Azle, TX  forecast
Click for Azle, TX Forecast
Click here other forecasts!

Got News?
Send it In!!
Computing
Cables
Home Theater
The "Theater"
Adire Audio Speakers
Toshiba 65H80 RPTV
HT Flexi-Rack
Media Cabinet
Feedback
Privacy Policy
About the Author
Contact Me via EMAIL
via Snail Mail
MONTAC Enterprises
ATTN: MTB Madness
Pending New...
Azle, TX 76020

 

 

Bullet Jump: Does less mean more! (page 2)

Article Index:
Introduction:

Setting precise bullet-jump to achieve accuracy gains is a common practice in rifle circles, but is much less common (non-existent?) in pistol shooting. Essentially, one reduces the distance the projectile must travel before engaging the lands in an attempt to avoid longitudinal misalignment of the projectile with the main bore.

A projectile whose long axis is perfectly parallel with the main bore axis will exit the barrel with an "ideal" spin about its long axis, less/no "wobble", and will generally travel to the target more accurately than one with a less than perfect bore alignment. A side benefit of eliminating the "wobble" is that the frontal area presented by the bullet is reduced, which will decrease in-flight drag and increase velocity at a given powder charge. The concept is similar to throwing a perfect spiral with a football. This is a highly simplified explanation of the subject, but sufficient for purposes of this article.

Bullet-jump reduction comes in basically three flavors: 1) adjusting bullet seating depth to place the projectile closer to the lands, 2) reducing the free-bore (lead) in the barrel design, and 3) a combination of 1 and 2 above.

My analysis of the stock Glock stock barrel and a KKM Model G22D1 "Match Grade Barrel" showed that it is impossible to reduce bullet-jump sufficiently by adjusting seating depth alone.

In the picture above, the round in the middle depicts a "typical" 40 S&W round with a cartridge OAL of 1.126". The round on the right illustrates how far the bullet seating depth must be reduced to achieve a zero bullet-jump in either the stock Glock or KKM G22D1 barrels. Obviously, a 1.301" long round isn't going to fit in the magazine. This is due to an overly generous free-bore specification in both barrel designs. It is my contention that a bullet-jump of 0.175" is excessive, increasing the probability of projectile misalignment to an unacceptable level.

The round on the left? Read on and I'll tell you about it...

And then?

 

 

Copyright (C)2003 MONTAC Enterprises.  All Rights Reserved©
Revised: March 03, 2006 .