Gunsmithing help fn action build

[specopsbrooklyn]

Im new to gunsmithing I have 7 rem 700 builds under my belt now a budy of mine wants me to work on a stripped FN action. I just need some advice on bolt nose resess angle depth any specks you guys can send me would be greatly appreciated tennon dimentions ect.

thanks in advance

 

[2156SMK]

Re: help fn action build

I would match the angle of the bolt and leave 0.010" clearance.

 

[northern50]

Re: help fn action build

Use the tool rest to find the angle by chucking up the bolt and then reverse that angle when cutting the barrel. Something in my mind says 40 degrees on some part from the one we did this spring but that was a long time ago. You will also have to mill barrel for the extractor.

 

[Mgordon]

Re: help fn action build

Also, when your cutting the 40-45 degree bolt nose recess to proper length, install the bolt in the action, screw it on the barrel and measure how much of a gap is in front of the action to the barrel shoulder. This will tell you roughly how much more you will need to take in with your compound. You will need to take in another .010" or so.

Mark

 

[Keith Johns]

Re: help fn action build

Mark you've done some of the nicest FN/Winchester work Ive seen.
I wish YOU'd post some tutorials. An FN or Winchester post 64 truing, barreling, and bedding tutorial would be sweet

 

[x ring accuracy]

Re: help fn action build

The tennon length is determined by the dimension off of the receiver/action with the bolt in place. There are no set dimensions. If the action is trued then any number given from a book is wrong. Must be taken from the action itself.

 

[Clark]

Re: help fn action build

Print this blank drawing I made and fill in the blanks for the receiver based on measurements you take with a depth gauge.

Then fill in the barrel requirements to match.

Then hang the drawing over the lathe.

 

[x ring accuracy]

Re: help fn action build

Simple.......dimensions taken from the action. Well put Clark.

 

[turbo54]

Re: help fn action build

I think the main question this guy is asking is how much clearance between the bolt nose and the chamber.

Someone mentioned 10 thou. Whats the rationale there? I'd prefer 2 or 3 thou.

 

[WhiteDingo]

Re: help fn action build

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">I think the main question this guy is asking is how much clearance between the bolt nose and the chamber.

Someone mentioned 10 thou. Whats the rationale there? I'd prefer 2 or 3 thou. </div></div>

For the cone breech on a Winchester, I'd want more than .002 or .003" for clearance, in case of dirt or grit making it's way forward. Same for the extractor cut in the barrel. .010" might be a little much, but I usually do around .006-.007"

By the by, my notes from the FN SPR that I barreled about a year and a half ago say 96° total angle, or 48° from center.

Just my $.02

 

[msalm]

Re: help fn action build

48 degrees from center is about spot on from what I remember. I've done a dozen or so in the last year. For the extractor cut you can get the special tool from PTG, or just use a small endmill and relieve it to the proper depth then file the corners square. With at least 1/4 of the ones I worked on, the action face was NOT square with the threads and required some sort of blueprinting. The PTG piloted mandrel tap .010" oversize works well to true the threads, then chuck the mandrel with the action on it in the lathe to face the action (make sure you center the mandrel on the chuck end).

 

[BlackOps Tech]

Re: help fn action build

Generally, the bolt nose (cone) angle won't be the same from one bolt to the other. It's a common practice for us to cut out the original bolt face and replace it. Afterwards, we re-cut the angle so we know exactly how the breech of the barrel needs to be set up. This is easy to do.

Of course, you don't necessarily have to re-place the bolt face, but we do numerous modifications to the fire control system that requires a new bolt face.

 

[specopsbrooklyn]

Re: help fn action build

Thanks all for the info sorry for the delay in showing my appreciation my computer was screwed for a bit lol