I have been shooting Rem 700's in 7 Mag since 1978. I would not have the throat lengthened, just seat the bullet out since 700's have very long magazines.
Pressure spikes in 7 mags are as common as trolls that live under bridges. Between dad, brothers, cousins, and friends, we have 20+ Remington 700's with a couple of Savages thrown in. We all shoot bullet weights of 150g and under with the exception of one guy that shoots 160g Sierra's and another that shoots the 162g SST. These pressure spikes must occur with heavy bullets or with certain powders because none of us have seen any issues.
I have a number of 700's in 7 Mag currently and not one of them shoots over an inch and most under 5/8" with 120g Tripple shocks and 140g Tripple shocks, 140 & 150g Nosler Ballistic tips and Accubonds, and the fantastic 154g Hornady SP.
Recently, I set up one rifle for a 162g SST at 3100 fps with Retumbo and another that is set up for a 154g SST with H4350 at 3150.
In every rifle I have, I seat the bullet touching the lands with the exception of the tripple shocks which I seat .040-.060 off the lands.
