Heavy bolt lift on sako: rifle has been hot rodded

[CBS]

Well, I've been pushing this one a bit too hard. 243 shooting Berger classics faster than I should. Great accuracy kept me going. Now my dry-fired bolt lift is noticeably heavy. First thing I'm going to do is back off the powder. But what can I do get the bolt lift back to normal? I've heard I can use some kind of compound on the lugs and work the action to loosen it up. Any suggestions on compound? Or am I going down the wrong road here?

Thanks for your responses!

 

[Darktimber]

You could use valve lapping compound on the back of the lugs and work the bolt up and down. I dont know you or your skill level so I'll warn you that doing so changes your head space dimensions and could cause a case head separation aka bad day. If you arent sure take it to a gunsmith and let them see how much lug set back you have and if you need to have your shoulder reset

 

[BoomFlop]

My guess is your lugs are galled.

If you mean that when opening the bolt without a round in the chamber that is my best guess.

If you mean on a once fired round, then it could be a shoulder setback issue. Try bumping the shoulder back .002 and try again.

Does your brass show pressure signs? Ejector smear will cause heavy bolt lift.

Steve

 

[CBS]

Thanks for the replies guys.

The bolt lift is stiff on an empty chamber.

After firing a round brass is showing pressure signs. The velocity has been fun but I need to back off.

 

[David Emerson]

Either galled which you could see on the lugs or you set the lugs back into the receiver a touch. But that would take many rounds of blowing the primer I would think. If the lugs look ok I would run a bore scope in and have a look see on the lug abutments. Another thing I just thought of. Does the bolt lift hard while still cocked? Just maybe your striker cam got galled. If you set the lugs back into the receiver some you should feel a step as you lift the handle. The more I think about this if you had set the lugs back I do not think you would have ever been able to get it open without unscrewing the barrel.

 

[ShtrRdy]

There are actually several things which can add to the friction when operating the bolt.

The first thing I would do is remove the firing pin assembly from the bolt body. See if there is a description online to do this. If not for Sako take a look at how the Tikka comes apart. With just the bolt body in the action do you still feel resistance to operating the bolt?

Try this step first and we'll go from there.

 

[CBS]

After removing the firing pin assembly the bolt lift is very light and smooth.

 

[David Emerson]

ShtrRdy, This has been in my mind all day and I was thinking.I wonder if he got some primer material back in beside his firing pin or he gas cut the firing pin hole. Good thinking on your part. Trying to diagnose some of this stuff can be tricky if you don,t have the rifle.

 

[ShtrRdy]

After removing the firing pin assembly the bolt lift is very light and smooth.

Okay, good. If you look at the back of the locking lugs, do they look smooth?

If so, clean the bore/hole in the bolt body and clean the firing pin assembly. You can use non-chlorinated brake cleaner and some patches on a loop style jag. You want to be able to pull that patch back out.

Now we need to place some lubrication in certain places. I dont like to lubricate the firing pin or spring. This is to avoid sluggish movement under cold conditions. Now if you look at the bolt shroud part. It has a portion which rotates inside the bolt body. Put some oil on the surface that rotates inside the bolt body.

Take a look at the cocking piece on the firing pin assembly and the cocking ramp on the bolt body. These slide against each other of should appear as smooth surfaces. Place some grease on this interface.

Put the firing pin assembly back into the bolt body and apply some grease on the back of the locking lugs. Now try the bolt back in the action. Does it feel any smoother?

If not then we need to take a closer look at the firing pin assembly.