I have owned quite few of both 700's and 721's, as well as 722's, 1917's, and even a 720 (and still do), so I think I know little about them. There is no difference whatsoever between the 700's and the 721's and the 722's, as far as strength. I don't know how they rate against a 1917 Enfield, which was also renowned for strength, all are very good. Little or no modification to a 700 bolt is required for it to fit the proper length 721 or 722, except for possibly fitting the bolt handle to the stock, and of course headspacing. Some people rate the 721's and 722's as being better made and fitted than the 700's, but that has not been my experience. I have to repeat my previous assertion, that for a custom rifle (NOT built for re-sale) a 721 or a 722 is entirely equal to a 700. My experience is that ignorant people will look at a custom built on a 721 or a 722 and turn their noses up at it, but I think that this is entirely based on appearance, not performance. Accuracy-wise, I have 721's, 722's and 700's, all custom, that shoot at or near the .250" mark, and would shoot better if my eyes would co-operate. I'm not as young as I used to be. Also, I have never experienced the dreaded "fire with the safety on" problem, and don't worry about it, but if it is an issue with you there are numerous replacement triggers on the market.