CZ 455 American Combo

A

Ariu

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Below is my experience with a CZ455 0.17hmr/22lr combo and I hope that my experience would help somebody who has or want to by this gun.
I bought this gun a couple of months ago and topped it lately with a Vortex Diamondback 4-12x40 AO. Ammunition used to test this gun (as described below) was 0.17HMR Remington AccuTip (17gr) and 22LR Remington Hollow Point (36gr)

Step 1.
I started with 0.17hmr and zeroed it in at 50y. I zeroed it further shooting at 100y and the gun was shooting very well. I never had such tight groups with my other rifles.​

Step 2.
When I changed the barrel to 22lr, I was completely off the paper at 50y. I retried at 30y and the POI has moved about 3” down.​

Step 3.
I changed the barrel back to 0.17hmr and did some shooting. The POI come back as in step 1 but was not exactly the same.​


At this point I left the range as I did not had a torque screwdriver and I could not prove if the changes on POI will remain constant after a barrel change. Yesterday I was back in range with my gun and a Wheeler FAT torque wrench.

Step 4.
Still with 0.17hmr barrel on the gun, I loosen up and re-tighten the screws (all of them) to 20lbs-inch. Did some shooting at 30y and saw the POI changed to about 1” up and 0.5” on the right compared to this of step 3. Continued shooting and zeroed the gun at 50y.​

Step 5.
Changed the barrel to 22lr with the screws tighten all at 20 lbs-inch. After some shooting at 30y, I saw the POI had moved to 2.9” below and 2.7” on the right compared with this on step 4. Applied the corrections to the scope and continued shooting and zeroing the gun at 50y. The total number of clicks applied to the scope at 50y was 39clicks on elevation and 35 clicks on windage.​

Step 6.
I changed the barrel back to 0.17hmr, applied the correction to the scope on reverse (39click on elevation and 35 clicks on windage) and BANG the POI come back at 50y as it was in step 4.​

Conclusions: The POI will change significantly after a barrel swap - in my case it was about 10MOA
If a constant torque is applied to the screws during a barrel swap, the difference on POI will remain constant. This will not be the case if the torque applied is random.
 
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Conclusions: The POI will change significantly after a barrel swap - in my case it was about 10MOA

I hope this wasn't a surprise for you...

Should not have been any surprise with the poi between the two cartridges as the 22 bullet is twice the weight and traveling half the speed of the 17 .
 
Yes I was. I was somehow led to believe (from some kind of internet review) that the POI will not change much after a barrel swap.
Now, with the gun zeroed at 100y, the theoretical drop between 0.17hmr and 22lr would be 2.1" and there would zero change in windage (assuming there is no change at all on POI after a barrel swap).
My findings were very different - in drop and in windage. POI was affected even for the same barrel when different torque was applied on screws.
 
My findings were very different - in drop and in windage. POI was affected even for the same barrel when different torque was applied on screws.

Do some research on barrel harmonics . different torque settings will give the same barrel different harmonics .
 
I am super lazy. I have one each in .17, .22, and .22 mag. I have an older Scopechief on the .17 and have only barely sighted it in and smoked a few gophers. The other two are waiting their turn.
 
rembolt said:
Do some research on barrel harmonics . different torque settings will give the same barrel different harmonics .
Click to expand...

Barrell vibration is (primary) a property of the barrel. It will not change for the same barrel, and for the construction of CZ455, even when the applied torque on screws is different. Barrel harmonics cannot change the POI in matter of inches at 30y - not for a 20" barrel shooting 17gr bullets.
 
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rhino62 said:
I guess this would not be the case with iron sights on a CZ455 when not using a scope, since the sighting plane is on the barrel only.
Click to expand...
Not necessarily true either! The front and rear sights are both adjustable for elevation, and the rear sight is adjustable for windage as well, so...

So it's totally conceivable that the irons on the .17HMR could be zeroed at 100y, vs 50y on the .22LR... :)
 
I have a Savage 93R17 TR, and a CZ 455 varmint tacticool SR. The guns are so similar other than caliber aside from the huge bolt knob on the TR(which is lacking in the CZ).I am wondering if it is worth it to sell the savage and just pick up a 17HMR barrel for the CZ, and just do the barrel swaps. Or is the swapping just too much of a pain?
 
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