Oh where were you when I did a review of the Dragon Me-262 A-1a/U-4? Master Models has released a four part set to replace the large 5cm canon which was added to the Me-262 U-4 and also was part of the Me410 in one variant.
The set consists of a turned aluminum barrel, a turned aluminum barrel head and two brass parts. The brass parts are the end of the barrel which has a perforated tip and a cap. You place the cap on the end and add the parts together and drill a hole in the kit part and you're done. Couldn't be simpler.
The holes drilled in the business end of the barrel are a work or art. I included several pictures and borrowed one from the Master Models site to show size.
In summary, this has superb detail, a very reasonable price, will make sure you don't have sanding and fit issues with the kit parts and is easy. Most highly recommended. My thanks to Piotr and Iwona Czerkasow of Master Model, and IPMS/USA fo this review sample.