Grrr, cut too deep

[bruce drake]

I went to chamber a new 260 Remington on a Yugo 48 Mauser this week and I cut the chamber a little too far.

I used my 308 Win Go and No Go guages and I knew I cut too deep once I stopped and slid the headspace gauges in with no resistance when I closed the bolt. Thinking I might still be within Field Specs, I built a couple of COW loads with some Unique powder to form the cases so I could tell how far I actually cut.

After fire-forming and measuring the blown out cases it looks like this rifle going to have to go back on the bench and be rechambered to 6.5x55 or 6.5x257 Roberts in January.

I'm thinking 6.5x257 due to brass availability as I hate to pay new for 6.5x55 Swede cases when I can use my current 7mm Mauser brass stocks or reform cutdown -06 cases. The dies are more expensive but the price of brass would definitely offset it and the cartridge will do everything the 6.5x55 Swede case can do.

This has been my first error in chambering a barrel, but I hate knowing my perfect record is gone.

As a home gunsmith, at least the customer (me) didn't freak out when he found out.

Bruce

[theperfessor]

Dumb question maybe, but is there any way to set it back one thread and recut the chamber?

[hornsurgeon]

best idea is to shorten the shank, move back the sholder, and recut the chamber. that is, unless you don't have access to a lathe. other wise, i'm sure someone here could do the lathe work for you.

[bruce drake]

Taking the rifle in to get the threads reset at the local gunsmith would cost more than my renting another set of reamers and buying another die set. And I am a heck of a lot faster to complete the project than my local gunsmith.

I'm already set up to spin on and take off Mauser barrels and normally I measure twice and cut once but I got distracted at the last moment when my wife came into the mancave as I was cutting the chamber. Not her fault. I should have pulled the cutter off the barrel when she came in and then flushed the chamber, checked the cut and started fresh after she left.

I posted this as a Mea Culpa event so others could learn from my error as well.

Bruce

[theperfessor]

Mea culpa, I assumed you had used a lathe for chambering. Don't really think you can go too wrong with any caliber that's based on the 7mm/8mm x 57 case. Have you thought about an AI chambering?

[bruce drake]

I'm sticking with standard chambers for now. A little easier to feed them when you can easily find or make the cases.

6.5x57 has been a European chambering for a long time so I should be able to use that data or at least 260 REM/6.5x55 data to start.

Just primarily angry with myself. 20 rechambers (I use a logbook) done correctly over the last few years and then I blow this one badly. I already have a 260 Rem chambered rifle but this one was going to be a Long-Range Match rifle for 1000 yard matches.

Bruce

[theperfessor]

Yeah, I know that pit of the stomach feeling that comes from screwing up a machining job. Well, no matter how good you are there will always be days like that...

[Casting Timmy]

This has my curiousity risen, so how are you cutting the chamber?

[largom]

This has my curiousity risen, so how are you cutting the chamber?

Same here. Do you have a lathe?

[deltaenterprizes]

Curious also, why not measure how much too deep the chamber is and set the barrel back.
Tin foil is .001'', stack small pieces until you feel resistance on the bolt closing.

Do you use short chambered barrels and then finish the chamber by hand?

[Mk42gunner]

Bruce,

There might be a problem with reaming the chamber to 6.5x257, the shoulder of the .260 case may be too big to totally clean up. I was going to buy a short chambered .260 barrel and ream it to 6.5-06 and one of the techs at Brownells advised against it, because of that issue.

If it is just a little too long, you could mark the barrel .264 BD and have your own wildcat. You might still have to make the brass from something longer than a .308 though.

Robert

[Pepe Ray]

Hi Bruce from Piscataquis County.

Here's what I'd do, K.I.S.S.
Treat the chamber as a wild cat. Reload as required.
I.D./Stamp the bbl with a new monica. Enjoy.

Think about it.
Pepe Ray

[bruce drake]

Unfortunately, no lathe.

I use short-chambered barrels usually but I did once (and only once) chamber a threaded barrel blank for a 308 Winchester by hand with a rough and finish chamber reamer set.

I use a T-handle extension and turn the reamer by hand. Depending on the depth of cut needed I may chuck the extension rod itself in a drill for the majority of the cut. I lube heavily with cutting fluid to help prevent chatter.

Right now, the case blows the shoulder out forward to roughly .456 in diameter at the end of the cartridge's body with the length going to 1.665" for the case body before the shoulder sarted to form into the neck. Right now the cases look like a 260REM AI with a very short neck.

Its a custom chamber right now...I'm not looking to replicate it again... Right now, 264 Win Mag, 6.5 Rem Mag and 6.5-284 Winchester are the cartridges that are feasible options to recut for. I just need to decide what will the next chamber be now.

Bruce

[Mk42gunner]

Will the .264 fit in the magazine? I can't remember which of the 48 Yugo's were the shorter action.

With either of the Magnums, you wil have to open the bolt face up to fit.

The 6.5x284 sounds like a good choice for this gun; 1. the case head will fit the bolt. 2. the reamer should clean up the chamber. 3. the loaded round should fit in the magazine. and 4. there is a good chance the rounds will feed without too much extra work to the feed rails.

Robert

[bruce drake]

I've been looking and thinking about the 6.5x284 cartridge as well today while puttering around the house doing winter chores.

You pegged the four primary reasons why the new cartridge will probably be 6.5-284. The fifth reason is that the cases would last a lot longer than the rimmed cartridges for reloads as well.

I did form a duplicate of the blown-out case today with a 308 Win case expanded to 358 Win and I then reformed the neck down with a 260 Rem Size die to form the short neck like the blown-out case. So at this point I had a case almost like the blownout case. I then took the case out and did a COW/Unique shot into the air which formed the case to almost exactly like like the original blown-out case. So at this point I have a couple of fire-formed cases to check for function later this week.

Now, its nice to see I now have a custom .264 BD chambered rifle but I doubt with several other rifles to choose from, I won't stick with the new "custom" chamber but instead will go with a complete rechambering. Besides I have to get back on my chambering average. 95% good isn't good enough. I need to raise the percentages back up again.

Bruce

[JIMinPHX]

I've cut a chamber too deep before. I fixed it by turning the shoulder & the face back a little bit & then turning the barrel into the receiver another 1/4 turn. Since I had not cut the dovetails for the sights yet, I was able to do just 1/4 turn, rather than a full turn. Making the two cuts on a lathe took less than 15 minutes, including set up time. Most local machine shops should be able to handle something like that for reasonable money. It's an easy job.

[bruce drake]

I called around and a friend of mine (an Allied Trades Warrant Officer (basically a super-Machinist)) who just recently retired from the military has a lathe and he's willing to recut the shoulder and face for me. Its going to be a 4 hour round trip but the time spent with him will be worth the gas and time. Now I just need to get the time to spend the day driving to see him around all the family holiday committments we both already have to deal with.

Bruce

[Hip's Ax]

Hey Bruce, I have not done a ton of 1000 yard yet, a few matches a year. I have been using a 260 and while it hammers at 600 you must really watch the wind at 1000 compared to a 6.5-284. Of course the 1000 round life expectancy of the 6.5-284 is something to consider as 260's last 2000+ I was assured that the 6.5-284 shoots so much better at 1000 it is the way to go. Wish I could personally verify this to you but I have not yet had my 6.5-284 to the 1000 yard line except for zeroing.

[bruce drake]

Barrel life was one of the reasons why I originally chose 260 Rem over 6.5-284 but I've been shooting 308 Win for several years at 1000 and if I can loosen a few inches of clicks off my windage with the 260 over the 308 will be a plus in the windier days.

I've visiting family in the Midwest for the next couple of days so pulling that barrel will have to wait for a few days or so before I can get it down to the smith for redoing the shoulder and threads.

Bruce

[felix]

Bruce, barrel life should be about the same, based upon the amount-of-powder/bore-size. I would go with the 6.5 over the 6.0 if range is more important than trajectory to you. ... felix