I worked up to 50 grains of H 4350 using the Hornady 139 which is the load a lot on this board use with 140s and the 7x57. Anyway, I'm average about 3050fps from my 21 inch tube. That seems about 100 fps more than anyone on this board reports using the same load.
The primers and brass looks fine and the bolt lifts easily. Likewise the load is consistent, the extreme velocity spread in the last 3 shot group I shot the other day was 6 fps.
Opinions?
........................If your bolt lifts, brass and primers are all ok, I wouldn`t worry at all. In fact, take that extra velocity as a gift especially from a 21" barreled handier rifle. You have some excellent long range punch without extra overall rifle length......My kinda rifle!
Each rifle has its own personality so to speak; faster bores, slower bores, different pressure capabilities and so on. So what can be done in your rifle, may not be able to be done without pressure signs in another identical 7x57 rifle using that same identical load of H4350 and COAL.
Not that you need any more than 3050 fps from a 139 grainer, but for curiosity`s sake, try going up another 1/2 grain at a time until you do see some pressure signs and then back off a 1/2 grain and consider that load as max for your rifle.
Compared to your H4350 velocity, accuracy and E/spread results, I don`t necessarily know how RL17 would do in a 7x57 as I don`t own a 7x57. But if it could work in your rifle like it did for my 16.5" tubed 300 WSM compact carbine, (175 gr "hunting" Berger VLD chrony`d @ 2983 fps with no pressure signs), you`ll have another winner there too.
It`s called,,,,,,,increasing your barrel length,,,,,"without",,,,,increasing your barrel length!!!!
Whooo-hoooo!!!