How does chopping a barrel alter velocity nodes?

[308ghost]

Alright guys, Just got back from the range with some testing 26inch barrel vs 16inch barrel same load same chamber.

bullet is the barnes 127
RL26-
26INCH=3162 FPS
16INCH= 2755
Velocity loss of 407fps
= 40.7 fps per inch with this powder. (SLOW burning powder)

RL-16-

26INCH=3078 FPS
16INCH= 2721
Velocity loss of 357fps
=35.7 Fps per inch

The velocity nodes and accuracy nodes did not correlate.

Did you cut and test each inch? Or just go straight to 16" from 26?

 

[BoltActionBrotherhood]

No just straight from 26 to 16.

 

[308ghost]

No just straight from 26 to 16.

Well that was a commitment!

 

[BoltActionBrotherhood]

Well that was a commitment!

Lol I wasnt worried about it, this is for a trunk gun/hunting rig. Not too worried about super performance. I have almost an identical rifle but built out for elr in the same caliber.

 

[steffen707]

I chopped 6" off my 6.5 creedmoor and lost 100fps. The load did not change. As I did another charge test at 600 yards. This was a heavier barreled match and is not noticeably any more or less accurate. I do however have the ability to put a suppresser on and have it be a manageable length. I didnt test any other combinations in this set up. I also just chopped the 24" tikka t3x super lite barrel to 21" (just in front of the flutes) for the same purpose. Again I lost velocity. I seamed to lose less velocity with heavier bullets though. (Fluke? I'm m not sure.) I lost about 60-70 fps with my 168 ablr load. And with the 190 ablr I lost 40-50. With the Berger 185 classic hunter I lost even less! I had to increase my powder charge .1 to maintain the former velocity with those Bergers. (Again I had the can on.) 185 bergers classic hunter 3000 FPS is a good combo. My 190 ablrs are moving 2905 and I'm in the middle of a seating depth test with these ones. All three of these bullets are shooting 3 shot sub moa at 600 yards. I have photos of the 168's ABLR and 185 bergers sub 3" inches. My 190's are super close to that but I'm still tweaking depth. I have detailed notes on this stuff if you interested in more. I know there are a few variables like the first 150 rounds on the barrel and once vs twice fired brass, barrels speed up and settle in about there. Twice fired brass may be a bit faster then new? Hope this helps.

Holy crap this is great info. Sounds like you've been playing around with a lot of things I want to be trying. Shorter for supressor, how does shorter barrel affect accuracy with same load. I too want to make a load with 168 ablr's on my 7rem-mag. Hopefully the gun likes those. I may hit you up when I get more into the nitty gritty of hand loading. =)

 

[steffen707]

The bigger question here is why you would want a short barrel 7 RemMag.

7remmag is what I decided is the sweet spot for a north american gun for me. small enough that its not overkill on smaller game, and can handle 160-175gr bullets without losing a lot of velocity like a 7mm-08, couple that with my desire to run a 7" Ultra7 supressor, and not have the barrel/supressor be 31" long.

Ultra7 says rated for 18"+ barrel length. So I don't want to go shorter, plus probably lose more FPS / Inch from 18-16" than say 20-18".

going from a 28 to 20" this guy lost about 26.6FPS per inch average over 4 different catridges tested. https://rifleshooter.com/2015/04/7mm-remington-magnum-7-rem-mag-barrel-length-versus-velocity/

This is his same data from 24" to 20", only 24.13 fps/inch reduced

24" 2881 2942 2897 2615
20" 2719 2836 2746 2455
Difference 162 106 151 160
27.00 17.67 25.17 26.67 Average 24.13

If i only drop 150fps, i'm willing to make that compromise for 6" less barrel catching on stuff.

 

[steffen707]

Alright guys, Just got back from the range with some testing 26inch barrel vs 16inch barrel same load same chamber.

bullet is the barnes 127
RL26-
26INCH=3162 FPS
16INCH= 2755
Velocity loss of 407fps
= 40.7 fps per inch with this powder. (SLOW burning powder)

RL-16-

26INCH=3078 FPS
16INCH= 2721
Velocity loss of 357fps
=35.7 Fps per inch

The velocity nodes and accuracy nodes did not correlate.

so you mean when you went to the 16" the same load WASN'T in a new velocity node at 2755? And it WASN'T of a similar accuracy as it was at 3162 and 26?

 

[Tripodmvr7]

I am surprised that very few people have used the Ruger No. 1 falling block action to build long range rifles. The short action ensures that even a 26 inch barrel does not look awkward and too long for a hunting rifle.

I have a No. 1A in 30-06 with the 22 inch barrel. The best bush rifle !!!!!. Hangs below your shoulder when stalking and handles very well. Looks more like a .22 than a 30-06. Should be a good call for making a handier suppressed hunting rifle. In a hunting scenario you very seldom need more shots after placing the first.

 

[308ghost]

Holy crap this is great info. Sounds like you've been playing around with a lot of things I want to be trying. Shorter for supressor, how does shorter barrel affect accuracy with same load. I too want to make a load with 168 ablr's on my 7rem-mag. Hopefully the gun likes those. I may hit you up when I get more into the nitty gritty of hand loading. =)

I can tell you I couldn't figure that bullet out in my 7 rem mag. I may try a different powder because I want that 168 to shoot. My tikka 7 mag is digging the 162 eldx bullets.

 

[BoltActionBrotherhood]

so you mean when you went to the 16" the same load WASN'T in a new velocity node at 2755? And it WASN'T of a similar accuracy as it was at 3162 and

so you mean when you went to the 16" the same load WASN'T in a new velocity node at 2755? And it WASN'T of a similar accuracy as it was at 3162 and 26?

Correct. Someone can get lucky and have their old load work, but in general, when you make a change like that it's starting over on load development.
because the barrel was shortened I'm not going to be in that same velocity node because the projo is not moving in that velocity range anymore. Also the barrel harmonics and complelty different as well.

 

[Tripodmvr7]

I can tell you I couldn't figure that bullet out in my 7 rem mag. I may try a different powder because I want that 168 to shoot. My tikka 7 mag is digging the 162 eldx bullets.

You not running into twist rate problem? Tikka use 1 in 11 barrels on a lot of calibres that are normally 1 in 10. A flat base 175gr might work as they are normally shorter than the newer boat tail 168 bullets. Check bullet lengths and twist rate and run it through a twist rate calculator.

 

[Tripodmvr7]

From that data can you correlate at what point 100% of the powder is burned or when pressure is no longer generated?

Played around in QL and it seems as though most of the propellant has burnt up in 19 inches of barrel. I used a 30-06, 168gr bullet and H4895.

 

[itchytriggerfinger]

Interesting. I'm very surprised that the entire charge is consumed in that short of barrel length.
it makes me wonder at what point on any given rifle how much unnecessary barrel I'm carrying around.
20 + years ago when I bought my first can I bought a Savage Tactical in 308 Win and cut the barrel from 24" down to 20" just for harmonics. The gun has always shot lights out.
Although I never did shoot it before making it shorter but it does not appear it would have shot any better. After working the load up, it shot a 100 yard 5 shot group that measured .387"

 

[BoltActionBrotherhood]

Interesting. I'm very surprised that the entire charge is consumed in that short of barrel length.
it makes me wonder at what point on any given rifle how much unnecessary barrel I'm carrying around.
20 + years ago when I bought my first can I bought a Savage Tactical in 308 Win and cut the barrel from 24" down to 20" just for harmonics. The gun has always shot lights out.
Although I never did shoot it before making it shorter but it does not appear it would have shot any better. After working the load up, it shot a 100 yard 5 shot group that measured .387"

Even if the powder is 100% burned, you will still get a velocity increase with a longer barrel,
Because there is still Pressure pushing that bullet out of the tube.