mount adapter ef eos-r can't mount 400mm lens

[lordaeron1]

need urgent help, 

just purchased Eos r + Ef adapter and 400MM F5.6 L lens.
Sadly I am unable to fit this lens inside this adapter i don't get it, what gives?
canon website shows that this lens is compatible with this adapter but it just can't fit.
if I turn it harder it moves a little bit even with a lot of force but not really moving at all, pushing it any harder will break it. so I wonder what is going on.

someone please help.

[normadel]

Does any other EF/EF-S lens work on the adapter? Is the 400 new or used? Where'd you get it from?

[lordaeron1]

Its second hand 400mm lens in Stellar shape. I tired it on the seller canon 200d body and it worked great. Went and purchased the adapter new from store on the way and used in store canon ef 24-105mm f/4 is usm. Worked great with the adapter on my eos r body. Got home now this happening. Any idea what is going on?

[shadowsports]

Greetings,

The 400 f5.6 was released in 1993.  Its 30yrs old.  After some brief research I see posts from people who say they are using the EF400 mm lens with an EF to RF adapter.  I cannot confirm or deny this.  I'm a little surprised though as I would not expect it to work (even adapted) on a R seried body.  Based on my searches it seems to be one of the few cases where a super old lens is working on an R series body.  Typically, the reasons why stuff like this doesn't work are...  It doesn't have the right optics, older type of lens coatings, AF motors are not fast enough and lenses this old do not support DPAF.  It could be any one or a combination of these.  

However, you've indicated that you can't even get the lens to mount on the adapter.  The EF side of the mount is identical to the flange on the front of a DSLR body.  You said it mounted on a 200D. It should mount on any DSLR, including the EF side of the adapter.

Since we aren't there to see what's happening, it's hard to do anything but speculate.  You simply line up the red dots and twist clockwise.

For the best possible experience, I would recommend the RF100-400.  If you need more reach, you can use a 1.4x TC as well.

While adapted lenses can work well, the best overall performance and experience will come from using an RF lens with your R series body.

[Waddizzle]

Was the seller an actual store?  My mount adapter was initially a little tight with some lenses.  Still is with most of them.

Try mounting the adapter on the camera?  The design intent seems to be for the user to mount it on the camera, not individual lenses.  This may provide more leverage for turning it to fit the mount.

[normadel]

In ANY case, don't force it. If you succeed in getting the lens on the adapter you may not be able to get it off!

[lordaeron1]

thanks, everybody the issues were sorted, all I needed was someone with a super strong hand to force this adapter on the lens. after a few tries and some strange noises, it got loose. the sad part is that it's a bit too loose for other lenses. guess I will use this one for this lens and for other lenses will get another adapter.

[shadowsports]

Greetings,

The word "force" and super strong hand sound like either the lens mount or your adapter was faulty.   

Now "too loose" sounds damaged or broken.  You shouldn't have to force a lens to mount, to an adapter or to a body.  I hope everything is OK with it.  

[lordaeron1]

Should have mwntioned that the strong guy was from canon Shop where i purchased the adapter in the first place. Needless to say, he said he wont replace it and my fault for gicinf him to try to do it.

[lordaeron1]

Giving"