Trouble with sporterized Mauser chamber

[jcinnb]

Long post, hope you don't mind.

1. I purchased a Sporterized Mauser in 25-06 from an online auction.
2. Shot mostly 100,110, and 120 gr bullets.
3. Reloaded these to what I thought was .01 off lands.
4. Decided to be a smarty pants and slugged the barrel
5. Discovered I had a 1:12 twist
6. Researched this and found the bullets I should be shooting were 75 - 90 gr
7. The wheels fell off!!!!
8. Stared getting impossible overall lengths based on Sinclair gage that were longer than bullet + case
9. Started getting EPIC keyholing, picture below
10. Went back to 110, no problem, even with slower twist that 1:10 optimum
11. Kept thinking about issue, made dozens of measurements
12. Just could not get the smaller bullets to get near lands and still be seated
13. Bit the bullet and bought go, no go, and field gage
14. Disassembled extractor on bolt, and tried to chamber the gages
15. Bolt closed effortlessly on go and no go. Uhoh!
16. Bolt almost closed on field gage, withing 20 degrees or so, with absolutely no pressure.
17. Don't know what to do.
18. I have thought, from day one, based on measurements that the throat is to longer, or longer than it should be, but I don't think the go, no go, and field address throat.
18. See 17
19. Any insight, comments, jibes, anything?
20. THanks in advance.

jcinnb



100 yards, 10th of 10 shots, first 8 on another target.

[Brian Pfleuger]

The gauges don't address throat length directly but a gun chambered with excess headspace will, by definition, also appear to have a long throat since the location of the rifling "moves" with the entire chamber.

You need to find a 'smith to get that chamber solid on the go-gauge and not closing on the no-go and THEN worry about OAL of your cartridges.

[F. Guffey]

11. Kept thinking about issue, made dozens of measurements
12. Just could not get the smaller bullets to get near lands and still be seated
13. Bit the bullet and bought go, no go, and field gage
14. Disassembled extractor on bolt, and tried to chamber the gages
15. Bolt closed effortlessly on go and no go. Uhoh!
16. Bolt almost closed on field gage, within 20 degrees or so, with absolutely no pressure.
17. Don't know what to do.

I do not push tools for any manufacturer, tools are nice, not necessary. problem, I find it impossible to convenes someone (a reloader) the go, no and beyond gage is not necessary.

I form cases to any length from the shoulder back to the head of the case. The options of length include cases for short chambers, from minimum length to .017” shorter than minimum length, that would be .012” shorter than a go-gage length chamber. Going the other way is possible to form cases that are longer than the chamber from the shoulder to the bolt face, if I can not find a case that has been fired in a trashy old chamber I use 280 Remington cases, there is no way a reloader can miss when forming a case that is .051” longer than the minimum length case.To form 25/06 cases from 280 Remington cases the 280 shoulder would require it to be formed .041” further back, that should get you back to .004” difference in length between the case and length of the chamber. The question never asked: “How would a reloader to that?” The answer is: Feeler gage! To form 280 cases to 25/06 cases the reloader would be required to adjust the forming die off the shell holder .041”.

I know reloaders are capable of accomplishing this method and or technique when sizing, I read it everyday “I bump the shoulder back .002” etc..” They never explain how, they just ‘do it’, me? I adjust the die off the shell holder with a feeler gage, after making the adjustment I verify the adjustment, you guested it, with a feeler gage. If I can adjust the die off the shell holder I can adjust the die off the shell holder .041”.

Forming cases for your longer chamber solves the problem of the ‘longer than no go-gage length chamber” and ‘shorter than a field reject length chamber”.

Then there is the almost closes, with the ‘within 20 degree (or so)’, I do not know what ‘almost’ is, then there is the 20 degree and within. For years I have said I can determine the length of a 30/06 chamber with a 280 Remington case and I always get the “I am so confused response”, when the bolt closes it advances on an incline plane, all a reloader is required to understand is the depth of the bolt when closed, when measuring the bolt protrusion caused by the field reject gage the differences should indicate to the operator of the depth micrometer the length of the chamber if they understand the protrusion must be subtracted from the length of the gage.

Bullet coming out of the case before it gets to the lands, back to the 280 Remington. The neck of the newly formed 25/06 case can be used to add .051” to the length of the 25/06 case, back to the part where I do not push tools of manufacturers, I drill the flash hole/primer pocket out of cases that fit the chamber from the shoulder to the bolt face, after I drill the primer pocket/flash hole I seat a bullet with a short overall length, after seating the
the bullet I remove the bolt and chamber the modified drilled out case, after chambering I push the bullet out of the case with a cleaning rod until it contacts the rifling, After pushing the bullet out I declare the modified case a ‘transfer’ I use transfers to transfer dimensions of the chamber to the seating die.

F. Guffey

[F. Guffey]

adding length to the neck of the chamber, it could require a neck reamer. Then the question should be about determining the length of the neck in the chamber of your rifle, I could say simple

Back to the long neck of the formed cases, rather than mindlessly trimming the cases use the long neck to determine the length of the neck in the chamber. I modify the case with a shoulder that is set back to far, meaning the shoulder can not contact the shoulder of the chamber, 'then!' I start chambering long neck cases that will not chamber because the neck is too long, it is possible to take one measurement, but it is better to trim a little/few/thousandths in increments of .002" until the case chambers and allows the bolt to close without sizing the neck at the throat.

F. Gufffey

[jcinnb]

Awesome response, I need to study all you told me. Suffice it to say you guys are way, way, way out of my league. Appreciate your time. Thank you!

[HiBC]

I suggest the fact it is a sporterized Mauser has very little to do with your problems.

If it were a rebarreled commercial rifle,you might have the same issues.

I suspect there are two separate problems.

Headspace,and throat wear

Headspace may be initial poor workmanship.It may be set back,it may be a locking lug lap job,it may be lack of a lug lap job before cutting the chamber,it may be a mis-matched generic mauser bolt that is only bearing on the safety lug...

I'm a little concerned about the 20 degree thing.Once the bolt turns past the corner chamfer,its not a screw thread,it is a square surface.

Seems like misguided lapping.

If it does not accept the field gage,it is still serviceable,purely from a headspace point of view,but I might investigate what is changed/changing.

As Mr Guffy suggests,that problem can be worked around through reloading technique.
Be diligent checking for stretch ring with the bent paper clip trick.

The pure headspace issue is less than .015.It is not a significant factor factor in your bullet seating issue

A 25-06 just does not have a long barrel life.Sounds to me like the throat is seriously eroded.

That barrel was probably on the downhill run after 10 lbs of powder was burned through it.

Suppose it had 30 or 40 lbs burned before you bought it?

Now,are those lighter bullets boat tails?

A 100 gr or less .257 boat tail bullet has a very short full cylindrical diameter.

Just close your eyes and picture what happens when that starts down an oversize,rough throat.Gas is blasting past,its wobbling.

Try bullets with long cylindrical bearing .Flat base,heavier.A 115 Balistic tip may work.

It does not matter that it is a Milsurp Mauser if the barrel is shot out.

That happens with 25-06 commercial rifles,too.

If you otherwise really like the rifle,a new tube might be appropriate.

Value received for money spent,I'd look at a pre-threaded,pre chambered Lothar Walther.You already have gages.

[iraiam]

I have been in this same position with a sporterized M1903, I formed brass for a few years, but I could not fire commercial 30-06 ammo, it would cause case separations.

I eventually opted to fix it with a new barrel.

[jimbob86]

What model of Mauser is it?

Running full power -06 cased cartidges through older 93/95/96 can make for excessive head space in short order .....

[jcinnb]

It is a 98K, I thnk I have a rifle purchased with the throat just about shot out. I have had some great responses. Thanks so much, I am going to gunsmith on Tuesday and having HER look at it!

[Scorch]

Easy cheezy! Either set the barrel back and recut the chamber or rebarrel. This will solve both issues.

[jcinnb]

Good info, will bring this option up, too!