Barrel length and speed 6.5 Creedmoor and others

[MRP]

I like this new article because it kinda supports all the short rifles I have in my closet.

http://https://westernhunter.net/gear-reviews/barrel-length-101/

Interesting that FPS increases at first when he cuts the barrel. Only a 45 ft./s loss from 26 to 20 inches.

I know my 300 short mag only gave up an average of less than 50 ft./s from 22 to 19 inches between four different powder loads and two factory loads.
My 8x57 only lost 70 Feet per second from 24 inches down to 19.
I wanted to try this with a 444 Marlin but somebody offered me too much money for it before I dug out the hacksaw.

 

[Rifleman87]

I like that you have a 19” 300 wsm! I’m sure the muzzle blast is noticeable with that one!

I chopped a 6.5 creedmoor from 22 to 19, lost something like 40fps. I’ve chopped some 308’s as well from 22 to 20 and 18.5, again only lost 30-40fps. My 22” 6.5 creedmoor is 50 FPS faster than my 20” creedmoor with the same load. It’s hard to compare different barrels for velocity though, ever barrel has its own personality.

I am really only interested in short rifles, the long ones mostly live in the safe.

 

[Hitzy]

Long pipes are great if you are target shooting long distance, loaded to max, and need that extra 100fps to stay super sonic to 1000m, for hunting with a short action cartridge, makes no difference really, the animal is not going to notice the 100fps in velocity when it hits them. Light and handy works better for hunting.

 

[Lead hammer]

I dunno, for the 6.5 CM, it needs a longer barrel. I hunt with a 24” with a brake. Think I might go 26” with a new barrel when it’s needed.

 

[Hitzy]

I dunno, for the 6.5 CM, it needs a longer barrel. I hunt with a 24” with a brake. Think I might go 26” with a new barrel when it’s needed.

It really doesn't, those high SD bullets penetrate great, and you don't need premium bullets for the 140gr velocities, cup/core do fine and hold together. 6.5x55 has been doing the job on everything up to moose for 120 years at similar velocities, 6.5 CM isn't doing anything different them the old Swede cartridge does except fit in a short action.

 

[BwanaDave]

It really doesn't, those high SD bullets penetrate great, and you don't need premium bullets for the 140gr velocities, cup/core do fine and hold together. 6.5x55 has been doing the job on everything up to moose for 120 years at similar velocities, 6.5 CM isn't doing anything different them the old Swede cartridge does except fit in a short action.

I agree, the 140 hotcore is my bullet of choice in the CM. Still this time I went with the 24" tube and a rifle with a longer throat and the difference is worthwhile. I got rid of a mauser M18 and went with a tikka superlight. Same powder/bullet/case combo and the difference in throat/barrel length changes the equation from 2670 fps @ the muzzle to 2800 fps @ the muzzle and no pressure signs with two more grains of powder in the tikka while the mauser was tapped out where it was. Primers are nice and rounded in the tikka and I'm quite sure I could push it harder safely but there's no need.

 

[SuperCub]

For the most part, bbl length has very little to do with the chambering but more so is one of the many specs you have when you decide what type of rifle you want.

I have a full sized 700 sporter in 6CM with a 24" bbl. with a bigger 4.5x14 scope OTOH, one could have the same chambering in a 20" Model Seven with MR contour and a lightweight 2-7.

Same chambers but two completely different rifles with two very different applications.

 

[blakeyboy]

I've been running 6.5 Grendel's lately and have run through three different factory barrel lengths from 3 different manufacturers. Factory Hornady Black 123gr Eld-m ammo rated at 2580 fps does the following. (5-shot string averages, rifles broken in, 60 plus rounds)

16.1" Ruger - 2386 fps
20" Howa - 2503 fps
23.5" CZ - 2552 fps

Between shortest and longest, 166 fps and 7.4" = 22.4 fps per inch.

In ballistics calculators this equates to a rule of thumb of approx. 15 yards per inch of additional range potential with approx .5 bc bullets. Ie; my 16.1" ruger lands 1800 fps impacts about 405 yards so the 23.5" CZ will do similar about 505 yards. (used .48 bc in the calculator for that, and for the 7.4" barrel length addition we gained 14 yards per inch range potential)

Something of interest, I took 3.25" off the CZ barrel and so it went from 23.5" to 20.25" and 2552 to 2529 fps losing only 23 fps or 7 fps per inch and I read somewhere the ideal barrel length for the Grendel was 19" from a test where they cut off 1" all the way down from full length 28-30" to super short pistol lengths. 6.5 Grendel burns about 30 grains of powder fyi.

Also note I put a 24" proof carbon (which are hand lapped) on the CZ and it ran that same ammo at 2605 fps...very quick barrel.

The Howa barrels are notoriously tight and slow...but accurate, you likely noticed that above also. Since knocking the CZ down to nearly the same as the Howa (20.25 - 20") but the CZ was still about 25 fps quicker.

Hope that data helps the ballistic nerds work out their shizzo.

Seems the rule of thumb of 20-25 fps per inch can be applied just about any ole time. My experience came out to about 22.4 fps per inch from 16.1" to 23.5" barrel lengths in a fairly moderate velocity cartridge.

The 6.5 Grendel for me 16.1" is the short end for burning 30 grains of powder, wouldn't want much shorter, muzzle blast goes up, it's healthy enough there. So...for a 6.5 Creedmoor which burns about 43 grains of powder...I'd want 20" on the short end to mirror the 16" Grendel for blast/efficiency, 22" maybe ideal and 24" for a bit more zang.

 

[BwanaDave]

I'm running a Grendal as well as a Creedmoor and the 120's are running 2625fps from my 22 inch barreled Howa with no pressure signs. I wouldnt consider that slow and the accuracy is stellar for a hunting rifle (leverevolution is the powder with this combo)

 

[guntech]

What are you guys using to measure velocity? There are some units that are fantastically accurate, others not so much...

 

[track]

I travel the opposite to short barrels; I prefer them longer. I have four custom rifles, three with 27" barrels and the forth one is 26.5". Two out of the four shoot 250 to 270 fps over and above the reloading manual. The other two rifles are in their infancy of load development. Barrel length, rifle twist and gun powder are factors of higher velocity. I love shooting and hunting with fast flat shooting cartridges, especially in the Great Plaines and semi-open terrain.

 

[Rifleman87]

I dunno, for the 6.5 CM, it needs a longer barrel. I hunt with a 24” with a brake. Think I might go 26” with a new barrel when it’s needed.

I think it depends on the application. For a long range target rifle, sure. Or even a long range hunting rifle. For your typical 400 yards max hunting rifle, the extra velocity is not really a big deal. My 20” x bolt micro maintains above 1600fps (Hornady eldx minimum expansion velocity) all the way to 1000 yards (5000ft above sea level). There’s no way I would ever shoot a deer that far, but the bullet would still be lethal (in theory). Wind drift difference (15mph 90 degree cross wind) at 1000 yards between the 143 eldx doing 2700 and 2900fps is 8”, that’s pretty diminishing returns when you’re talking 80” of drift.

I would say with cartridges that shoot lower BC bullets velocity is more important. The 143 eldx (.625bc) just cuts through the air. Even downloaded to 2350fps it has a further effective range than my 243 shooting a 100gr interlock at 2800fps.

Application will determine what setup works best.

 

[freddyfour]

Great thread, I have a 24" 260Rem that I wanna have cut back to 20".