Crosman/Mendoza RM 422 rifling

[happymecanic]

While giving my airguns their periodic/mid-winter check, I just noticed the particular rifling in the barrel of my Croman/Mendoza RM 422 rifle. I don't know the twist rate, but there are 24 lands and grooves. The rifle is very accurate and consistent - 3/8'' to 1/2'' groups @ 100 feet with CPUM pellets, this barrel is excellent. I'm just curious to know if this style of rifling is common in Mendoza-made rifles, asking y'all that have one?

[Hoosier Daddy]

I am going to chime in with my LIMITED knowledge of Mendoza's.
 While researching info on them, I read they only rifled the first 2/3's of their barrels and over bored the final 3rd.
I thought this was odd and did not understand the reasoning, surely it can't be a cost savings.... I mean the tooling is already in place.
 But when I ran a cleaning patch down my RM-600, it had a definite let off of resistance about 2/3'd the way from breech to muzzle.
Placing a mark on the rod where this "let off", I then laid it along side the barrel and there is a slight change in the blueing right where this happens. 
  I just now dug it out and with a bright LED flash light, looked down the muzzle and see no rifling, BUT mine does have a muzzle weight/ brake and I can not see an actual crown.
 At the breech end the rifling looks exactly like yours shown.
Hope that helps.

[Hoosier Daddy]

FYI: Septicdeath and lefteyeshot are much more knowledgeable on them than I am.