Better Ignition on CZ 455

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Picher

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I've been getting some low shots in groups fired from my CZ 455, with .17 HMR, so decided that it was because the firing pin was hitting high on the rim fold, so I ground the top of the pin to eliminate the poorer ignition and, after trying several groups, found that the low shots have been eliminated.

It's a cure that we've used to eliminate the problem on .22LRs and I was getting them on the .17 and .22 WMR. The groups are now much rounder!

JP
 
Good to know. Both my CZ's have ruined groups by some shots low. I will have to try this.
 
I've been getting some low shots in groups fired from my CZ 455, with .17 HMR, so decided that it was because the firing pin was hitting high on the rim fold, so I ground the top of the pin to eliminate the poorer ignition and, after trying several groups, found that the low shots have been eliminated.

It's a cure that we've used to eliminate the problem on .22LRs and I was getting them on the .17 and .22 WMR. The groups are now much rounder!

JP
I'll have to keep that in mind.
 
Appreciate the heads up. I just bought a CZ 455. I haven’t gotten to take it out yet. But it’s good info!
 
Good to know. Both my CZ's have ruined groups by some shots low. I will have to try this.
I think that some of the low shots may have been caused by the ammo, but not on every group. I'm very pleased with the improvement! All but one 100 yard group was rounder and 1 MOA or less, despite shooting off my portable benchrest on top of a Black and Decker "Workmate". I decided to shoot on the woods road, due to the wind velocity/direction that day.
 
Having trouble picturing what you did. Any chance of a diagram for us unimaginative types?

Kevin
 
Having trouble picturing what you did. Any chance of a diagram for us unimaginative types?

Kevin
IMG_4017.JPG

The firing pin top edge needs to be ground to hit just below the rim fold, which is stronger than just below it. The strike then gives greater force to the area that the back of the case pinches the priming compound against the straight part of the case, making better ignition and flame spread. Hope this helped, even if it's out of scale. Take it easy with the grinding and check it before taking too much off (by using a fired case).
 
View attachment 861517

The firing pin top edge needs to be ground to hit just below the rim fold, which is stronger than just below it. The strike then gives greater force to the area that the back of the case pinches the priming compound against the straight part of the case, making better ignition and flame spread. Hope this helped, even if it's out of scale. Take it easy with the grinding and check it before taking too much off (by using a fired case).

Got it! Thank you.

Kevin
 
@Picher This is cool stuff, thank you for posting this. Do you know if the shape of the firing pin matters? I've seen some firing pin indents on rimfires' that were rectangular and some that are circular.
 
Firing pin noses shouldn't have sharp corners that could pierce a case. Rounded edges seem to work well because they spread the primer flame evenly to make the powder burn more consistently.
 
Very interesting and informative. None of my rimfires currently need any fixing but if I ever come across that condition I'll have to remember that. Especially my CZ-455...... Thanks for posting.
 
View attachment 861517

The firing pin top edge needs to be ground to hit just below the rim fold, which is stronger than just below it. The strike then gives greater force to the area that the back of the case pinches the priming compound against the straight part of the case, making better ignition and flame spread. Hope this helped, even if it's out of scale. Take it easy with the grinding and check it before taking too much off (by using a fired case).
Thanks. one of the most useful posts on here.
 
Good info, Picher.

For others asking, here's about how you want the firing pin strike on the cases to look.

vju1nyn.jpg

Here's another shot of a different shape firing pin. You want it like the strike on the right, not the one on the left.
Ds6hrzw.jpg
 
IMG_4019.JPG
How complicated is it to did assemble the bolt to remove the firing pin?
Actually, I didn't remove the pin, but had a very small Moto-Tool bit that did the job well, working very carefully. Took all of 5 minutes, after clamping the bolt in a padded vise.

The "Before" is on the left and "After" is on the right. (The other pictures recently submitted by 16Turbo show the change better than mine, but I didn't know about it before this.)
 
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Excellent tip, Picher! I have a CZ 452 which is a great rifle but I never paid attention to my fired cases before. I'll keep my eye on them and see if my firing pin needs fettling.
 
It probably won’t need it on the 452. The 455 has a different tip on the firing pin because of using the same firing pin on three different calibers, 22, 22 mag and .17. If anyone needs more info on grinding the tip, Rimfire Central has plenty on the CZ/Brno section.
 
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