thu Jul 08, 2021 12:32 am, edited 1 time in total.

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