Engine Fit?

There has been a lot of Forum talk about the fit of the new Quest Q-Jet composite motors in BT-20 sized tubes. There has been occasional engine fit problems since I can remember.

The top picture shows a slip fit of an Estes 18mm engine in a regular BT-20 tube.

Here's the same engine in a Quest Viper model. The engine tube is a 20mm diameter with no yellow sleeve tube inside. I usually will do tape wraps for loose fit like this.

The previous Chinese made Quest 18mm engines wouldn't usually fit in an Estes 20mm tube. The stick-on label made the diameter too wide. I would typically peel off the label and the fit was fine. 

Sometimes Estes engines won't slide all the way into their own BT-20 tubes. Nozzle ends can have a bulge, from compression during  manufacture. You see this more often in 13mm Mini engines.

In the past I've lightly sanded down the wide end of the casing with a sanding block. Don't sand much, just enough to get the engine in without crimping the rocket body.

This probably could be looked on by some as altering or "tampering" with an engine. I've never had an engine failure when a layer or two of the paper casing was sanded down.