Friend, the US M-1917 rifle has ENFIELD rifling: 5 grooves, lands and grooves of equal width, deep grooves.

A friend and myself experimented with near a dozen of them over the years and we found that they ALL responded best to flat-based bullets.

That can be a good thing, flatbase bullets generally being less expensive than boat-tails.

Following the Springfield 1903 disaster (a million near-new rifles declared only marginally safe at best, by their own top experts), the US gave serious consideration to standardising on the M-1917 rifle, of which they had more than 2million in stock. They gave up on this idea because they also wanted to adopt the M-1 cartridge, which used a 173-grain boat-tailed bullet. The new bullet stabilised fine in the Springfields with their Mauser-type rifling and gave vastly better performance. The performance, however, did not improve to nearly as great an extent in the 1917 rifle. The upshot of it all was that the 1917 rifles remained in storage, many were sold off, and new Springfields were made with the new double-heat-treated receivers.

So give flatbase bullets a good try. You just might be surprised.

Hope this helps.
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