Gunsmithing Coned bolt face - advantages and disadvantages

308nate

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Re: Coned bolt face - advantages and disadvantages

For the most part I would say not for tactical shooters.
For a .223 they will definitely not work as they will not pick a shell out of the mag. I have made the .308 and the magnums work, but there is more positive case pick up out of the mag with a traditional bolt head. The magnum is kind of a trade off, I do like to do some of the magnums with a cone face.

FWIW,
308nate
 

bohem

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Re: Coned bolt face - advantages and disadvantages

Can you explain what a cone bolt face would be a positive thing for?

Other than feeding and stuff, what's the accuracy improvement of it?
 

308nate

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Re: Coned bolt face - advantages and disadvantages

In order to pick a shell out of the mag you are relying on a flat on the bolt front to push the case forward engaging the ramp which pushes the case up and into the chamber. The problem with the coned bolt face is the cone carries on through the bolt body diameter. A picture is worth a thousand word here, but I will do my best to explain.

With a magnum bolt face, the wall from the inside of the bolt face to the outside of the body is approx. .072 on a .700 dia bolt. The cone carries to approx. .050 from the inside of the bolt face. therefore you loose .022 of flat off the bottom of the bolt head..this is exaggerated with smaller cases such as a .223 case where the cone still carries within .050 of the inside of the bolt face. In short, with the .223 you would loose approx. .100 of flat from a .700 dia. bolt body,therefore when the case pops up it would need to come up a fair bit over .100 for when the case hits the ramp the back of the case can tip down slightly, if the case is hitting the cone on the end of the bolt it will try to push the case down instead of forward causing a jam.
 

308nate

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Re: Coned bolt face - advantages and disadvantages

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body">Can you explain what a cone bolt face would be a positive thing for?

Other than feeding and stuff, what's the accuracy improvement of it? </div></div>

bohem,

The benefit of a coned bolt face is to have a ramp in the end of your barrel instead of a flat. I believe most coned bolts are used in single shot actions
with small dia. cases. Or larger cases with steep shoulders for smoother chambering. There are definitely many ways of doing things and all my experiences have been with PTG coned bolt faces, there may be other coned bolts that would work better, but in general this is what I have found. If you are center feeding out of a mag, I would say go for it...down to a .308 if you are pushing cases off the side I would strongly advise a standard bolt head with all cases.
No accuracy loss or benefit in my experience.

308nate
 

AKA-Spook

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Re: Coned bolt face - advantages and disadvantages

coneheadcopy.jpg

Here's your pic Nate.

I've got one on a Rem 223 ack (PTG bolt) that works fine.
I've also read (here actually) that they work better on single shots that repeaters, which sort of defies logic.
 

RBros

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Re: Coned bolt face - advantages and disadvantages

+1 on the coned bolt face working with the 223's. It actually makes the Ackley's feed a little smoother. I haven't had any problems using them with a bdl assembly or Seekins mags that I have built off of.
 

eddybo

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Re: Coned bolt face - advantages and disadvantages

I always thought the benefit of a coned bolt face was that less of the case was unsupported.
 

selfbowhunter

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Re: Coned bolt face - advantages and disadvantages

i think the cones bolt face probably spawned from the benchrest genre. they are almost all single shot and they found feeding was smoother with the coned bolt face. the cone cut into the barrel acts as a feed ramp.


chuck