Canon 300mm ll lens with and without T.C.

I thought I would post this so another might save themselves the hassle. I have the new 300 ll lens and use it with the old 1.4 ll. T.C. With a 7D.
When it gets dark this lens and T.C. is a nightmare on a 7D. It is pretty much hit and miss 10, hit and miss 10. Very frustrating. Really much worse than the old 300mm f.2.8 l. IMO anyway. Just a very poor lens for birding compared to the old 500mm IS lens and the new 500 ll lens. Really the threads and talk about this lens being used for birding is a joke period. For serious birders. When it hits it is great, but 9 out of 10 shots it misses. BACK TO CANON.... what a mess.
In really good light it still gets confused? My 500 hits almost all with and without a T.C.?
Does it play better with other cameras? I don't know and don't care. I want the 1.6 crop and Canon sells it so why does it not work? The new 500 ll works fine.
I am at a loss here? A lot of money to pay for a lens that will not AF properly.

If interested in a few shot with the 500 ll and 300 ll I have them here.

www.flickr.com/photos/​avianphotos

Now go and try it with the NEW improved mk3 1.4 and 2x extenders. Tried on both the 7D and the 1Dmk4 with no problems at all.

As for the 1.6 crop 'effect' that is an old argument that we wont go into (and for the record - the AF is slower on the 7D - my wife hates it and is saving for the 5D iii)

.DAVID.

Something must be wrong with the lens or TC. I have the older 300mm f2.8 IS I and like it very much but I never used it for birds. I prefered my 500mm f4 IS I.

I have heard very good things about the newer II model. I would definitely do some more tests. Maybe you can try different camera, TC.

I used to have the 300f2.8 I and used it with 1.4x II, 2x ii, and 2x III with a t3i, 5D3, and 1DX. In my experience, no AF problem with any camera and the 1.4x II. It's of course significantly slower with the 2x II and 2 x III. Recently I bought a 500f4 II and yes for birding it is no comparison. The 500f4 II is a different class of lens! I loaned the 300 to my brother who shot it with 1.4x II and a 7D. We were at Conowingo dam last December and him shooting with a 7D, 300, 1.4x II while I with a 1DX, 500F4, anspd 1.4x II. It was a partially sunny day turned to 100 percent cloudy. Both of us had decent shootings and no complaint from him with the 7D. So, could be your copy had a problem?

I have both lenses (mkII) but the mkIII TC's and 1Dx 5D mk3
They all work exceptionally well. Couple of things to consider and I am by no means an expert.
Could the "miss" rate on the 300 be from a MF adjustment being out of whack?
You also have a much shallower DOF with the 300 wide open. Are you on a tripod? Using IS?
Just thoughts. I did have to adjust the 500 with the 2x TC on the 1Dx. It was about 4-5" out. Which at 1000mm doesn't seem like much but when birding is huge.
As it is different for every combo, my 5D mk3 with the same combo was fine.
I'd look there first. Every lens/body combo is different. I haven't had a chance to do the MF adjust on the 300 but since I've been shooting aircraft I have a little bigger target!