Problem with chambering new brass

Ammunition, reloading, shooting, etc
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Parashooter
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Re: Problem with chambering new brass

Post by Parashooter »

Zac952 wrote: Mon Apr 26, 2021 3:23 pm. . . These are Clymer guages which have a good reputation but they are out of spec. . .
According to SAAMI, your gauge's rim diameter is within "spec" - ".555+.012". Note that these are chamber gauges, not cartridge gauges.
(Spelling hint: "a" before "u" in "gauge" - think of the abbreviation, as in "12 ga.".) :roll:

Chamber drawing Image
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Zac952
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Re: Problem with chambering new brass

Post by Zac952 »

Parashooter, yes the chamber would have a larger spec on the rim diameter, but as far as I know the headspace gauge needs to fit within the bolt head recess, which is sized for the cartridge not for the chamber dimensions. Although I may be wrong on this I am not a professional but this is my understanding. So unless I have a undersized bolt recess, which I suppose is possible. I will measure and take pictures when I get home, also I may not be spelling many of these things correctly, and my Grammer is not the best, I try to communicate the best I can lol

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butlersrangers
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Re: Problem with chambering new brass

Post by butlersrangers »

We have had errant head-space gauge performance reported before in KCA Forum threads.

I recall a situation in which a KCA participant's model 1898 rifle bolt would not close on a "Go" gauge or on a "No-Go" gauge. Mysteriously, the bolt would close easily on a "Field" gauge! (The rifle had excessive headspace).

As I recall in the seemingly 'paradox' situation, the gauges were made by at least two different manufacturers.

The thinner rims of the "Go" and "No-Go" gauges had too large a rim diameter and there was no radius or rim bevel.
These gauges DID NOT fit properly inside the 'flanged' Krag bolt or make proper contact with the Krag bolt-face.

The gauges gave erroneous results because the 'sharp & square' "rim" either hung up on the bolt's flange or on the rounded corners, left where the flange meets the bolt-face.

I am positive we are seeing a similar situation with what 'Zac952' is reporting. The Clymer gauges are not fitting properly against his bolt face. (He has been given invalid results).
Hopefully, his Bolt's actual free travel (or 'headspace'), after he completed 'finish reaming' , is less than .073".

IMHO - (I suspect Clymer has built their headspace gauges to work well with the non-flanged .303 Lee-Enfield bolt-face.
I don't think they have properly fitted their gauges to fit inside the flanged Krag bolt).

I have a "knock-off" Field Gauge with a .073" thick rim. The edges of the rim have a radius. The rim of the gauge easily enters the bolt flange and squarely meets the bolt face. My gauge can not hang up like the Clymer gauge, in your photos.

None of my Krag bolts close on this 'no brand' Field Gauge. I bought it off of ebay, years ago, and it has proved to be very useful.
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Last edited by butlersrangers on Tue Apr 27, 2021 2:38 am, edited 1 time in total.

Zac952
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Re: Problem with chambering new brass

Post by Zac952 »

Butlersrangers thank you! I have a forster field gauge on the way from brownells, and I hope it doesn't close on that gauge, we will see, in the meantime I have sent an email out to Clymertool with included pictures. I hope they will correct their future gauges as I hope nobody else will potentially ruin a krag barrel due to the incorrect reading with these gauges. It is very hard to stomach potentially having to buy a barrel to fix this, but what is even harder to stomach is the destruction of an original barrel with crisp rifling and little wear. I due take responsibility for not ensuring that the gauge sat correctly on the bolt face, but I cleaned the boltface and didn't consider something being out of spec like this. The hardest part is I was also checking the chamber with a case and considered stopping when a case would chamber but I figured some tolerance would be necessary if switching brands of case or using factory ammo so I continued until the go gauge would close tightly. Darn it I was so close to having it fixed. But at least I learned a lesson I won't soon forget and possibly somebody will see this thread and it will prevent them from ruining a barrel.

FredC
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Re: Problem with chambering new brass

Post by FredC »

I think we have solved two mysteries. The other one Br mentioned and this one. I turned and faced a .550 piece of brass on the tool room lathe and checked it in 3 NOS bolts. It was tight in 2 of them and did not want to turn when bottomed out. One of them it did not want to sit flat like that Clymer gauge. Looking closely in the of these 3 bolts there is a taper leading to a very short parallel bore that meets the face. The parallel bore is probably a few thousands smaller than .550 inch. I really think that head space gauges for Krags should have a bevel that is slightly larger than the largest seen on commercial brass, then there will be no issues when used with a Krag bolt.

I can think of 2 other guns (Ruger #1 or #3s and the old lever action Winchester) that might be chambered for 30/40 both of those would probably work with a beveled gauge meant for a Krag bolt.
Zac, if you get that field gauge and it needs a bevel let me know, i should be able to chuck it in my spin fixture on the surface grinder and put a professional bevel on it. you too Br if yours needs it.

Br, is that your field gauge in the photo with the 2 bolts facing up, one with a cartridge and one with a gauge? if so your gauge is smaller than the recess in the bolt end by several thousands even allowing for the taper bore. I re read your reply and it is plain your no name gauge fits a Krag bolt very well. My test with the .550 test piece proves your conclusions. Forgot these gauges were also used for 303s, maybe that leads to this issue.
Last edited by FredC on Tue Apr 27, 2021 3:07 am, edited 1 time in total.

Zac952
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Re: Problem with chambering new brass

Post by Zac952 »

FredC thank you for all the help and your hard work in the shop helping to prove I'm not crazy! I will let you know how that field gauge comes in and I will surely take you up on the offer if it is improper, this has been an uphill battle since its purchase and well I may be downtrodden I'm not ready to give up yet. This forum has been a wealth of knowledge with very helpful and informative people and that has been very instrumental in getting as far as I am into this project. Hopefully this will advocate change in the gauge specifications and lead to less trouble for others down the road. Truly I can not give thanks enough for all the help along the way and I look forward to getting this Krag right and shooting.

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butlersrangers
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Re: Problem with chambering new brass

Post by butlersrangers »

'Zac952' - I have a hunch that you did not ruin your barrel and its chamber.

If excess case 'free travel' has been introduced, you can use 'Parashooters' fishline 'spacers' to position the cartridge base against the bolt-face. The case-shoulder upon 'firing' will fire-form to your chamber.

When reforming the case during reloading, backoff the .30-40 F.L. Resizing Die one turn. This will Neck-Size the case and leave the shoulder alone. A .308 Winchester Die will also work for neck-sizing.

I use a Lee 7.5X 55mm ('Swiss') Collet Die. It sizes about 2/3rds of the .30-40 case-neck, requires no lube, and causes no 'expander-ball' case stretching.

You can make a 'stop-gap' Field Gauge by Super-Gluing a metal shim or thin washer to the base of a .30-40 case. This homemade gauge 'rim' is about .070" thick.
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butlersrangers
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Re: Problem with chambering new brass

Post by butlersrangers »

'Zac952' - If you find your Krag has a bit more 'free travel', between the barrel breech and bolt-face than you are happy with, you might gain a closer fit with a 'new old stock' Bolt.

Amazingly, there are 'mint' Krag bolts available, that have been in their wrapper since the early 1900's.

I used one of these on a Krag with a bolt that closed on a 'field gauge'. The new Bolt totally corrected the situation.

'FredC' may still have some NOS Bolts for sale, from a 'research project' he embarked on, a couple of years ago?

Zac952
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Re: Problem with chambering new brass

Post by Zac952 »

Just for reference the reamer measured out at exactly .555 at the rim part, my bolt face depth was around .057, the gauges both have a square bottom with no chamfer and I included a couple of pictures.
I think we have the answer now but I was just posting this to verify what you all have helped me to figure out!
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Also the bolt face is clean with no dings or other issues that would interfere with measuring headspace.
Last edited by Zac952 on Tue Apr 27, 2021 3:27 pm, edited 1 time in total.

FredC
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Re: Problem with chambering new brass

Post by FredC »

There is a small parallel section on the bolt recess and could not get my ID mikes to "bite" on that portion of the recess. So i took another 5/8 bar end and started turning in .002 increments till I got the bolt to spin freely on the faced and turned stub.
So the drawing below is a screenshot taken with a camera of the CAD drawing. The drawing is backwards of a normal drawing. Dotted line is the outside of the bolt. solid line is the interior for clarity. IMO no Krag 30/40 head space gauge should be more than .535 on the rim. If you are reaming a Ruger #1 or #3 it does not matter. The dimensions on the drawing are averaged between measurements of the 3 NOS bolts on hand.
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