Specific ZCO Comparison Question

[CoriolisEffect]

Okay, so I've read pretty much every single 420 to 527 comparison I can find on multiple forums across the 'web, and none of them really seem to do a great job of explaining one particular thing.

When both scopes are compared side by side at an identical power through their overlapping range of 5x-20x, is there any meaningful difference between any of the typical subjective qualities like IQ, CA, or eye box?

It seems that every comparison I have found focuses on the obvious differences like size, weight, FoV, etc., or they make a comparison at min or max zoom which isn't apple to apples.

For context, I'm currently trying to decide what to put on top of an AI AT I recently purchased. It currently only has the factory 20" 308 barrel, but I plan to add a 24+" 6.5CM barrel in the future.

 

[Secant]

Okay, so I've read pretty much every single 420 to 527 comparison I can find on multiple forums across the 'web, and none of them really seem to do a great job of explaining one particular thing.

When both scopes are compared side by side at an identical power through their overlapping range of 5x-20x, is there any meaningful difference between any of the typical subjective qualities like IQ, CA, or eye box?

It seems that every comparison I have found focuses on the obvious differences like size, weight, FoV, etc., or they make a comparison at min or max zoom which isn't apple to apples.

For context, I'm currently trying to decide what to put on top of an AI AT I recently purchased. It currently only has the factory 20" 308 barrel, but I plan to add a 24+" 6.5CM barrel in the future.

I don't notice a difference between my 4-20 and 5-27 in terms of IQ or eyebox. I don't see any CA at all in my ZCOs.

 

[Covertnoob5]

Yea not really any difference at equal mag setting. The 420 is phenomenal.

 

[CSTactical]

Okay, so I've read pretty much every single 420 to 527 comparison I can find on multiple forums across the 'web, and none of them really seem to do a great job of explaining one particular thing.

When both scopes are compared side by side at an identical power through their overlapping range of 5x-20x, is there any meaningful difference between any of the typical subjective qualities like IQ, CA, or eye box?

It seems that every comparison I have found focuses on the obvious differences like size, weight, FoV, etc., or they make a comparison at min or max zoom which isn't apple to apples.

For context, I'm currently trying to decide what to put on top of an AI AT I recently purchased. It currently only has the factory 20" 308 barrel, but I plan to add a 24+" 6.5CM barrel in the future.

Both are absolutely phenomenal, I personally debated back and forth on this recently for a 20" 6.5CM setup and went with the ZC527 since I am also considering a longer 6.5 PRC barrel when we shoot longer distances. Eventually when I just have a different rifle dedicated to longer distances I'll move the ZC527 to that build and grab a ZC420 for this one. At the magnification ranges I'm use to at 1,600 yards and in, the ZC420 would be just as well suited. Feel free to call me at 916-670-1103 and I can try to help you better decide

 

[Huskydriver]

@Glassaholic

Or @MNTC

 

[CoriolisEffect]

I don't notice a difference between my 4-20 and 5-27 in terms of IQ or eyebox. I don't see any CA at all in my ZCOs.

Yea not really any difference at equal mag setting. The 420 is phenomenal.

It really seems like the only aspects of their optical performance that differ meaningfully is that the 420 has a 7ft FoV advantage at low power, and the 527 has the 7x extra zoom up top. Just looking at it like that, it seems like the 7x zoom is potentially a lot more significant than 7ft at a zoom level that I may not really use much (this isn't going to be a hunting rifle). I wonder what the difference in FoV is between them from 5x-20x.

 

[Secant]

It really seems like the only aspects of their optical performance that differ meaningfully is that the 420 has a 7ft FoV advantage at low power, and the 527 has the 7x extra zoom up top. Just looking at it like that, it seems like the 7x zoom is potentially a lot more significant than 7ft at a zoom level that I may not really use much (this isn't going to be a hunting rifle). I wonder what the difference in FoV is between them from 5x-20x.

I’ve ran just the rough approximation calculation, and there’s no difference in FoV on similar magnifications and that anecdotally matches my real world experience.

I don’t have a hard on for ultra shorts as I’m not using clip-ons, but there’s something special about the 4-20 IMO. The 4-20 gives nothing up to the 5-27 except the top end magnification. I don’t think I’ve ever shot my 5-27 over 20x, so that’s probably why I like the 4-20 so much. If you use high mag a bunch, the 5-27 would obviously make more sense.

 

[CoriolisEffect]

I’ve ran just the rough approximation calculation, and there’s no difference in FoV on similar magnifications and that anecdotally matches my real world experience.

I don’t have a hard on for ultra shorts as I’m not using clip-ons, but there’s something special about the 4-20 IMO. The 4-20 gives nothing up to the 5-27 except the top end magnification. I don’t think I’ve ever shot my 5-27 over 20x, so that’s probably why I like the 4-20 so much. If you use high mag a bunch, the 5-27 would obviously make more sense.

Are they really? Mind if I ask how you ran the calculation? I was trying to do that with similar triangles and was only able to figure out what the "cone" angle difference would be at 100 yds. I do think the 420 is the "sexier" form factor, but I also keep telling myself it's just a tool (of course that argument falls apart when I think about how I had to have thumbhole skins on the AT just for appearances )

 

[Secant]

 

[Secant]

FOV2 = FOV1*(mag1/mag2)

Edit: and feel free to check my work . I put that together pretty quick.

 

[CoriolisEffect]

FOV2 = FOV1*(mag1/mag2)

Edit: and feel free to check my work . I put that together pretty quick.

That's great, I agree with it. For some reason I was stuck on the whole 100 yds thing even though I knew it was irrelevant.

 

[Glassaholic]

@Glassaholic

Or @MNTC

Not really much to add with what has already been discussed. The 527 is a longer design and inherently offers better DOF and eyebox, I've never put the two side by side long enough to give a far evaluation, but I can say that the 4-20 is extremely impressive for an ultra short.

This past weekend @MNTC and I were out shooting ELR to 1.5 miles and we used 12-16x the whole weekend, too many people get caught up in thinking "I need magnification if I'm going to shoot long distances" when what you need is a clear sight picture which often times, when the heat waves are rising, means lower magnification. In a dynamic shooting environment (multiple targets at varying distances), using higher magnifications can be a hindrance which is why I backed off to 12x at one point and left it there for a while and wasn't hindered at all with being able to hit the distant targets.

If the low end FOV doesn't really matter much, I would choose the longer scope for the aforementioned benefits even if they are minor.

Mostly shooting at the 1000 and 1500 yard targets in this pic below using 6.5 Creedmoor ammo, we used 300 Norma for the longer distances with great success even though temps were above 100 and winds 20-30 mph.

 

[rhsc]

Nice chart, @Secant. If I'm reading it correctly, the AMG essentially overlaps the ZCO scopes within its magnification range. Is that right?

 

[Secant]

Nice chart, @Secant. If I'm reading it correctly, the AMG essentially overlaps the ZCO scopes within its magnification range. Is that right?

Yes, the AMG has similar FoV.

 

[CoriolisEffect]

I ended up getting to have a short conversation with Jeff Huber yesterday and he walked me through some of the finer points of the comparison. Basically that the 527 will have slightly more light gathering capability thereby extending usability in twilight by a handful of minutes. The 527 also has slightly better resolution. I believe his exact statement (which I'll probably butcher) was something along the lines of the 527 being able to resolve text that is 2.9 60'ths of a second tall, vs 2.2 60'ths of a second tall for the 420 (when both are at 100 yds, I believe). He also commented that the 420 is more forgiving on parallax. Lastly, he added that at trade shows, 8-9 out of 10 customers will tell him if they had to choose one they would go with the 420. Pretty interesting.

 

[NiteQwill]

I have a few ZCOs (527s and 420) and TBH, it's hard to choose between the two. The simple small size of 420 makes is soooo nice. The 527 shines in low light situations, though.

 

[Covertnoob5]

If it helps any back in 2019 I ran the 420 in PRS for most of the season while also having a TT525P and never felt held back. I only swapped to the 527 because zeroing at 100 is easier with 27x lol and with as many different chassis and calibers I use I have to rezero a good bit.

 

[4O6shootist]

I have a 527 and just picked up a 420. I personally feel the eyebox is more forgiving on my 420. The elevation turret also feels better on the 420. The elevation vs windage on my 527, noticeable difference, Jeff told me to send it in, which I will do, but just haven't had the time. I am planning to get a March 4.5-28 which has same form factor and FOV as the 420, but larger mag range than the 527.

 

[chevy_man]

Where I'm at it's typically fairly dry, moderate to cold temps. I run my stuff maxed out quite often. The worst mirage I see is spring when the sun is hitting the snow.

As I don't have to deal with mirage much, I always gravitate towards the higher powered scope.

If I lived in Florida, I'd probably never be much over 10x with the humidity and heat.


I would let your use and location determine which scope to get. They're so close in all the specs the only right answer is what works for you, not which is better.

 

[deersniper]

Not really much to add with what has already been discussed. The 527 is a longer design and inherently offers better DOF and eyebox, I've never put the two side by side long enough to give a far evaluation, but I can say that the 4-20 is extremely impressive for an ultra short.

This past weekend @MNTC and I were out shooting ELR to 1.5 miles and we used 12-16x the whole weekend, too many people get caught up in thinking "I need magnification if I'm going to shoot long distances" when what you need is a clear sight picture which often times, when the heat waves are rising, means lower magnification. In a dynamic shooting environment (multiple targets at varying distances), using higher magnifications can be a hindrance which is why I backed off to 12x at one point and left it there for a while and wasn't hindered at all with being able to hit the distant targets.

If the low end FOV doesn't really matter much, I would choose the longer scope for the aforementioned benefits even if they are minor.

Mostly shooting at the 1000 and 1500 yard targets in this pic below using 6.5 Creedmoor ammo, we used 300 Norma for the longer distances with great success even though temps were above 100 and winds 20-30 mph.

View attachment 7897896

@RickyRodney aka the magnification slut

 

[Glassaholic]

I have a 527 and just picked up a 420. I personally feel the eyebox is more forgiving on my 420.

That would be an interesting phenomenon as an ultra short design is inherently more difficult to get better eyebox (and DOF and parallax forgiveness) but it’s possible the ZCO engineers did their job and created a design that corrected for this well, like you and others I’ve found no shortcomings with the 4-20!

The elevation turret also feels better on the 420. The elevation vs windage on my 527, noticeable difference,

This is not uncommon unfortunately, the good news is ZCO is willing to take care of any scope you are not fully satisfied with and turnaround usually under a week, one of their greatest assets if you ask me.

Jeff told me to send it in, which I will do, but just haven't had the time. I am planning to get a March 4.5-28 which has same form factor and FOV as the 420, but larger mag range than the 527.

You should contact @MNTC as he just got a bunch of March 4.5-28’s delivered

 

[4O6shootist]

That would be an interesting phenomenon as an ultra short design is inherently more difficult to get better eyebox (and DOF and parallax forgiveness) but it’s possible the ZCO engineers did their job and created a design that corrected for this well, like you and others I’ve found no shortcomings with the 4-20!

This is not uncommon unfortunately, the good news is ZCO is willing to take care of any scope you are not fully satisfied with and turnaround usually under a week, one of their greatest assets if you ask me.

You should contact @MNTC as he just got a bunch of March 4.5-28’s delivered

Jake at mountic has costs me a lot of money as of late. These damn marches may cost me some more!