what makes some barrels "slower"?

[Surtr]

Was watching Lowlights video on the tikka tac A1 and he mentioned that the stock tikka barrel was a lot slower than other barrels velocity wise and when he switched barrels to a shorter barrel he gained velocity over the tikka barrel.

What makes some barrels shoot projectiles slower than other barrels of the same or shorter length?

 

[Dthomas3523]

Short answer, several things. Quality of manufacturer, condition of tools at the time the barrel is cut (tooling could be worn out), and just “dumb luck” when things happen when you’re cutting metal (stress, friction, etc).

 

[Crang]

The Tikkas seem consistently slower. Mine sure was too till I put a PVA on it. Wondered if its the cold hammer forging or slight dimensional differences. Be interested if say Styers also with CHF barrels are known to be a bit slower? Perhaps FN as well. The only FN barrel I own is only 16.25" on a 308 so its damn slow anyway lol.

On a side note the Tikka barrel sped up after a 200-250 rounds break in but was still slower than others. The length of the breakin surprised me and had me chasing numbers working up a load after just a 100 round break in.

 

[JohnDeereGuy1996]

I had a 24 inch ctr that shot fantastic but was extremely slow.
42.3 grn of h4350 would push a 140 grn berger 2667 FPS

 

[Ledzep]

Groove/land diameters and ratio, and surface finish.

 

[coltm4]

All of the above seem plausible. But my Tikka barrel was also slow, so it isn't anyones imagination.

 

[Supersubes]

I’m with ledzep, primarily it must be bore/groove diameter, then land/groove ratio, with surface finished in a distant third.


I suppose chamber dimension can be in there somewhere, but I’ve never inspected brass from one so that'd be a guess.

 

[roamin]

I recall Rob Ski's Tikka being slow as well.

 

[dannySH]

My Tikka CTR 6.5 CM shoots 100 fps slower than my Tikka with PVA barrel with the same load. That's a fact.

 

[patriot07]

I agree that Tikkas are slow. Accurate, but slow. Not sure what causes it. Maybe a microscopically smaller diameter?

I am running 43.2 grains of H4350 in mine (pretty hot load) behind 140 ELD-M and getting 2,775 fps. I would expect to be well over 2,800 in a standard speed barrel with that load.

The original load I worked up was 42.3 grains, which shot small 100 yard groups but showed some velocity dispersion at distance. It was running upper 2600s, as someone above me said theirs did with 140 Bergers and the same powder charge. That load should really be around 2,750 in an average 24" 6.5 creedmoor barrels.

I'll probably go to a Bartlein or PVA pre-fit once this barrel is done, and I'm hoping to see a velocity gain or powder reduction, or both.

 

[dannySH]

I agree that Tikkas are slow. Accurate, but slow. Not sure what causes it. Maybe a microscopically smaller diameter?

I am running 43.2 grains of H4350 in mine (pretty hot load) behind 140 ELD-M and getting 2,775 fps. I would expect to be well over 2,800 in a standard speed barrel with that load.

The original load I worked up was 42.3 grains, which shot small 100 yard groups but showed some velocity dispersion at distance. It was running upper 2600s, as someone above me said theirs did with 140 Bergers and the same powder charge. That load should really be around 2,750 in an average 24" 6.5 creedmoor barrels.

I'll probably go to a Bartlein or PVA pre-fit once this barrel is done, and I'm hoping to see a velocity gain or powder reduction, or both.

Here are my numbers on a 6.5 CM.
Hornady Match BTHP 140 gr, 42.4 gr of IMR 4451, CCI #200, Hornady brass
Tikka CTR 24" - 2715 fps
Tikka PVA Rock Creek 26" - 2835 fps

 

[patriot07]

Yep, looks like you're giving up aroudn 100 fps when you account for the barrel length difference. 42.4 gr of 4451 is pretty hot as well. 2835 on the PVA barrel makes for some nice ballistics I'm sure.

How does the PVA shoot accuracy-wise and velocity-wise?

 

[dannySH]

Yep, looks like you're giving up aroudn 100 fps when you account for the barrel length difference. 42.4 gr of 4451 is pretty hot as well. 2835 on the PVA barrel makes for some nice ballistics I'm sure.

How does the PVA shoot accuracy-wise and velocity-wise?

Awesome barrel. Fast, very easy to clean. 3 shots group at 300 yards this Saturday. 1/4 MOA. I can't complain.