Beretta 390 Shim Adjustment

Dear Technoid,

Through what must have been divine intervention, I recently stumbled across your web sight at about the same time as my old Remington 1100 (purchased used) gave up the ghost. After hearing you singing the praises of gas guns, particularly the AL390, I reconsidered my intention to run straight to the store and buy a Browning Gold or Citori right off the rack. The chrome bores and chambers, adjustable stock, and touted durability weighed heavily in my decision to go with the AL390.

I have since shot a couple of rounds of skeet and downed a few geese with the gun (first baby on the way assures that I will be a one-gun man for awhile longer — at least until that tax deduction kicks in).

I really like the 390, but am wondering how much I should tinker with the drop and cast spacer system. I want the gun to fit correctly right away, so that I don’t learn to “fit myself to the gun” over the long run like I did with my 1100. Forgive my ignorance, but maybe I could use a quick lesson in gun fit (especially drop and cast) in order to determine my need for stock adjustment. Also, some specific tips on adjusting the AL390 would be helpful, as the manual seems to be written for someone with more gunsmithing knowledge, or at least better tools, than I… which leads me to my last question, do I really need to have a qualified gunsmith do the adjustments as the manual advises, or is this just a disclaimer for Beretta?

Thanks for your help.


Dear Aaron,

The Beretta gas gun may not come with very good instructions, but they are a heck of a lot more detailed than the instructions your child is going to come with. Still, in both cases, I am sure that you will do just fine.

No, you don’t have to take your Beretta 390 to the gunsmith to make simple shim adjustments. You can definitely do that yourself. Just take a Phillips-head screw driver and unscrew the recoil pad. Then take a large screw driver or a socket head and remove the nut on the end of the magazine tube. Remove the washer (first carefully noticing which number is at the top rear), then remove the stock, then the plastic shim (also remembering which number is at the top rear- should be same as washer).

Now, by turning the plastic shim around and about this way and that, you can set it up so that you get the cast and height you want from that set. The manual should tell you. The number that is to the top and rear of the shim when it is in place is the one that governs the setup’s cast and height. When you reassemble the whole affair, just make sure that the steel washer has the same corresponding number at its top rear.

If you look VERY carefully, you will see that the plastic shim is thicker on one side than the other. Ditto the bottom vs the top. This will quickly show you which way the shim will influence the stock.

All in all, the maximum shim adjustment you can get isn’t all that much, but it will accommodate most people. With the set that comes with the gun, you can never get cast on for a lefty, but it will go either cast off for a righty or neutral. Other shim sets are available if you want more adjustment. Contact Cole Gunsmithing, Rt. 123, Harpswell, ME 04079, Tel: 207-833-5027, <>.

So how do you know when your gun fits your properly after all this adjusting? You know it fits your right when you can hit stuff with it. That’s really the bottom line. There really isn’t an set of measurements to give out before hand. Handsome is as handsome does. Some shooters are very hard to fit because they have the ability to adjust to almost any gun.

You might try setting the gun up so that when you mount it with your eyes close, and then open your eyes, you are looking right down the rib or just a tiny bit above it. You can also judge how well it fits by shooting a round or two of skeet with full choke. If you can center many of your birds, it fits. Pay particular attention to the equal hitting of right to left birds and of left to right birds. This will determine cast for you. If you hit low houses just as hard as high houses from station four, all is well.

Best wishes on the new shooter in your family.

Best regards,

Bruce Buck The Technoid writing for Shotgun Report, LLC

This entry was posted in Shotgun related, Shotguns and tagged , , . Bookmark the permalink.

1 Response to Beretta 390 Shim Adjustment

  1. Jerry says:

    Be aware Beretta has quite a few shims and stock drop plates out there that are either manufactured wrong or marked wrong. I have a 1992 390 that came with an incorrectly marked stock plate, one side was backwards and recently ordered shims and stock plates from Brownells and one set was marked 40/45 but was actually a 55/60.


Leave a Comment

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.