ZaneV
New member
Hey guys,
I’ve got a new model 70 in 416 rem mag, it’s had some issues with light strikes/duds on cci primers, and there isn’t a heavier firing pin spring available yet for the FN/portugal model 70.
I found a post somewhere where a guy with a similar Issue had used a modified Remington 700 shirt action firing pin spring to get a couple extra pounds of spring pressure. My dad had a couple on hand for his benchrest rifles, so I figured I’d give it a try.
The ID of the 700 spring is slightly smaller the Winchester spring, the stock Winchester spring had 0.010” clearance between the firing pin and the spring (this allowed the spring to bulge to the side a bit and rub the inside of the bolt which doesn’t help anything), the 700 spring had 0.003” between pin and spring but it was an inch or so longer. The wire diameters on both are 0.050” but the 700 spring had more tightly wound coils. I counted the coils on the stock spring (24 in my case) and cut the Remington spring to have 3 extra coils (27) and test fit, I could feel the spring binding when closing the bolt as the firing pin was drawn back. After some trial and error I ended up with 24.5 coils for it to operate without bind (it did operate with 25 coils, but I took another half coil off just to be safe. The result was 23.5 lbs of spring pressure vs 20 lbs on the stock spring. Attached is a picture of the stock spring vs the 700 spring on a primer strike only (no powder or bullet) to better gauge the depth of strike. I think it was a worth while mod, and maybe it’ll help someone else with the same issue.
Zane
I’ve got a new model 70 in 416 rem mag, it’s had some issues with light strikes/duds on cci primers, and there isn’t a heavier firing pin spring available yet for the FN/portugal model 70.
I found a post somewhere where a guy with a similar Issue had used a modified Remington 700 shirt action firing pin spring to get a couple extra pounds of spring pressure. My dad had a couple on hand for his benchrest rifles, so I figured I’d give it a try.
The ID of the 700 spring is slightly smaller the Winchester spring, the stock Winchester spring had 0.010” clearance between the firing pin and the spring (this allowed the spring to bulge to the side a bit and rub the inside of the bolt which doesn’t help anything), the 700 spring had 0.003” between pin and spring but it was an inch or so longer. The wire diameters on both are 0.050” but the 700 spring had more tightly wound coils. I counted the coils on the stock spring (24 in my case) and cut the Remington spring to have 3 extra coils (27) and test fit, I could feel the spring binding when closing the bolt as the firing pin was drawn back. After some trial and error I ended up with 24.5 coils for it to operate without bind (it did operate with 25 coils, but I took another half coil off just to be safe. The result was 23.5 lbs of spring pressure vs 20 lbs on the stock spring. Attached is a picture of the stock spring vs the 700 spring on a primer strike only (no powder or bullet) to better gauge the depth of strike. I think it was a worth while mod, and maybe it’ll help someone else with the same issue.
Zane
