LMT MWS barrel R& R question (accuracy)

[problemchild]

I removed my barrel the other day to have a birdcage removed. I got to the range this morning and my rifle was shooting 3-4 inch groups. All ammo was shooting horrible. Black hills, FGMM, Hand loads all was no go.

I thought something had happened to the barrel. I took the new brake off and put the birdcage back on, no-joy. I removed the birdcage and left just a threaded barrel and no-joy. I tried a 5th ammo, no-joy.

I was really bummed and thought my barrel got wrecked. I was shooting some steel jacketed copper flashed LC by mistake a week ago and between the barrel vise and steel jacket I just figured the barrel got destroyed.

I took the barrel off the gun and looked down the tube. I couldn't see any fouling in fact it has a mirror finish. I stood the rifle on its butt and reinstalled the barrel. The time before I had installed the barrel was the rifle was prone on its bipod.

I took one last shot with 5 FGMM 175's. BAM they all stuck together in the center under 1/2 inch. So removing the barrel and reinstalling solved some problem.

My question is what the hell happened?

 

[rifleman0321]

Re: LMT MWS barrel R& R question (accuracy)

Maybe a torque issue?

 

[Cross C]

Re: LMT MWS barrel R& R question (accuracy)

I had nearly the same issue with a MRP in 5.56 with a load that I knew consistently shot very well. I took the barrel off and cleaned/tourqed everything down correctly according to spec and just like you said, everything went back to the norm.

 

[problemchild]

Re: LMT MWS barrel R& R question (accuracy)

I have a torque wrench set to a specific torque and it never changes. Set the same both times.

Only difference was installed the barrel with rifle standing on its butt.

 

[trident1982]

Re: LMT MWS barrel R& R question (accuracy)

The actual torque value honestly has no play in the accuracy of the rifle. The barrel is indexed inside of the chassis. The cross bolts and associated torque value on them just ensures that the barrel stays captured.

You can obviously sheer a bolt by over torquing them(which won't hurt the chassis in the least), but outside of that you cannot screw up a barrel install if your able to fit the two bolts into the chassis.

I'm not sure what the deal was with your particular situation though.

 

[cz777]

Re: LMT MWS barrel R& R question (accuracy)

dont ask me but some times a reseating of a barrel does works wonders at times ...weapons can have hair balls or ghosts in them too ...

 

[JimGnitecki]

Re: LMT MWS barrel R& R question (accuracy)

This is just a theory on ym part, but it is possible you changed the barrel's harmonics with the removal and re-install.

I know you said you used the pre-set troque wrnech both times, but LMT compromised for the sake of prevent8ing disatser when they preset and SEALED the torque wrnech at the factory. Let me explain.

Torque wrenches shoudl NOT be left preset to any setting more than about 1/3 of their maximum capacity. If you do leave it preset for extended storage times at settings higher than about 1/3 of their capacity, the setting might not be accurate.

You used that torque wrench MULTIPLE TIMES within a few days - once to remove the barrel, again to re-install the barrel, and again to remove and re-install. I think it is possible that the multiple uses "restored" the torque wrench to its proepr setting, or at least, chnaged it again.

That would create a slightly different torque on the barrel. Even though the barrel is, as someone else pinted out, kept aligned by its fit in the upper, the two moutning screws STILL affect the tension on the barrel.

It is also entirely possible that a ew ladder test will suggest a slight load change, as a result of the changed torque.

I know that the LMT-provided wrnech DOES vary, because of my own recent experience. This last Saturday, I removed my barrel for the first time, in order to more conveniently clean the lugs and chamber in preparation for using the Stoney Creek OAL cartidge gage later this week. When I remounted the barrel, and started to sue the LMT wrnech to re-torque it, I became suspicious that the setting might not be correct for 2 reasons:

1. The instrucitons that come with the wrnech clearly state that it should not be left "set" to a settign higher than about 1/3 of scale, and LMT had actually SEALED the setting via a signed label taped onto the wrnech's adjsutment collar

2. I noticed that the wrnech had already roatetd the bolt a bit more than I expected, but had not yet clicked.

I pulled out my own Craftsman inch pound torque wrnech, set it to the recommended LMT setting, and sure enough, it clicked immediately.

I backed off the bolt a bit, and re-tightened with MY torque wrench until it clicked. Then, I applied the LMT torquue wrnech. It did NOT click yet.

I plan to use my own properly stored (relaxed) torque wrench from now on.

IF you ever run into the problem you encountered AGAIN, I suggest you just relax the torque on the 2 bolts, and then re-tighten to a slightly different setting. That'll lilely solve the problem if I am correct.

Jim G

 

[997/2man]

Re: LMT MWS barrel R& R question (accuracy)

This one is going into the FYI pile. I don't/won't use the supplied torque wrench, I've got my Snap-on which I know is correct.

 

[BCP]

Re: LMT MWS barrel R& R question (accuracy)

Faulty torque wrench

 

[problemchild]

Re: LMT MWS barrel R& R question (accuracy)

I thought it felt different from time to time. Like I was cranking it too much. Oh well that's why I asked.

Thanks for the replies......

I hate to ask but is there a decent torque wrench that wont break the bank. Money is a bit tight again...

Should I get a beam or clicky?

 

[Solid_Squirrel]

Re: LMT MWS barrel R& R question (accuracy)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: problemchild</div><div class="ubbcode-body">I thought it felt different from time to time. Like I was cranking it too much. Oh well that's why I asked.

Thanks for the replies......

I hate to ask but is there a decent torque wrench that wont break the bank. Money is a bit tight again...

Should I get a beam or clicky? </div></div>

Yes. I have seen testing that showed cheap beam and clicker-types to be surprisingly accurate (I have a Snap-On TechWrench which tested out to be more accurate than even claimed, but that's still around ~1% error or less; even a cheap torque wrench can easily yield ~3-4% accuracy, in other words good enough). I would get something which can be re-calibrated.

I would look at Craftsman, MAC, etc.

 

[R.O.U.S.]

Re: LMT MWS barrel R& R question (accuracy)

I need to keep this in mind for my MWS rifle. I remove my barrel for detailed cleaning. I thought I noticed some wandering POI. The bolts that hold my barrel in are showing some wear. Is that evidence of over torque?

 

[Solid_Squirrel]

Re: LMT MWS barrel R& R question (accuracy)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: R.O.U.S.</div><div class="ubbcode-body">I need to keep this in mind for my MWS rifle. I remove my barrel for detailed cleaning. I thought I noticed some wandering POI. The bolts that hold my barrel in are showing some wear. Is that evidence of over torque? </div></div>

The extent to which a fastener has been permanently deformed, and therefor of reduced clamping load, through being overly torqued, can be directly measured, by measuring the length of the fastener.

ETA: If you really over-torque them, the heads may just pop off the next time you go to loosen it.