Leuchtkafer
Member
While I had my milling setup installed for the last project I was working on, I took advantage of it to do this mod before I changed back to a standard lathe setup. There are a number of ways to do this job, even using a file and some patience. I selected a single flute end mill and the part angled at 45 degrees.
There's some play in the firing pin channel vertically, so I had to see how it actually rides and hits the rim. I cut to a safe depth then started to test fire, taking small cuts each time until the correct dimension was achieved.
The casing in the 4th row is the only one showing when I had done enough cutting. I split a casing open to examine the hit in detail. This looks good, the rim is closed up fully, no evidence of deformation that might occur with too strong or deep of a strike, and the edge of the hit looks like it clears the folded case wall section. Nice.
So why do this? Chances are, unless there was a pre-existing condition of poor ignition, which can happen when factory tolerances stack the wrong way, this mod is unlikely to make an obvious difference in accuracy. However, if you do it right, it's not going to hurt anything, just be sure you're committed to the caliber you're modding the pin for, or you'll need additional firing pins if you still want to swap calibers. This is one of the things to do when one wants to cover all bases and wring out the absolute best performance their rifle is capable of. By itself, it's a bread crumb, a fraction of a percent improvement. Combined with other things, enough bread crumbs can be rolled into a little dough ball, and you end up with something tangible.
Most of your accuracy is going to come from a high quality barrel blank chambered and fitted well to a reliable action. From there, it's diminishing returns to make small gains. The work can be difficult, time consuming, and expensive if you're hiring someone else to do it. Do you even need that small improvement for the shooting you do? Most of us aren't shooting competitively at a high level, so there's no real need for it. However, if you've been bitten by the accuracy bug and have the means to do some modding and simply want to, go for it!
Something I might explore later is installing a reduced power striker spring. By avoiding crushing the folded rim section, less impact force is required to close up the rim, plus the hit is concentrated into a smaller area. By virtue of being a multi-caliber design, the firing pin is over-sprung for .22 lr as it is. There's no need for excessive force beyond what's required to fully close the rim, and that extra force carries with it the potential to have a negative effect on accuracy.
There's some play in the firing pin channel vertically, so I had to see how it actually rides and hits the rim. I cut to a safe depth then started to test fire, taking small cuts each time until the correct dimension was achieved.
The casing in the 4th row is the only one showing when I had done enough cutting. I split a casing open to examine the hit in detail. This looks good, the rim is closed up fully, no evidence of deformation that might occur with too strong or deep of a strike, and the edge of the hit looks like it clears the folded case wall section. Nice.
So why do this? Chances are, unless there was a pre-existing condition of poor ignition, which can happen when factory tolerances stack the wrong way, this mod is unlikely to make an obvious difference in accuracy. However, if you do it right, it's not going to hurt anything, just be sure you're committed to the caliber you're modding the pin for, or you'll need additional firing pins if you still want to swap calibers. This is one of the things to do when one wants to cover all bases and wring out the absolute best performance their rifle is capable of. By itself, it's a bread crumb, a fraction of a percent improvement. Combined with other things, enough bread crumbs can be rolled into a little dough ball, and you end up with something tangible.
Most of your accuracy is going to come from a high quality barrel blank chambered and fitted well to a reliable action. From there, it's diminishing returns to make small gains. The work can be difficult, time consuming, and expensive if you're hiring someone else to do it. Do you even need that small improvement for the shooting you do? Most of us aren't shooting competitively at a high level, so there's no real need for it. However, if you've been bitten by the accuracy bug and have the means to do some modding and simply want to, go for it!
Something I might explore later is installing a reduced power striker spring. By avoiding crushing the folded rim section, less impact force is required to close up the rim, plus the hit is concentrated into a smaller area. By virtue of being a multi-caliber design, the firing pin is over-sprung for .22 lr as it is. There's no need for excessive force beyond what's required to fully close the rim, and that extra force carries with it the potential to have a negative effect on accuracy.
I did my 457 VMTR with a file last Fall. It works fine but not quite as tidy.