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Posted: 10/12/2003 10:18:06 AM EDT
I am quoting myself from something else but I was curiosu to see what other peopel results have been (if they recorded them) with the different barrel lengths.


Since the factory 16" bbls appear to be identical in accuracy out to 500m so far as their 20" factory brothers - my interpolation is that the Diemaco made 1:7 Midlength could/should be a sub-moa factory barrel (based on my shooting a countless number of other D bbl's in both 14.5" C8 and 20" C7).
Thus out to our 300m 'max' point tgt range (book value) there would be no decrease in accuracy.

For point two - no decrease in effectiveness, one either buys in to the Col Fackler M.D., 5.56mm data or not - and the corresponding Gel Test protocols.
If one does (as I do) the 2500fps impact velocity is the key for the C77/SS109 projectile for it to yaw then fragment and 2700fps the preferred.
C77 has a MV of 3150fps out of the C7A1, and it drop below 2700 fps around 130m, and 2500fps @ 185m.

From the 14.5" C8 it has a MV of 2925 fps, dropping below 2500fps @ 130m and 2700fps @ 60m.

With the 16" it drops below 2700fps @ 90m and 2500fps @ 160m

This data was assembled off an Oehler Chronograph for MV's and G1 drag co-eff w/ .304BC for the C77rd using the MCTRAJ4 program.




Thoughts?
Link Posted: 10/12/2003 12:43:34 PM EDT
Just M855 or other ammo too? My 14.5" 1/7 M4 does 2660 with Mk262.
Link Posted: 10/12/2003 1:17:36 PM EDT
DevL - I have some other stuff For work my main issue is C77/M855 and that is what I excerpted. The Mk262, I crono'd it at 2590 from teh 14.5... Hmmm [img]http://photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=17970[/img] The HSM with 77gr SMK [img]http://photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=17971[/img] SWISS GP-90 [img]http://photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=17973[/img] I guess I never did a chart for the M193 or the 55gr Fed SP... It is part of my quest against the infernal C7A2 project... [img]http://photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=18087[/img]
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