275 Yard Pop Can Run... Ignition Issue

[Maple57]

So I had an interesting day out at the farm today. It became interesting particularly because I forgot to put my ear protection on. I have an MSA headset but since I was only shooting a 22, it slipped my mind… at first.

Anyway there I was shooting pop cans from 275 yards with my CZ452, I wanted to shoot from 300 yards, but the corn has gotten too tall, so for now, 275 yards is as far as I can get.

I was doing well, at first and then I got a low shot… really low, like a foot… it was weird… and I could hear that shot was nowhere near as loud as the others. Then the next couple shots were normal, then another 2 low quiet shots in a row, then normal again.

Usually I run a Labradar but forgot the battery pack today, so it wasn’t running and I don't know the speed differences.

If I had been wearing earpro I probably would not have noticed the audible difference.

At first I thought it might be light firing pin strikes causing poor ignition, maybe I need a better firing pin spring, and then I thought about how long it’s been since I cleaned the rifle… about 1400 rounds.

Then I started thinking I must have a donut in the chamber that is preventing rounds from seating in the chamber. The crud in the donut must be holding the bullet back so the rim can’t sit against the back of the barrel.

This also got me to thinking about the ammo I was using… RWS Pistol Match… which has a waxy lubricant on them that feel more or less like Chapstick. Maybe this lube is contributing to this imaginary donut.

Normally I shoot Eley Force, which has a dry graphite like coating, but I’m running low and can’t seem to find any at the moment, so I’m shooting RWS P.M. instead.

So now I’m thinking this donut is to blame, but I want to have a look, so I got home and got out the bore scope. As expected the rifle is certainly getting dirty, but the throat is not anywhere near as bad as I had imagined it would be. To my surprise, the back of the barrel had a layer of crud, and now I’m thinking the bolt might be being held back by this crud and inhibiting a good firing pin strike.

Either way, the rifle is overdue for a cleaning, and I hope it resolves my ignition problem, because I don’t want to believe it’s the ammo, since I’m using respectable stuff.

I know that reliable ignition is critical to rim fire accuracy so I’m going to clean the action really well which I should have already done, my bad, and I’ll clean the throat just to be sure, even though it doesn’t look too bad.

Have any of you guys had such a problem and how did you correct it?

 

[Dwayne Cyr]

The only problem I had with a CZ452 Varmint was after I replaced the factory firing pin spring with an aftermarket "Chrome Silicon Increased Power Striker Spring". During a benchrest match the gun developed light firing pin strikes, intermittent ignition and terrible accuracy. Everything straightened out after the original factory spring was put back in.

 

[Maple57]

The only problem I had with a CZ452 Varmint was after I replaced the factory firing pin spring with an aftermarket "Chrome Silicon Increased Power Striker Spring". During a benchrest match the gun developed light firing pin strikes, intermittent ignition and terrible accuracy. Everything straightened out after the original factory spring was put back in.

I read a post on Snipers Hide where a guy said that 452s are fussy about keeping the bolt clean. I've never cleaned it, but I'll have a stab at it today.

 

[scuba52]

Curious what the rims looked like

 

[Maple57]

Curious what the rims looked like

Good question... I should have saved the cases.

 

[Maple57]

I had a video camera running and when I watched the video this morning, I could see the impacts better than I could through the scope yesterday.

Here's a link to the video from yesterday if you want to check it out.

https://www.youtube.com/watch?v=XkhOqz605X8

The low shot wasn't as low as I originally thought even though it sounded off pitch. It's hard to notice in the video because it spikes the max sound level on the camera for all shots but you can detect a slight pitch change even in the video on the 3rd and 6th can.

The resolution on the Diamondback Tactical scope isn't the greatest and the reticle is cluttered with hash marks making impacts hard to spot sometimes.

 

[colinjw]

A number of years ago, myself & some other club members had a similar problem when shooting a bullseye match.
We had just got in a number of boxes of Winchester T22's.
We could hear the difference in the volume of the ignition and several of us could see a drop of 2 to 3 inches
at 25 yards with some shots.
Winchester agreed that they had a bad lot of T22's with low powder charges .

 

[scuba52]

Any chance same ammo went through other gun? Would rule out ammo possibly

 

[RabidM4U5]

Either way, the rifle is overdue for a cleaning, and I hope it resolves my ignition problem, because I don’t want to believe it’s the ammo, since I’m using respectable stuff.

It more than likely is just the ammo, boxes that say "match" on them usually ain't... A foot of vertical can show up easily at 200 yards, never mind 275.

I would also strongly suspect your shooting technique. If you're right handed, some inconsistent tongue pressure on the inside of your right check can transmit into variations of pressure on the butt of the rifle, and slight inconsistencies in shooter technique absolutely result in significantly wayward shots. Grauhanen can confirm this phenomenon

Visit RFC for details on tuning CZ ignition. Your theories on the "doughnut" not allowing the rim to seat or crud on the barrel face holding the bolt back are a little abstract. It's a bolt action, and the camming force is very strong. The bolt cannot be held back by soft crud, it will squish it out of it's way as you cam the bolt closed. If your headspace in the rifle is excessive, the rim will seat back against the recess in the bolt nose, be pushed through the "doughnut" (getting swaged down in diameter in the process), and leave a small gap between the rim and breech face being the sum of headspace minus rim thickness of the round. You will only ever seat the rim on the breech face when headspace is exactly the same as rim thickness or a slight 0.001" crush fit.

Otherwise...

 

[Maple57]

RabidM4U5, I'll have to checkout that RFC you suggested... thanks for that.

Conditions were pretty good out there on Saturday and I did shoot 2 groups on paper from 275 that was a bit better than you have pictured, maybe conditions were better for me, or just a lot difference. One group was with RWS and the other with Eley Force. I have pictures I could post later when I get home.

In case something very subtle is going on with the ignition I completely disassembled the bolt and gave it a good cleaning with brake cleaner, cleaned the action and the barrel.

I don't like to clean my 22 barrels very often, but I cleaned it anyway, but that turned out to be a pain. The minor diameter on my barrel must be smaller than most because I could not find a cleaning rod that was small enough to pass through without being a tight squeeze. I just cringe at the thought of damaging the rifling with a cleaning rod.

Maybe I can get a .17 cleaning rod and use that next time.

As for shooting technique... I cant rule that out... I've felt certain accuracy changes depending on how hard I grip the rifle, especially with a 22.

At the end of the day Saturday I zeroed the Anschutz from a bag on the bench but that was not my zero once I put on a jacket and sling and shot prone... the impacts moved to about an inch low and right, and that was only 50 yards.

Your mention of headspace has me thinking about sorting based on rim thickness... I'll have to give that a try next time and see if that correlates to a velocity spread.

 

[Mystic Precision]

Ammo QC.... wouldn't use that lot in competition but for plinking, have at it.

Jerry