Trouble chambering 7x57 Mauser

[7x57Mauser]

I have 3 1916 Spanish Mausers. All had excessive headspace when I got them (meaning, they'd close on a nogo gauge. I don't have a field gauge.). I've fired a few hundred rounds through the lot of them with no case head separations or any other failures. One shot well and is still in its original, military configuration. The other two shot maybe 20" groups at 100 yards.

The first of these, I got the Green Mountain 7x57, short chambered barrel from Midway, rented a reamer and gauges and everything went fine. It closes on the go, does not close on the nogo and has shot very well (Note that I'm chambering by hand. No power tools.).

The second, I got the same barrel, rented a reamer and gauges from the same company and am using the same procedure, but it has not gone well. When it closed on the go gauge, it took a lot of force on the bolt handle to chamber a factory-new round (any of many I tried), so I kept going, figuring the bottom line was that the ammo had to fit, and these guns all would close on a nogo gauge in their original configurations anyway... Well, now it closes on the nogo, but it still takes some force to chamber a round. Even so, when firing, I got 3 case head separations in 5 rounds, and it took considerable force to get the bolt back open for all of them. At that point I decided I was livin' dangerous continuing to fire the thing and set it aside.

So it seems like the headspace is excessive, but it's also overpressure? And note that this is the same type of receiver, with the same barrel, the same tools, same ammo, and the same procedure that worked before, so I'm baffled.

Any idea what could be wrong?

[Hick]

I had a similar chambering problem with a Mauser. Take a properly sized piece of brass and blacken it with a sharpie and chamber it-- when you take it out you should see rub marks where the problem is. Mine was just a slightly tight shoulder.

[7x57Mauser]

Mine was just a slightly tight shoulder.

I'll give that a try. How did you fix the tight shoulder?

[bruce drake]

Check with the reamer company and see if they sent you a match chamber reamer. They cut to the minimal SAAMI spec which makes for some difficulty chambering brass that may have been used in other chambers previously. I had the same difficulty with a 6.5 Creedmoor barrel with an AR10 upper recently. I went with using RCBS Small Base sizing dies and fixed the issue with that rifle.

Regarding that rifle with the long chamber, you might consider recutting that rifle to 280 Remington if the 1916 Mauser is a Large Ring. If its a Small Ring, go find a new barrel if you really want to shoot that rifle.

Bruce

[B R Shooter]

Yes, the problem with short chambered barrels, is the reamer used first may not match the reamer used to finish. If the first was a minimum, you will probably be OK. As Bruce says, things may be reversed.

[Petrol & Powder]

I'll second what Bruce said.

[1Hawkeye]

Remember mauser's are designed to feed from the magazine so the case rim is under the extractor. Just dropping a round in the chamber and closing the bolt may cause difficulty when closing the bolt. Because the extractor has to snap over the rim and some mauser's are to tightly built to allow that.

[gnoahhh]

And that brings to mind another question. Did you remove the extractor like you should when trying the gauges? To do otherwise can give a false reading.

[Texas by God]

Case head seperations means the brass is searching for the shoulder. That chamber is overdone. If you have enough steel, cut off 1/4" from the shank and recut the threads and stop shoulder. And start over reaming the chamber. All this lathe work may cost more than another barrel.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[waksupi]

When loading, there should be slight projectile contact with the rifling. This eliminates headspace problems. As was said, Mausers must feed from the magazine. Otherwise you can break the extractor, if relief has not been cut to allow for it to pass over the rim.

[Tackleberry41]

May be the reamer, its a rental. I rented a 357 sig reamer to convert a 9mm barrel. Something was not right, it would load factory jacketed ammo, most of the time. Nothing cast would begin to fit. A new reamer I bought for another barrel fixed it right up. My guess the reamer I rented was questionable, sharpened to many times, who knows.

[7x57Mauser]

May be the reamer, its a rental. I rented a 357 sig reamer to convert a 9mm barrel. Something was not right, it would load factory jacketed ammo, most of the time. Nothing cast would begin to fit. A new reamer I bought for another barrel fixed it right up. My guess the reamer I rented was questionable, sharpened to many times, who knows.

I think this is most likely the case. The reamer said on it "7mm Mauser, Finisher, Clymer." I did note that it had a secondary bevel ground on the outside of the flute. I don't know if that's normal for Clymers. I did not notice that on the reamer I previously got from them which I believe was a PTG. I suspect it had been sharpened and is now a bit on the narrow side to work well, at least with this action.

I've tried to contact the rental company by e-mail and by phone but no response. I'll give it one more try and if nothing, I guess I won't rent from them anymore.

[7x57Mauser]

Case head seperations means the brass is searching for the shoulder. That chamber is overdone. If you have enough steel, cut off 1/4" from the shank and recut the threads and stop shoulder. And start over reaming the chamber. All this lathe work may cost more than another barrel.

As it happens, I had ordered 2 of these barrels. They're fairly inexpensive as these things go. I intended to hold the second one in reserve to replace a shot-out barrel on one of these guns some day.

What I actually did is to chamber the second one just to see if maybe I screwed it up. This time, I did stop when the bolt closed on the go gauge but not the nogo. It's still a tight fit, but I can chamber and fire a round without case head separation, which I think confirms my narrow reamer theory. At some point, I should be able to get a different reamer and very carefully run it into this chamber to fix that problem without cutting it any deeper.

The other barrel, I didn't go THAT much farther. It could certainly be salvaged by cutting back the shank one thread at the most. Probably .030" would be enough. I'll set it aside as the spare and perhaps by the time I need it, I'll have my own lathe. I've read that it's possible to do that with a file, but that seems beyond my precision filing abilities. Have you ever heard of anyone doing it that way?

[7x57Mauser]

Although, all the above said about the reamer seeming too narrow, I did measure it and it seems to match the SAAMI chamber drawing for 7x57. So, at the shoulder it measured .433 and at the head it measured .472. These are the minimum specs if I'm reading the drawing right, so maybe the average reamer would be a hair larger than that?

Also, I did what someone above suggested and colored a case with a sharpie. It rubbed off just above the shoulder and just before the head. Approximately the same points those two measurements above were taken.

[Wolfer]

When I chambered my 7x57 I stopped as soon as it would close on a go. Bolt would turn about halfway down on a no go.

BUT. Start loads in my minimum chamber would give me close to max load velocities. Below book max would lock up the bolt.
The loads that I would shoot in my military chamber are way too hot for my minimum cut chamber. Haven't lost a piece of brass since I started loading for it accordingly.
My hunting buddy now has my military chambered gun and we load for it accordingly.

[bruce drake]

As it happens, I had ordered 2 of these barrels. They're fairly inexpensive as these things go. I intended to hold the second one in reserve to replace a shot-out barrel on one of these guns some day.

What I actually did is to chamber the second one just to see if maybe I screwed it up. This time, I did stop when the bolt closed on the go gauge but not the nogo. It's still a tight fit, but I can chamber and fire a round without case head separation, which I think confirms my narrow reamer theory. At some point, I should be able to get a different reamer and very carefully run it into this chamber to fix that problem without cutting it any deeper.

The other barrel, I didn't go THAT much farther. It could certainly be salvaged by cutting back the shank one thread at the most. Probably .030" would be enough. I'll set it aside as the spare and perhaps by the time I need it, I'll have my own lathe. I've read that it's possible to do that with a file, but that seems beyond my precision filing abilities. Have you ever heard of anyone doing it that way?

If your barrel has a shoulder on it, you will have to trim the shoulder back the same depth you are cutting off the face of the threads to ensure it properly seats flush with the receiver. filing that shoulder will not be advisable but it is too easy for the gunsmith to face the barrel threads the same distance as the shoulder with two cutting operations on the barrel when its mounted in the lathe.

[flounderman]

the best place I have found to rent a reamer is White Rock, Tool and Die. 6400 North Brighton Ave, Kansas
city MO. 64119. He doesn't do internet, you have to write him or find his number. You can face off the end of the barrel a thread, or less, and remove that much from the shoulder and clean the chamber up. You probably only need a few thousands.

[Drm50]

How about the ammo? Is it possible shoulder is set back?

[country gent]

One thing not mentioned is a to tight pilot can make feeding hard to do and cause problems. a dull reamer may cut right to size or even slightly undersized.

Shoulders can be filed back but its a tough job requiring a lot of spotting and fine removal of stock .002-.005 is a lot of removal. to do the shoulder you ink the receiver ring then screw the barrel in hand tight remove and with a fine jewelers file remove the ink spots maintaining square. repeat to finished point. I have done this on revolver barrels to adjust windage. If there are screw holes or forearm screw holes then 1 turn needs to be removed to maintain barrels timing. The same removal is required on back of barrel, extractor cuts, cones or feed ramps.

[waksupi]

How about the ammo? Is it possible shoulder is set back?

Good question. Neck size only.