XLR stock issues

[tacomHQ]

There is at least one component that is adding to the "loosening" of take down screws in my theory.
Slickness of smooth anodized aluminum chassis against the slickness of fine surface finishes of the receiver. The friction on receiver and chassis when clamped down with torqued takedown screws is diminished greatly.
If the recoil lug is not fitting tightly in the mortise, and the receiver is moving, that would tend to "yield" those 2 takedown screws at some point during firing. After all, they need re-torquing, so those screws aren't rotating loose, they are getting "yielded". If one has to continually re-torque after shooting sessions, those screws cannot do the job by themselves.

Has anyone bedded the recoil lug/ mortise?

Harmonics, surfaces, temperatures, torque on the system.
Starting with surfaces- friction torque and bolt torque are not the same thing. Think Rod bolts. You tighten to a "stretch value" or an angle value. However, if you miss your mark you don't keep on going. You loosen then retorque again. Loctite is a bit of a Bandaid. Pure friction torque- an anodized surface on an anodized surface (scopes) is a totally false read without precautions.
Temperatures- what is my operating temperature? Even though the load is relatively low the difference on the stretch of the bolt at 0deg and 110deg is significant. Think of expansion coefficient of aluminum.
Torque- how does it deform your action? Without a 100% contacted surface you will "bend " something" as you add torque. Now change the temperature- change the shape- change my impact point. We settle optics for at least one day to determine if "relief" occurs due to a misloaded component. How many times have you heard people not change in group sizes and position based on how they torqued their action? That inherently says there is a problem.
Harmonics- don't stop at the bolt face, or throat, or lands... and they do not necessarily always reduce as they transition. You can induce gain into a harmonic. By design or accident.
We completely divorce our actions and lugs from the chassis. There is no metal to metal or metal to epoxy contact. O-rings and adhesives. Dead is the game.
Concerning fasteners (being simple minded)- my .308 Savage has the same fastener as is found in my 375CheyTac action... How many main bolts are in a current LS motor as compared to the first small block Chevy.
Our fasteners are set at 30-40inch pounds. More of a safety device versus a retaining device.

 

[XLR Industries]

Hey all, I bought a 300 Norma built by lane precision off here and about e dry 5 rounds fired everything comes loose, muzzle break, bipod, rear pad, action bolts and I just noticed my bubble level moved forward about 1/2 in 12 rounds I fired today. I also would get a flier every third shot. First 2 were same hole usually unless I pulled.

I just received a barreled action from Shawn in 300 terminator (defiance anti-X, proof, t3 terminator brake) and I don't have my new xlr 4.0 yet so I decided to pull the xlr the 300 Norma sits in and borrow it to start load development and same exact thing. 5 shots in, muzzle break could be removed by fingers, action bolts came loose, bipod bolts came loose, and bubble level shifted forward half an inch.

Would bedding this stock and my new 4.0 solve this issue?

Sorry for the late response on this one! I have only heard of this a couple of times and they have all been on lightweight bigger 30/338 calibers on the MG chassis. For the couple of customers we have had with this issue, we have told them to use a small amount of white lithium grease on the action screw and it allows them to get a full torque. What we think is happening is tolerances are clashing between the action screw and the action. On the one rifle that we were able to replicate this, we torqued it down to the recommended 65-inch lbs and then marked it. Then we kept hitting the torque limiter and it would inch in another small amount every time until it hit what we believed was the full torque. We then marked it again there. Then we put white lithium grease on the action screw and torqued it down and this allowed the screw to reach its full torque without having any false reads. This has been the best solution and has worked for everyone else that has had this issue (which has only been a few). That is for the chassis side of things. As far as your muzzle brake goes I have been putting rockset on all of my brakes and haven't had one come loose in a while! If you get one stuck all you have to do is run a little hot water over it and the rockset clears out!

 

[Rick Richard]

Sorry for the late response on this one! I have only heard of this a couple of times and they have all been on lightweight bigger 30/338 calibers on the MG chassis. For the couple of customers we have had with this issue, we have told them to use a small amount of white lithium grease on the action screw and it allows them to get a full torque. What we think is happening is tolerances are clashing between the action screw and the action. On the one rifle that we were able to replicate this, we torqued it down to the recommended 65-inch lbs and then marked it. Then we kept hitting the torque limiter and it would inch in another small amount every time until it hit what we believed was the full torque. We then marked it again there. Then we put white lithium grease on the action screw and torqued it down and this allowed the screw to reach its full torque without having any false reads. This has been the best solution and has worked for everyone else that has had this issue (which has only been a few). That is for the chassis side of things. As far as your muzzle brake goes I have been putting rockset on all of my brakes and haven't had one come loose in a while! If you get one stuck all you have to do is run a little hot water over it and the rockset clears out!

I guess I was one of the lucky few unlucky ones. Lol.

 

[XLR Industries]

I guess I was one of the lucky few unlucky ones. Lol.

I am sorry to hear that! I am glad to hear that it is good to go once you retorqued it!

 

[BrentM]

I would say no. If you have no more issues, it's fine. Why are others going thru it 2x or more, something is wrong.

Dissimilar metals reacting in harsh environments and heavy use can produce repeatable issues with chassis, any stock for that matter, that require a proper bedding process. I have yet to find a top level shooter in any comp style that doesn't bed their rifle system so I guess you can put your money on whatever works for you. I am still on the fence about it overall. I've bedded every rifle I've owned or built except for 2 chassis, a MDT and this xlr. Both chassis had shifts. I am about to pull my xlr apart and swap barrels so it might be a good time to field trial. Confirm zero, loosen the action bolts, retorque, check zero.

 

[XLR Industries]

Dissimilar metals reacting in harsh environments and heavy use can produce repeatable issues with chassis, any stock for that matter, that require a proper bedding process. I have yet to find a top level shooter in any comp style that doesn't bed their rifle system so I guess you can put your money on whatever works for you. I am still on the fence about it overall. I've bedded every rifle I've owned or built except for 2 chassis, a MDT and this xlr. Both chassis had shifts. I am about to pull my xlr apart and swap barrels so it might be a good time to field trial. Confirm zero, loosen the action bolts, retorque, check zero.

I do not think any of our sponsored shooters have bedded their chassis and a few of them actually talk about doing this test with their chassis and seeing very minimal shift when taking barreled actions in and out. If you listen to the Straight Dope podcast, Chris Way talks about it and he wants to shoot a match where he takes his barreled action out after every stage. I know personally when I take my rifle apart completely (barrel off the action, scope off, and obviously action out of the barrel) everything lines up within 1 moa. I think as far as the shift goes, it can be very dependent on how meticulous you are with the chassis-to-action connection. If you are taking it out and cleaning the bottom of the action and the chassis with a little bit of acetone and a q tip then you should have better results.

It would be a great experiment though to see whether that is caliber-dependent, or if a muzzle brake affects it. I had a customer tell me that with his 300 Norma and a 5 port brake, the port catches enough energy to slide the barreled action forward after every shot. I am not sure how he measured this at all but I would love to test it out. I just got done testing a 300 PRC in a Magnesium chassis this week and I did not see any POI shift over 100 rounds in 3 days. I also know that my 6 BRA has zero POI shift over 100s of rounds.

One note here too is a lot of guys talk about POI shift in their equipment but body position, natural point of aim, and even correct parallax can also have a large effect on your poi. Even guys in the PRS world shooting 25 lb BR variants see a shift from their prone zero to a positional zero. So with a heavier recoiling rifle that is 10 lbs, the effect is going to be even more transparent. Just some food for thought from my end but I would love to see some more guys testing it!

 

[BrentM]

I do not think any of our sponsored shooters have bedded their chassis and a few of them actually talk about doing this test with their chassis and seeing very minimal shift when taking barreled actions in and out. If you listen to the Straight Dope podcast, Chris Way talks about it and he wants to shoot a match where he takes his barreled action out after every stage. I know personally when I take my rifle apart completely (barrel off the action, scope off, and obviously action out of the barrel) everything lines up within 1 moa. I think as far as the shift goes, it can be very dependent on how meticulous you are with the chassis-to-action connection. If you are taking it out and cleaning the bottom of the action and the chassis with a little bit of acetone and a q tip then you should have better results.

It would be a great experiment though to see whether that is caliber-dependent, or if a muzzle brake affects it. I had a customer tell me that with his 300 Norma and a 5 port brake, the port catches enough energy to slide the barreled action forward after every shot. I am not sure how he measured this at all but I would love to test it out. I just got done testing a 300 PRC in a Magnesium chassis this week and I did not see any POI shift over 100 rounds in 3 days. I also know that my 6 BRA has zero POI shift over 100s of rounds.

One note here too is a lot of guys talk about POI shift in their equipment but body position, natural point of aim, and even correct parallax can also have a large effect on your poi. Even guys in the PRS world shooting 25 lb BR variants see a shift from their prone zero to a positional zero. So with a heavier recoiling rifle that is 10 lbs, the effect is going to be even more transparent. Just some food for thought from my end but I would love to see some more guys testing it!

Yeah the poi from this event is consistent tho. Not a variable that changes like positional issues or shooter error etc. With those events the zero will change back and forth. I try and be consistent with mounting. Ensuring the lug all the way back, tightening the front screw to half value, rear to half, and then finish off using my snap on torque wrench set to 65 inches. This is a hunting rifle that experiences a 70 f house for storage to a 0 to 10 f day chasing wolves. The rifle is not baby in any shape or form. PRS rigs get used but rarely see the same abuse as a weekly hunter being packed all over the place. I think I'm shooting wednesday and plan to test a theory. I may very well be wrong or right…. Ha ha