CZ 457 PRS Build

Leuchtkafer

Leuchtkafer

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I've been wanting to get into PRS shooting, especially since my range started building out targets and barricades this year. As good excuse as any to build a rifle :cool: I ordered up an MDT ACC Premier Gen 2 as soon as it became available for the 457 action and now have it in my possession. I got my butt into gear this week to start fitting the barrel. I like the setup with a 4-jaw chuck and a spindle spider (which I made) to do barrel work. This is a 0.900" Shilen barrel. Finished length from shoulder to muzzle came out at 17.5" and total length including tenon is 18-11/16".



Got the tenon cut and it's time to chamber. The pilot size on this barrel is 0.2166"



I was curious by how much the bore is out from the outer diameter of the barrel, so I measured it before dialing in the bore for chambering. This bore is running out about 0.003". All things considered with what's involved in deep drilling a blank, that ain't bad, I was expecting more.



I upgraded the DRO on my tailstock since I did the factory barrel experiment, the previous unit would power off after a time and lose it's zero, very annoying. This unit remembers it's last zero if it powers off, much better. The stainless machines easier than the factory barrel carbon steel, I can really tell the difference while reaming by hand. It's kinda like fishing, but in reverse. Little "nibbles" are OK, back off a bit if you feel a big nibble, but the last thing you want is a big bite! :LOL:



The copper chuck jaw caps and brass tipped screws in the spider do a great job of protecting the barrel finish, there's not a mark on it from them.



I'll update as I move this build along, before I changeover to a milling setup to cut the extractor slots, I've got another barrel to fit to an action and chamber so just to streamline my workflow I'm going to do all the work on both barrels in one setup before I do a major tooling change. I also have to crown them before the milling changeover, that just involves swapping out my solid tool post mount for the compound slide, but I'll chamber the second barrel first since I only want to setup the compound angle for the crown once and then do both barrels.
 
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EugeneM said:
I'm already excited to see more information on where this is going.

PS. First three pictures in the post are not showing
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Yeah my photo hosting site seems to do that when I first post. Give it a day and they should all appear. *Edit* Apparently not... Well, if you click the X picture square it'll take you to the hosting sight to see the pic.
 
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Over the last few days I got my other barrel fit to the action and chambered. I got the crowning done tonight, nice 11 degree crown.





I had enough time tonight to changeover to the milling setup and cut the bolt guide lip relief. Tomorrow's job will be to change the setup angle to 45 degrees for the extractor slots and a slight chamfer on the lip relief. She's coming along, will be ready to fix to the action very soon.



It's a nice quality of life improvement having a collet chuck now and I got a collet block for holding the barrel. Orienting all the features is as easy as rotating the block in the vise 90 degrees each way from where the bolt guide lip was cut. You don't even want to know the fiddling I had to do last time when I was using a V-block to hold the barrel :oops:
 
Extractor slots are cut and all the machining on this barrel is now done :cool:





It's rather chilly out in the garage so I brought everything inside to warm up. You'll notice I didn't do the grub screw cuts on this barrel. When you want to maximize the performance potential of a rifle platform, details matter, little things add up. For CZ's, the grub screw cuts are a weak point that can cause distortion of the bore. I've got a nice match grade barrel custom fit to this action, but I still have to attach it somehow. I'm not using the grub screw system to avoid the risks of bore distortion. What I'm going to do is "glue in" the barrel with green loctite. It's a zero stress method of attachment, only the weight of the barrel hanging will put any stress on it. The action will then be dedicated to this barrel, no more easy swapping of barrels. That's the tradeoff, though this rifle is being built for a specific purpose and I really don't have any reason to swap barrels on it anyway. With any luck, the weather next weekend is supposed to be a little above 0, and I'll have this build ready for some preliminary trials.
 
There's also the 20k psi in the .224" hole force pushing the barrel forward and out of the receiver. And the torque of the 40grain bullet experiencing rotational acceleration from 0 to 50k RPM within something like 1ms acting to twist the barrel in the receiver.
 
I am neither a ballistics expert nor engineer but it seems to me that at the moment of ignition and for whatever period the projectile is in the barrel the recoil is rearward. In terms of rotational force exerted on the barrel, I think it is minimal. My thought is only supported by the fact that I have shot rimfire barreled actions sans stocks and they did not seem to rotate to a noticeable degree. Ditto with a handgun and rotation is largely because of the grip not being in alignment with the forces of recoil. I'm not say you are incorrect, these are just my speculations to ad to an excellent posting.
Regards to all and Merry Christmas
 
I would think that if rotational forces were a big concern, then my centerfire barrels in my Impact 737 would tend to come loose from repeated firings at obviously much higher pressures. Many shooters only hand tighten their barrels. Im also not an expert but have not seen any of the different guns or barrels loosen.
 
Holy, wish I was setup to do this. Awesome and really nice work. Wanting to build a 457 as well but can’t do what you are. What are you planning to use for a scope and scope rail? I am a bit torn between trying a MTR barrelled action from CZ versus buying the cheapest gun and getting an aftermarket barrel. Looking strongly at a WOOX chassis.
 
Dnu69 said:
Holy, wish I was setup to do this. Awesome and really nice work. Wanting to build a 457 as well but can’t do what you are. What are you planning to use for a scope and scope rail? I am a bit torn between trying a MTR barrelled action from CZ versus buying the cheapest gun and getting an aftermarket barrel. Looking strongly at a WOOX chassis.
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CZ 457 MTR is one of the most cost-effective ways of getting into precision shooting. Unlikely any custom barrel will cost anywhere near and deliver as decent results
 
Heh, I was only talking about stress on the barrel from the attachment method. Certainly there are forces imparted on the barrel from firing a shot, that fact can't be changed. What we can do is modify how the barrel responds to those forces. You can put a pressure pad in the forestock that stiffens the barrel and dampens vibrations, or use a muzzle device.

Dnu69 said:
Holy, wish I was setup to do this. Awesome and really nice work. Wanting to build a 457 as well but can’t do what you are. What are you planning to use for a scope and scope rail? I am a bit torn between trying a MTR barrelled action from CZ versus buying the cheapest gun and getting an aftermarket barrel. Looking strongly at a WOOX chassis.
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Thanks. For scope I've got a Sighttron SIII 8-32x. Haven't decided if I'm just going to mount on the dovetail or get a rail yet.
 
Got the barrel glued in tonight. I degreased the action and barrel tenon before applying the green loctite. First I held the action in the vise to drop the barrel into place and make sure it's fully seated. I then coated the grub screws with shoe polish so that they don't get stuck and lightly tightened them to hold the barrel in place. I then flipped the assembly around so that the barrel is held by the vise with the action sitting on top, minimal stress. I removed the bolt guide, which I had in place to orient the barrel correctly when first installed, so that it doesn't get locked in and cleaned up all the excess locitite that squeezed out. Now I wait a couple days before I can assemble the rifle. I'll borrow a scope from another one of my rifles for first testing until I figure out what I want to do with the Sighttron and order the rings and rail it needs.

 
Leuchtkafer said:
Got the barrel glued in tonight. I degreased the action and barrel tenon before applying the green loctite. First I held the action in the vise to drop the barrel into place and make sure it's fully seated. I then coated the grub screws with shoe polish so that they don't get stuck and lightly tightened them to hold the barrel in place. I then flipped the assembly around so that the barrel is held by the vise with the action sitting on top, minimal stress. I removed the bolt guide, which I had in place to orient the barrel correctly when first installed, so that it doesn't get locked in and cleaned up all the excess locitite that squeezed out. Now I wait a couple days before I can assemble the rifle. I'll borrow a scope from another one of my rifles for first testing until I figure out what I want to do with the Sighttron and order the rings and rail it needs.

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Nice. Is the barrel also a “slight” interference fit? I don’t know much about this but thinking I have heard that some machine for slight interference (cold barrel and hot receiver to install). I am not sure about the pros or cons of doing so. Really curious to see how yours shoots. You should sell them, really nice work!
 
With all the care and meticulously precise machining you’ve done, I’m quite confident it’s going to be a real tack driver. Just need to find some lot numbers worthy. Happy Holidays and New Year
 
Dnu69 said:
Nice. Is the barrel also a “slight” interference fit? I don’t know much about this but thinking I have heard that some machine for slight interference (cold barrel and hot receiver to install). I am not sure about the pros or cons of doing so. Really curious to see how yours shoots. You should sell them, really nice work!
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We used to install bearing races with green loctite, and the interference fit was close enough that we would freeze the race before insertion. I don't know if that is the case here, but it would certainly add to retention. - dan
 
Dnu69 said:
Nice. Is the barrel also a “slight” interference fit? I don’t know much about this but thinking I have heard that some machine for slight interference (cold barrel and hot receiver to install). I am not sure about the pros or cons of doing so. Really curious to see how yours shoots. You should sell them, really nice work!
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Thanks! If there's an interest, I'm certainly open to doing some builds for people. No interference fit here, Kenny at DPG was doing that fit method for awhile before he got a CNC and started threading the receivers. Anschutz has used that extensively in their actions, but rather than a thermal fit they pressed the barrels in and then pin them. The downside to it is that it puts a constricting force on the barrel, imparting stresses and maybe even slightly distorting the bore. With the 54.30 action they did a threaded fit and say this about it:

  • Unlike match actions in the past, the new Match 54.30 features a threaded receiver and barrel connection.
  • This change removes stresses in the chamber area and further increases accuracy.
  • Longstud said:
    With all the care and meticulously precise machining you’ve done, I’m quite confident it’s going to be a real tack driver. Just need to find some lot numbers worthy. Happy Holidays and New Year
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Cheers man, I'm looking forward to the range day :)
 
Leuchtkafer said:
Thanks! If there's an interest, I'm certainly open to doing some builds for people. No interference fit here, Kenny at DPG was doing that fit method for awhile before he got a CNC and started threading the receivers. Anschutz has used that extensively in their actions, but rather than a thermal fit they pressed the barrels in and then pin them. The downside to it is that it puts a constricting force on the barrel, imparting stresses and maybe even slightly distorting the bore. With the 54.30 action they did a threaded fit and say this about it:

  • Unlike match actions in the past, the new Match 54.30 features a threaded receiver and barrel connection.
  • This change removes stresses in the chamber area and further increases accuracy.
Cheers man, I'm looking forward to the range day :)
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Great info. I can’t wait to see your results. Really intrigued by what you have done. I am familiar with DPS threading the receiver. I know some other companies are doing that with 10/22 type receivers as well (Volquartsen and Grey Birch maybe). I get the reasons why but once you do that there is no turning back. What you are doing may be better, so curious how it shoots and holds up. I hope you keep us updated.
 
Dnu69 said:
Great info. I can’t wait to see your results. Really intrigued by what you have done. I am familiar with DPS threading the receiver. I know some other companies are doing that with 10/22 type receivers as well (Volquartsen and Grey Birch maybe). I get the reasons why but once you do that there is no turning back. What you are doing may be better, so curious how it shoots and holds up. I hope you keep us updated.
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I got out to the range today, not a bad day, got up to +10C. Was overcast and foggy/misty, target papers got moist. Good things first. Function wise, everything is good with the build. I've seen some express concerns that repeaters will have an issue feeding into a tight match chamber, so that's why they usually have looser chambers than true single shot bench guns. While I did most of my shooting with a single shot adapter, I also spent some time ringing steel using 10-round mags. I had no feeding issues despite the tight benchrest style chamber. I did give the chamber mouth a slight chamfer, rather than having it as a sharp 90 degree edge. Feeding the wadcutter Eley bullets from a magazine might yet be an issue, but anything standard round nose should work fine. Extraction and ejection was good, able to pull live rounds and only one or two spent casings didn't eject properly over the whole day. I had a lot of ejection issues before when I was shooting with the factory barrel. I did some light stoning of the claws and it seems to have done the trick.

Results wise, I didn't come away with anything I'd brag about. I shot mostly new-to-me ammo ordered this year, and am unsure of it's quality. I came back to the first target and shot the bottom row of RWS Target Rifle again after getting up to a higher round count, to see if some degree of "break in" would make a difference. Not sure, other than I suspect this RWS Target rifle is just crappy ammo. It shot all the ammo here like what I'd expect a factory MTR to do, with a few bad groups.



Onto some higher grade ammo, a row of the new stuff followed by a row of the old stuff. Other than a few fliers, the old Special Match shot like what I'd expect out of it, while the old R-50 did not shoot as well as it should. Also shot the bottom row with Rifle Match again at the higher round count, maybe better than the first run with it? Rifle Match was giving me a number of fail to fire, recock and hit again would fire though. Only ammo that happened with. Fliers are ruining my day. See how many groups have 4 rounds packed tight and then a stupid flier... Some really nice groups here though, 5/25 in the 0.2's is more than just a random act of accuracy.



I had been cleaning every 50 rounds, at this point I thought I'd see what'd happen if I went up to 75 rounds with the Center-X. This ammo hasn't impressed me out of any rifle of mine to date, I'd long ago written it off as a bad lot. Some really nice groups with it... but those fliers again. I shot one group with 10 rounds, not intentional but I kinda zoned out... so my round count is off by -5. I'm only counting "for score" shots, not foulers, so exact round count isn't there anyway. SK High Velocity Match looks like it might be serviceable for PRS, hope so since I bought a case of it :p SK Semi auto.. ooof, crappy ammo. That or this rifle really doesn't like it, a lot of vertical. If I get a tuner working on this barrel it might be worth revisiting.



Now that we're getting into winter, the weather isn't really conducive to serious accuracy testing for the next few months. I haven't run any Eley through it since their wax gets real stiff in the cold. What I think I'll do is take the SK HV out to 100 yards and see how it does, then focus on finishing the build setup for PRS. I'll need to get some fore end weights to balance it and rings for the scope I intend to use. I'd also like to make a custom bolt knob for it. Looking over the results today, they're somewhat demonstrative of what a rigid barrel does, not a drastic difference from one ammo to the next, though nothing really stood out as exceptional. That's what gets me, usually when I run through a selection of ammo like that, something does well. Has ammo quality lately declined so much that rather than hoping for a good lot, we're hoping to get something that can do a 1/2" challenge? I'll need to do a sanity test and run the ammo through a known good performing rifle for comparison. Tuner wise, the short stiff barrel doesn't suit commercially available tuners. Calfee has said that a standard Harrells is bordering on too heavy for a 24" 0.900 barrel, with mine at 17.5" I can't see it working well. What I could try is removing the rotating half of a Harrells, and machining a little aluminum ring for it in it's place. That could lighten it up enough to work with my barrel, and still be adjustable.

Yeah so test the SK at 100, finish the setup/build, and basically just practice banging steel until I've got a couple more bricks through it before I revisit accuracy testing. Test my ammo with my good rifle so I know whether or not those fliers are just the ammo or there's some issue with this build. My good rifle took a few thousand rounds to settle down and really start showing it's stuff, we'll see what happens with this build over time. I also got a case of that SK Semi Auto, I can have some fun with it banging steel to get the round count up without burning the "good stuff". It's a nice rifle to shoot, I never mentioned I also put a Timney trigger on it. Good trigger, nice and crisp.
 
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