CZ 455 Bedding Advice

[11aaguilar]

Hello everyone. Several months ago I purchased one of the last actions DJ Dillon built. CZ 455 action with his bolt work, non-permanently attached Lilja barrel (non-threaded), and Rifle Basix trigger. I placed the action in a McRree's Precision stock. I have an Athlon Ares ETR in a Larue LT120 mount and shoot the rifle prone, with a Harris bipod and rear bag.

I've shot a mix of a bunch of ,22 from the cheaper stuff to Wolf Match Target, SK Plus, etc. Thus far I've been unhappy with the results. Some groups will come in beautifully in the .2-.3 range at 50 yds. Then the next group will have crazy flyers. Occasionally a 5 or 10 round group will produce two distinct groups that by themselves are great, but together make a lousy group . I've read this could be a bedding issue and to test the fit, I removed the action screws from the rifle and with just the action resting in the chassis, it moved back and forth roughly 1/4".

My question to you is, is this a bedding issue? If so, any gunsmith recommendations to get this completed the right way and what is a fair price (ex. SAC offers bedding but at $375)? If bedding is not the issue, what do you all think is the issue? Thanks in advance for all the help.

 

[jbell]

I have found McRee's chassis to have excellent bedding, but that is not to say this one is not in need of skim bedding (either from the inlet being off or the OD of the action, or both...)

First confirm all fasteners are properly torqued (scope mounting, action screws, barrel forcing screws).

Second try a different scope.

Third test the bedding for stress: hold the rifle with the muzzle up pointed about 1 o'clock (like your shooting at a very high angle, so the rifle is oriented with the scope on top, not sideways or upside down). Alternately loosen the action screws noting barrel movement relative to the forearm. You can do this with a dial indicator or simply with you finger lightly placed at the barrel forearm junction. Anything more than a few thousandths of movement could use a bedding job any extremely large amount of movement (like if you can watch it moving) there is DEFINATEELY a problem some where!).

Also repeat this with the magazine hanger and trigger removed (one at a time) to isolate them from the equation. If you see a difference look for contact with the chassis.

Last before sending it out remove, inspect, and reinstall the barrel and play with the forcing screw torque. I know that is critical and can make a big difference.

 

[11aaguilar]

Wow, wasn’t expecting all of this advice thank you. I’ll do as you recommended and note the results. Worst case scenario if this was your rifle and you wanted the most accuracy you could wring out of it, what are a few places you would trust sending it to?

 

[jbell]

It kind of depends on what you find with the test. Let me know and I can make some recommendations.

 

[11aaguilar]

Ok, so I have some preliminary results from your recommendations.

1) Unfortunately I have never been able to get an accurate figure for the action screw torque in this rifle. The design of the McRee chassis is such that the rear action screw is deep within the trigger guard and the hole to access it is just wide enough for the appropriate Allen wrench. The only torque wrench I have is a Wheeler FAT wrench and the bits aren't long enough to reach the screw. I've placed an extended bit set on order and hopefully it arrives this week. My scope torque settings were at the Larue recommended setting.

2) Will go to the range this week and report. I incorrectly stated this rifle wears an Athlon Ares ETR. It actually has a 4.5-21x Bushnell DMR II on it. I'll try it with the Ares next range trip.

3) So hopefully this will help diagnose some of the issues. There was immediate and significant movement of the barrel relative to the forearm with any movement of either action screw. When I would tighten the forward action screw it would bring the barrel closer to the forearm. When I would loosen the rear action screw it would also bring the barrel closer to the forearm. The movements appeared to be consistent and the barrel would continue to move predictably and immediately upon any tightening or loosening of the screws. By that I mean there was never a time that I was tightening/loosening the screws that the barrel wasn't moving. It would move with any amount of movement of the screws.

4) I don't have a metric Allen wrench set (shame on me) so I wasn't able to remove the magazine hanger and I didn't attempt to remove the trigger until I can do both. I also have a metric wrench set on order so will report when it arrives.

 

[jbell]

It is basic, but have you checked to make sure the action screws are not too long and bottoming out in the action??

 

[11aaguilar]

By looking at it, it appears they are not. I'm using the supplied screws from McRee's but they appear to be the correct length and are not protruding from the chassis at all. Also, would this be an issue if the barrel moves at the first sign of tightening? As soon as I would begin to tighten the screws upon putting them in the barrel would begin to move, not only at the bottom of the screw's travel.

 

[A-Rob]

Something is definitely off. I have the same setup with zero movement when tightening the screws. I just took the action out to check it and with the screws out there is maybe a 1/2mm or less of back and forth travel. There is zero barrel movement when the screws are torqued. Looking at mine, I don't see how this could be happening without some inletting or screw length issue. Is it possible for you to post a picture of the chassis's inletting?

 

[11aaguilar]

Hm, definitely something weird happening. For your SA I did misspeak. There’s 1/8” of play in the action with the screws removed, not 1/4”. That equates to about 3mm. Looking at the chassis nothing seems strange although this is my first 455 chassis. Let me know if there are any other photos you’d like to see. I measured the front action screw as well, it’s just shy of 1 1/16” or 29mm long.

 

[jbell]

From the looks of this pic there is a little tightness in the tang inlet (seen in the very rear of the inlet as a shiny spot, **on the vertical portion of the inlet). I am not sure if this is a problem but definitely something I would examine close!

 

[jbell]

But from this angle it may just be from installing the action, again hard to say from a picture. But in this picture the right side of the tang looks to be binding on the inlet some. Ideally the tang should not be touching on the vertical sides of the inlet. Check that area out close too.

 

[jbell]

If it were me and I liked the chassis I would open the inlet up slightly where the action is only touching on the bottom and then skim bed the thing.

 

[Science.Ninja]

One issue I had was accessory screws (for bipod attachment) in front (near muzzle) were too long in my MPA and barrel was touching. Had to grind them slightly. Easy to check free floating with dollar bill.

 

[11aaguilar]

Ok, so ideally the action is only touching the chassis on the bottom and no where along the sides? Now on to gunsmiths, who would you recommend open the inlet and skim bed the chassis?

 

[11aaguilar]

After inspecting the chassis more closely, it does appear that perhaps the tang is touching just lightly on the rear of the inlet. It's very obvious however that up front towards the end of the action there is some serious contact. It's rubbed the finish off the inside of the chassis on both side of the action.

 

[jbell]

There are some areas that need be touching and others that do not need to be. Chassis are set up in a V block configuration, so you take a round action and put it in a V there will be two lines of contact along the bore axis on each side, they should be equal in length, thickness, and location in the V on their respective side. So if this is what you are seeing then no worries, but if you see major irregularity from side to side then that may be an indicator there is a problem.

I was hesitant to post about the tang as when I bed a 455 I set up the rear of the tang as the recoil lug, so it does contact in that same area. However your chassis looked like there was a little more than simply some contact, it almost looked like a "ding" or "damage" at the top of the inlet for the tang. It is hard to convey what I am seeing via written word, and even harder to make an accurate assessment from a picture.

Where are you located? Maybe you have someone local that can check it out.

 

[A-Rob]

I would remove the magazine well and check to see if there is any interference there first. Probably not, but you're just ruling out things now. I would also remove the barrel (if it's not a DJ glue-in) and see how the bare action fits. It should drop in with no resistance. As for the clearance, you are looking at a few thousandths of material, probably not much more than the thickness of the Cerakote finish. You could try to clean that up yourself with emory paper or something. The skim bedding is easy enough to do yourself if you watch some instructional videos, protect the finish of the chassis, use very little epoxy and plenty of release agent. If there are clearance issues, it is probably due to the machining of the CZ, not the chassis.