A sear is, basically, a piece of metal.  It&#x27;s part of the trigger assembly.  Speaking simplistically, it is the thing that gives the trigger pressure -- it holds back the striking mechanism until your trigger pull releases it.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sear_(firearm)" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sear_(firearm)</a><p>This is an animation of a semi-automatic sear (in which the sear is the green part):
<a href="http:&#x2F;&#x2F;mcb-homis.com&#x2F;blog&#x2F;trigger-animation.gif" rel="nofollow">http:&#x2F;&#x2F;mcb-homis.com&#x2F;blog&#x2F;trigger-animation.gif</a><p>This is an animation of a fully automatic sear (in which the sear is blue):
<a href="http:&#x2F;&#x2F;mcb-homis.com&#x2F;blog&#x2F;m16animation1ww1.gif" rel="nofollow">http:&#x2F;&#x2F;mcb-homis.com&#x2F;blog&#x2F;m16animation1ww1.gif</a><p>Taking out a semi-automatic sear and replacing it with a fully automatic sear is trivial.  Converting a semi-automatic sear is slightly more difficult, as it requires precision, and a supplementary catch (to keep the firearm from always firing always).<p>If people aren&#x27;t committing crimes with fully automatic firearms, it isn&#x27;t because the process of obtaining fully automatic firearms is difficult, because it isn&#x27;t.  You can get butt stocks that replicate fully automatic fire for less than $50.  Fully automatic fire is just silly to use.  If you miss with the first shot, you&#x27;re almost certainly going to miss with subsequent shots, so for anything requiring accuracy (which is almost everything you would do with a firearm short of perhaps intimidation), converting to full auto makes it less effective.