Options for detachable magazines
Rules for detachable magazines
Configuring a semiautomatic rifle to have no prohibited features allows a marksman to use fully detachable magazines of any capacity. If a semiautomatic centerfire rifle does not have any of the prohibited features it can accept normal detachable magazines. An important note of caution is that it is easy to overlook a flash hider when assembling a featureless rifle. Make sure that you either have no muzzle device or a muzzle brake on a featureless rifle. It is also common to see featureless rifles with what appear to be adjustable or telescoping stocks. These must be pinned or otherwise fixed in place so that they cannot adjust.
If a person legally possess large-capacity magazines, there are no restrictions on using those magazines with a featureless semiautomatic rifle.
The Monsterman Grip is a pistol grip alternative that allows AR or AK style rifles to be used with detachable magazines. The Monsterman Grip is not a pistol grip as it is defined in the California Code of Regulations. The CCR defines a pistol grip as "pistol grip that protrudes conspicuously beneath the action of the weapon” means a grip that allows for a pistol style grasp in which the web of the trigger hand (between the thumb and index finger) can be placed below the top of the exposed portion of the trigger while firing (CCR 5469 (d)). Monsterman Grip on an Off-List AR-15
Kydex Grip Wrap
The Solar Tactical Kydex Grip Wrap is a Kydex plastic wrap that is molded and fastened over an existing pistol grip. It has a large fin protruding from the rear such that the thumb of the shooting hand cannot extend behind the grip. This prevents the user from holding the grip with a pistol style grasp. The wrap is available for a wide variety of centerfire rifle styles and makes.
The California Rifles U-15 Stock is a pistol grip and stock alternative. It is not a pistol grip as it doesn't meet the definition of pistol grip from the CCR. Further it is not a "thumbhole stock" which is defined in CCR 5469 (e) as "thumbhole stock" means a stock with a hole that allows the thumb of the trigger hand to penetrate into or through the stock while firing." There is actually no hole in the U-15 Stock which allows a thumb to penetrate into or through it. U-15-equipped Off-List AR-15
In June of 2008 the Department of Justice convinced a Solano County District Attorney to charge John Contos of Sonoma Firearms with offering to sell a prohibited Assault Weapon based on the theory that the U-15 was a thumbhole stock. The Calguns Foundation successfully defended Mr. Contos in People v. Contos which was dismissed by The People in December of 2008 when the District Attorney came to the conclusion that he could not meet his burden of proof to show that a U-15 was a thumbhole stock as defined in the CCR.
The Exile Machine Hammerhead is a rifle stock adapter which bridges the AR-15 receiver's pistol grip mount to the user's choice of buttstock. The Hammerhead can be used either with a pistol buffer tube (receiver extension tube), or it can be used as a simple pistol grip replacement with the buttstock mounted to the lower receiver. The Hammerhead is not a pistol grip, as it is not possible to get the web (between thumb and forefinger) of the shooting hand below the top of the exposed portion of the trigger while firing. Photo of a typical Hammerhead-equipped Off-List AR-15 A grip-only modification can be made without affecting legality by sawing off the threaded tail section.
Some owners chose to keep and fire their AK style rifles without a pistol grip or other prohibited features. A different version of the same concept is the Russian American Arms (RAA) Saiga which is an unlisted sporterized AK style rifle. Note that it's earlier incarnation as a "Kalashnikov USA Hunter Rifle/Saiga" is a listed/named Assault Weapon while the RAA Saiga is not.
There are also purpose fit Monsterman Grips and adapters to fit the AR style Monsterman Grip to AK style rifles. http://www.monstermangrip.com/images/albums/NewAlbum_1de38/mmgakbtypc02.jpg