Optimum barrel length on 17 HMR, I am confused

[Prebanpaul]

So I have been looking at purchasing a higher end 17 hmr. I was going to build a CZ 17 HMR and started looking at a lot of things.

I noticed that the all the higher end guns had 22-24 inch barrels. Anschutz and Sako . So I thought that is what I wanted to do.

I looked up the optimum barrel length and came across Bullberry arms test that was completed. From looking at the test there was only a 16 foot difference in speed between 21,22,18 inch barrels. 21 was the fastest and the 22 and 18 where with in one feet per second of each other. There was a huge difference in spread though. The longer barrels had a SD of over 80 FPS and the 18 inch Barrel had one in the 40's. From this research I would say that the 18 inch is the optimum barrel. I did not come across any other information in reference to this testing.

My question is this. Why would the higher end performing guns put this round in a longer barrel. I know that their a lot smarter than me, so what am I missing.

Thanks for any help I am about a week out from purchasing a higher end 17 and trying to figure out exactly what I want.

Paul

 

[chorizo]

Bullberry Barrel Length vs. Velocity DATA 22 inch = 2517 fps, 103 fps spread 21 inch = 2523 fps, 66 fps spread 20 inch = 2515 fps, 86 fps spread 19 inch = 2538 fps, 83 fps spread 18 inch = 2522 fps, 41 fps spread 17 inch = 2505 fps, 43 fps spread 16 inch = 2492 fps, 53 fps spread 15 inch = 2477 fps, 27 fps spread 14 inch = 2432 fps, 70 fps spread 13 inch = 2419 fps, 32 fps spread 12 inch = 2387 fps, 57 fps spread 11 inch = 2338 fps, 45 fps spread 10 inch = 2276 fps, 45 fps spread

the Test Data for 17 HMR

 

[chorizo]

It would appear 18" would be perfect, especially if you mount a can on it as you may gain a few FPS back. I had a Ruger 77/17 hmr target version with the heavy barrel with a 24" barrel and a ruger 77/17 hmr light profile barrel that I had cut to 20" and threaded for a Gemtech GM-22. The light profile barrel out shoots the heavy barrel version hands down, no matter what I did to improve the heavy barrel version. I finally sold the heavy barrel version.

Unfortunately I found this study AFTER I had cut down the barrel. I wish I had it cut to 18" and may in the future.

http://www.predatormastersforums.com...Number=2862866

http://riflebarrels.com/shop/drop-in.../cz-455-17hmr/

IMG_20160403_095748_868 by ChorizoUSMC, on Flickr

 

[Prebanpaul]

Hey thanks for posting that information. That is what I was talking about.

 

[Prebanpaul]

I am sure they used their own barrels. I see where a guy did the same test and he cut a barrel down. So it was the exact same barrel. It was within in 12-13 feet of this test.

 

[JePhyllis]

Savage A22 has a 21'' barrel.

 

[justin amateur]

Bullberry Barrel Length vs. Velocity DATA 22 inch = 2517 fps, 103 fps spread 21 inch = 2523 fps, 66 fps spread 20 inch = 2515 fps, 86 fps spread 19 inch = 2538 fps, 83 fps spread 18 inch = 2522 fps, 41 fps spread 17 inch = 2505 fps, 43 fps spread 16 inch = 2492 fps, 53 fps spread 15 inch = 2477 fps, 27 fps spread 14 inch = 2432 fps, 70 fps spread 13 inch = 2419 fps, 32 fps spread 12 inch = 2387 fps, 57 fps spread 11 inch = 2338 fps, 45 fps spread 10 inch = 2276 fps, 45 fps spread

the Test Data for 17 HMR [IMG2=JSON]{"data-align":"none","data-size":"full","src":"http:\/\/varmintal.com\/17bbl.png"}[/IMG2]

You can't look at that data and assume the the ES is a result of the barrel length.
ES is a direct result of the individual cartridge differences, primer/powder/brass/bullet.
With the minimal data set provided, the information is enough to plot the velocity curve relative to barrel length,
not to determine if the barrel length affects mv consistency. The curve peaks at 20 inches,
which explains why Lilja offers 17 hmr barrels 21.5 inches long.

 

[Tucker301]

This makes me question the validity of the spread numbers across the entire chart.

16 inch = 2492 fps, 53 fps spread
15 inch = 2477 fps, 27 fps spread
14 inch = 2432 fps, 70 fps spread

 

[justin amateur]

I run a chronograph any time I'm punching paper for precision.
Shooting rimfire, it's the only way to determine if the results are me or the ammo.
Last box of 17 gr vmax had an ES of 261 fps from a box of 50, SD was 58 fps.
Think about how that would affect testing results when 2 out of 3 shots fall within 58 fps of average
but 1 of 3 fall outside those results. Gotta love rimfire.

Just because the box is labeled 2550 fps doesn't mean those bullets are coming out at 2550.
That is the calculated number based on perfect engineering, manufacture and physics.
Problem is, CCI has been running those machines for a long time
and wear and tear are affecting the quality of the ammo produced.

 

[JG26_Irish]

I run a chronograph any time I'm punching paper for precision.
Shooting rimfire, it's the only way to determine if the results are me or the ammo.
Last box of 17 gr vmax had an ES of 261 fps from a box of 50, SD was 58 fps.
Think about how that would affect testing results when 2 out of 3 shots fall within 58 fps of average
but 1 of 3 fall outside those results. Gotta love rimfire.

Just because the box is labeled 2550 fps doesn't mean those bullets are coming out at 2550.
That is the calculated number based on perfect engineering, manufacture and physics.
Problem is, CCI has been running those machines for a long time
and wear and tear are affecting the quality of the ammo produced.

Yes, pay attention to this. The variation in the ammo could well be more than the variation in the performance of the bbl at each length. Before I would put too much weight into that study, I would want to know how large the statistical sample was for each length? and how repeatable the test would be? I would also want to know how each bbl length grouped when fired in a indoor range or tunnel. While ES and SD are indicators of the consistency of the ammo sample, the barrel harmonics which are largely determine by diameter and length would greatly affect the overall accuracy. In my opinion you still lack enough data to draw any solid conclusions. My Savage BTVS has a 21" bbl. It shoots reasonably well. A highend 22 will still out shoot it at 50y and 100y.I am talking about a mod 52 Winchester or a Anschutz M54.

Irish

 

[Damned Lil Bullet]

Hi! I am NO expert, BUT... This was written in 2017. But I can close my eyes and see a bunch of people cutting off their barrels today
based on the test that is used as a basic fact in this chat. It is a good test, I don't want to "poo-poo" it by any means. BUT. While its a
well done experiment, what it is basically showing us what happens with the ammo they load. From here we are assuming that a very
similar thing might be happening in every barrel. Let's start by bringing to mind the speed at which the powder burns as well as the
amount of propellant and the chamber pressure targeted.
An extremely fast burning powder might indeed have been consumed in 17 inches of a barrel, so its maximum chamber pressure is achieved
at that point, and now friction begins to play against an enemy that remains almost constant in pressure, but not in inertia. So yes, the bullet
might slow down a bit. The opposite is just as bad, meaning the powder being to slow and being consumed outside of the barrel. This didn't
happen in this experiment, you could argue that at pistol lengths that was the case, but it wasn't the intent of the experiment, so I will ignore that part.
Now at the end of 2022 we have ammon such as CCI's A17, which IN MY RIFLE, a 22 inch barrel, shows me a velocity the actually exceeds the factory
rating of 2650 by just a bit, avg being around 2720 this being a nice difference from the test results mentioned here. Would it be faster if I took
3 inches off my barrel? Honestly, I don't know and I'm not going to destroy my barrel to find out. So I spoke a lot and said very little! Don't worry,
I'm not a politician! All I want to say is there are many variables and reasons to consider before you start chopping up your barrel; Some are very valid ones.
Think things through and have fun, rabbits, squirrel's or paper!