Home Forums Hunting & Shooting Gunsmithing misfires

Or a dud, whatever you want to call it... it doesn't fire.

My Winchester M70 has one occasionally, not often, it's hard to remember how often but one of my last recent trips to the range I had one. Why I let it go is beyond me ! To me I don't believe it was bad primers, they were light strikes. I watched a vid on you tube of a guy with a home made disk looking tool it appears he made with a u slot and a recess for the spring to rest in while depressing it to remove the retainer clip and bushing. The spring he replaced with the one that came with the firing pin was quite a bit longer.

So.. here's my take. My spring, after the pin is put back in the bolt shroud, doesn't protrude past the end of the pin, it comes short about 1/4 inch. I looked up a new spring length and it says approximately 5.39 inches. The OAL of my spring is just shy of 5 inches. In your experience would the extra 3/8 of an inch make a difference ? Can't hurt to replace it, I get that.

Well, one way to find out! Replace the spring and see if it helps. I assume you've already gave the inside of the bolt a deep cleaning? Did the gun sit with the bolt cocked for years? (I assume you know better, but a previous owner may have.)

Bolt body is clean, scrubbed it out awhile ago. I take care of my guns. And no the rifle didn't stay cocked for years. LOL The only time it stays cocked is while I'm deer hunting. But being cocked for extended periods of time would compress it to the point of loosing pressure on the pin. There was a light film of oil on the pin, but nothing to inhibit the spring from functioning. It's just compressed but wondering if that extra length would make the difference.

With the pin assy out of the bolt, just check the spring pressure. -Al

And how do you do that ? I already took the spring off the pin. I have to work a flat washer as a tool to put it back on yet.

Take a block of wood and drill a hole through it a bit bigger than the pin. Make sure it's thick enough so the tip won't protrude...a small piece of 4x4 works good. Then drill a bigger hole for the pin collar to rest against. Put the wooden block on a scale and either zero it or note the weight. Now, push down on the pin assy until the spring starts to compress and note the weight. That's your spring tension. -Al

Think l just buy a new spring but thanks

Friend had this problem and bought it to dinner recently. Was a puzzle, replaced spring with Wolff spring etc. Had up to five misfires in a row.

When he went home he looked down the bolt bore of his New Haven Mod 70 Classic, renown for perfect craftmanship. Said it was very roughly machined to say the least. Smoothed it up, and seems like it has a lot better Spring upon dry firing.

Thanks RD, l did notice the spring being a bit resistant as l inserted the assembly in the bolt body. I doubt that’s the issue only because it’s a light strike once in a while, however if that nice buck creeps up and this happens l won’t be happy about. Can’t hurt to smooth out the bore. Thanks. Work on it later.

The bore is not rough causing the spring to hang up. I ran a paper clip bent like one I use to check a case for stretching, The bore is smooth. I am convinced the spring needs to be replaced. Unless there is something else I can check, which I doubt, but fire away.

Update…

A bit of rough gouging above the cocking piece on the bolt shroud hanging up free travel of the firing pin. Some filing freed up and eased the travel. Checked strikes with snap cap. The deep impressions left from other strikes needed a mark with a red permanent marker. Solid strike wore off marker, at the base of solid strike.

Are you using reloads or factory ammo? Not throwing rocks at your reloading skills but reloads add a couple of variables into the equation. Poorly seated primers or over sized brass can cause light strikes. If you are using factory ammo, ignore the primer issue but check the headspace.

LC brass I'm using troubled me with the pocket crimps. I used a RCBS military pocket crimp remover, it's an older version, which after this I won't use any more. It fools me sometimes to see, and I know I should measure the depth of the primer. I remember now I did over uniform the base of the of one pocket. Usually I just cut the edges off at the base and call it a day, but one case I went to far and appreciate you reminding me, we all need that for time to time. I just picked out the case that was cut too much and most likely the culprit. However... I did get an occasional misfire even with other brands from time to time, that I didn't uniform the pocks, odd, but I should have looked into it right off but dismissed it as a bad primer.

As far as headspace, .004 shoulder bump is all I set them back and factory is alot more than that. I do believe I needed to do some mods on the firing pin assembly, and it strikes fine now. Even with .004 HS the strikes are well deep enough before I worked on the firing pin assembly.