My Browning M-71 Carbine is a nice little rifle. The main reason you'd go to the Ackley Improved version is to reduce brass stretching, but a bit more power is available.

Here's the difference. The photo is of a slightly different modification, but the overall dimensions are the same. Left to right: .348 Winchester factory case; .348 Winchester necked up to .358" dia; .35-.348 Winchester Ackley Improved.

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Be aware that Hutton loaded the Lever Power series fairly hot, and the powders are not what they were then. Always reduce loads and work up carefully. Also, rimmed cases don't show excessive pressure as obviously as rimless. Rebarreled and necked up to .35 caliber allows a wider range of bullets from more manufacturers. Notice how the neck shortened when form fired, common to Ackley Improved cartridges.