At least it sounds as if you didn't drop any bits (as I, er, may have done in the past).

I'm afraid I haven't disassembled a Sigma lens either, but have found that the mechanism used to link the "A" button/setting with its associated contact on the mount uses a second ball-bearing on some lenses. If the aperture ring still clicks between f-stops, it may be this one that has fallen out on yours.

You have a PM

I have a Samyang branded copy of this lens and have been very happy with the results when I get the focus right. However, as other people have mentioned, manual focussing at f/1.4 is not easy and my ratio of in focus to out of focus shots is not as good as my other MF lenses.

I also have a Takumar 85/1.9 and in practice find it much easier to focus accurately for portraiture than the Samyang. I think that this is because the focus throw on the Samyang is longer and not as light and silky smooth as the Takumar.

The build quality is really good and for static subjects the Samyang works really well, but for subjects that move or hand held work, I've found that it is not the easiest lens to get good shots with.

I'm in a similar position - I have an 80-320 but have been looking out for a 55-300 for some time. The reviews for the 80-320 on the 'other site' are mixed, but some seem to rate it quite highly and I haven't got any complaints for the price.

The 55-300 seems very higly regarded and sounds like a better lens, but for my occaional usage, I'm not sure the difference is worth 2-3x the price of the 80-320.

You have a PM

Keep the 1.4, sell the M50 2.0 and M50 1.7 and you should have enough to buy an A50 1.7.

That way you can have the best of both worlds, F1.4 if you need/want it and, as Algi says, the A50 1.7 is a cracking lens.

Fair enough (always worth asking though!). The 105/2.5 is highly regarded - hope you get on well with it.

Make sure you have it adequately insured - I've sent a total of two items to Spain using Royal Mail small packets and lost one of them.

I now prefer to use Royal Mail Airsure where possible. A quick look on the post office web site suggests that it is available in Spain, so may be worth a look if what your posting is of significant value.

Bump - price reduced to £250.

I'd be interested in the 105 if you decide to sell it (or alternatively I have some spare adaptall mounts and a range of other kit if you'd like to do some kind of swap)