My bad, I saw Pachmayr and thought grips, didn't know they even made mags for the SIG 226. I know they used to for the 1911 but that was it. If thats's the case I'd return them or exchange. I'd stick with factory or MecGar which is suppose to OEM the mags for SIG.
If you can't return them then I'd do the dremmeling or contact Pachmayr and see what they say.