6bra brass chambering issue?

[Zack_va248]

Alright gents I've been having a strange occurrence that I can't seem to figure out.

Action is a lone peak fuzion with a benchmark barrel chambered by Travis from TS customs.
With both virgin brass and several times fired Lapua and Alpha brass when closing the bolt it gets hung up almost as if its getting caught on something. Once over that "snapping" point it closes smooth all the way down to full bolt close. Almost feels like chambering a cartridge that hasn't had the shoulder bumped but only when the bolt first begins to close.

The bolt when run in dryfire doesn't do this at all and feels just like my other LP action. I use the wheeler method for headspacing the cartridge and also finding my touch point with a projectile. I'm seating bullets .040" off so there's plenty of space there nor does this "catching" feeling at initial bolt close feel like a bullet engraving in the lands.

The brass is sized .002" of bump and still causes this feel with a projectile loaded. With fire control removed the bolt drops freely as it should both with the brass inserted and not. This tells me it's something with either the projectile touching the lands or more likely the neck being too tight and dragging in the chamber. But again I checked the bullet jump and it's definitely not touching and the neck if it were tight I would expect to feel a consistent drag all the way through bolt close.

Unloaded neck dimension is .267" OD and loaded is .269"
Fired headspace dimension is 1.112" and once FL sized is 1.109"- 1.110" using a SAC comparator.
Brass is trimmed chamfered and deburred on a Giraud to 1.554"

 

[spife7980]

This tells me it's something with either the projectile touching the lands or more likely the neck being too tight and dragging in the chamber.

Unloaded neck dimension is .267" OD and loaded is .269"
Fired headspace dimension is 1.112" and once FL sized is 1.109"- 1.110" using a SAC comparator.
Brass is trimmed chamfered and deburred on a Giraud to 1.554"

Whats your fired neck diameter? That vs the sized and loaded should tell you if you have adequate clearance or not.

Edit: but if a round that does it with the firing pin in and then doesnt do it with the firing pin out then its the firing pin thats causing it as 918v alludes to.

 

[918v]

“With fire control removed the bolt drops freely as it should both with the brass inserted and not. This tells me it's something with either the projectile touching the lands or more likely the neck being too tight and dragging in the chamber.”

If the bolt closes freely on brass or on an empty chamber with the fire control removed then it’s the fire control that’s the problem.

 

[Zack_va248]

Whats your fired neck diameter? That vs the sized and loaded should tell you if you have adequate clearance or not.

.272" fired neck diameter. Good point. I just talked to Travis and he brought up that LP had changed their primary extraction on the action a bit to make it have more aggressive extraction power. I hadn't thought about it until on the phone with him but the bolt not doing this with fire control removed means there's a good chance it's the ejector being stiff or slightly longer which he said they do also offer a shorter ejector plunger to reduce pressure some.

 

[Zack_va248]

“With fire control removed the bolt drops freely as it should both with the brass inserted and not. This tells me it's something with either the projectile touching the lands or more likely the neck being too tight and dragging in the chamber.”

If the bolt closes freely on brass or on an empty chamber with the fire control removed then it’s the fire control that’s the problem.

I think it's a combination of ejector pressure on the case and the extractor snapping over the case rim, after thinking about it more. I'll check when I get home and swap my other older Lone peak bolt in this action to see if that solves the issue. I'll report back just so if someone else has this issue they'll have something to go on.

 

[Raufoss]

So when you remove the firing pin and chamber a loaded round everything is fine ?

Issue with the trigger or the extractor/ejector interaction.

If you have another bolt test it out and swap the firing pin addy.

You can also test it without a trigger and then try another trigger.

 

[Zack_va248]

Yeah when the firing pin/ ejector plunger and spring are removed it chambers like butter both with loaded brass and unloaded brass.
I'll play with it when I get home and report back.

 

[Raufoss]

Yeah when the firing pin/ ejector plunger and spring are removed it chambers like butter both with loaded brass and unloaded brass.
I'll play with it when I get home and report back.

Good , your doing good in troubleshooting.

Test one aspect at the time and you’ll find your issue quickly.

 

[918v]

I think it's a combination of ejector pressure on the case and the extractor snapping over the case rim, after thinking about it more. I'll check when I get home and swap my other older Lone peak bolt in this action to see if that solves the issue. I'll report back just so if someone else has this issue they'll have something to go on.

I had a similar problem with my TRG42. The bolt would not want to rotate into battery unless the extractor clicked over the rim and the bolt head bottomed out. But it wore in over time and doesn’t do it anymore. So maybe that’s how your action will wear in?

 

[Zack_va248]

I had a similar problem with my TRG42. The bolt would not want to rotate into battery unless the extractor clicked over the rim and the bolt head bottomed out. But it wore in over time and doesn’t do it anymore. So maybe that’s how your action will wear in?

Hopefully so, I’ll find out when I swap in my older bolt