Barrel torque--updated

[tywest]

Ohh and the pictures upside down so POA was the top of the bullseye at 50yrd range......but you get the point regardless of POA or target orientation

[tywest]

Originally Posted by gunplumber

actually it is anecdotal, not proof, but still interesting. You'd need a lot more trials . . .

Anyway, what was the difference in torque between the two? It seems that the barrel would have to have been shimmed the second time to use the same barrel at a higher torque on the same receiver.

Ok ok true very anecdotal haha, enough for me to torque properly

First torque was 40ftlbs on a #4 shim i believe id have to mic it again
Second torque was 162ftlbs on a #8? (.060)


The grouping on the second shim and torque is more what i expected per sellers description as he had test fired it for accuracy sometime prior.

[kotengu]

That is a good shooter, sir! Thank you very much for the follow-up, and for putting up with all of our ramblings and thread diversions. Over 100 replies for a simple question about torque - I love this place!

[tywest]

Sometimes many lessons are learned and things pondered on the long road home

[gunplumber]

that you had a shim in both is very interesting - it makes them a lot more comparable than I understood from your original post.

So I guess now the hypothesis is, a higher torque results in greater accuracy. Is it a a parabola? I wonder if the group you are getting at 140 is actually larger than 120?

[tywest]

yeah the first shim hand time to about 11:10 but when I checked the torque 40 ft/lbs was scary to me

so i decided to order the largest shim, see where it hand timed (10:10ish) and check torque to 12 o clock.

i understand that a handtight barrel might shoot aweful due to ability to move wildly but,
its interesting that the torque might reduce or impart some kind of change to barrel harmonics and accuracy at above handtightness.....maybe the receiver and barrel stabilize better at greater torque? or the receiver stabilizes the barrel harmonically?

makes sense though from my profession.......undertorqued or overtorqued fasteners can exacerbate vibratory issues. there is a just right

[garyd1961]

Originally Posted by tywest

yeah the first shim hand time to about 11:10 but when I checked the torque 40 ft/lbs was scary to me

so i decided to order the largest shim, see where it hand timed (10:10ish) and check torque to 12 o clock.

i understand that a handtight barrel might shoot aweful due to ability to move wildly but,
its interesting that the torque might reduce or impart some kind of change to barrel harmonics and accuracy at above handtightness.....maybe the receiver and barrel stabilize better at greater torque? or the receiver stabilizes the barrel harmonically?

makes sense though from my profession.......undertorqued or overtorqued fasteners can exacerbate vibratory issues. there is a just right

Interesting but doesn't prove anything. I can take a rifle out one day and soot a 5 inch group and take the same rifle out another day and shoot under 3 inches. It would have been better if you took it out at least three times before you re-torqued the barrel. There could be a lot of factors why your groups got better. Parts seating together, weather, or you just getting use to the rifle.
The only real way to tell is to let someone else torque the barrel and not tell the shooter. If you are anticipating it to shoot better with more torque you will shoot better.

[gunplumber]

Originally Posted by garyd1961

Interesting but doesn't prove anything. I can take a rifle out one day and soot a 5 inch group and take the same rifle out another day and shoot under 3 inches. It would have been better if you took it out at least three times before you re-torqued the barrel. There could be a lot of factors why your groups got better. Parts seating together, weather, or you just getting use to the rifle.
The only real way to tell is to let someone else torque the barrel and not tell the shooter. If you are anticipating it to shoot better with more torque you will shoot better.

certainly true, but I think the anecdotal report is interesting enough to pursue with additional tests. An inch pattern would be ideal since one could just change breeching washers.

[tywest]

Originally Posted by garyd1961

Interesting but doesn't prove anything. I can take a rifle out one day and soot a 5 inch group and take the same rifle out another day and shoot under 3 inches. It would have been better if you took it out at least three times before you re-torqued the barrel. There could be a lot of factors why your groups got better. Parts seating together, weather, or you just getting use to the rifle.
The only real way to tell is to let someone else torque the barrel and not tell the shooter. If you are anticipating it to shoot better with more torque you will shoot better.

I see your point and can agree to a point, but i never notice a change in group size in my rifles regardless of ambient conditions. But im not shooting submoa off a benchrest rifle with hand loads and a datasheet. So for me its as gp said.....anecdotal.....enough to raise my brow and study something ive never considered

[garyd1961]

I would love to see the outcome of such a study myself.

[tigerfans2]

Originally Posted by tywest

Ok so installed the barrel into the reciever tonight and it handtimes to about 11:10. I torqued it over to 12 by hand.

Now im an auto tech and pretty brute but this didnt feel like alot of force to get it there......but its by no means loose or easy haha. I just assumed it would have felt tougher the way you guys talk about yours in gigantor vises and huge breaker bars. Ill stick a torque wrench on it tomorrow as well.

ok so checked torque tonight and very unhappy......40ftlbs!! So if i get a larger breeching washer and kick it back to 10:30 ish with the breeching washer then the torque should go up considerably correct?
Is this going to change headspacing at all?

You can tell what 11:10 is?

http://www.falfiles.com/forums/showthread.php?t=195562

Look at post #17
If you can determine 11:10 (using a digital angle protractor ?) you'll be at (360/12 = 30, 30/60=.5, .5*50=25) 25 degrees.

[tywest]

Originally Posted by tigerfans2

You can tell what 11:10 is?

http://www.falfiles.com/forums/showthread.php?t=195562

Look at post #17
If you can determine 11:10 (using a digital angle protractor ?) you'll be at (360/12 = 30, 30/60=.5, .5*50=25) 25 degrees.

So i gather your saying then that as long as you have 18* rotation to 12 from 11 that your ok regardless of whether its 10ftlbs or higher?

[tigerfans2]

I can assure you that if you're doing a metric that has a steel barrel mating to a steel receiver, a 30 degree movement (that's 11 to 12) will be significantly higher than 10 ft. Lbs. of torque. As for a rifle using a shim (Inch FAL for instance) the material used as a shim would come into play. Assuming a steel shim I'd still posit that 18 degrees of movement will significantly exceed 10 ft. Lbs. of torque.

[tywest]

Originally Posted by tigerfans2

I can assure you that if you're doing a metric that has a steel barrel mating to a steel receiver, a 30 degree movement (that's 11 to 12) will be significantly higher than 10 ft. Lbs. of torque. As for a rifle using a shim (Inch FAL for instance) the material used as a shim would come into play. Assuming a steel shim I'd still posit that 18 degrees of movement will significantly exceed 10 ft. Lbs. of torque.

If you read my previous postings its an inch barrel on a metric reciever. And if 11-12 turn is 30* then i measured about 40ftlbs.......so i cant agree that 18* on the same rifle with an even smaller shim would "significantly" exceed 10 ftlbs when tightened from its new approximate position of 11:30 to 12.

[tigerfans2]

Originally Posted by tywest

If you read my previous postings its an inch barrel on a metric reciever. And if 11-12 turn is 30* then i measured about 40ftlbs.......so i cant agree that 18* on the same rifle with an even smaller shim would "significantly" exceed 10 ftlbs when tightened from its new approximate position of 11:30 to 12.

360/12(hours on a clock)=30 degrees

You can measure what you wish however a 30 degree crush is more than 40 ft. lbs.

Sorry, it is what it is.

Caveat: a 30 degree crush using a foam barrel and foam receiver will be significantly less

[tywest]

You wantee turn my torquee wench??
I hear what your laying down good buddy but as you said numbers dont lie and neither do calibrated torque wrenches. You cant make a blanket statement like that, too many variables........and besides i said 11:10 anyways

You stay on your lawn i stay on mine

[kotengu]

18 degrees on a 16 thread per inch joint is a little over 0.003" axial movement (the "crush" you're referring to). It is perfectly reasonable that a joint would move that much just during the alignment phase of tightening, which means things are deforming easily and the joint is just getting lined up. The real torque happens during the next phase, so it's very likely if you're hand tight at 18 degrees before top dead center you'll be way under torqued at top dead center.

Seems like somebody said the 18 degree number was bunk in that old thread too.

The only way I can see that working is if there was another spec we were missing - like torque to 40 ft-lbs at 18 degrees BTDC, then tighten to TDC. A minum torque plus an angular measurement is much more accurate than one or the other, so I can see a factory saying that maybe.

[tigerfans2]

Originally Posted by tywest

You wantee turn my torquee wench??
I hear what your laying down good buddy but as you said numbers dont lie and neither do calibrated torque wrenches. You cant make a blanket statement like that, too many variables........and besides i said 11:10 anyways

You stay on your lawn i stay on mine

You're right, I forgot that 10 minutes. What a difference a few minutes makes.

[Aeroscout]

Interesting discussion but not alot of feed back about "over" torqing.

It would seem that with GP's comment of having to jump on a long ass breaker bar from 2 feet in the air to get some barrels to break free that over torqing is not really a concern?

[shlomo]

Originally Posted by Aeroscout

Interesting discussion but not alot of feed back about "over" torqing.

It would seem that with GP's comment of having to jump on a long ass breaker bar from 2 feet in the air to get some barrels to break free that over torqing is not really a concern?

Just because it was done, doesn't mean it was a good idea.

[Aeroscout]

Originally Posted by shlomo

Just because it was done, doesn't mean it was a good idea.

Indeed true.....I am also kind of fishing here...

I guess the point I am actually trying to make/question I am asking/driving at...... is that given the sampling he has received of the multiple variants he has encountered it is a mere fraction of the thousands of rifles out there and he has had to do that on multiple occasions.

Given that.....it would appear that one could infer that over torqing was both common as well as not really very impactful as to the reliability/accuracy/longevity of the rifles....obviously they had been like that for a long time as these rifles ain't no spring chickens.

I also post this as one who has read that 10:30 to 11 is the hand timing starting point for torqing the barrels....and the couple I have done hand timed to at least 10:30 and I torqued them on from there using a 2 foot 1/2 inch breaker bar with a 3 foot cheater.....I know I am beyond 120 ft lbs as I could see the breaker bar flexing and it took some ass to get it to 12 (one arm pulling on the bar and one pushing on the side of my cabinet...so not a complete 2 handed monkey swing on the bar).

I did forget to put the handguard ring on one and had to take the barrel back off and did notice that it was no longer as easy to screw the receiver off or back on again by hand as it was when I first put it on....Not hugely so but definately noticeable.

I guess maybe I am hunting for an "It's all right don't worry about it" kind of thing.....or should I be concerned and take the barrel off and take a little more off the shoulder to get it closer to 11 and re torque?...Chase the threads as well?....or leave it be?

[gunplumber]

Originally Posted by Aeroscout

Interesting discussion but not alot of feed back about "over" torqing.

It would seem that with GP's comment of having to jump on a long ass breaker bar from 2 feet in the air to get some barrels to break free that over torqing is not really a concern?

To make that determination, the rifle would have to be shot - maybe 10 ten round groups. Then the shoulder turned back to obtain a lesser torque, then ten more ten round groups. If there is a statistically significant improvement in accuracy, then it suggests that more than (135?) foot pounds is detrimental. If there is no statistically significant variation, then it suggests that upward limits are not important.

Since I use a wrench, and not a hydraulic ram, I keep my torque below the point where the wrench flats are likely to deform.

I suspect that the high torque rating is the result of a barrel installation method that has all the force one could want, without fear of deforming anything. When all your barrels are of exactly the same contour, as is likely in the IMBEL factory, a barrel holding fixture that does not allow the flats to deform under high torque, is used.

[kotengu]

Originally Posted by Aeroscout

I guess maybe I am hunting for an "It's all right don't worry about it" kind of thing.....or should I be concerned and take the barrel off and take a little more off the shoulder to get it closer to 11 and re torque?...Chase the threads as well?....or leave it be?

It's alright don't worry about it.

Seriously though - the danger of over-torquing is in deformation of the threads. Taking the barrel off and shaving the shoulder would be pointless now that you've already torqued it hard. Any damage that could have been done, has already been done. I suspect everything is fine and you should just enjoy the rifle as-is.