Last fall I noticed that my 270 Montana would miss a cartridge every once in awhile. The cartridges wouldn't push up far enough for the bolt to catch them.
I tried bending the spring to create more push but never could get it functioning 100% of the time. Thought I had it fixed but never fully trusted it.
Tried ordering a spring from Kimber but they were out of stock.
So I ordered a few springs from Brownell's.
A Remington ADL spring works great. Cycled a full mag-well about 8 or 9 times and it didn't fail to feed one time.
Brownell #767-170-280.
And before the anti-Kimber girls get all twisted up I had the exact same issue with a Sako 85 so it does happen.