Muzzle velocity difference between manufacturers

[BarnOwl 6.5]

Muzzle velocity is mainly a function of the ammunition and barrel length (time under pressure). It seems reasonable to expect minor speed differences between manufacturers (all else being equal), but I wouldn't expect substantial differences. That being said, I have seen posts that suggest otherwise. Here it is.

I'm trying to build a light weight, short, suppressed back country hunting rifle chambered in 6.5 PRC. I was looking at the Tikka T3x with 24" barrel, but found myself attracted to a shorter 20" barrel made by Seekins precision in their new Element Hunter. When I considered how much speed it would cost me for the shorter barrel by Seekins I looked up speeds on other outside forums that guys had posted. The results are below.

Rifle Model	Barrel Length	Muzzle Velocity (fps)	Bullet / Ammunition
Seekins Element Hunter	20"	~2,865	143gr Hornady Precision Hunter ELD-X
Tikka T3x (discontinued I think)	22"	~2,690	140gr Hornady ELD-M
Tikka T3x Roughtech	24"	~2,860	143gr Hornady Precision Hunter ELD-X

I was surprised to see that the shortest barreled 6.5PRC (by Seekins) had the highest muzzle velocity. If we assume those posted numbers to be true, the only explanation I can think of is that maybe Seekins has tighter manufacturing tolerances.

Is it even reasonable to think that might have such a great effect as to completely offset a decrease of barrel length by 4"?

 

[oldrifleman]

Each manufacturer and even within the same manufacturer targets a specific application for their load targets. A 308 for hunting will likely have a different recipe and outcome than one for say target work. A 168 OTM for target will get a different powder mix (manufacturers do not use commercial powder mix's) than say a 168 for law enforcement or a budget blaster load. You have to check each load/lot for velocity. Generally a Hornady backpacker load (same Bullet) will be different than a similar load by Winchester or Federal.

 

[DemonicLemming]

Is that averaged data across multiple rifles of the each barrel length/ammo, or individual reports for each? It's not uncommon for people to bump their "recorded" speed up a bit when posting online (sort of how a gun that shot a 0.5" group once is now a "half-MOA rifle").

One thing to note is that Tikka is generally known for having slow factory barrels. I don't know if Seekins falls on the slow, average, or fast part of that chart. I also wouldn't expect different ammo (even if all Hornady and similar weight) to have the same velocity, which is why the ELD-X is likely faster than the ELD-M.

Either way, I wouldn't worry about 4" on a hunting rifle. Ease of carrying and use beats maybe 75 - 100fps.

 

[Emerson0311]

Tikka barrels have longer throated chambers, so shoot factory ammo slower than other barrels with shorter throats that mean higher pressure. Yes, I’ve got several, and have compared factory vs custom barrel velocities with a Garmin, and seating depth requirements for reloads in each barrel.

 

[Oldloser]

You should go with the rifle you like. All in all, shorter is better. You can then get the ammo to where it needs to be.

Too many variables in the published numbers to make sense of things. Your powder charge, powder relative humidity, case firings, and then chamber dimension variability are the big ones vs barrel length. A new case alone and a looser chamber will take away 100 fps.

 

[diggler1833]

Barrels are individuals, so your results WILL vary some even within a specific manufacturer. I agree with the above that Tikka/Sako barrels are generally a tad slower, and that their throats are long. I'm out way over 2.9XX" in OAL in my TRG in .260 Rem.

I'd certainly be buying based upon what specifications I wanted in a rifle, rather than which one shot factory ammo faster. Tikkas and Seekins will both serve you very well...but perhaps the Seekins will meet what you want in a rifle more.

 

[BarnOwl 6.5]

Is that averaged data across multiple rifles of the each barrel length/ammo, or individual reports for each? It's not uncommon for people to bump their "recorded" speed up a bit when posting online (sort of how a gun that shot a 0.5" group once is now a "half-MOA rifle").

One thing to note is that Tikka is generally known for having slow factory barrels. I don't know if Seekins falls on the slow, average, or fast part of that chart. I also wouldn't expect different ammo (even if all Hornady and similar weight) to have the same velocity, which is why the ELD-X is likely faster than the ELD-M.

Either way, I wouldn't worry about 4" on a hunting rifle. Ease of carrying and use beats maybe 75 - 100fps.

Those numbers are not averaged. They are just single reports which I know makes it hardly worth thinking about. It sounds like your understanding is that there is slight variation between muzzle velocity due to barrel make. That alone is helpful. Im leaning toward your line of thought that it's better to have a easy to carry rifle than a hard to carry rifle that shoots 100fps faster. If all I am giving up is speed I think that is a worthwhile trade. Is there anything else I would be giving up or compromising? Is a 20" enough barrel to stabilize a 6.5 PRC bullet for longer trajectories? Would that short of a barrel compromise inherent rifle accuracy at distance? I know most hunting shots will be under 400 yards so the question I'm asking may be irrelevant to most of what that rifle will do, but I would like this rifle to be capable of accurate kill shots out to 650 yards and steel targets out to 1000 yards.

 

[DeathBeforeDismount]

Welcome to the party pal. We have known tikkas have slow barrels for like 15+ years now. If velocity is all you care about then look elsewhere.

 

[diggler1833]

Those numbers are not averaged. They are just single reports which I know makes it hardly worth thinking about. It sounds like your understanding is that there is slight variation between muzzle velocity due to barrel make. That alone is helpful. Im leaning toward your line of thought that it's better to have a easy to carry rifle than a hard to carry rifle that shoots 100fps faster. If all I am giving up is speed I think that is a worthwhile trade. Is there anything else I would be giving up or compromising? Is a 20" enough barrel to stabilize a 6.5 PRC bullet for longer trajectories? Would that short of a barrel compromise inherent rifle accuracy at distance? I know most hunting shots will be under 400 yards so the question I'm asking may be irrelevant to most of what that rifle will do, but I would like this rifle to be capable of accurate kill shots out to 650 yards and steel targets out to 1000 yards.

-The twist rate is what is going to determine bullet stability most (based off of bullet length mostly). Velocity is that small, fractional portion of the equation.

-A 20 inch barrel will not compromise inherent rifle accuracy at any distance.

- Your skill, bullet construction, and velocity will be what determines "accurate kill shots" out to 650. And by that I mean you need to make sure that you use the correct bullet for impact velocity, and develop the skillset necessary to hit a small target at that distance on the first shot. Targets at 1K are going to be just plain fun for you man...knock yourself out there... a 20" 6.5 PRC will get there without issue.

 

[SRPowah]

The best part about this game is you could buy a Seekins based off the single data point you found, and end up with a barrel slower than all the Tikkas that stacks dimes. Its real exciting when you get a short barrel on the high side of velocity, but man does can it suck when you buy a shorty that shoots at the low end of the range.

Less of an issue with a PRC.

 

[memilanuk]

Something else to bear in mind... as you go shorter, the bigger cartridges like the 6.5 PRC show less gain over something like the 6.5CM.

Will it be faster? Probably. Are you likely blowing a fair bit of unburnt powder out the end of that short barrel? Probably.

There's even some evidence that peppering the base of the bullet with unburnt powder kernels just as it exits the crown is not conducive to accuracy. Whether that would be evident in the context you're looking at (hunting, and plinking at steel) is debatable.

 

[DeathBeforeDismount]

-The twist rate is what is going to determine bullet stability most (based off of bullet length mostly). Velocity is that small, fractional portion of the equation.

-A 20 inch barrel will not compromise inherent rifle accuracy at any distance.

- Your skill, bullet construction, and velocity will be what determines "accurate kill shots" out to 650. And by that I mean you need to make sure that you use the correct bullet for impact velocity, and develop the skillset necessary to hit a small target at that distance on the first shot. Targets at 1K are going to be just plain fun for you man...knock yourself out there... a 20" 6.5 PRC will get there without issue.

Velocity is not a small factor. It's why you can get away with a 8 twist in a prc but a regular 65 creed needs a 7.5 to stabilize the heavies. Twist rate and velocity go hand in hand( as well as atmospherics).

 

[Frank Green]

Muzzle velocity is mainly a function of the ammunition and barrel length (time under pressure). It seems reasonable to expect minor speed differences between manufacturers (all else being equal), but I wouldn't expect substantial differences. That being said, I have seen posts that suggest otherwise. Here it is.

I'm trying to build a light weight, short, suppressed back country hunting rifle chambered in 6.5 PRC. I was looking at the Tikka T3x with 24" barrel, but found myself attracted to a shorter 20" barrel made by Seekins precision in their new Element Hunter. When I considered how much speed it would cost me for the shorter barrel by Seekins I looked up speeds on other outside forums that guys had posted. The results are below.

Rifle Model	Barrel Length	Muzzle Velocity (fps)	Bullet / Ammunition
Seekins Element Hunter	20"	~2,865	143gr Hornady Precision Hunter ELD-X
Tikka T3x (discontinued I think)	22"	~2,690	140gr Hornady ELD-M
Tikka T3x Roughtech	24"	~2,860	143gr Hornady Precision Hunter ELD-X

I was surprised to see that the shortest barreled 6.5PRC (by Seekins) had the highest muzzle velocity. If we assume those posted numbers to be true, the only explanation I can think of is that maybe Seekins has tighter manufacturing tolerances.

Is it even reasonable to think that might have such a great effect as to completely offset a decrease of barrel length by 4"?

Your leaving out too much information that the average shooter will never know or can measure to even know what is really going on.

Can and does barrel length effect velocity? Yes. Caliber/chamber can have a impact on this as well. A 308win chamber barrel will have a less of an effect vs barrel length vs a 30cal barrel chambered in 300WM. The 300WM the barrel length will have a bigger impact on velocity loss or gain because of case capacity.

The Seekins barrel being shorter and faster than the others? Without knowing all the details it's possible but if it's true... you need to know all the variables. Such as.....and I will list just two.

1.) Was the chamber cut to the same spec as the other barrels? Was the chamber even a Saami min spec. chamber?

2.) Where all the barrels made to the same spec and held to the same tolerance? So min spec. is .2560" X .2640" +.0005" for each.

Without even getting into more things...those two above are huge!!!!!

If a barrels bore spec is tight / undersize that will have a impact on pressures and velocities. A barrel with a bore and groove even just .0005" undersize from min spec and I know this for fact with actual ammunition pressure test barrels I seen with 6.5CM that it drove up pressures like 8-10k psi and it drove up velocities like +150fps if I recall correctly. You might not see heavy bolt lift or flat primers etc... but the spike in pressure etc.. is there.

If you don't know the barrel spec's for each gun and chamber... your not even comparing apples to apples let alone the barrel length being a variable.

Later, Frank
Bartlein Barrels

P.S. I'm not picking on your or poking at you in a bad way.... I'm just saying without knowing all the details of the barrels.... you have a huge gap your trying to cover. That's all.

 

[tacoman69]

A 18-20 inch 6.5 PRC is still likely to be a 700plus yard gun with 143/147s at density altitudes most are hunting deer and elk at. Far more capable gun than most should be taking shots at game. Even though they are a little slower, the reliability of the Tikka makes it the easy choice for me. They shoot and they work.