Benelli MP90S problems - help!

[Joddi]

I'm having problems with my Benelli MP90S .32 S&WL. 30-50% of the bullets are not stabilized and the bullet holes are not round at 25m. I've tried 4 different bullets and various loads + factory loaded ammo from Fiocchi and they're all the same. I've slugged the barrel and all measurements are fine .314" all way through. But looking inside the barrel with a bore scope it seems to me that the grooves are very shallow and the edges of the lands are not sharp but very smooth. Perhaps the previous owner used some harsh methods when cleaning the barrel.
Unless someone suggests something else I will order a new barrel.
Can anyone tell me how to remove the barrel? There are 2 screws through the bottom of the frame called "barrel grub screws" in the manual. The barrel does not come out when I remove these. Any help would be appreciated.
Best regards from Volcanic Iceland,
Joddi

[Rover]

Before spending any money on the gun, try shorter (non-HBWC) bullets and/or hotter loads. It sounds like the rifling twist is too slow (common).

If you decide on a new barrel, buy one with a smaller bore and faster twist (aftermarket, not factory).

This problem can also be caused by "breaking" the wrist on discharge. Keep a firm grip with good follow-through.

Do a search (hit Search above) and you'll find a lot of info on the subject.

[FredB]

Can anyone tell me how to remove the barrel? There are 2 screws through the bottom of the frame called "barrel grub screws" in the manual. The barrel does not come out when I remove these. Any help would be appreciated.
Best regards from Volcanic Iceland,
Joddi

From what I've heard from the US Benelli dealer, the Benelli barrel is a press fit, and is sometimes quite difficult to remove. He told me that their shop has developed a special press for the purpose. Even if you are able to remove and replace the barrel, you would still need to be very careful about headspacing on the refit. Perhaps a gunsmith is called for?

HTH,
FredB

[Rover]

I didn't know about the press fit.

What I have seen (in air rifles and S&Ws) is that such a thing causes a constriction at the start of the barrel. This must be removed by lapping or fire-lapping for optimum accuracy.

You will be able to tell if this is the case by forcing a slug down the bore from the muzzle. If it gets harder to push near the breech, you have a problem.

[jbshooter]

Take out the two screws under the barrel and then drift the barrel out with a plastic drift. It only needs a light hammer tap. There is not much to see once you have got it out. I'd only take it out if you were going to do something serious with it.

[Joddi]

Thank you very much for your input gentlemen. There is obviously some testing I want to do before ordering a new barrel. -Joddi