Tightening a 1903A3 barrel ?

[Jocko]

When re=barreling a 1903A3 can the barrel be to tight ?

I installed a new GI barrel and I actually bent the handle on
my CMP receiver wrench about 2 inches getting the index marks to line up.

Just wondering if to much tension might damage the threads internally.


Thanks

[chuckindenver]

45 to 50 pounds is ideal..yes, you can go to far...its best to stop before you break something...

[Dave in NGA]

Yes, it can be too tight. The witness mark should be within about a quarter inch of the mark on the receiver. If it's more than that you might need to face off a couple thousands from the contact face on the barrel prior to seating. Don't go too far in removing material.

[Jocko]

My index marks are lined up perfectly on the rifle now, so - if I tightened the barrel
to much am I or anyone else in danger firing the rifle ?

All long as I did not create a crack or anything all should be fine - right ?

[ClaudeH]

Did you lubricate the threads, like with anti-seize or something?

[chuckindenver]

no lube should ever be used on square threads.. it will give you a false crush.
if your witness marks are on the money, and no damage...you should be fine..
i would look for damage on the receiver ring, and on the bottom flat behind the recoil lug...common areas damaged with cheaper tools. iv seen them mushroomed out pretty bad..
that in itself isnt a safety issue...but it could lead to a crack..
also.
its possible to crush the reciver ring itself. to the point the the bolt will rub the opening just as it goes ito the chamber area..

[Marine A5 Sniper Rifle]

Chuck, I agree with your torque figures; but I thought all torque values were for lubricated threads, square included (from Machinist's Handbook).

Allow me to add to my comment. Torque values for lubricated threads are less than for non-lubricated (differing "K" values).

K = 0.20 for non-lubricated threads
K = 0.15 for lubricated threads

I personally use 40 ft-lbs for lubricated 03/A3 threads. SA did a study on torque values versus accuracy, and 40 ft-lbs seems to be in the middle of the "sweet spot".

jt

[chuckindenver]

in my experiance.
what happens when you lube, grease or other wise put something on the threads.
hydrolock for lack of a better term happens.. grease or oil creates pressure, making it feel tight...heat and time the grease gives way, and then you have a loose barrel.
i cant count how many times a customer has sent me a barreled action that they couldnt get to index..
they were close, but not close enough..
i remove the barrel to find loads of grease, oil or other slick goo on the threads...
i spritz a little brake parts cleaner, and brush..whipe it with a rag...
they index up fine after that..
this has happened 2 times in the last week..
then now and then i get the barrel that was over indexed, and wouldnt stay tight..so rather then roll or peen the should...lets just slobber the threads with plumbers putty or other sticky goo...yea, that works... wonder why i cant get a barn door???now ya know..

[chuckindenver]

some likely reasons square threads were used on most U.S. weapons...until the M16.
they are loose fit, but tighten up very well.. and next to impossible to cross thread...though anything can happen with the right monkey on the wrench.
barrels are easy to interchange without special machine tools in the field, ect..
with a large shoulder crush, safety, and accuracy is a good mix...
as most of the crush is at the shoulder to receiver face with square threads..

[pelago]

damn

.its best to stop before you break something...
this is why you do what you do, and why i trade green stamps for that, i can punch out a pin and replace the front sight blade, pull trigger out, but doing a barrel is something that i pay to have done