Yes, I think some rifles are designed to balance well at 22" or 24" but when chopped down the handling goes to all hell. I think the 600 and Model 7 are probably some of the better options since they were designed with short barreled balance in mind. Chopping down a RUM-chambered Sendero would be hilarious though.
Velocity, barrel length, and actual consequences
- Thread starter Grizzlypeg
- Start date
Yes, I think some rifles are designed to balance well at 22" or 24" but when chopped down the handling goes to all hell. I think the 600 and Model 7 are probably some of the better options since they were designed with short barreled balance in mind. Chopping down a RUM-chambered Sendero would be hilarious though.
The only CF rifle in my safe that has a barrel shorter than 22" is a Marlin 336, 30-30.
If I needed a quicker handling/pointing rifle though, I would not hesitate to lop the
barrel off one of the other rifles.
The velocity loss depends largely on the actual chambering. For example, you lose
more shortening a 264 Win Mag or 257 Weatherby Mag than you do lopping off some
of your 308 Winchester barrel.
I owned a 22" 308 Norma Mag many years ago. Compared to a 26" that I later bought,
the loss was about 140 fps, but N205 [now MRP] still gave the highest speed, even in
the short barrel. Dave.
If I needed a quicker handling/pointing rifle though, I would not hesitate to lop the
barrel off one of the other rifles.
The velocity loss depends largely on the actual chambering. For example, you lose
more shortening a 264 Win Mag or 257 Weatherby Mag than you do lopping off some
of your 308 Winchester barrel.
I owned a 22" 308 Norma Mag many years ago. Compared to a 26" that I later bought,
the loss was about 140 fps, but N205 [now MRP] still gave the highest speed, even in
the short barrel. Dave.
So, have you tried; I have.
Let me spell it out...
Extruded powder burns slower (why they have burn rate charts), if it takes the time a bullet spends in a barrel to burn it all to optimize the pressure; then you shorten the barrel 6-10", a portion of the powder is not going to be fully burnt and expelled with the bullets. As I posted above, using lighter bullets that accelerate faster, with a faster powder that will achieve peak pressure, will partially or completely compensate for the loss of velocity with a short barrel, giving similar flat shooting performance, naturally with a bit less terminal energy with a heavier bullet. However, the slower big bullet and faster lighter bullet may have almost the same energy at range, but the lighter bullet will have dropped less, as it took less time to get to the target.
Judging by what you highlighted, you chose to miss the point of my post, and try to discredit what I wrote. Last I heard, this is an open forum.
The only way your post has any credibility is if you use the same bullet weight and push the pressure up to an unsafe range.
The only way a bullet will continue to accelerate in a long barrel is if powder continues to burn.
Load a fast pistol powder in the correct quantity to reach peak pressure in a 30-06, and it will not keep accelerating, it will be stuck somewhere in the barrel.
Load a pistol round with slow rifle powder, and unburnt granules will be spewed all over.
It is a balance of burn rate, barrel length, bullet weight; why do you think we reloaders work through load development.... Now if only I could get more primers.
I believe that's peak pressure not peak velocity
otherwise a longer barrel will produce less velocity which is usually not the case
see ballistics by the inch website
Suther said it very well, and you're simply incorrect.
There are a number of points about your post that could be discussed, but the BOLDED part seems to be at the foundation of your misconceptions.
All the powder that will burn, burns within about 4" of the boltface regardless of whether it's Bullseye (Peak Pressure at perhaps 1/2") or US869 (Peak pressure at perhaps 4"). You can map where that happens by looking at the pressure curve - it's where PMax (Peak Pressure) is reached. Slower powders can produce higher MV's because more can be used without exceeding safe Peak Pressure - it's still used up very early.
After that 4" or so, pressure decreases uniformly as the bullet traverses the barrel, and unless it's a very long barrel, the bullet will still continue to accelerate (as Suther stated).
Assuming equal Peak Pressures, and pressure that is where the powders are designed to operate, the only situation where a faster powder provides higher MV's than a slower powder regardless of bullet weight, would be a barrel in the 1-4" range, most of which is in the Prohibited Firearm range of barrel lengths.
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If such were the case, why are we not able to attain rifle velocities with pistol powder?? Peak pressure would be made in those 4"; the bullet will not exit the barrel because it stops accelerating because peak pressure has been met, the gas begins to cool, and pressure drops rapidly.
To continue accelerating you need peak pressure for the length of the barrel. At 20" down, the internal volume behind the bullet is 5 times more than it is at 4", if the powder burns completely in that first 4", a pressure drop will occur, which will cause it to decelerate; especially as the hot gas contacts a colder barrel, and contracts, further causing a pressure drop.
I stand by what I have written. Thermo-dynamics are a big part of the physics of Ballistics because that is what burning powder and the pressure it creates is..
1. Because we are required to use less of it. The more powder you use the more gas that is produced. A pound of powder has about the same amount of energy within it regardless of how fast it burns, so if you can load 40.0 grs of H4895 at 50K psi, but only 10.0 grs of Bullseye at 50K psi, you'll produce less energy, less gas and a lower MV with the Bullseye than with the US869.
2. Not true. As long as the pressure in the barrel is high enough to accelerate the bullet, it will accelerate.
Attachments
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Ugh. Yes. Typo on my part. Sorry about that, I'll correct it...
I would have no qualms about chopping down your barrel. No animal is going to notice the drop in velocity at normal hunting distance, say out to 300 yards or so. I would shoot a moose with my 16.5" .308 to about 300 yards.
With all the engineering types involved in this discussion, I'm surprised the "work integral" is not being discussed. The optimal (ie highest velocity) powder for a given bullet/barrel is the one that gives the largest work integral for a given maximum peak pressure. Obviously, a pistol powder that achieves the same peak pressure as a rifle powder in a rifle barrel is developing a much lesser work integral, as evidenced by the mass/heat of combustion of the powders. An important part of the work integral is the area under the pressure curve after peak pressure is reached.
Right on both accounts; but slow powder in a short barrel will not develop those pressures before the bullet exits the barrel, as slightly faster powder will.
My point is that the speed of the powder, bullet weight, and barrel length all affect the pressure curve.
Results
How much did muzzle blast change?
The rifle with a shorter barrel was louder. This was noticeable from 19 inches and below.
| 308 Winchester Barrel length in inches versus Muzzle velocity in feet-per-second (ft/sec) | ||||
| Barrel length | Winchester 147 FMJ | IMI Samson 7.62 150 FMJ | Federal 168 Gold Medal | Winchester 180 PP |
| 28 | 2965 | 2823 | 2706 | 2632 |
| 27 | 2962 | 2800 | 2697 | 2607 |
| 26 | 2955 | 2801 | 2673 | 2597 |
| 25 | 2917 | 2769 | 2659 | 2585 |
| 24 | 2909 | 2766 | 2635 | 2553 |
| 23 | 2877 | 2744 | 2618 | 2553 |
| 22 | 2837 | 2718 | 2597 | 2527 |
| 21 | 2807 | 2683 | 2580 | 2507 |
| 20 | 2804 | 2679 | 2565 | 2478 |
| 19 | 2757 | 2634 | 2532 | 2441 |
| 18 | 2739 | 2595 | 2523 | 2411 |
| 17 | 2707 | 2577 | 2481 | 2401 |
| 16.5 | 2682 | 2561 | 2466 | 2373 |
| AVG velocity loss fps/inch | 24.6 | 22.8 | 20.9 | 22.5 |
How much did muzzle blast change?
The rifle with a shorter barrel was louder. This was noticeable from 19 inches and below.
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manbearpig
CGN Ultra frequent flyer
- Location
- Somewhere in the Third World
I have several 16" .308s.
I have yet to experience the famed "flamethrower muzzle-blast", and the report isn't much worse than a 22" barreled .308. IMHO the 120-ish FPS loss is negligible in typical hunting situations. If you're planning on taking 300+ yard shots then it would seem wise to bring a longer-barreled rifle (I wouldn't know since I don't hunt at those ranges).
IMO everyone should try it for themselves. The problem with the hunting community is that it's rife with ultra-traditionalists who have conniption fits at the mere sight of a 16-18" barreled hunting rifle.
Meanwhile most people that actually own them and hunt with them love them.
I have yet to experience the famed "flamethrower muzzle-blast", and the report isn't much worse than a 22" barreled .308. IMHO the 120-ish FPS loss is negligible in typical hunting situations. If you're planning on taking 300+ yard shots then it would seem wise to bring a longer-barreled rifle (I wouldn't know since I don't hunt at those ranges).
IMO everyone should try it for themselves. The problem with the hunting community is that it's rife with ultra-traditionalists who have conniption fits at the mere sight of a 16-18" barreled hunting rifle.
Meanwhile most people that actually own them and hunt with them love them.
I don't always need to be right and when I'm not, I don't dig in my heels and stick with my story, I embrace the new knowledge.
You made several incorrect statements some of which I bolded above, but I realize that nothing beats a picture, so here's a chart that illustrates what I have stated in my posts.
This will probably be of no use to you, but others might benefit.
View attachment 591073
You will notice that all three powders have roughly the same Peak Pressure, but where/when it occurs differs. The faster the powder, the sooner it occurs and so on.
Even though the slow powder has its peak later than the fast powder, we're talking milliseconds later which translates into ~2-3 inches of travel. After Peak Pressure no more gas is being produced, and the smooth curve after Peak Pressure is representative of the pressure drop in a tube as its volume is increased.
There is only one example velocity curve shown, which could represent any of the powders, but if all three were shown they would differ from each other, with the fast powder producing the least velocity, then Medium, then Slow producing the highest velocity.
You'll also notice that the area under the three pressure curves increases from A to B to C, and that reflects that there is more energy being produced as more of slower powders are used which results in increasingly higher velocity.
IMO "Quickload" is largely responsible for the mistaken belief that powder burns all along the barrel well past 4", as they "calculate" "% Powder Burn". As I stated, if pressure is at or higher than where the powder is designed to operate (could be 15K psi for Bullseye and 50K psi for US869), all that will "burn" will be consumed within a few inches of the boltface. Those whose "proof" that this is not true is such things as "Muzzle Flash", or debris are mistaken. There are always by-products of combustion - some is expelled (and can result in muzzle flash), and some is left in the bore for later cleaning.
Hope this helps.
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Big JD-From the hills
CGN Ultra frequent flyer
- Location
- Saskatchewan.
The ruger ranch in 7.62x39 with its 16.5" bbl seems to suffer no velocity loss vs the sks, yet the muzzle blast is really bad to the point that with earplugs it is seriously uncomfortable. A linear comp takes care of that..... but now we are adding length again.
