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Velocity increase for a longer barrel

josh cox

Hello,

I've just replaced a 30 inch barrel with a 32 inch barrel ( I really like this Bartlein ).

What sort of FPS increase would one expect for the same load out of a longer barrel ?
 
20-30 fps for a generic guess, but will be impacted by barrel, powder, caliber, etc, etc.

Edit: Just saw the "same load" part. Could even be slower, but 20-30 fps potential increase with load development. Drew
 
If you load to OBT nodes, you may not see a velocity increase at all, possibly even a slight drop. However, the pressure required to reach that node will be reduced, giving better brass life. Once you get past 26" or so barrel length, the gains per inch barrel length are not nearly as significant, but you will usually observe a drop in pressure and ES at a give accuracy node.
 
It could go either way . Each barrel , rifle , is a rule unto itself . Bore dimensions , # of land , depth of grooves , chamber , leade , etc.

Same chamber?
 
Not very much. I'm about to start testing on a new 32" that I'm planning to cut to 30" after a couple of hundred rounds just to prove to myself whether the extra 2" is worth it. (I no longer believe it is)

I recently tested 4 of my old barrels in 308. Two are 30" two are 32", Kriegers and Bartlines. My velocities with the exact same loads, in chambers cut with the same reamer indicated that the difference in average velocity was within the extreme spread of the loads. That is that the average velocity from the 30s was right about 10FPS slower than the avg from the 32s. I've posted this before, and everyone jumps on the "every barrel is different" hook, yea, to a degree, but that was with 4 barrels, and I'm running a WW case slam full of H4350, not Varget or H4895. Slower with a longer pressure curve.

I'm going to test this new tube with a load of Varget and 200s like most guys are running to get results that should be similar to what most can expect.

I'm also thinking I want to take my oldest barrel and whack it back to 29" and see what happens compared to 32".

About 4 or 5 yrs ago I chambered up a new 34" Kreiger on my F-TR rig. After shooting about 100 rounds with it I chronoed it side by side with my 30" shooting 185s over Varget. It was 40FPS slower. Lopped off 2" before the next match.
 
As I mentioned earlier in this thread, if you load to OBT nodes, you may not see an increase at all, possibly even a very slight drop in MV, with the 32" barrel. However, the pressure required to achieve that velocity will be lower in the longer pipe. This can be important if pressure and brass life are poor. It's also important when setting up a new build. As an example, a friend decided to set up a .284 Win Open rifle. Unfortunately, he chose to go with a 30" barrel. He found he really couldn't hit the desired OBT node (velocity) without generating undesirable pressure levels. A few minutes spent beforehand with Quickload would have saved him a to of time and $$$.
 
gstaylorg said:
As I mentioned earlier in this thread, if you load to OBT nodes, you may not see an increase at all, possibly even a very slight drop in MV, with the 32" barrel. However, the pressure required to achieve that velocity will be lower in the longer pipe. This can be important if pressure and brass life are poor. It's also important when setting up a new build. As an example, a friend decided to set up a .284 Win Open rifle. Unfortunately, he chose to go with a 30" barrel. He found he really couldn't hit the desired OBT node (velocity) without generating undesirable pressure levels. A few minutes spent beforehand with Quickload would have saved him a to of time and $$$.
Click to expand...
If he built the gun with OBT the reason I think he should of tryed paper.
I know of 7 or more dashers with all different taper barrel lingth stocks and actions Shooting the same powder and bullet with the same amount of powder drop. Larry
 
Stocks and barrel contours have little to do with OBT nodes. As far as different length barrels producing similar velocities with comparable charge weights when loaded to an accuracy node, that's exactly what I said. Extra barrel length may not mean extra velocity at all. However, the pressure required to reach that velocity will usually be lower in the longer barrel.
 
gstaylorg said:
Stocks and barrel contours have little to do with OBT nodes. As far as different length barrels producing similar velocities with comparable charge weights when loaded to an accuracy node, that's exactly what I said. Extra barrel length may not mean extra velocity at all. However, the pressure required to reach that velocity will usually be lower in the longer barrel.
Click to expand...
The Speed are all different and all shoot very accurate . The node is tuned with a tuner. When working with a tuner OBT means nothing.
I think and have had great success using a tuner the same way rim fire has done for years Tune the barrel to the load . Yes barrel lingth has effect on bullet speed . And the powder used changes the amount of difference . Larry
 
Using the same powder, the difference in velocity between a 30" and 32" barrel is almost meaningless, even at 1000 yd. It will certainly fall within the window of lot to lot powder variation. You can argue this all you want, but the fact is that small increases in barrel length past about 28" or so make very little difference in velocity, usually well under 10 fps gained/lost per inch of barrel length. Quibbling about 10-20 fps difference is a waste of time...you simply can't shoot the difference. However, dropping the pressure with the longer barrel might make a big difference in brass life because most of us are running loads at or near max pressure. This is the third time I've stated the same thing, but you want to argue about for reasons I don't understand. Go right ahead, but what I've stated is correct.
 
gstaylorg said:
Using the same powder, the difference in velocity between a 30" and 32" barrel is almost meaningless, even at 1000 yd. It will certainly fall within the window of lot to lot powder variation. You can argue this all you want, but the fact is that small increases in barrel length past about 28" or so make very little difference in velocity, usually well under 10 fps gained/lost per inch of barrel length. Quibbling about 10-20 fps difference is a waste of time...you simply can't shoot the difference. However, dropping the pressure with the longer barrel might make a big difference in brass life because most of us are running loads at or near max pressure. This is the third time I've stated the same thing, but you want to argue about for reasons I don't understand. Go right ahead, but what I've stated is correct.
Click to expand...
Why would anyone change from a 6br to a dasher ? Long distance is all about bullet time in the air . Larry
 
savagedasher said:
Why would anyone change from a 6br to a dasher ? Long distance is all about bullet time in the air . Larry
Click to expand...
You lost me. I thought the thread was about barrel length relative to velocity? The obvious answer to your question is more internal cartridge case capacity. I may be wrong but once the powder charge is burnt up in the barrel, would not the extra length serve as friction and cause a loss in velocity?
 
timeout said:
You lost me. I thought the thread was about barrel length relative to velocity? The obvious answer to your question is more internal cartridge case capacity. I may be wrong but once the powder charge is burnt up in the barrel, would not the extra length serve as friction and cause a loss in velocity?
Click to expand...
Bullet speed will increase till the resistance pressure gets greater then the pressure pushing . The amount of gain depends on the burn rate of the powder .
Many of the f class shooters at shooting 32 " to 34" They must have a reason . Larry
 
And how much more velocity does one get from a Dasher as compared to a 6BR, Larry? You're talking about a 10 or 12% increase in case capacity and an increase in velocity with the same bullet of anywhere from 75 to 150 fps, which is significant. An increase of 10-20 fps is not. You really don't know this stuff very well, do you?
 
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