Bolt fitting question

[jonh172]

After reading over Peter Laidlers "fitting rifle bolts" (more than once) I have a question regarding bolt head fit.

I understand the least amount of bolt head over turn is desirable, but is there any advantage to a very light under turn?

Would this help give a tight fit to absorb recoil down the bolt body and evenly onto the locking lugs?

With this underturn the bolt locks tight with even contact on the lugs..

Thanks in advance,

Jon

Information

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[englishman_ca]

The brunt of the recoil forces are not carried on the threads, in fact, they have a slight clearance. The force is transmitted through the anuli of the end of the bolt body and on the back of the bolt head. These areas will appear as shiny rings when you inspect your bolt.

A sloppy fit with lots of bolt head over turn isnt good, but my belief is that the thread fit being tight isn't that critical. As long as the overturn is within limits, good to go.

[jonh172]

The brunt of the recoil forces are not carried on the threads, in fact, they have a slight clearance. The force is transmitted through the anuli of the end of the bolt body and on the back of the bolt head. These areas will appear as shiny rings when you inspect your bolt.

A sloppy fit with lots of bolt head over turn isnt good, but my belief is that the thread fit being tight isn't that critical. As long as the overturn is within limits, good to go.

Thank you Englishman, but if the bolt head overturns and there is no contact between it and the bolt body, as Peters article states, the recoil is taken up on the threads, which to me makes sense. Please correct me if i am wrong!
Less over turn helps accuracy as the recoil is taken up on a square bolt body, as opposed to angled threads giving a straighter axis of recoil.

I'm wondering if this tight bolt head will help get maximum accuracy, or at least eliminate one of the many variables to achieve max accuracy.

Jon

[jonh172]

Or am I just out to lunch on this and the extra tightness does nothing but make a stiffer bolt throw?

[englishman_ca]

You are not wrong with your concept, Jon.

The time when you wont get recoil transfer thought the bolt body anulus is when a new replacement bolt head is fitted on an old bolt and there is too much overturn.

An old sloppy bolt head and with its long time mated bolt will always bear on the body, not threads. I guess that the worn bolt threads allow more axial movement and the slack is taken up by the extractor pushing on the ramp on closing.
I've seen bolt heads so worn that they were wobbly on the bolt, 45 degree overturn. But the bolt head would bear on the body.
The rest of the rifle was also tired, I don't think a new new tight bolt head would have helped unless accompanied by a new bolt and receiver.

Tight is good, I agree.

If the bolt head sits tight with a slight under turn, one would have problems installing it into the receiver bolt way. Bolt head and lug have to be able to align.

[jonh172]

If the bolt head sits tight with a slight under turn, one would have problems installing it into the receiver bolt way. Bolt head and lug have to be able to align.

Great information thank you!

My current bolt does VERY slightly under turn but i am still able to install it in the body, It gives a tight lock up, is this an accuracy advantage over if i were to relieve it a bit to over turn by 1 degree or less?

[Peter Laidler]

Personally, and maybe it's just me, but why not just fit the bolt head into the bolt body as per the instructions passed down from my old and wise apprentice masters to me in the 60's and passed on to the flock so that the correct way isn't lost in the future

[jonh172]

Personally, and maybe it's just me, but why not just fit the bolt head into the bolt body as per the instructions passed down from my old and wise apprentice masters to me in the 60's and passed on to the flock so that the correct way isn't lost in the future

I was curious to see if this was something you had encountered or ever tried?

I just have a tight bolt head and was wondering what the general consensus is on the matter.

[browningautorifle]

was wondering what the general consensus is on the matter.

It's not really about a consensus...

[muffett.2008]

All you are achieving with a tight bolthead, is excessive wear on the bolt guide channel, excess load on bolthead threads and a stiffer operation, requiring excess force to operate.

Go with Petes recommendation, he's correct.