I am trying to install replacement Siglight 4045 sights on a P229. Old sights came off without incident, and the new front sight was installed without any problem.
The new rear sight is extremely tight, and I could only get it on approximately 75% of the way towards the center.

I am using a Sig sight adjustment tool.

Any help on getting this sight on would be appreciated.

You are pushing the sight off from right to left and back on from left to right looking through the sights as you would use them while shooting.

You might push it back off and file on the sight a little to clean the burrs up and take off any anodizing/paint etc then oil the sight and dove tail up ant try again..

File on the sight only and not the slide.

If its still to tight the work a little more on the sight/re-lube and try again until it goes freely.