i got no response at the shotgunning page so i thought i would put it hear, if its ok. i will be using a shotgun a few times this year and i bought some Hornady 12 ga 2 3/4" sst slugs and on the box it says for weapons proofed by 1370 bar and then under that it says max 1050 bar. what does this mean i have never seen this before.

Possibly you should contact Hornady and ask them?

1050 bar is about 15,400 psi. What is the pressure generated by a normal slug load?

With rifle cartridges there is the SAAMI or CIP pressure rating in CUP or PSI. This is the MAX pressure for the particular cartridge. The proof pressure is higher by some factor.

Sounds like this is a higher pressure than the normal 12 ga. and thus only suitable for guns capable of handling (proofed) the higher pressure.

From SAAMI.org web page:
SAAMI Rifled Slugs Pressure Specifications
Maximum Average Pressure (MAP) in PSI
12 gauge 2-3/4in. 1 oz. 11,500 psi

according to hornady its there on the boxes for the European market they legally have to put it on there shotgun ammo boxes.

If the gun will handle high base shotgun shells you should be fine with the slugs..The loading companies would not put out a dangerous load on the market as they are overly carefull due to frivolous law suits IMO..

you are correct they told me the same thing , its just a lawyer thing for the European market.