I have a 416 Rigby, which was built on an Enfield action. It was done very well, and it's a great rifle.
I have had problems getting 400gr Barnes Banded Solids to feed reliably. They sometimes hang up on the flat meplat.
I left it at the smith's earlier in the week, and just called him.
He polished the feed ramp, which I expected. He then said he replaced the magazine spring with a softer one, and now he can't get it to jam.
All this is good news, but usually I hear of problems with a weak magazine spring. He said that the old one was actually pushing the round off to the side. This rifle feeds round noses like hot butter, but I have been wanting to use a flat meplat solid on a bull ele hunt I have in a few months.
I have some time to play yet, and could certainly put the old spring back if I sense a problem. I hate the notion of having to choose between reliability and penetration.
I was just wondering if a "too strong" magazine spring has caused problems for anyone else, and if I am inviting problems by using a softer one.

I tried to improve my pre 64 Win 70 in 375 H&H by putting in an extra strong magazine spring. It would pop rounds out of the gun. I put the factory spring in and it functions fine, just as it did before I tried to improve it. I have tried to use that spring in my 416 Rem and 300 Weatherby with the same issues. It did work in a 30-06.