Receiver raceway vs bolt, how much clearance

livetohunt

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I’m currently working up a receiver and bolt. I’m wanting to know the clearance to put on my bolt (or raceway) in order to get a very smooth but not loose feeling action. Also, the engagement amount for lug lockup.

As a general practice, is the clearance put on the receiver?

Also have some other questions...

Receiver material is 4140. Would 17-4 work for the bolt? I can harden the materials to whichever hardness I need to.

Any help is appreciated.

Thanks.
 

Edd

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I was hoping the experts would reply to your question, but since they haven't, I'll give you my opinion on clearance. My opinion is based on the Model 700 style actions I've handled and the assumption they will be Cerakoted.

The receiver bore should be the same diameter end to end. The bolt diameter from the front of the bolt handle cam surface to about .750 inch in front of that surface should be .003" smaller than the receiver bore. The bolt diameter directly behind the lugs, for a length of about .500" should be .003" smaller than the receiver bore. The bolt diameter between those two points and the area between the lugs should be .008" smaller than the receiver bore.
 

livetohunt

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Thanks. I think I’m going to run the receiver diameter at .705 and go .701-.702 on the bolt diameter. I plan on cerakoting both.
 

Roeder

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I’m currently working up a receiver and bolt. I’m wanting to know the clearance to put on my bolt (or raceway) in order to get a very smooth but not loose feeling action. Also, the engagement amount for lug lockup.

As a general practice, is the clearance put on the receiver?

Also have some other questions...

Receiver material is 4140. Would 17-4 work for the bolt? I can harden the materials to whichever hardness I need to.

Any help is appreciated.

Thanks.
There are some custom actions of 17-4 with 4340 bolt. None with the reverse as you propose. 17-4 can be very gall prone if used as a heavily loaded surface. I suspect you would have issues with the cocking cam.
Common bolt to receiver clearance is about .002 for bench rest actions, more like .004 to .006 for tactical and hunting. Some have been known to grind the bolt slightly elliptical to allow small clearance in battery and more when the bolt is unlocked.
 

livetohunt

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I stoppped by BAT Machine Thursday and gathered all the remaining info I needed to finish the designs and start finishing the raceways and bolt. I got The first receiver in the wire EDM and I will have it done this weekend. Bolt clearance will be .004” minus plating/coating thickness. I have an open thread I will be updating as I progress through my first custom rifle, in which I am machining everything I can.

Thanks for the input!
 
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