You will just have to see how it shoots in YOUR rifle...but I think the 42gr is more for semi auto actioned rifles vs bolt action...the tiny bit of extra weight helps the bolt cycle backwards...it is certainly be just fine shooting out of your rifle but might not be as accurate as a 40 gr match round. As far as wind delfection....I am not sure...but you can run the numbers on a ballistics calculator..others will be aling to answer with more authority

 

Heavier bullets are less affected by wind than light ones. Considering the couple grains we are talking about I doubt it matters.
It has been said the change at eley from 40 to 42 grain bullets had to do with replacement or adjustment of some of the weights and measure machines they use not a change in production.

So far I have found contact ok in bolt guns. I am just breaking in a brand new Kidd rifle and at least right now the contact won’t cycle the gun. Other types of eley sk lapua and even aguila run fine.
I bought a bounce of contact when it was available cheap ( under 50 bucks a brick ) and for ammo in that price range it is good. With prices now listing in the $65+ range, I would look to other options.

 

I'm new to this rabbit hole of shooting, so bear with me. I bought several different types of ammo to see what works best in my gun, a cz457. I see that Eley Contact is 42 gr while everything else is 40 gr. Would not the extra weight help to lessen the effect of wind?
Related question, why is all the subsonic ammo 40 gr? Wouldn't 38 give a flatter trajectory for longer distances?

Q1. Yes.

Q2. The speed of sound is a fixed value [not a constant, because air pressure variations w/ temp & altitude], so the 38gr can't flatten the trajectory because it's moving at the same velocity as a 40gr pill if they're both just subsonic. So the 38gr bobo [technical term] gets blown around more than the 40gr one, but they both drop the same amount at the same distance [per Galileo & Isaac Newton. Go argue w/ them if you don't like it!] because they both took the same amount of time to get there.

Also, see your Q1; clearly not all subsonic ammo is 40gr, since the Contact [& some others] is 42gr. Nyah!

 

I have no experience myself with 42 grain bullets but the guy I bought one of my rifles from is a seasoned benchrest shooter. He says the Eley Contact with the 42 grain bullet will perform better in the wind. I hope to try it myself when I can find some.

 

I wanted a decent ammo that I could shoot in my vintage iron sight rifles, also wanted good practice ammo for the Sav. MKII FVP.
I think that's a bit of an oxymoron...but for the price, I will not complain.
Not good on the ES & SD's but it's subsonic & for sure 'minute of golf ball' @ 50 yards...

 

Contact and Force both have the 42 grain pill and work well on steel targets. It helps dwell time therefore making steel targets fall better. Force has a bit more power than Contact.