My screw ups are on top of screw ups chambering

C

Clark

New member
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I cut threads and chamber for a 6mmRem 1903 Turkish Mauser #3 taper Douglas 12" twist barrel.

Then i realized that the 257 Roberts/ 7x57mm go gauge was too long.
I should have used a 6mm Remington go gauge.... which was in an unopened package. I assumed they were the same, but I must have known better at one time, I would not have ordered the 6mmRem go gauge.

The SAAMI chamber drawing for 257 Roberts shows the 0.375" shoulder datum at 1.7937".
The SAAMI chamber drawing for 6mm Remington shows the 0.375" shoulder datum at 1.7767".

Sounds like 0.0170" too much headspace..

So I put the barrel back in the lathe, dialed in the annular disc of the shoulder edge... I cut 0.0170" off the breech in 3 places.

but wait... there's more..

The SAAMI chamber drawing for 257 Roberts shows the 0.375" shoulder 20 degrees 39 minutes.
The SAAMI chamber drawing for 6mm Remington shows the 0.375" shoulder 26 degrees.

That doubles the error.

So I cut again.. but I cut too much.
So I got out the reamer.
But I reamed too much.

So I cut a little bit off the shoulder and measured. Then I cut some more. Then I measured, then I cut.
Same thing for the breech face.
Then I have to chamfer so the step of 0.012" from bullet to case mouth will feed.

So I made two big mistakes:
1) Wrong go gauge
2) Thinking I could cut an accurate amount without going in baby steps.
 
At least you've got enough metal that you can keep cutting until you get it right. Of course, if you keep it up, at some point you'll have to cut some more threads... :D
 
Almost sounds like you are in some sort of hurry.
The old adage about measuring twice and cutting once applies here.
Check, double check, and triple check everything before even starting.
Also, if you know your distances, do the chamber first, thread last. As you move the step back and undercut, you are slowly losing thread engagement. Its the thing thats hardest to adjust, so do it last, after you know you have the chamber right, or just barely shallow, so it can be easily finished later.
 
Keep going and you'll need to get NFA approval for a SBR...

Still: Respect! as I wouldn't even know where to begin doing any of this stuff!
 
If you're not making any mistakes, you aren't doing anything at all
Some days it's better to walk away for an hour or two and then try again
 
Sounds like the guy who was supposed to set back and re-chamber my .308 barrel. He cut, measured, re-cut, cut incorrect threads, tried to re-cut threads, cut the wrong thread again, and finally quit after using up about an inch of the barrel which put the chamber out into the the tapered area.
He's buying me a new Shilen replacement and I'm getting someone else to install that barrel.
 
ok, here is a pic of the fixed breech, and the rifle is ready to go to the range.

$125 Douglas Chrome moly 27" #3 taper 6mm 12" twist 6 groove Ebay
$45 1903 Turkish Mauser 8x57mm Century Arms
$92 Boyds laminated painted stock pro Varmint 1903 Turkish Mauser
$49 Bolt trigger with safety
$50 Bolt handle TIG welding and extension the late Randy Ketchum
$12 Weaver grand slam S46 steel scope base Midway
$12 Weaver grand slam S45 steel scope base Midway modified to 1" diam bottom and thinner by 0.037"
$60 Karsten's Custom Cheek Rest A-Model Tactical Works
----------------------------
$445 total for basic rifle


SWFA SS-Tac 30mm / 1" Rings LOW Ebay
USO 1.8-10x37 Ergo Upgrade, used off SH forum
KMW Pod-Loc Brownells
Harris Engineering S-BR Hinged Base 6 - 9-Inch BiPod $100 Amazon
Holland field bag from Dog Gone good bags
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loosely attached accessories

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13 pounds to take to the range
 

Attachments

  • 1903 turk 6mmRem assembled 7-5-2015.jpg
    1903 turk 6mmRem assembled 7-5-2015.jpg
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  • 1903 turk 6mm Rem barrel breech after re headspacing 7-5-2015.jpg
    1903 turk 6mm Rem barrel breech after re headspacing 7-5-2015.jpg
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  • 1903 turk 6mmRem assembled L 7-5-2015.jpg
    1903 turk 6mmRem assembled L 7-5-2015.jpg
    150.2 KB · Views: 42
It was hard enough to clear a space in my junk to make a 3rd world photo studio with butcher paper...... now I need a path to the 257 Roberts brass to form some 6mmRem cases.

The range will be open Wednesday.
I have (4) bullets to try with the wimpy 12" twist:
65 gr Vmax
85 gr HNDY IB
90 gr Nos BT
95 gr Not BT

On paper the Inner bond hornady looks best.
 
I had a 6MM I made from a $20 .244 take off barrel (1-12). I got reasonable accuracy for deer hunting with Hornady 100 Grain RN, should you want to go that way. They don't seem to like the heavier bullets to much.
 
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