Home Forums Hunting & Shooting Competitive Shooting To shorten, or not to shorten. That is the question…

This pic grabbed off the Interweb show a typical set up for precision indicated crowning. In a precision lathe fixture like this, the bore of the muzzle end is precisely indicated to have as little runout as possible. This is done using a snug fitting pin generally referred to as a 'Deltronic pin'. These pins are precision ground in .0001 increments. Once indicated with as little run out as possible, good ones will be .0001-.0002 of T.I.R. (Total Indicated Runout). The crown is then cut perfectly perpendicular to the bore.

Crowns done in this manner will allow for equal pressure from the expanding gas on the circumference of the back end of the bullet as it leaves the muzzle. The bullet will leave the muzzle 'cleaner' and with less yaw, giving better on target accuracy.

Whether or not you'll actually see this type of improvement on the target depends on a lot of factors. Primarily, it's the bore of the barrel itself at the muzzle that's the big determiner. That's why many accuracy 'smiths prefer a barrel with a bit of gain-twist and a .0001-.0002 tighter bore at the last 2 inches before where they will put the crown, if possible.

For what it's worth...... -Al