340 C, SUPER accurate but slow

[Double 30]

My 340 C , with 22 inch barrel, is superbly accurate.With a variety of factory loads and reloads , her 50 yard open sight groups average in the 5/8 to 7/8 inch range for 3 rounds.Cant wait to find an aperture sight for her! Her barrel is however alittle slow... Everything is about 125 to 150 fps slower than the same loads out of my old 20 inch Marlin 336 . Its alittle frustrating. With a 22 inch barrel I expected alittle more oomph.
  One thing that I do have to correct is she jams the 2nd round out of the mag into the rear of the barrel. Pointed bullets go in fine , but I like round noses and flat point ALOT and no amount of seating depth tinkering has helped. The 1st and last rounds go in nice as you please its really wierd.A friend has 2 340's and their mags dont even fit in mine. The one I have is a very tight fit btw.Anyone have this problem ? How'd you fix it? Anyone try the Gun Parts corp repro mags?
  I love this rifle. But, if she's gonna go hunting she's gotta feed 100%. Any thoughts and help appreciated!   

[Double 30]

Fixed the mag problem! I noticed the front end of the feed lips were alittle wider than the rear end.This allowed the cartridges to sit higher in the mag and jam on the barrel face.I gave the lips a squeeze, I was surprised that hand pressure was enough,and VIOLA she's a garbage can now! She feeds everything but empty cases. WE'RE GOIN HUNTING!!!!!