6.5 Creedmoor optimum barrel length

wahoowad

wahoowad

Member
Is there a minimum barrel length to ensure you get optimum propellant burn in a 6.5 Creedmoor? I'm asking in consideration of getting an AR upper.
 
I may not have the numbers correct, but I have read (for example) that the 300AAC Blackout burns all it's powder in the first 9" of the barrel, such that it works very well with shorter barrel.
 
"Burns all the powder within 9 inches"
Burn (out) rate depends on powder type, case capacity, weight of the projectile, friction in barrel, and can be tailored to barrel length.
And even though the powder burn is effectively over, the trapped high pressure gas still accelerates the projectile within the bore.
My 6.5CM is 22" & plenty for hunting, but a 26" would be ideal for long range targeting, imo.
 
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I run 26" barrels on both of mine. For a hunting rifle, I'd go with a 20" or 22" barrel if it's going to be carried in the field.
Mine are as long as an old musket with my suppressors attached!
 
22 seems like a good number for the medium sized 6.5s.

After that, every inch is just a pain to carry unless it's a strict bench gun then why not 28"...
 
My kimber has an 18" tube.. my 143 are getting 2516....manufacturer lists 2700 for that load... but I figure most embellish those numbers a bit.. realistically I think you might lose 20 to 25 fps per inch below 24...
 
.308 is a pretty efficient cartridge and (generally) burns up most of it's powder in 18-20". 6.5 CM is basically a necked down .308 so it also does well in shorter barrels, but benefits more from longer ones. For a long range/PRS rifle I would go 24-26", but for hunting I would keep it 18-22". It's all in what you plan to do with the rifle. The velocity loss per inch isn't that severe anyway if you wanted it more compact. Overbore cartridges (larger case with smaller caliber bullet) like .243 need the length for velocity or it suffers quickly.
 
I like getting the concussion away from my head, so a longer bbl is preferable. Also, I shoot a lot. So, I think in terms of at least 1 Chamber set back on the barrel as the leade gets shot out.

So, a 24-25" #5 contour is preferable, figure cut off 2" on the first barrel set back.

R#26 is a slowish buring powder and barrel length is needed to take advantage of it. We are finding amazing velocities shooting tiny groups, shooting 140's at 2850 with top end is 3000 with R#26 and fed 215's, this is real world, not a figment of my imagination in Hornady brass, no ejector marks or difficult extraction.

You reloaders may want to give this some thought.

Gun I am now shooting is Model 7 with a #5 heavy sporter contour, with a 24", 8T, Brux with .146 Free Bore. I may get two chambers on this barrel but would have to go to a Savage Barrel nut on the second chamber.
 
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