Does a Mainspring break-in and become more accurate

[Plinkmaster]

I have a QB36-2. .22 cal. with open sights.  I just replaced the stock spring with a Jim Maccari  E9870 Euro universal spring. The stock spring was .117 wire and 15" long.  The E9870 is .120 wire and 13" long. I was shooting 5 shot groups average  of 1.75" @ 25 yds.  with the stock spring.  Now the new spring is shooting  2" groups @ 15 yds.  The new spring is a little harder to cock. but the stock spring, was a year old. Is it that the longer lighter spring unwound slow and smooth. And the heavier wire unwinds faster and more violently? I did not add any more spacers than I had with the stock spring, I did not want to stress the stock plastic spring guide.I just have 2 polished metal washers, moly greased, to reduce spring tourqe.

[jct842]

What did you gain in fps?  you really havent lost all that much, but,  you might find that the gun likes a different pellet with the new spring.

[Plinkmaster]

I got this gun from compasseco March '08 .  It had a very weak spring. Compasseco sent Me a new spring. And when it was new, it was pretty powerful. But this season it seemed to cock easier. It broke a few weeks ago, so I got the JM E9870. I'm hoping for a longer spring life. I don't have a chrony, but I did a penetration test into a phone book, comparing to my RWS 48 and B-3. all are .22 cal.  I  figure it's shooting a .22 @  700 f.p.s.

[jct842]

I think if you try other pellets you may get better accuracy.  The guys here should be able to help on what you need to do as far as tuning it.  tuning it should tame the recoil.