Is a 200fps velocity loss normal going from an 18" to a 16" barrel?

[Ole timer]

Both rifles are chambered in .223 Wylde, both are AR type rifles.
The 18" inch is in an AREO upper, and the 16" inch is a Ranier UltraMatch II.
The load is 22.5grn of VV-N-140 behind 77grn Berger OTM, CCI NO. 41 primers, and Starline brass.
The load in the 18" rifle averages 2,660fps.
The same load in the 16" Ranier barrel averages 2,440fps.
I tried both loads using Sierra MK's and velocities were virtually the same in both rifles and nearly as accurate.
Both rifles shoot less than 1 MOA, function fine with no failures of any kind, both rifles were shot using a MagnetoSpeed V3 mounted to the hand-guards with a Wiser mount.
The load is accurate in both rifles, functions perfectly in both rifles, but I don't understand how 2 inches less barrel could make 200fps difference. Is this normal?

 

[Benchrest Braxton]

Both rifles are chambered in .223 Wylde, both are AR type rifles.
The 18" inch is in an AREO upper, and the 16" inch is a Ranier UltraMatch II.
The load is 22.5grn of VV-N-140 behind 77grn Berger OTM, CCI NO. 41 primers, and Starline brass.
The load in the 18" rifle averages 2,660fps.
The same load in the 16" Ranier barrel averages 2,440fps.
I tried both loads using Sierra MK's and velocities were virtually the same in both rifles and nearly as accurate.
Both rifles shoot less than 1 MOA, function fine with no failures of any kind, both rifles were shot using a MagnetoSpeed V3 mounted to the hand-guards with a Wiser mount.
The load is accurate in both rifles, functions perfectly in both rifles, but I don't understand how 2 inches less barrel could make 200fps difference. Is this normal?

they are different barrels, lots more going on than just 2" barrel difference. same reamer, freebore, land/groove dimensions, bore condition? lots to consider

 

[Ole timer]

I hadn't considered all that. I guess I just wanted to hear if it was possible. Thanks for posting.

 

[Big_Daddy]

Yes it is possible but not necessarily the only factors.

 

[XTR]

Commonly misunderstood is the number of variables that go into a MV number on two different rifles. 200 fps is certainly a big difference for 2 inches.

while surely not a “slow” powder, N-140 is on the slower side for 223 loading. It may just be that your crossing the sweet spot for burning.

 

[karrarararararar]

That 18" seems pretty fast for that charge weight.

 

[David Christian]

For what it is worth, I only shoot larger calibers, but when I have everything the same (reamer, components, load, etc.) each inch of barrel length is worth 20-25 fps. Who knows???

 

[fkimble@charter.net]

The only way to know for sure is to cut 2 inches off the longer one. Then both barrel length being equal, see what the difference is in muzzle velocity. Your barrel lengths are at a point where a complete powder burn is probably not happening. Obviously the shorter barrel will burn less powder in the barrel, hence less velocity. So apples and oranges ref velocity!

Also different brand barrels, so different reamers. Throats are most likely different, even if they both claim being the same chamber type. And many other small differences as already noted.

If it shoots good then just be happy!

Frank

 

[joshb]

I would try a faster powder.

 

[Zero333]

Also keep in mind new barrels speed up after so many shots... sometimes up to 200

 

[MisterHelix]

That’s a pretty significant difference.
I only lose about a hundred foot seconds going from a 16” to a 12.5” barrel with 77’s.

I’m using benchmark powder, which is pretty fast for .223.