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The Range
NFA & Class III Discussion
10.5” 5.56 SBR Ammo Recommendations
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<blockquote data-quote="JEVapa" data-source="post: 3681926" data-attributes="member: 41176"><p>Sorry bro, but you might want to go back and check this info. You lose or gain about 25fps per inch of barrel. A reduction of 5.5" is only about 137.5 ish fps reduction in velocity.</p><p>For your "heavy bullet" comment I'll use MK262 with it's 77gr SMK traveling at the advertised 2750fps from an 18" barrel as an example.</p><p></p><p>18" - 10.5" = 7.5" reduction in bbl length</p><p>7.5" x 25fps = 187.5fps reduction in velocity</p><p>2750fps - 187.5fps = 2562.5fps</p><p>MK262 out of a 10.5" SBR is traveling at around 2562.5fps using the advertised base velocity for MK262. It'll vary but put a chrono on it to see the actual. It certainly isn't going to be moving less or barely over than 2000fps out of a 10.5".</p><p></p><p>M193 55g is moving at 3250fps so out of the 10.5", it's leaving at approximately 3062.5fps or less because the advertised velocity is probably for a 20" barrel.</p><p></p><p>BTW, as long as you're running a tight twist, like 1-7 or less, >70gr projos work just dandy. 77gr from a MK18 or M4 is very accurate well past 500m.</p></blockquote><p></p>
[QUOTE="JEVapa, post: 3681926, member: 41176"] Sorry bro, but you might want to go back and check this info. You lose or gain about 25fps per inch of barrel. A reduction of 5.5" is only about 137.5 ish fps reduction in velocity. For your "heavy bullet" comment I'll use MK262 with it's 77gr SMK traveling at the advertised 2750fps from an 18" barrel as an example. 18" - 10.5" = 7.5" reduction in bbl length 7.5" x 25fps = 187.5fps reduction in velocity 2750fps - 187.5fps = 2562.5fps MK262 out of a 10.5" SBR is traveling at around 2562.5fps using the advertised base velocity for MK262. It'll vary but put a chrono on it to see the actual. It certainly isn't going to be moving less or barely over than 2000fps out of a 10.5". M193 55g is moving at 3250fps so out of the 10.5", it's leaving at approximately 3062.5fps or less because the advertised velocity is probably for a 20" barrel. BTW, as long as you're running a tight twist, like 1-7 or less, >70gr projos work just dandy. 77gr from a MK18 or M4 is very accurate well past 500m. [/QUOTE]
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10.5” 5.56 SBR Ammo Recommendations
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