A gun at 95% and only 300 shells thru it ...are not consistent ...and it makes me wonder a lot about what you're being told.
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300 shells for many of us ...is one week's usage / maybe 2 weeks ...
and dents and scratches ...( while things happen) .../ I have guns that had thousands of shells thru them before they got their first scratch...
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Whether it has a Browning box or not / to me is irrelevent. If we save the boxes ( and I don't ) mostly because if you own a dozen or more shotguns - the boxes are too bulky to keep unless you stick them up in the rafters of a garage or somewhere out of the way - and unless I want to give the gun as a gift down the road .... I've never had a need for a box. I don't buy guns with the intent to resell them down the road ....so having a box or not to me ...is just no issue.
If I were going to sell a gun ...and the buyer insisted on a box or discounting the price / I might raise the price just because the buyer was irritating me - and making up petty issues to pay less. You're buying the gun - not the box ...so whether its there is irrelevent to me.
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The OEM Browning finish is difficult to match. Steaming a dent out of a stock can be done - with damp towels and a steam iron ( and patience ) ...but in almost all cases, its still visible in some kinds of light unless you're willing to sand it a little. If you touch the stock with sand paper ....now you've created a monster. Once you rough up, or scratch, or marr that varnish on the stock ...about the only thing you can do is strip it off ...and refinish the whole gun ( and if you get into the color in the wood / its way tougher).
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Or, if you buy it ...living with the dents and marrs on the finish - is probably what you should do..../ and I don't blame you for questioning it ...if every time you pick up the gun - those dents and marrs bother you - then don't buy it !!