I'm currently building a varmint rifle in .223 caliber. It's going to be a PD rifle with a McMillan Stock (rem 700). I just got the bbl blank in from Brownells. Originally I was going to make it 26" but I can get a few more inches out of this blank. At what bbl length does a .223 reach the point of diminshing returns. it's a 1 in 12 twist and I plan on shooting 50 grain moly coated bullets out of it.
Diminshing *useful* returns is about 16 inches depending on the burning rate of the powder used.
ALWAYS trim at least an inch (inch and a half is better) from both ends of any barrel. The chamber usually takes care of the breech end. This area of the bore is almost always a little oversized and somtimes scarred up from pilots.
I would go with a 28' tube, this will probably give you a little more volocity. But this will make the gun handle a little slower. If you go with a 28' tube start on the low end of the reloading manuales, the longer tube will increase preasure.
Posts: 23 | Location: canyon lake california | Registered: 03 March 2003
Let's clear a couple of things up real quick. First, the longer the tube the "less" the pressure. Once the pressure within the barrel peaks, any added barrel length reduce velocities. It would be like accelerating a vehicle with the emergency brake engaged. If you haven't released the brake the minute you let off the gas, you will grind yourself to a halt.
With todays burn rates and selection of powders, there is no longer a need for loooonnnnggg barrels. If you just like long barrels and can do without the velocity, then go for it. My guess for the .223, the most efficient length would be somewheres between 16 and 20 inch. Again, depending on the powder. The only thing you will gain with the 28 inch barrel is being some 8" closer to the prarie dog...
quote:Originally posted by G.Malmborg: With todays burn rates and selection of powders, there is no longer a need for loooonnnnggg barrels. If you just like long barrels and can do without the velocity, then go for it. My guess for the .223, the most efficient length would be somewheres between 16 and 20 inch. Again, depending on the powder.
According to Saeed's own tests ( http://www.accuratereloading.com/223sb.html ), cutting the barrel length from 22" down to 16" REDUCES the velocity approximately 225 FPS, regardless of powder type or charge. 22" certainly isn't an unreasonable or inconvenient length, and it makes a noticeable gain over the 16" mark. I would imagine that more velocity gains can be had by going out to the 28" mark.
quote:Originally posted by G.Malmborg: Let's clear a couple of things up real quick. First, the longer the tube the "less" the pressure. Once the pressure within the barrel peaks, any added barrel length reduce velocities. It would be like accelerating a vehicle with the emergency brake engaged.
Sorry, Malm, but unless I am badly misreading you, your physics is lacking again. A bullet moving down the bore is being accelerated by the chamber pressure, and is being decelerated by friction with the rifling and by the pressure in the bore ahead of the bullet. As long as the force of acceleration is greater than the combined forces of deceleration (or acceleration in the negative direction), then the bullet will continue to increase in velocity with time (or equivalently, with increased barrel length.) Those conditions hold well beyond peak pressure, which typically occurs within a couple of inches of bullet travel. If we were to follow your reasoning, then peak velocities would be acheived with barrels of about 4" length or less, and that's just not the case. After peak pressure is acheived, the rate of acceleration decreases slowly for quite some time, but that is a far different proposition than there being no acceleration or net deceleration.
For most rifle cartridges, the point where there can be no further velocity gain with increased barrel length doesn't occur until many feet down the bore. Barrel lengths of a couple dozen feet are quite obviously impractical, and the extra few feet per second of bullet velocity gained with the last foot or more of barrel length are obviously not worth quibbling about or worth extending the barrel to acheive. Exactly the same kinds of judgements must be made for practical rifles: How long of a barrel is too long? How much barrel length is needed to burn essentially all of the powder? How much muzzle pressure (which increases with shorter length) will generate too much blast? How much velocity loss is too much? Different shooters will answer these questions differently, but it is almost never the case in a practical hunting rifle that the answer to the question "Will increasing the barrel length increase bullet muzzle velocity?" is "no."
Yup, I see the typo. I meant to type "the point which peak velocity occurs" not peak pressure. Once you hit peak velocity that is it, anything extra is drag. I doubt the velocity that one would experience with a 28" barrel over even a 22" tube would be worth the reduced handling characteristics... It becomes a question of what is a practical length for the velocity gained.
quote:Originally posted by G.Malmborg: I doubt the velocity that one would experience with a 28" barrel over even a 22" tube would be worth the reduced handling characteristics... It becomes a question of what is a practical length for the velocity gained.
I'm currently building a varmint rifle in .223 caliber. It's going to be a PD rifle
This is meant to be a prairie dog rifle, so it's not gonna be carried far. Most likely it will be shot from bags or a bipod. Different criteria than a deer rifle meant to be carried through the trees for miles.
I'd say that in this situation, a 28" tube makes perfect sense.
All the theory aside, I have a Ruger #1 chambered in .22 K-Hornet, 26" bbl that sends 40 gr bullets downrange in the high 3400 fps range with 13.3 gr of Lil Gun. You may note that this is well below Hodgdon's max load and well above their published velocities for a max load. 45 gr. Hornet bullets make 3250 fps with 12.7 gr of LG. It is a factory barrel w/reamed chamber, dimensions 'normal'. The only thing I attribute this performance to is barrel length. It is for the most part, the easiest way to increase velocity, and far safer than pushing pressure limits. My .02 worth...
Jack, if I am not mistaken, and according to Doug Shilen, the muzzle end of one of his button rifled blanks can be crowned at the length they furnish them. I used to be under the impression that 1" had to be taken off, but I believed this applied only to cut rifled blanks that the cutter is "catching up" in the first inch of the muzzle. This apparently is different from what the other guys say, including Lilja and Pac-Nor, who normally make a small saw cut one inch from the muzzle. So...what the hell do I know?
Posts: 5534 | Location: Minnesota | Registered: 10 July 2002
Interesting take on the cut rifling explanation. I was always under the impression that the reason we were supposed to cut that last inch or so back was due to the lapping process, and uneven wear/belling of the ends of the bore from the rod & lap. As stated, the chamber "fixes" one end, but the muzzle could be "loose".
However, I've got some that were done just like you say, finished just by facing back enough to be sure it's all square, crowning it, and shoot away! I can't tell any difference.
My experience with prairie dogs is probably not as much as some folks. The only place to hunt them around here is north in Wyoming, where the average distance from the tailgate to the mound is only several hundred yards.
When it came to varmint guns, I used to think long was good. I have built a multitude of 26", .223 prarie dog rifles for the die hard hunters from around here, only to later end up cutting these barrels back so they were more manageable. Most of these folks spoke of "increased" velocities with the shorter barrels when using the same loads they had been using in their 26" barrels.
This affirmed my line of thinking, that choosing the correct powder for a given barrel length is more important to performance, than the length of the barrel itself. Of course, these die hard dog hunters would cover long distance's by foot while stalking and setting up on different dog towns so their guns had to be somewhat portable.
My weapon of choice for slaughtering these critters is likewise a .223 which sports a 20" barrel, and which I shoot off a bipod from the bed of my truck. The speed of handling and performance that this little 20" barrelled rifle provides, based on the body counts in the dog towns, confirms my beliefs, you don't need long barrels to reach out a kill something in the .223 class of cartridge. My 20" barrelled gun is everybit as effective as any 28" barrel gun when the correct powder is used.
Migra is asking for opinions. I volunteered mine based on MY personal, actual, out in the field experiences. He is wanting a 26" barrel but thinks perhaps even longer may be better. I think he is going in the wrong direction. With "todays" powders, in this caliber, there is no need for barrels of 26" or better unless you just want to have one. I don't feel that there is any added benefit to the use of longer barrel in this class of weapon. Others may or may not agree, but if someone wants to have a .223 rifle with a 28" barrel, I will defend their right to have one...
quote:Originally posted by G.Malmborg: Most of these folks spoke of "increased" velocities with the shorter barrels when using the same loads they had been using in their 26" barrels.
Others may or may not agree, but if someone wants to have a .223 rifle with a 28" barrel, I will defend their right to have one...
Malm
Malm-
From all your other posts, I respect you too much to turn this into an argument, so I'll step aside. You've graciously answered & avoided direct confrontations, so maybe I better quit before we "inflame" others.
However, before I go, I just can't follow your first line above, but hey, if that's what they told you, and want you to chop their barrels, well, that's what you get paid to do.
On your second line, I guess I'll reverse that. If somebody wants to chop their stuff down, I'll defend their right to handicap themselves. I respect a man who gives up some advantage in the name of being more sporting.
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I respect a man who gives up some advantage in the name of being more sporting. ![[Razz]](images/icons/tongue.gif){kind=icon}
