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Heres a vid as an FYI and u can make your own judgement. Keep in mind the Glock does not lock up at the muzzle so the small gap is of no concern. A conversion barrel is ideal but not a must if u are budget limited. I have been doing this since the 90's in 22/17 as well as 23/19. It only works if you are going down from 40 to 9 and not the reverse because of barrel diameter. I wouldnt recc this if you are using for competitive scoring, but for sh*&s & giggles, its just dandy.
dB https://www.youtube.com/watch?v=ttRjBOL6emw and another one, less detailed https://www.youtube.com/watch?v=aSiXT4I8ZT8