I have a few ideas for attachments for the KS-23,
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extended barrel and stock, the version of the KS-23 featured in insurgency sandstorm is the KS-23M, which was a shortened version that had a cut down barrel and a pistol grip instead of a stock.
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extended tube, there was a variant that had an extended tube with a capacity of 4+1 called the KS-23-2. A common criticism of the KS-23 is that it has a low ammo count of only 3+1, I believe this may be a slight amendment to this problem.
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Specialized ammo tubes, the KS-23 had a large variety of ammunition types, examples being the "Zvezda" flashbang and the "cheremukha-7" which was a tear gas round. Another idea for the KS-23 is improving the slugs, in real life the slugs were capable of knocking out a car's engine block up to 100 meters away, I believe adding this would add extra usefulness to the gun.
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4x PU scope, the KS-23 was capable of mounting a mosin PU scope via a dovetail mount. evidence of this is in this old soviet training footage linked here. https://www.youtube.com/watch?v=AN0FPqED2oM 5. The KS-23 fired a monstrously large round being the 23x75mm shell. To demonstrate the sheer power of this round I believe it would be nice to add a slight ragdoll effect with enemies killed with it.