"New" gun with a tight chamber.

[morcey2]

Here's the latest victim, er, acquisition...

It's a Dominican Republic 1908/53 or whatever it's called dated 1959. It started life as a short rifle with the 21" barrel and is now wearing a monte-carlo stock, a Dayton-Traister trigger and safety, and a Redfield mount. It's still chambered in it's original 7x57.

But the chamber seems to be slightly too small. I have both the field and go gauges for 7x57/257 bob and this one won't quite close on the go gauge. I can get it to close with a little force on some of my reloads for my other 7x57, but they're minimally resized for my other rifle so that's not surprising.

I bought it originally as a donor and was going to move the stock to my spanish M44 and rebarrel the rest of it, but still in 7x57. But after I took it apart and saw that it was glass-bedded and had the aftermarket trigger, I decided I wanted to shoot it to see what it would do in the condition I bought it.

Then I checked the headspace. I don't have any commercial ammunition at the moment so I may pick some up to see if it chambers easily, but it probably will. My guess is that it will since the bolt will close about half-way (about 45-degrees closed.) If that's the case, I'll just shoot it. I ran a 45-cal bore brush with a little bit of chore-boy bronze scrubber on it with some oil on it through the chamber and that didn't help either.

I'll still probably re-barrel it, but the bore looks really good. It just has a really long throat, but not as long as my mexican mauser. Unless it shoots really well as-is, then I'll have a decision to make. Maybe just have a smith just touch the chamber with a reamer to get it in spec.

I _am_ going to strip the stock. I hate the feel of polyurethane on a wood stock. It's just wrong.

Matt

 

[fguffey]

Morcey2, You did not mention press, die and shell holder. I cut short chambers, it is popular to grind the shell holder and or die, it is not necessary, but, it is popular as an option.

The RCBS shell holder is a loose fit for cases, with a feeler gage a reloader can raise the case off the deck of the shell holder .012”, I would suggest you place a .005” thick feeler gage between the deck of the shell holder and case head when trouble shooting, if the cases do not chamber increase the thickness of the feeler gage.

The case when full length sized is considered minimum length, the difference between a go-gage length chamber and a minimum length sized case is .005”, meaning the person that chambered the rifle cut the chamber for minimum length/full length sized cases. When using the feeler gage to trouble shooting a problem is is believed the reloader is stuck, for the rest of their life, using the feeler gage, The feeler gage is a tool, before cutting a chamber I determine the length of the chamber as is in ‘if it is short, I want to know how short’ in thousandths.

It is possible to determine the length of your chamber with a field reject gage and or a no-go gage in thousandths, it is possible to determine the length of your chamber with your go-gage. It is the gage that is coveted, not knowledge. I would not suggest using work hardened cases, new cases and or once fired cases is preferred.

I form cases for 8mm57 and 7mm57, forming cases for short chamber is an option, forming cases for long chamber is also an option, before I size cases for a chamber I determine the length of the chamber first.

F. Guffey

 

[morcey2]

I use a Lee single stage press from their anniversary kit. I have both Lee and RCBS die sets and shell holders. I haven't loaded any for this particular rifle yet. I'm going to pick up some commercial loads today and see if they will chamber, which I think they will. Using my hornady case length gauge, the headspace gauge measures at 1.792" to the 0.375" datum line, which I'm sure is slightly incorrect because I'm using cheap calipers. My loaded cases (loaded for my other rifle) measure 1.802" in the same setup.

I may have to try the feeler gauge trick if I can find some once-fired cases kicking around. I may have to go make some once-fired cases which wouldn't necessarily be a bad thing.

Matt

 

[fguffey]

morcey2,

http://www.saami.org/PubResources/CC_Drawings/Rifle/7mm Mauser.pdf

The head space gage will not allow the bolt to close, meaning when measuring the length of the case from the .375 datum to the case head the case must be shorter than 1.792”, remembering the bolt will not close on the head space gage. You have a short chamber.

Your cases are longer than a go-gage length chamber, there are methods and techniques that would allow you to determine by ‘how much’. There are methods and techniques that would allow you to determine how much the head space gage protrudes from the datum/shoulder in thousandths.

When you find a case that will chamber it will be shorter than the head space gage , problem, your chamber is shorter than a head space gage. The cases that you have measured are 1.802” from the datum/shoulder to the case head, the 1.802 is close to no-go gage length.

If your press, die and shell holder will not allow you to full length size the case to minimum length (minimum 1.794”, maximum 1.804) the ability of the press to overcome the cases ability to resist sizing must be increased.

F. Guffey

 

[morcey2]

morcey2,

http://www.saami.org/PubResources/CC_Drawings/Rifle/7mm Mauser.pdf

The head space gage will not allow the bolt to close, meaning when measuring the length of the case from the .375 datum to the case head the case must be shorter than 1.792”, remembering the bolt will not close on the head space gage. You have a short chamber.

Your cases are longer than a go-gage length chamber, there are methods and techniques that would allow you to determine by ‘how much’. There are methods and techniques that would allow you to determine how much the head space gage protrudes from the datum/shoulder in thousandths.

When you find a case that will chamber it will be shorter than the head space gage , problem, your chamber is shorter than a head space gage. The cases that you have measured are 1.802” from the datum/shoulder to the case head, the 1.802 is close to no-go gage length.

If your press, die and shell holder will not allow you to full length size the case to minimum length (minimum 1.794”, maximum 1.804) the ability of the press to overcome the cases ability to resist sizing must be increased.

F. Guffey

I appreciate it, but you keep explaining stuff to me that I already know and fully understand.

I haven't even tried to start reloading for this one yet. The cases I used are minimally-resized cases specific to another gun, or commercial cases that are measuring slightly longer than SAAMI spec (1.801" v. 1.7925-1.7995"), but that still could be the calipers. I also want to make sure that the chamber is actually short and that I don't have a couple thousandths of gunk either in the chamber or on the locking surfaces. I'm pretty sure that I got the chamber cleaned out, but I'm still suspicious of the locking surfaces inside the receiver because of the varnish looking gunk I got off of a couple of spots inside the receiver. It reminds me of the varnish that builds up from a slow fuel leak and evaporation around a carburetor. If that's on the locking surfaces, it doesn't take much to mess with the headspace. I'm going to use some brake cleaner, acetone, and mineral spirits inside the receiver to make sure that it's spotless prior to doing anything else. If anything is left after that, so be it.

Matt

 

[morcey2]

Update:

I cleaned up the recesses in the receiver really well and that helped somewhat. It still doesn't want to close on the go gauge, but I forced it to enlarge the chamber slightly. Just kidding.

I dug through a bunch of ammo boxes and found a couple of fired cases. I pulled out the RCBS dies and screwed the die down to 1/2 turn past contact with the shell holder. About half way through the first case, I repented and lubed them. They sized to 1.789-1.790" and chambered and cycled nicely. I'm going to pick up some new cases, size them down, and load them specifically for this rifle to see what it will do. If it shoots really well, I'll be in a position to have to buy another donor rifle instead of this one. If it shoots ok, but nothing to write home about, I'll probably rebarrel it anyway.

Now, if it does shoot really well, I'll probably put it in a synthetic stock as much as that pains me. I think it would make a good tote-around rifle that way.

Matt

 

[morcey2]

Added a cheap scope. (Centerpoint 4-16x40 that looks out of place but will work for a couple of weeks) I'm rust bluing another gun today, so I won't be able to shoot this one until sometime next week.

Matt

 

[morcey2]

Got it out to shoot today, and it can shoot.

That was with factory Remington core-lokt rounds. I didn't get a chance to shoot any reloads because of a prior commitment that cut the session short. The two fliers on the right are from me jerking the trigger. They're the first two shots in the series. Between the second one and each of the other three in the small group, I did a couple of dry fires to get everything calmed down. Worked great. This is the best group, but I had several others that were in the 1" range. So it's definitely a shooter. Once I get a more appropriate scope on it with slightly lower rings, I'll have a better cheek weld and that'll help it even more.

That and some ball and dummy drills to help with flinch/anticipation control

Matt