Setting back a CZ455 22lr barrel

[HadesPrecision]

Ok, short story first, then questions. I have a cz455 Tactical that's turning into a perpetual project rifle. I shot it stock out of the box for about a month before I started tinkering with it. Initially, it shot about as well as the test target that it came with, roughly 2 MOA with some vertical stringing. Fair enough but I wanted better. So I stripped down the rifle, deburred everything (not that there were many burrs to take down), recrowned the muzzle, cerakoted the bolt, barrel, and receiver (which actually really tightened up the barrel fit in the receiver so there's no wiggle there), and pillar bedded the stock. I even drilled and tapped a set screw to reduce the over travel on the trigger. Now it's a true 1.5 MOA rifle, skirting on 1 MOA if the wind plays nice and the stars and moon line up right.

After reading through all the wisdom the internet has to offer, setting back 10/22 barrels seems to have been a thing that people did/do to shorten up the long chambers they have in the quest to improve their rifle's accuracy potential. Anywhere from .050"-.080" seems to be the norm. So I had to ask myself, would this technique work on my rifle too? For the sake of brevity, I made a gauge to measure the length of my chamber to the start of the rifling and another one to measure 22 ammunition from the forward face of the rim to that lip on the bullet where the ogive begins.

My chamber measured out to .731" putting it right in line with a stinger chamber of .735" (Google also found me a list of 22LR chamber dimensions)

SK Match measured at .728" rim to ogive
Norma Match at .7325"
CCI Green Tag at .7305"

Now, here's where I'm getting confused. PTG and Lilja Match chambers show a rim to rifling length of .630"-.635" and the old Winchester 52 D Match at .580"

Basically it looks like match 22LR ammo is getting jammed into the rifling .100"+ with these chambers. I get they're nice soft lead bullets, but still. I'm fairly new to precision rimfire shooting so I'm just curious if this is normal or a known thing. Would I be wasting my time setting my barrel back .010"-.025"? Are there any safety issues with jamming a 22LR that far into the rifling? Also, I get it's a factory rifle with a factory barrel blah blah blah. I know if I want the best in accuracy I could buy a better barrel and trigger..., but thats not the point here. Just looking for knowledge and insight. Has anyone else tried anything like this?

 

[djdilliodon]

On 455, your not actually setting the entire barrel back. What your doing is setting the shoulder back only in order to tighten the headspace. On older Lilja drop ins this was working out perfectly but it’s kind of annoying spending money on a match barrel and then having to put it in a lathe. For me at this point I moved on to custom fitting and permanently attaching the Barrels. I worked with Lilja to design a newer style drop in that can work for those that wanna do things themselves. Not custom fit level but as good as your gonna get without custom fitting. These new Barrels use a longer shank with shims to set headspace to whatever you want.

depending on what you call ideal accuracy, the factory pipes won’t satisfy the bunch that wants one hope accuracy. No matter how much you work them over they are not even close to the level of a match barrel.

 

[HadesPrecision]

On 455, your not actually setting the entire barrel back. What your doing is setting the shoulder back only in order to tighten the headspace. On older Lilja drop ins this was working out perfectly but it’s kind of annoying spending money on a match barrel and then having to put it in a lathe. For me at this point I moved on to custom fitting and permanently attaching the Barrels. I worked with Lilja to design a newer style drop in that can work for those that wanna do things themselves. Not custom fit level but as good as your gonna get without custom fitting. These new Barrels use a longer shank with shims to set headspace to whatever you want.

depending on what you call ideal accuracy, the factory pipes won’t satisfy the bunch that wants one hope accuracy. No matter how much you work them over they are not even close to the level of a match barrel.

I get that, and I'm not trying to make this into something it's not. More just wanting to make it the best it possibly can be as it is. I know it's the shoulder that needs to be set back for chamber length but my headspace is right at .043" so whatever I take off the shoulder I have to take off the face too. Not that big of a deal though. If it comes down to it I'll buy a barrel blank and cut/chamber it myself. Just curious about chamber lengths and seating the driving band of the bullet well into the rifling.

 

[djdilliodon]

If your able to fit a blank to the gun, sell off the factory pipe and call it a day. If you want to experiment there ain’t nothing wrong with that. I’ve tried everything you can imagine with these from custom fit Barrels, many different custom chamber reamers I came up with, custom striker springs, various types of bedding, tons of ignition work etc. I had a ton of fun doing it but I wasted a lot of money along the way lol.

A little something about chambers. Don’t worry too much about the dimensions, depth, leade angle etc of a chamber. The goal is running a chamber for the intended use of the rifle. I’ve designed custom reamers for all out benchrest that the rifles where totally insane in accuracy. The problem is these chambers where useless on a rifle that needed to feed from a mag and run in tactical style matches. 50-75 rounds the barrel had to be cleaned as groups would open right up along with other issues. There are some pretty good off the shelf reamers that will satisfy most needs. The eps and Lilja Match are pretty solid reamers to start off with.

 

[djdilliodon]

Also if your headspace is at .043”, you are extremely lucky! Most actions with factory Barrels headspace at .046” or greater measuring both the barrel shank length and receiver face to bolt face recess while cocked using a quality depth micrometer.