Barrel Speed?

[charger 1]

Ya you heard right, barrel speed. Keep getting told I have a slow barrel with regards to a certain gun. Can someone explain this slow/fast barrel thing, and how to make a barrel faster? I'm serious

[Bass Ackward]

Depends on proper diagnosis of the problem how you make it faster or slower if you even can.

You could be a little rough or rough in your dimensions. That's an easy fix to fire lap or just shoot it. Doesn't mean it will pay dividends, it will alter the friction pattern and thus change the vibration pattern. Could be for the good, or .... the bad. Guns change this as they go through their life cycle and require different things at different stages.

Simply shooting it clean or dirty can make a difference. Which is why all the hubabaloo about barrel break-in and cleaning philosophy. A certain barrel may want to shoot fouled, so breaking it in so that it doesn't foul, can ruin accuracy. A certain friction level may be required to get that steel tube to vibrate correctly / consistently at a certain velocity range. If you break it in or fire lap, you may just take that barrel out of the range for that cartridge or gun.

If it alters vibration pattern in a temperature range, you're kinda screwed. Most steel lengthens when warm. Stresses are relieved with heat and some bores bend or walk. Particularly when the rifling method induces stress into the steel such a buttoning. Why the POI changes. But the stress can be there before machining so you can get it with any rifling method. And heavier barrels react slower than thin.

But if your barrel oscillates in a weird pattern at a certain velocity range, you have two realistic options. You have bedding or in the extreme case, rechambering to a different caliber. We had a match 30 that was absolutely horrible as a 308 Win. When rechambered to 308 Norma just cut holes. And my 223 began it's life as a 220 Swift for a customer that was abysmal. And don't think I am claiming any knowledge here, I had no idea either way. These were just expensive barrel failures that could not be sold as such that were recycled. In other words, just gambled and surprise!

That's what you can't see and you can't control with a barrel is "consistent" vibration. Friction determines the vibration, so if you can alter that in any way, you stand a chance to change the barrel. I suppose another way to alter friction would be to open the groove diameter as with military rifles. This may result in the pattern going the other way from what you wanted though, so it all depends on the steel which you cannot see.

Since you asked this in this section, you got this answer. If you had been in another section, you would have gotten all the reloading steps like altering powder speed, bullet weight, hardness, etc.

[JSnover]

Probably means you have a slow twist for that caliber. If I remember correctly, your barrel should do better with lighter boolits or lower velocities.

[2muchstuf]

To the best of my knowlege, the only difference in barrel speed is the rate of twist.
1 in 66" for my ML with round balls,1 in14" in my .222(much faster).
There's a lot of science with twist rate to boolit weight, don't know as much as I'd like to about this subject. I'm patiently waiting for someone else to jump in on this and we are both going to learn alot.
Hope this helps till we learn more.

2

[2muchstuf]

alot happened since I started to type.

[cajun shooter]

Barrel speed in my 61 years on this earth always meant the rate of twist in a certain barrel. Now I know times have changed as crack no longer refers to that place on your body. A slow twist as a rule will do better with big lead and a faster twist with the little ones. The Army found that out when trying to go from the old 55gr to the newer 63 and above. They had to change the twist. Speaking of the twist; it seems I remember Friday night dances and some guy called Chubby Checker!

[trickg]

There has been a lot written about the twist rate of rifle barrels that I have read over the last six months or so. I'm not sure how much of it is hype and how much of it is real science that is applicable to the average shooter. Also, it seems to be more in terms of fine accuracy as much as anything else.

I have read where a barrel with a slower twist - say 1:14 - isn't as good for smaller, lighter bullets because they don't have enough spin to maintain stabilization and the bullet at distance will begin to tumble. I have also read that if the barrel twist is too fast - say 1:9 or faster - and if you are trying to push that bullet too fast, the bullet can't take the torsional stress and can actually break apart when exiting the barrel. I read about a guy who had a .22-250 who had worked up a good fast load with a lightweight bullet, but when he tried it in his rifle that had a fast twist, it literally disintigrated and never even made it to the target.

Here is a chart that lists the "standard" rate of twist for various rifle calibers:

http://www.accuratereloading.com/twist.html

[John Taylor]

I have always heard that it referred to twist rate. The old muzzle loaders with round ball might have a twist of 1 in 40" on out to 1 in 140" depending on caliber. The 50 EX Winchester started with a 1 in 60" twist and a 350 grain bullet to get the high velocity. It would not hold at long range so Winchester went to 1 in 56" and then 1 in 48". The 50-100-450 started with the 1 in 48" and whet down to 1 in 36" trying to get it to shoot. Winchester played around with twist rates a lot in the later 1800s. A heavy long bullet requires a faster twist than a short ( round ball) bullet. Velocity also plays a roll, if the revolutions per second are not fast enough the bullet will tumble. If you have a 1 in 12 twist and a velocity of 3,000 FPS then the bullet is spinning at a rate of 3,000 RPS. If you change the twist to 1 in 24" the RPS will be 1,500. Long skinny bullets need to spin fast to keep from tumbling.
A barrel with to fast a twist will effect velocity. Some of the power will be used to spin the bullet faster. Many years ago I built a 300 Win Mag with a 31" bull barrel. I went with a 1 in 14" twist because I was trying to keep the velocity up. Using 180 grain bullets I was getting over 3,300 FPS and was able to win several shoots at 600 yards. If I would have used a 220 grain bullet it may not have shot as well.
Hope this helps

[felix]

The more the barrel/gun accelerates, the more energy is taken away from the projectile coming out of that barrel/gun. ... felix

[trickg]

The more the barrel/gun accelerates, the more energy is taken away from the projectile coming out of that barrel/gun. ... felix
That's correct in a way - it really boils down to plain physics:

The formula is:

Energy (in ft lbs) = .5 * weight * velocity² / 7000 / 32.175

Where weight is in grains, and velocity is in feet/second.

7000 is grains per pound, and 32.175 is acceleration due to gravity.

It can be re-written:
Energy = weight * velocity² / 450450

So, if the twist rate of the barrel slows down the velocity of the bullet, yes, in effect, it reduces the energy, but not because of how fast it's spinning, but only because the bullet is traveling slower. It would have the same energy if it was traveling at the same velocity and it wasn't spinning at all.

[yondering]

How did this thread get focused on barrel twist? Charger 1 asked why he has a "slow" barrel, and how to make it shoot faster. Twist is only one small contributor to velocity.

Charger 1, I've tried to figure out the answer to this question as well. I've had a lot of guns that shoot "slow", and only one so far that shoots "fast". The "fast" barrel is a custom piece from Benchmark Barrels, it's a 28" heavy stainless in 6mm Rem AI, and will throw 70gr j-bullets a good 400 fps faster than I would expect, even accounting for the extra length and Ackley chambering. (It can get up to 3,950 fps with 70gr HP's.) I'm not sure what makes this barrel so fast; twist rate is 1:10, which is common for that caliber. I suspect the bore dimensions may be slightly tight, but can't verify that accurately. The barrel was hand lapped at the maker, so it was nice and smooth, but performance hasn't changed and I've got close to 1,000 rounds through it. I'm sure the throat isn't that smooth any more.

On the other end of the spectrum, I have a 30-06 barrel that was "average" regarding velocity, but always copper fouled heavily. It was a micro groove barrel from Marlin (actually marked Western Field) that appeared to be a little on the rough side. I decided to fire lap it to get rid of some of the fouling, and ended up destroying the barrel. 18 rounds of firelapping (using the beartooth bullets kit and following instructions) resulted in severe copper fouling after only one shot, and velocities 300-400 fps slower than before lapping. I think what happened was the lapping opened the bore up too much, creating a slow barrel. Slugging the bore shows it to be right at .308" or just over, so I suspect there may be only a tiny difference, dimensionally, between a "slow" barrel and a "fast" barrel.

I have a 22 Hornet barrel which I've polished using the Tubb Final Finish System which is like firelapping, but only polishes the bore. I did chronograph before and after, and was surprised to find no significant difference, even though the bore was obviously much smoother afterwards. The barrel was much more accurate and easier to clean, but didn't shoot any faster. I did find that I could increase the powder charge a little more without running into pressure signs, which makes sense.

These are the only contributing factors I've figured out, hopefully someone else will have more input.

I guess my input on making your barrel faster is that I don't know anything that will help for sure, and some things, like lapping the barrel, may hurt it more than help it.

[trickg]

How did this thread get focused on barrel twist? Charger 1 asked why he has a "slow" barrel, and how to make it shoot faster. Twist is only one small contributor to velocity.
This thread got focused on barrel twist because that, probably more than any other factor except in special circumstances, affects bullet velocity, and it's what is usually referred to when talking about barrel speed.

1:14 twist is a faster barrel
1:9 twist is a slower barrel

The initial thread wasn't terribly descriptive and since he has yet to weigh back in on the subject, we don't know if what he was talking about was similar to your situation, or if it was in fact due to the twist rate.

[yondering]

He did ask about barrel speed, not specifically twist rate. Fast twist doesn't always make a barrel shoot slower than a slow twist, a lot of other factors contribute as well. My point was that twist rate isn't the only thing that determines whether a barrel shoots fast or slow.

In my example above, I described how my medium twist 6mm shoots much faster than other slow twist 6mm's. (Remember the .244 with it's slower twist, same cartrige as my 6mm Rem).

[trickg]

He did ask about barrel speed, not specifically twist rate. Fast twist doesn't always make a barrel shoot slower than a slow twist, a lot of other factors contribute as well. My point was that twist rate isn't the only thing that determines whether a barrel shoots fast or slow.
The laws of physics are what they are - all other things being equal, a barrel with a faster twist WILL shoot slower than a barrel with a slower twist. Again, he wasn't specific enough about it, so we don't really know what he was referring to. There may well be some other factor that makes his barrel a slow barrel, but all other things being equal, we're talking about twist rate and I believe his question was because he wanted to know why it might be slow and what could be done about it. The answer might be a new barrel with a different twist rate, or it might be to have the barrel lapped, or it might even be to replace the barrel with a new barrel with the same twist rate - at this point, we don't have enough information to know.

[felix]

Things never will be equal between guns and/or loads, so this discussion must be for fun only. ... felix

[charger 1]

How did this thread get focused on barrel twist? Charger 1 asked why he has a "slow" barrel, and how to make it shoot faster. Twist is only one small contributor to velocity.

Charger 1, I've tried to figure out the answer to this question as well. I've had a lot of guns that shoot "slow", and only one so far that shoots "fast". The "fast" barrel is a custom piece from Benchmark Barrels, it's a 28" heavy stainless in 6mm Rem AI, and will throw 70gr j-bullets a good 400 fps faster than I would expect, even accounting for the extra length and Ackley chambering. (It can get up to 3,950 fps with 70gr HP's.) I'm not sure what makes this barrel so fast; twist rate is 1:10, which is common for that caliber. I suspect the bore dimensions may be slightly tight, but can't verify that accurately. The barrel was hand lapped at the maker, so it was nice and smooth, but performance hasn't changed and I've got close to 1,000 rounds through it. I'm sure the throat isn't that smooth any more.

On the other end of the spectrum, I have a 30-06 barrel that was "average" regarding velocity, but always copper fouled heavily. It was a micro groove barrel from Marlin (actually marked Western Field) that appeared to be a little on the rough side. I decided to fire lap it to get rid of some of the fouling, and ended up destroying the barrel. 18 rounds of firelapping (using the beartooth bullets kit and following instructions) resulted in severe copper fouling after only one shot, and velocities 300-400 fps slower than before lapping. I think what happened was the lapping opened the bore up too much, creating a slow barrel. Slugging the bore shows it to be right at .308" or just over, so I suspect there may be only a tiny difference, dimensionally, between a "slow" barrel and a "fast" barrel.

I have a 22 Hornet barrel which I've polished using the Tubb Final Finish System which is like firelapping, but only polishes the bore. I did chronograph before and after, and was surprised to find no significant difference, even though the bore was obviously much smoother afterwards. The barrel was much more accurate and easier to clean, but didn't shoot any faster. I did find that I could increase the powder charge a little more without running into pressure signs, which makes sense.

These are the only contributing factors I've figured out, hopefully someone else will have more input.

I guess my input on making your barrel faster is that I don't know anything that will help for sure, and some things, like lapping the barrel, may hurt it more than help it.


For example ,if I shoot my lott along side of buddies 458 with the same twist rate in the same gun, and we both are boiling the heck outta 500 grains I'm pretty much garaunteed to be at least 150 fps faster right? NO, were about neck and neck. Of the tons of folk I've asked all I can get is"i must have a slow barrel and buddy a fast one" They know all factors such as twist and barrel length are identical, so what gives? It dont bug me, other than I'd love an explanation

[John Taylor]

another thing that will effect velocity is bore and groove diameter. I have seen many factory barrel that are on the large side. This may be to keep pressures down for safety. After market barrel are a little closer to bullet size and in most cases will shoot better. If the pressure is down then the velocity may be down also.
Slug the barrel and see what size it is.

[yondering]

For example ,if I shoot my lott along side of buddies 458 with the same twist rate in the same gun, and we both are boiling the heck outta 500 grains I'm pretty much garaunteed to be at least 150 fps faster right? NO, were about neck and neck. Of the tons of folk I've asked all I can get is"i must have a slow barrel and buddy a fast one" They know all factors such as twist and barrel length are identical, so what gives? It dont bug me, other than I'd love an explanation

Yeah, I hear ya Charger 1, it's weird when you get a slow one like that. Disappointing too, for me anyway. I'm sure if you wanted .458 Win Mag velocity you would have bought one of those, not the Lott, right? I agree that you should expect the Lott to give significantly higher velocity, especially with the heavy 500gr pills.

Are those Ruger #1's?

Like John Taylor said, it would be interesting to slug the bore of both guns to see if you can find any differences. I'd wonder if the bore in yours is slightly larger? Or maybe a longer throat? There's enough variation in factory barrels that while the twist rate and barrel length may be the same, some of the internal dimensions could be different.

You might also check for any slight constriction in the barrel, which might affect velocity.

Could be that your gun has a rougher bore, but that would probably be evidenced by significantly more fouling (copper or lead) than your buddy's gun.

One more thought, are you using factory ammo or handloads? Are both guns shooting the same 500gr bullet? Some bullets will go faster than others with the same load of course. If handloads, are you both using the same powder, or are you using a slower powder to take advantage of the Lott's larger case? Keep in mind I don't know you from Adam, you may be a very experienced handloader and have already thought of all this; I'm just offering up what I can think of. Wish I had a better answer for you.

BTW, there's definitely something cool about the .458 Lott. I built a .458 Win Mag on a Mauser action a few years ago, but really liked the idea of the Lott when Ruger started chambering their #1's in it. Never did get one yet though.

[floodgate]

Back inthe early Black Powder / Round Ball days, when rifling was first coming into common use, it was felt that the addition of twist (early "rifling" was often straight - no twist - mostly to provide a place for fouling to be deposited) held the ball back and built up pressure, so that the faster twists actually ended up giving HIGHER velocities at the muzzle. It'd be interesting to try this out, using - say - several pairs of Lyman GreatPlains barrels with "slug" and "ball" twists, to see which one actually DOES yield the higher velocity for the same powder and ball load. Hmmmm... is that an excuse to spend some more $$$$?

floodgate

[Buckshot]

..............A rifle is a heat engine and it's performance is the sum of it's parts with the barrel being the most important component. Two rifles off the line one after the other will be different. Benchresters speak of "Hummers" (barrels, not the SUV) which are not known to be so via visual inspection, but only by shooting.

Just to pick a name, Hart for instance manufactures their barrels from fully certified and traceable lots of steel from a specialty steel supplier. Then they get checked over by the people at Hart before any work is ever done. They all get the same treatment during manufacture. Once done they all get the same inspections done. Borescoping, slugging, lapping, air gaugeing etc.

While all these barrels are of the very highest quality, a couple out of that lot which showed no peculiatrities upon final inspection, will end up being "Hummers". Barrels that will shoot previous match winning ammo into groups a hundredth or several thousands smaller in size then the several previous barrels.

I read where BR Hall of Famer Tony Boyer was in some conversation about the so called Hummer barrels. He said on the few rare occasions he'd been lucky enough to have one he spent an inordnant amount of time trying to figure out WHY, to no avail. He summed up by saying you'll know them by shooting them. Count yourself lucky and enjoy them while they last!

................Buckshot

[waksupi]

Back inthe early Black Powder / Round Ball days, when rifling was first coming into common use, it was felt that the addition of twist (early "rifling" was often straight - no twist - mostly to provide a place for fouling to be deposited) held the ball back and built up pressure, so that the faster twists actually ended up giving HIGHER velocities at the muzzle. It'd be intersting to try this out, using - say- several pairs of Lyman GreatPlains barrels with "slug" and "ball" twists, th see which one actually DOES yield the higher velocity for the same powder and ball load. Hmmmm... is that an excuse to spend some more $$$$?

floodgate

I'd played with that concept a bit, and found I got greater velocity from a smooth bore than a rifled barrel, given the same powder charge and ball size.