Firing pin springs and accuracy

[Blackwater]

Have any of you ever played with different powered firing pin springs to see if and how they effected accuracy? I read an article once by a renowned BR gun builder of .22 RF's, and he said this was an often neglected but significant part of accuracy with rimfires. I can, I think at least, see how that could be material, but I never got my round tuit to check it out. Have any of you done this?

[Mk42gunner]

I never have, but I can see how it would make a difference if the ignition of the primer was borderline.

The downside to checking accuracy with differing strength firing pin springs would be that you would have to redo the test every time you switched lots of ammo.

It would take a lot better shot than I am; or maybe just a strong case of OCD to want to open this particular can of worms.

Robert

[CHeatermk3]

I read somewhere, RFC match forums I think, that it is pretty standard practice for serious RF benchrest competitors to replace their firing pin springs at the start of each shooting season.

[Pakprotector]

Since primer ignition is so critical to consistency in terms of delivered velocity, it sure looks like more is better. At some point a light hit is going to be lighting the charge( and starting the bullet on its path )in an inconsistent fashion. I am going to be replacing the spring in both my Annie and the Son's 40X over the winter.
cheers,
Douglas

[Bent Ramrod]

I bought a Remington Model 37 that had a weak firing pin spring. Cheaper ammunition that would have one misfire per box of 50 in other rifles would have two or three in this one. (Indexing the round for another try generally got it to fire the second time.) Accuracy, even with match ammunition, was at best a fairly tight cluster of shots with a couple or three flyers to spoil them at 50 yards. I got a new spring from Wolff and things began to approach the one hole at 50 yards level, with an absence of flyers. And even the cheapo stuff almost always went off.

That little rimfire needs everything going for it, including ignition impulse.

[country gent]

Firing pin strength not only affects primer ignition blow strength. It also affects lock time a new full power or heavier spring moves the firing pin faster meaning from trigger pull to primer firing is quicker. Always thought a rimfire would benifit from double pins hitting 180* apart on the rim. Weak hits can be annoying and wreak havoc on accuracy.

[Forrest r]

Have any of you ever played with different powered firing pin springs to see if and how they effected accuracy? I read an article once by a renowned BR gun builder of .22 RF's, and he said this was an often neglected but significant part of accuracy with rimfires. I can, I think at least, see how that could be material, but I never got my round tuit to check it out. Have any of you done this?

Absolutely!!! It's the only way to dial in a rimfire.
I like to work on my rimfires in the winter/cold weather. The cold brings out the worst in a firearm & rimfire ammo's accuracy falls off in cold weather. I buy cases of ammo for testing purposes, when I find a lot of ammo that has acceptable accuracy @ 25yds and a low sd, I'll buy a case of it to test/tweak rimfires with it.

Typical testing:
Decided to tweak a cz lux back in 07, so I mounted a target scope on it and took it to the range with the test ammo and played with the torques on the action screw until I got round bughole in the 25yd targets. Typical baseline targets for the luz, it shot right @ .2" groups for an average of 4 5-shot groups.

[IMG][/IMG]

Most people would be happy with those groups, but with a little work, the rifle will easily do better.

So I took the bolt apart and polished the insides of the bolt and fp and then heat treated everything with moly. And re-tested the rifle with the test ammo and the groups shrank. Not allot but the difference was measurable. Then I replaced the striker spring with an extra power spring from power custom and re-tested. Again the groups shrank. I didn't like the looks of the fp hits on the spent brass cases so I reshaped the end of the fp and tested the fp hits on some rock hard vostoc ammo (russian match ammo from the 80's). This is what the reshaped fp hit look like.

[IMG][/IMG]

After re-working the bolt, fp & a new striker spring, this is what typical groups look like now from the cz luz.

[IMG][/IMG]

Same ammo same firearm, but a 30% reduction in group size. I've done this same thing to over 15 different rimfires and normally get 30% to 40% tighter groups. It doesn't sound like much but as with anything, accuracy comes at a cost. And this is the cheapest way to improve accuracy in a rimfire.

After consistent/excellent ignition is established, reading/finding problems is allot easier. Getting my favorite lite weight squirrel rifle ready for cold weather. I was readjusting the action screw torques on the cold (30*) wood, last time i used the rifle it was 70+*'s outside. I simply tightened the screws instead of using a torque wrench and shot the top 2 groups. Shook my head @ the result and for me being lazy and got out the torque wrench and di it right this time & shot the bottom 2 groups.

[IMG][/IMG]

[M-Tecs]

I never checked rimfires but I rebarreled a buddies 1,000 yard match. It didn't shoot as well as we hoped. I started double checking everything and I noted the primers seemed like they had shallow hits. New spring and it shot lights out.

[bstone5]

In the BR-50 days new springs in the Remington 700 RF made a bid difference in the groups shot by the rifle.

Lapping a little taper in the barrels, tighter at the muzzle made the biggest improvement in the shooting of the 22 rim fire rifles.

Spent many hours lapping 22 rim fire barrels.

[Blackwater]

Thanks, guys. I suspected the article was dead on, and you guys have proved it out. The article, IIRC, was in an old Accurate Rifle magazine. I've heard a few people who've had some older .22's redone say that a new firing pin spring really helped their accuracy, but never having done it myself, I'm always reluctant to believe what I read, even when it seems to make sense. Nothing's proven until it's proven, even when we suspect something is right to start with.

[Bigslug]

INNNNNTERESTING. . .

In .22's especially, I would assume this benefit to be almost entirely lock-time related?

Since much of loading competitive centerfire ammo hinges on concentricity of the round and getting the bullet to enter the rifling as straight as possible, I've often wondered about the effect of crushing the rim on maintaining that overall desired "squareness". Faster lock time is obviously better - especially for non-bench position matches, but a more-crushed rim might be detrimental. As I recall, the dimple in the middle of the higher end Federal Gold Medal was intended to help deal with that by stiffening the tail end of the case.

Dual firing pins. . .more reliable ignition with uncertain priming obviously, but I wonder if starting the primer burn in two places would speed up / improve overall combustion.

[M-Tecs]

In .22's especially, I would assume this benefit to be almost entirely lock-time related?

On centerfires light hits give inconsistent ignition -- you can see the velocities spread on the chrono.

[Hooker53]

If this fenom causes that much Vari and a newer gun like a CZ, I'm thinking now, how much it would cause it on these old Remington Rolling Blocks like I shoot. Gonna have to check into this.

Roy