30-40 Dies

[tbeck]

Now that I've shot the 96, a small problem has shown up. It has the early tight chamber. My RCBS dies don't reduce the area just ahead of the rim quite enough for easy chambering. They work fine for 98s and Win 95s, but not this '96. Does anybody have a recommendation for dies that have a .002" smaller base diameter?

Information

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[jon_norstog]

Tbeck,

I have a set of CH dies that I bought years ago used. They size down OK. I originally used them in a 94 or 96 carbine, SN 31,224. long gone. They've worked well in every krag I've had since then including 2 custom jobs that had tight chambers.

Does green box ammo load OK in you '96? All my Krags, the case swells a bit ahead of the base web, and no amount of resizing will take out that swelling. it's the nature of the beast. You might consider taking a cast of your 96's chamber and miking it.

just a thought. good luck with it!

jn

[tbeck]

The cases are R-P. They have been fired a dozen times or so in a Win 95, and the problem is just ahead of the web. I have a new bag of brass, which I think is Winchester. It's been laying around the shop quite a while. I'll try that and keep the R-P for the 95. I'll do the chamber cast too. Would be interesting to see what the throat looks like. Maybe I'll even get the CH-4D dies. Thanks!

[andiarisaka]

Early, tight chamber? The chamber dimensions were tightened up around serial # 213,000. Probably more of a case of dies made for the old chamber and rebarrel with a barrel made to the newer dimensions.

[JBS]

If you are talking about the web area just above the rim you can make a small base die by cutting up a standard resizing die. First cut the shoulder resizing area off the die ( not needed ). Then a few thousandth at a time trim the base of the die until it goes down on the brass enough to resize the web to fit your chamber. This is best done with a good lathe. Do not do this more than twice on a brass as the head area is hardened and cannot be annealed without case failure.

[tbeck]

I found the problem, and it's an odd one. Checked a new 30-40 case, still tight, reformed 303 cases, tight too. Painted a case with ****m blue and chambered it. No hits on the case body. Tried a case in the bolt head to see if it's tight in the flange, no problem. Finally, chambered a 44 Long Ballard, which is formed from 303 brass with the rims thinned, and it chambered perfectly. Next thinned the rim on a 30-40 case by 0.005" and it chambered fine. The problem is not enough headspace! Now I can lap the bolt lug until the safety lug contacts the receiver and the headspace will be right! (The bolt is a M-98 replacement.)

Thanks for the tip on the chambers andiarisaka. I read Mallory backwards.

[andiarisaka]

Glad you found it, I was just coming back to suggest your press might be flexing and leaving a gap between die and shellholder. Someone probably swapped the bolt with another over the years, oh, now I see you did. Nothing wrong with tight headspace. When you lap the locking lug, don't go too far to get that safety lug to bear though. A field gauge is .070 thick, and that thickness shouldn't go.

[tbeck]

Actually the '98 bolt came on it. I suspect this one has seen a few campaigns and rebuilds. Looks like I can take 0.010 off the locking lug and it would still miss closing on an 0.070" gauge, and the safety lug is currently a loose 0.010" off the receiver. My plan is to take off just enough to close easily on a 0.062" case head, which probably won't bring the safety lug all the way down. Thanks for the input.

[Alfred]

Rim specs in the Krag manuals call for a .060 rim thickness while case drawings for the .30-40 allow for a .064 thickness. I have an old Krag cartridge here with .063 rim.

Due to lug set back and cracking when a slightly higher velocity cartridge was issued the Springfield Armory offered free replacement bolts to civilian owners of the Krag. Could be they sent a later model bolt to an owner who's Krag bolt had failed.

I have read that bolts were lapped to fit at the arsenal just as you are doing.

Also i've seen it recommended to target shooters of the era to lapp their bolts till the safety lug made contact to even out the resistence on firing and provide better support.

On a side note I ran across a reprint of an arsenal test early in Krag development where tests run starting with zero head gap and increasing head space by .002 revealed that best accuracy came with .004 head gap.
Any tighter than .004 and groups began to get looser, and any looser and the groups became larger.
If I 'm not mistaken the specs were set at between .004 and .006. They even went into the average grain size of western desert sand as being .004, with European sand found in Loam at .006.

I figure it was due to case neck stretching during firing. The case mouth contacting the end of the chamber neck before the bullet left the neck.

[tbeck]

Great info! Thanks.