It breaks my heart to part with this lens! I don't need to tell everyone how good it is. However whilst I am keeping my beloved K3 for everything else I am trying to do more action wildlife stuff and have succumbed to Nikon for this aspect due to its better AF system for this and so am not using this lens enough.
It is in superb optical and mechanical condition with everything working smoothly and perfectly. It has been well looked after and protected for the most part by a neoprene cover although I have now lost a couple of bits of this. It does have the paint rubbed off on the knurled knob on the tripod mount ring and the bottom of the foot does also have worn away paint from use. There are one or two other very small marks of paint removed. Also I have lost the original lens cap in the last couple of weeks although it has continued to be protected with the same style pinch cap without the Pentax logo on the front. Comes with original soft case and possibly the box as well.
The asking price is £525 including what will probably be expensive P&P !
I will post some images tomorrow but it will only be on here for a day as will be using Ebay as I have an offer which ends tomorrow evening.
Dave

I thought I read somewhere that, for example you could change , say, a 150-500mm from Nikon to Pentax as that mount was made for that lens. But not a 150-600mm (new) Nikon to a Pentax mount because that lens has never been made in a Pentax mount. I could be wrong but that was my understanding.

Mine works great with the DA*300 and the 100mm macro with virtually no IQ loss.

My Shazam says it's "Jump Start" by Moonlight Bride or vica versa !

Well unless there is a quantum leap in AF speed I won't ever change from my K3. After lots of concerns about AF speed I bought myself a Nikon D7200 primarily so I could get the brilliant Sigma 150-600mm and it is in a different league AF wise. But in almost all other respects it I prefer the K3 which feels like a level higher towards a pro camera.

Depends what is considered important to the user. AF speed, accuracy and tracking are very important to Sports and Wildlife photographers for example. The bigger issue is that it is clear that they can't do anything about the main generic criticism of Pentax cameras that has been going on for years.
Shame because in all other aspects they seem to consistently beat anything in the same price range.

Oh dear. I was hoping it would be quite good by Pentax standards.

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Yes I had/have them both as well. The Tamron was good at macro I must say but I will change my "streets ahead" to a more useful "noticably sharper" at 300mm.
Neil is right of course about budget but if you only have a low amount of money you are a bit limited. I don't want to demean Gedski's pics but I am sure I had much better BIF with the 55-300mm. I will look back and see if I can post some examples.

............... and I've just seen the "real world sample gallery" on DPreview. I normally disparage these because I have seen poor images from known excellent and expensive cameras on there before. But have a look anyway - they are simply stunning !! Some of the ISO 4-6000 are particularly impressive. Many taken with 18-135mm lens. Maybe it was just a very good photographer but they look good to me!
Dave