If I was not traveling, I'd attach a picture of my 10.4 inch barrel, 9 inch rail with integrated sight, and a SureFire Mini attached free and clear. Depending on how much free barrel space the suppressor takes up by design, a suppressor CAN fit on a 10.4 inch barrel with a 9 inch rail. (The 9 inch rail is essential identical in length to a short Geissele rail, though it will fit over the sling attachment points without the need for their removal). As noted in the pics posted above by JNAP94 (albeit on a 14.5 inch barrel) the gas block will mostly be covered by the A5 9 inch rail but the entire barrel/muzzle device is not covered.

The 9 inch rail (With three full slots and a half down its length) will fit on a 10.4 inch barrel. (HK also has HKmod rails but they are not yet widely available.) The 9 inch and 11 inch quad rails come with or without integrated sights. For the HK416A5 there is a 9 inch quad rail, an 11 inch quad rail, and an even longer quad rail that will only fit 16.5 and 20 inch barrels.

9 inch or 10 inch quad rail