I have a bunch of G20s, like 8 or so.

Over the past year have tried:

Storm Lake x 2
KKM x 3
Lone Wolf x 4

NONE of the barrels will reliably feed Buffalo Bore or Underwood 220gr full power hardcast, through any of my G20s. Multiple lots of ammo.  I have sent barrels back to KKM and Lone Wolf to have the chambers "opened up for reliability" and made no difference.

Tonight I was shooting a Lone Wolf threaded and it was choking on Federal Trophy bonded 180gr JSP. Decided to try a box of Buffalo Bore 10mm 220gr "Tactical Low Recoil" which is about 200fps slower than their full power stuff. That ran 100%.

What about the factory barrels? 

Also, probably has a lot to do with the whole 220 grain thing when 200 is the norm.  Maybe the low recoil stuff had less powder volume and ran a shorter OAL? 
Could always cover a bullet in machinists dye and find out where it hits, or, measure the OAL and check it against saami specs, just to make sure. 

ETA- Double check they are not loaded for revolvers.

eta2- what weight recoil spring do you have? Heavier bullets might be slowing the slide velocity down, a quick good shows people upping to 22 and 24 pound recoil springs in glocks to help feed issues and is a good idea anyways for hot ammo

Maybe it is not the barrel but the recoil spring you are using.  Are you using an increased or decreased weight spring or just stock weight?

The stock barrel runs them fine. Running a 22lb recoil spring. Have tried stock spring weights also.

The bullet gets jammed at an angle on the side of the feed ramp

I could understand the LWD barrels they usually have tight chambers but the others ...... Leaves me scratching my head.

If the stock barrel runs them fine you have your answer! Just run the stock barrel and keep an eye out for excessive leading ( which in my decades of shooting cast in a factory barrel has never been a problem for me)

Can't run a suppressor on a stock barrel

and before anyone asks the aftermarket barrels jam without the suppressor... slightly more reliable with it

Maybe buy the oem 6" hunting barrel and have it threaded?

KKM has stated in the past that the 220s aren't seated deep enough for their chambers.

I just got done loading up 550 rounds of SNS 220gr hard cast

I ran into a problem because I was using mixed brass, and this particular batch had a higher quantity of >0.4020" bullets than the sample pack I bought from them.

The 220s are so long, that on brass with thick walls, they cause a bulge in the case at the base of the bullet that measured 0.4250". This is due to the tapering case wall thickness.

I ended up needing to run a Lee FCD down to the base of the case to basically swage the bullet down inside the case in order to get it to an OD of 0.4230" at the base of the bullet, which now allows them to chamber and spin.

Do the rounds fit into a case gage? What is the OD of the case at the base of the bullet?

All I can tell you is that for my 10mm G40, I decided (at least for now) to forego the aftermarket barrel ritual just to shoot "heavy & fast" hardcast loads.

I simply handload the heavies using SNS's coated 220gn HC boolits over either AA-7 or AA-9.  My loads with the AA powders get into the 1200fps range.  With  the coated hardcast boolits, there are no leading issues, and I've gotten 100% feed-reliability, great accuracy, and the barrel cleans up quick and spiffy.

That said, the two or three of boxes of BB's 210 HC 10mm ammo I ran through the factory tube of my G40 shot just fine, with no lead build-up. Wouldn't hesitate to load any one of my 10mm Glocks with those if I was facing a long duration in the backwoods or boonies.

I always use a 10mm LFC die when handloading the 200gn-and-above bullet-weights.  In fact, I used it when I loaded up about 300 of SNS's 220gn coated bullets, and there was not one jam, bobble, or hiccup at the range.

I've ran 220's before and still have some SNS 220's lying around, but to be honest if I want heavy I'm perfectly okay with a 200gr WFNGC.  I think you might get slightly better penetration out of the 220's but the wider meplat of the WFNGC 200's will not only still penetrate deep, but cut a bigger wound channel.

They're so expensive though.

If you don't find you need the GC, look at Blue Bullets' coated 200gr FN. About 1/3 the price of the WFNGC.

I use that in 40SW in my Limited gun, and have loaded them in 10mm, over 1200fps. Pretty fat meplat on them, compared to the 220gr SNS/Ibeji.