Take the information posted on Ranftt with a grain of salt - although it's a great general resource, it has it's limitations.Yes, theoretically it should.
Notice the mainspring dimensions in the two Ranfft archive entries below:
bidfun-db Archive: Watch Movements: ETA 2892-2
bidfun-db Archive: Watch Movements: Omega 1120 (ETA 2892-2)
Oddly enough, the cal. 1120 appears to have 5 hours of power reserve more than the standard 2892, so while they theoretically share the same mainspring, there must be more to that- I don't pretend to know what exactly causes that difference, though.
As always, the cavalry has arrived. Thanks for the clarification, Al. Well, every resource does have its limitations indeed... If I recall correctly, the good Doctor's using manufacturer's tech specs, quite certainly also Bestfit- most of the movements in his archive are ones he has handled himself, but some photos and info come from his acquainted watchmakers and watch collectors. It may well be, that the one he has been checking out has been running for 47h. Or he has made a typo... He's on WUS, posting in the Vintage forum from time to time, so you can ask him if you want.Take the information posted on Ranftt with a grain of salt - although it's a great general resource, it has it's limitations.
The ETA 2892A2 has a rated power reserve of 42 hours. The Omega 1120 has a rated power reserve of 44 hours - this is directly from Omega's documentation, so I have no idea where Ranftt gets 47 hours from.
Coincidentally I recently finished a Longines with an ETA 2892 inside, and in my power reserve testing after spending time on the final test winder, it ran for 50 hours - I have had many 1120's run that long and a few even longer. The power reserve indicated by brands will typically be underestimated, so if the movement is in good condition and has been properly serviced, it will run much longer than the rating.
I don't believe you will find that there are any dimensional differences between a 2892 mainspring and an 1120 spring. They are both made by Nivarox, and the only thing I'm not 100% sure of is that they are the same alloy, as I have no way to test that.
Not sure where the OP is getting the Omega spring from, but the prices are pretty much the same for me...
Hope this helps.
6 pounds is very cheap for a branded mainspring, so does it come in an ETA package, like this:I'm not an expert, but I can only guess the longer power reserve of the Omega is due to the barrel pivots sitting in jewels rather than plan sleeves?