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Posted: 1/25/2009 4:05:50 PM EDT
My father in law is planning a build using a DPMS stripped lower and a Stag kit. He wants to use a 20" barrel for accuracy at longer distances but the latest kit he found comes with a 16" barrel. What parts besides the barrel will need to be changed if he starts with a 16" and buys a separate 20"?
Link Posted: 1/25/2009 4:27:41 PM EDT
[#1]
At a minimum, a new rifle-length gas tube & handguards.  The gas tube should come with a new roll pin; if not, re-use the old one.  I'm assuming the new barrel comes with a Front Sight Base & handguard cap in place.  If you are re-using flash suppressors (from one barrel to the other), then you will need a new crush washer as well.  It's simpler than it sounds.
Link Posted: 1/25/2009 4:31:20 PM EDT
[#2]
Quoted:

My father in law is planning a build using a DPMS stripped lower and a Stag kit. He wants to use a 20" barrel for accuracy at longer distances but the latest kit he found comes with a 16" barrel. What parts besides the barrel will need to be changed if he starts with a 16" and buys a separate 20"?


First,

Define "longer distances" ...



Link Posted: 1/25/2009 4:52:44 PM EDT
[#3]
He figured the 16" would be good out to around 300yds but the 20" would be better for 400 - 600 yds.
Link Posted: 1/25/2009 5:13:06 PM EDT
[#4]
He's about right from my, albeit limited, experience.
Link Posted: 1/25/2009 5:20:03 PM EDT
[#5]
Quoted:
He figured the 16" would be good out to around 300yds but the 20" would be better for 400 - 600 yds.


For 168gr Match Ammo, 20 mph crosswinds, out of a 16" barrel you are looking at the following:
- 400 yards: 40" elevation drop, 33" windage, 1720 fps
- 600 yards: 121" elevation drop, 83" windage, 1420 fps


For same ammo as above out of a 20" barrel:
- 400 yards: 35" drop, 31" windage, 1800 fps
- 600 yards: 110" drop, 78" widnage, 1490 fps


Not really a big difference.  For the most part I only go 20" for looks, and ofcouse every single fps counts when you are shooting distance, don't count for much but counts none the less.
Link Posted: 1/25/2009 7:41:01 PM EDT
[#6]
Quoted:

Quoted:

He figured the 16" would be good out to around 300yds but the 20" would be better for 400 - 600 yds.


For 168gr Match Ammo, 20 mph crosswinds, out of a 16" barrel you are looking at the following:

- 400 yards: 40" elevation drop, 33" windage, 1720 fps
- 600 yards: 121" elevation drop, 83" windage, 1420 fps


For same ammo as above out of a 20" barrel:

- 400 yards: 35" drop, 31" windage, 1800 fps
- 600 yards: 110" drop, 78" widnage, 1490 fps


Not really a big difference.  For the most part I only go 20" for looks, and ofcouse every single fps counts when you are shooting distance, don't count for much but counts none the less.


.308  

Is this not a 5.56 build ?
Link Posted: 1/25/2009 11:55:02 PM EDT
[#7]
Sorry about that. It is 5.56
Link Posted: 1/27/2009 8:58:46 AM EDT
[#8]
Quoted:

He figured the 16" would be good out to around 300yds but the 20" would be better for 400 - 600 yds.


IMHO, a 16" bbl. is GTG out to 400m.

However, if he's wanting to spend some time shooting out to 600 then I'd say go with the 20" for sure.

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