The M-6 is an interesting approch to the multi-purpose survival firearm. The advantages of having both a rifle and a shotgun are pretty obvious.
That being said, the M-6 has several serious limitations:
.410 bore shotshells are only effective at close range since they carry a lighter shot load than, say, a 20 gauge. The small bore also tends to extend the shot string
Slug loads for the .410 are not effective on deer size game because of low power and relatively low weight. Many juristictions which permit slugs for hunting whitetail deer do not allow the .410 for that reason.
The .22 Hornet is needlessly powerful for small game such as squirrel and rabbit. Use solid cartridges to minamize meat destruction. On the other hand, the Hornet's pretty light for hunting deer size game.
As mentioned previously, the trigger pull (squeeze?) is rough, heavy and has a unconventional feel, although I must admit I like the concept of firing with heavy mittens.
For a better, though larger, combination gun look at the Savage 24s, particularly some of the older models with the 20 gauge shotgun barrel.

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