Here is my Ruger 10/22. I have posted several times regarding the high capacity magazines not functioning properly. The factory mags work fine.

The bolt will go forward and the base of the cartridge with the rim will be in the magazine and pushed forward, while the nose of the bullet is sticking upwards. See the picture.

What is causing this malfunction?

My first guess is your magazine, but you said you mag work great, so the second guess would be your feeding ramp on your barrel?  Are you certain it is NOT your mag?

have you tried different ammunition to see if all feed the same?  
Mine seems to like solid bullets better than hollow point bullets.

The factory mags, work fine. The aftermarket high caps are the ones which have malfunctions.

i'm certainly no expert, but that's something that happens often w/ aftermarket/high cap mags in many guns...

it's been my experience that it's usually caused by how the mag is held in position...the weight of the long curved mag is pulling downward more on the "pegs" that support the mag in the gun... on some highly curved ones, it way pull downward on the front, and push upward on the rear.....

to determine if this is caused by where the mag lips are positoned in the gun, insert a loaded mag, pull bolt back, and try supporting/lifting the mag.... you will want to lift just the front, also, while you try to get the gun to cycle...  you can also check the front "peg" on the mag for excessive wear on the lower side...this would let the front of the mag drop....if the mag has a plastic "peg", chances are that's it..

i've seen alot of factory metal lips have a slight flashing left from the casting process on the inside front of the lips, just at the very begining of the "feed ramp" area...this sometimes causes probs w/ certain bullet shapes

i hope one of these helps....and, keep us posted on what works!!

skintback

Which aftermarket hi-caps are you buying?  American Eagle, Ramline?

The only aftermarket hi-caps I have ever had any luck with are ButtlerCreek Hotlip 25rnd mags.

Looks like exactly the same sort of malfunctions I have with the BC mag if I put more than 20 rounds in it. Does this only happen for the first few rounds of a fully loaded magazine?

Try pushing forward on the base of the mag and see if the bolt strips off a round properly this way.
If it does it is definitely because the mag isn't sitting correctly in the rifle and you'll have to do
some tweaking to the front peg to get it to work.
If it doesn't it most likely is a problem with the feed lips.
I had a couple of BC mags that did this until they were broken in.  I guess the lips were causing
a little too much drag on the round being fed.

The thing is it doesnt happen all the time. And it happens with Ramline 50's, and Butler Creek 25 hot and steel lips.

to much spring pressure holding the round up to high? have you let them (the magazines) sit loaded for a week or two?

It happens with my after market mags too, you're not alone

think it has to do with the mag not sitting snug in the mag well.