Barrel/Action Torque

C

Curious

New member
Guys,

I dont have a torque wrench set up to incorporate into my action wrench so quoting figures has never really been useful to me.

Do any of you guys torque your barrels to a degree or movement figure?

On a 16tpi thread it seems to me that once the shoulder touches the action a further turn of around 0.125" further movement around the circumference will give around 0.002" crush and this seems more than tight enough for a barrel/tenon fit.

I established the crush figure with feeler gauges between the action and shoulder and it looked like an accurate way to work, what do you think?
 
You're over thinking this. The amount of rotation depends on the perpendicularity of the threads with the action face. Also thread alignment the first few times the barrel is torqued on. There are other factors such as pitch diameter but we're getting into the deep end of the pool. I don't know what action wrench you're using but lean on it and grunt a bit. That will get you around 70-80 Ft/lbs
 
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The 90/110ft pounds is about what I use.

Here is how to arrive at that on my 16tpi Farley's. Seat the barrel firmly against the action face with your wrench. Then, with a sharpie pen, make a mark from the action ring to the barrel. Turn the action until there is about 3/32 to 1/8 advance between the marks.

Like Dave said, there are several variables involved. At least the witness marks insure that he barrel did tighten.
 
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for rifles that do not come apart on a regular schedule, i torque TIGHT.
i like the joint to be close to one solid part.
125-150 ftlbs with a torque wrench
 
Curious said:
Guys,

I dont have a torque wrench set up to incorporate into my action wrench so quoting figures has never really been useful to me.

........ snip.............
Click to expand...


Why? The most basic torque wrench, a 1/2" drive, 150ftlb model, costs less than eighteen bucks. It may not be a precision tool suitable for rocket surgery, but it's a LOT better than guessing at whatever torque you're looking for.
 
Before the final torquing, put a light film of a good grease on the barrel threads and the action face. Screw the barrel in place to spread the grease. Snug the barrel to the action a few times at a light tightening, about 30...40 ft/lb or so. This will help burnish the mating surfaces together. Then as Dave said, tighten to a grunt or grunt and a half for final fitting.

Probably 75-100 ft/lb for final tightening. Be aware you can over tighten making the barrel hard to remove.

Some will scream that much tightening will distort the chamber and screw up the headspace. Don't worry about that. Regardless how much you do manage to tighten, the chamber shoulder is beyond the tenon shoulder and will not be effected.


.
 
I've installed over a 1000 barrel extensions on barrels for precision sniper rifles over the past few years. Kind of working in reverse. Using less than perfect extensions and using a proper thread fit once the shoulders make contact about 85 ft/lbs is all you need. And yes I do use a torque wrench on those. Rotation stops around 70-80 ft/lbs. Lubricant is Loctite 272

Just to stir the pot I never get more than few tenths change in head space. Another benefit of properly fitted threads.
 
If a snap fit is good enough for swap-barrel benchresters, it's good enough for me! A little tighter on a sporter... :cool:
 
Fussy1 said:
If a snap fit is good enough for swap-barrel benchresters, it's good enough for me! A little tighter on a sporter... :cool:
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I think some a' you'se are missing a salient point....."good enough for benchresters" most often translates to the term "benchresters" actually meaning "real benchresters" which means PPC/BR cases, 100-200 grp or score........ which leaves out a whole schmear of Benchresters who shoot stuff bigger than PPC. It also completely ignores the rest of the population, giving heavy weight to the "fact" that relevancy to benchresters must set the bar for the rest of the world.

It doesn't.

In absolute FACT the bolt thrust on a 1000 yard competitor's 300WSM is nearly double that of the 6PPC.........and you start pushing a 300gr bullet at near 3000fps and you WILL find flex issues that just don't exist in the 6PPC.

My point is, just because something is "good enough for the most accurate rifles in the world" doesn't make it meaningful. And an answer like this re "snap fit" most certainly comes from someone who's never actually built a 1/4" 338 Lapua Mag....... Tooley has, and if Dave says 80fp is enough for his BooBoo's and big 338's then I'm not arguing, but I prefer more.
 
I do not believe that most benchrest competitors use the snap tightening method. I think that a remark or two made it into print, and have been immortalized in folk legend. If you want to read some actual research that was done on the subject, get a hold of a copy of Harold Vaughn's book Rifle Accuracy Facts and read chapter six. Some of the people who have posted on this thread have excellent credentials. Their remarks deserve your close attention.
 
Mozella said:
Why? The most basic torque wrench, a 1/2" drive, 150ftlb model, costs less than eighteen bucks. It may not be a precision tool suitable for rocket surgery, but it's a LOT better than guessing at whatever torque you're looking for.
Click to expand...

Cost or availability isn't the issue, I use a Brownells style action wrench, it has no provision to add a torque wrench so exactly how tight Im torquing something is purely guesswork. At least marking from point to point can be consistent, considering Im usually working in 1.000-16 or 1.0625-16 spec tenons and they are machines the same by me then surely its a reasonable place to start?

Consensus seems to be quite similar, either 1/8" of movement or a bit of a grunt which seems to equate to the same :)

I asked this because I was told to allow for 0.002" of crush while calculating chamber depth but feel that I need to go crazy tight on the torquing to get the bolt to stay open on the no go gauge. I think I will follow Daves lead and try the next one allowing for next to zero crush.

Can I ask what do you guys do?
 
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Allowing for zero crush requires having the capability of measuring the HS of the barrel in tenths. I use a direct reading tenth micrometer thimble in a collar. I have three for different lengths and diameter tenons. Both it and my depth mic are calibrated on a surface plate with gage blocks. Some of my most recent work was dependent on the surface finish of the barrel extensions. I took each extension and polished the face on a surface plate with 240 grit paper. For this job the HS was go +.004". That didn't leave much room for error. Too cut small you have to measure small.
 
Curious

If you're using the cast wrench for 700's with the T-handle put a 12" extension on each handle. That reduces your grunt factor and lets you have more feel as you tighten the barrel.
 
head space reading

When chambering for a short cartridge like 6PPC or 222 rem with a head space of 1.115. What would your reading be on the micrometer or depth gage be to have the so called crush at 80 to 100 lb. torque of the barrel when fitted to the action?

Thanks Chet
 
coyotechet said:
When chambering for a short cartridge like 6PPC or 222 rem with a head space of 1.115. What would your reading be on the micrometer or depth gage be to have the so called crush at 80 to 100 lb. torque of the barrel when fitted to the action?

Thanks Chet
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Guess to technical of a question with over 195 views and not one reply.
When I chamber a 6ppc for a Panda action with a head space reading of 1.115 of the action and cut the barrel chamber to 1.1150 I get no crush of and kind but the bolt has zero movement with about 80/100 lb. torque. Just wanted to know what others where calling crush and how much.

Chet
 
Maybe others use "tool" numbers...different tools different numbers, was my first thought when i saw the question.
Just a thought. End product is the same

coyotechet said:
Guess to technical of a question with over 195 views and not one reply.
When I chamber a 6ppc for a Panda action with a head space reading of 1.115 of the action and cut the barrel chamber to 1.1150 I get no crush of and kind but the bolt has zero movement with about 80/100 lb. torque. Just wanted to know what others where calling crush and how much.

Chet
Click to expand...
 
Something that I would classify as a related matter is the effect of barrel tightening on long bodied magnum chambers. A friend who builds rifles has found that tightening down barrels that have long magnum chambers causes a reduction of the IDs of those chambers in the area of the action threads, and that if this is not dealt with, that extraction problems can result, particularly with hot loads. To remedy this situation, after the barrel is tightened in the action, he goes in with the reamer on a T handle and cuts out the slight choke. This would not be an issue with shorter chambers. Magnum chambers have in less steel thickness around their bodies within the length of the tenon.
 
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