So I have a 12FV 223 bolt that's probably between 1500-2000 rounds. The bolt has been bushed.
I was thinking of replacing the firing pin spring. My thought was to measure installed spring height and make sure the new spring matches the old measurement.
Sound right? I guess I'm basing my installed height on the notion the bolt busher set it correctly.
People over think this to much. You don’t have to measure the spring height. The only thing to measure is the firing pin protrusion from the bolt face. Set that first. It should be approx .035” from the surface of the bolt face. I would never set it over .040”. (Actually I wouldn’t even set it that high.. it’s a waste!) Next thing it install the spring & the Cocking Piece. Then turn the cocking piece on as far as you can, to get the Cocking Pin (once installed), as close to the edge of the bolt sleeve, in the fired position, as possible. Setting Protrusion to .035” and the Cocking Piece down as far as possible maximizes the firing pin Travel, or Fall, it’s also sometimes called. Firing Pin Travel is a very crucial part of the operation. And it’s often overlooked. The system only starts with roughly .250” to begin with! Setting pin protrusion to .050”+, having the Cocking Piece set way back, not to mention other minor losses, could result in .080” or more could be lost. This is one of the first things I check (besides broken or damaged parts), when addressing light primer strike misfires. Just getting back the full travel could very well fix many of the problems of light strikes out there. Another trick is to thread the Cocking Piece all the way through, and use a set screw in the back of the Cocking Piece. (Picture below) Screw it in until the set screw touches the Cocking Pin. It is threaded 1/4”-28 and I use 3/16” long set screws that I then shorten even more & round the head. This eliminates the play between the Cocking Piece hole & Pin and prevents the Cocking Pin from leaning due to the tension under cocking. Look at it while cocked, you’ll see what I mean. The Cocking Pin will be canted Backwards slightly, thus allowing the Firing Pin to lurch forward and ultimately losing even more Travel.
I actually found this older thread talking of the very thing I’m referring to. https://www.savageshooters.com/showt...tilted-in-bolt
Making a new Cocking Piece is also a remedy. I’ve already machined a new Titanium Cocking Pin & using it. I was planning to also make a Cocking Piece from Titanium. Just haven’t yet. Besides, the set screw just works so well.
Great reply. Thanks for the info. Can you suggest a SA firing pin spring for my 12FV. One that hopefully will not increase bolt lift. Thanks!
Why do you believe yours needs replaced? Actually, you have a Model 12FV correct? So I believe you actually have the 1-Piece, non adjustable firing pin with the shorter stack 2-spring setup. Is that correct?
Unfortunately, no…No better springs for those as of yet, except Savage has made 1 of the springs slightly longer to combat the problem of Misfires/light primer strikes which are happening. By the way, is this by any chance the reason you had the bolt head bushed in the first place? Anyway, the slight revamp that Savage has done is nothing more than a bandaid. I do know of someone working on something of a fix with better springs. But it will be some time. Unfortunately right now the only thing to do is purchase the updated spring from Savage via GunShack.
https://www.gunshack.com/savage-part...nspring-1-2018
I had the bolt bushed because it was cratering primers.
As for the reason to replace the spring? It's just a habit I go into on my Remington style actions. New season, new spring.
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