In order to participate in the GunBroker Member forums, you must be logged in with your GunBroker.com account. Click the sign-in button at the top right of the forums page to get connected.
Big argument with dad. Need help
uni82
Member Posts: 416 ✭✭
Alright. I have a 35 Remington that has been re-chambered to a 358 Winchester. It is only a 16 inch barrel but has a 1:16 in twist. the 35 Remington mainly uses a 200 grain bullet but the velocity is significantly less of the 358, which lets the barrel stabilize the bullet. Even if I reload a 180 grain bullet for the 358, I don't believe it will stabilize the round. What are your guys thoughts?
I have a scope on it and I might reload some shortly (depends on how much work I need to do) but should I even reload the 358 or save the powder and primers? Oh yea the rifle is a Remington 760 pump re-chambered to a 358 win. Thanks a lot guys!
-JD
I have a scope on it and I might reload some shortly (depends on how much work I need to do) but should I even reload the 358 or save the powder and primers? Oh yea the rifle is a Remington 760 pump re-chambered to a 358 win. Thanks a lot guys!
-JD
Comments
You will surely be OK with a 200 gr bullet and maybe a 250.
-JD
IOW Sierra's 225gr Boat tail spitzers may be to long for the twist even at the increased velocity.
You'll simply have to try them to see if your rifle likes them, or give Sierra a call, they're happy to offer suggestions.
-JD
As an example, if you have a 1-12" twist (to make the math easier), and you fire a bullet at 2,400 fps, it will be spinning at 2,400 revs per second. But fire it at 3,000 fps and it spins at 3,000 revs per second.
(For the dense, those work out to 144,000 and 180,000 rpms, respectively.)
Either way, the bullet fired at a faster speed will spin faster, AND be more stable.
And the CORRECT rule of thumb is: longer (heavier) bullet, FASTER rate of twist.
Period.
Higher velocity does not make a bullet spin faster. It only makes the bullet get there faster. Rule of thumb, heavier bullet, slower twist.(period)
B17-P51,
That would apply to diameter not weight (actually length). Rocky is right in that for each caliber, the heavier weight, thus longer bullet will need a tighter, not slower twist.
Twists loosen up as diameter grows. That's why you can stabilize 208/210 gr. bullets in .30 cal with a 1-12" twist. That same twist in .257" only allows you pretty much to stabilize 100 gr. and anything heavier needs to be a round-nose.
Big diameter rifles like the .35, 9.3mm(.366") and .375 only require 1-16" twist. My 9.3 only has a 1-16" twist and it stabilizes 286 gr. bullets @ 1.250".
A 1-12 twist will still be one full turn every foot if it is 1000fps or 3000fps.
True and the RPM will be higher at 3,000 FPS.
quote:Originally posted by EhlerDave
A 1-12 twist will still be one full turn every foot if it is 1000fps or 3000fps.
True and the RPM will be higher at 3,000 FPS.
I was thinking if the target is 1 mile off the bullet will spin (with a 1-12 twist)5280 times before it hits regaurdless of how quick it covers the ground. If it takes 3 min at 1000fps it would take 1 min at 3000fps but the same amount of twists.
Am I flawed in my thinking? If so I am more messed up than most nights. [8D]
In terms of Rev's / distance you would be correct, in terms if Rev's / time the others are correct. It's a question of perspective.
Edit: Thinking even deeper (and my head is starting to hurt), and as rotational velocity does not decrease as fast as forward velocity, the above holds true over the early distances, but as the bullet travels down range (say to 1000yd) the rev's/time would still be close to the same, but the rev's/distance would be MUCH HIGHER down range
The confusion arises in the fact that to achieve a higher or lower spin rate, we change the twist rate in the barrel - and we define that as turn per distance. But it is only a definition of convenience, because what we are truly trying to adjust is the spin rate of the bullet, and that is determined by the pitch of the rifling AND the velocity at which it is launched. We could just as easily define the pitch as the angle at which the rifling is cut. The effect would be identical: a spiral cut into the bore. But it's easier to envision "one turn in x" than it is to envision " a pitch of x.xx degrees".
To slow the twist we must change the bbl. same to increase.
What is happening on this thread is a confusion between RPM and RPD "Rotations Per Distance".
A bullet shot from a 1-12 twist is the same twist at 2400 fps as it is 3000. The bullet will spin the same number of times in 1000 yards.
But rather than continue a pointless discussion to the point of rancor, I'll bow out knowing I'm right.
I don't care what people say a rifle with a 1-12 twist will have the same twist no matter what velocity the bullet travels. Velocity has no effect on twist rate, that is what I am saying. I understand that it will slow down from the time it leaves the bbl. but I have no idea how to figure that equation.
To slow the twist we must change the bbl. same to increase.
What is happening on this thread is a confusion between RPM and RPD "Rotations Per Distance".
A bullet shot from a 1-12 twist is the same twist at 2400 fps as it is 3000. The bullet will spin the same number of times in 1000 yards.
I agree with you. The rpm is SET by the rifling twist rate. In fact,
in all real time and space areas, the bullet should be turning slower
as it gets farther from the muzzle. Bullet speed only will affect how many times it revolves before it hits something. Bob
The bullet twist in a barrel becomes a "spin rate" factor, if you will, once it leaves the barrel.
Mathematically if you shoot a bullet from a 1-12" barrel @ 2400 fps it will leave the barrel spinning at a rate of 2400 revolutions per second. Because it is rotating once each foot and moving @ 2400 fps.
If you fired the same kind of bullet @ 3000 fps it would then rotate at 3000 revolutions per second because it is rotating, again, once every foot but is now moving @ 3000 fps.
The twist rate remains the same, but by speeding the bullet up, the rotation increases.
This is almost the same thing as having 15" tires and moving at either 45 mph or 60 mph. The 60 mph tire is rotating faster to get the faster speed. In the bullet world rotation doesn't dictate speed though. That is dictated by powder charge and case. Rotation in a given twist (like the 15" tire) is dictated by speed.
In a vacuum, where each bullet would continue to rotate at that given speed, The number of rotations for both bullets to reach 1000 yds would be 3000. Again because each bullet rotates once each foot.
Two problems come into play at this point. One, we are not in a vacuum, bullet velocity slows down and so does bullet rotation. Although the latter slows down at about 10% of the rate of velocity loss. Which brings us to problem number two, stability. In order for a bullet to fly through the air relatively straight it has to be spinning at a high enough rate. Say the bullet traveling @ 3000 fps, and thus rotating at 3000 revs per sec. is just barely stabilized by that spin rate. That bullet certainly won't stabilize at 2400 revs per sec.
Conversely, uni82 is looking to start firing the .358 bullets at the (I use as an example) 3000 revs per sec. which will stabilize the bullets as opposed to the 2400 revs per sec which already stabilized the bullets. The faster speed will actually help stabilize longer (heavier) bullets. Speed, though, needs to change quite a bit for it to be a go/no-go for stabilization. Twist per caliber plays the major role in that. In this case he can increase his chamber to the .358 and shoot the same or even slightly heavier bullets and have them stabilize.
-jd
so yea, my 358 should take a 225 gr bullet with a 1-16 twist. sry for starting the argument. hah!
-jd
Just so you know, Rocky Raab is absolutely 100% correct. RPM is a measure of revolutions over a period of time, not distance.
The strange thing is you may find a bullet that according to all the charts will not be stable. In your gun, at X distance it could be just fine. Buy the weight you want to shoot and give it a spin.
Pun intended!
sry for starting the argument. hah!
-jd
Argument: fools yelling at each other
Discussion: adults exchanging information, in a calm manor
We've been having a discussion, not a argument (you want to see an argument, head over to the toilet bowl political forum)
quote:Originally posted by uni82
sry for starting the argument. hah!
-jd
Argument: fools yelling at each other
Discussion: adults exchanging information, in a calm manor
We've been having a discussion, not a argument (you want to see an argument, head over to the toilet bowl political forum)
I was just there. That gets dumb. Stuff that ain't never...happening tomorrow? IDTS. Not that someone won't try. But I certainly believe if a discussion is to start and ensue to reasonable course of action (reasonable decided by us here not someone else) that the direction and protocol needs to be followed. Over there, it doesn't. Every day I read what is about to happen to me tomorrow.
Rocky you are wrong on this one also.
Ehlerdave is right.
Are you just trying to pull Rocky's chain? He is 100% correct.
While EhlerDave may make what seems like a legitimate point Rocky is dead on with what actually happens. Rotation in the open air doesn't really mean a hill of beans other than the bullet remains stabilized. There is nothing to counter-affect the bullet from slowing down. both in velocity and rotation. Remember, once it's out of the barrel they aren't tied to each other anymore.
That was what my whole last post was about. Explaining to EhlerDave that while what seems right, actually through the course of firing a bullet, is not right. Spin doesn't slow as much as velocity and therefore a bullet will spin a lot more than what it would as if it were in a barrel all the way out to the target.
Much like the 15" tire I described. Lets use slipping in the snow as a different example. If the tire rolled one mile on dry pavement @ 60 mph.(like a bullet would in the barrel, but slower). It would get there in 1 minute and have rotated 672.27 times. But as the bullet leaves the barrel it slows down. It's not going 3000 fps anymore. It's going 850 fps. But, its' still rotating at around 2700 rev's per second when it gets there. With a flight time of about 3.85 seconds to get to one mile, that pretty much puts total rotations out to about 10395. Add in the factor of losing about 10% rotation per 1000 yds and you have 3.38 seconds.
No I am not pulling Rockys chain. His points are quite correct, mathmatically.
If you go back and read your own post, particullary the part that you underlined, you may understand why I felt comfortable making the statement I did. (about Rocky)
As you also stated (thank you) that "speed needs to change quite a bit" this furthur caused my finger to type comments about Rocky.
I respect Rocky and his expertise sharing on GB but the ORIGINAL question was about rate of twist as opposed to RPM's. If RPM's were the deciding factor then, in theroy, reduced loads, frequently given in manuals, would never work. How could a bullet fired at 3000 FPS normally, even hit the target at say 13 or 1400 FPS? But they do.
Again Rate of twist comes into play over a wide range of velocities, as is commonly known, and stated by you.
I went through this dilemma in reballeling a .308 last month and choosing between a 1-10 or a 1-12 twist.
Hope this clear up any misunderstandings and I am truly sorry if I have offended anyone.
The reason reduced loads can still be stable (sometimes only marginally so and over only a short distance) is that rate-of-twist calculations always err on the side of over-stability. They do so to allow longer than standard bullets OR slower than standard speeds.
No matter how you look at it, it is the speed of rotation that makes bullets stable. Speed of rotation means revolutions per time. Period.
You've got to read my whole post. Especially the first line. In the barrel, a 1-12" twist, the bullet will leave the barrel twisting/spinning at the speed rate at which it was fired. Once it's out of the barrel, not being pushed by hot gases through a controlled tube (the barrel) it will no longer adhere to the rate the barrel pushed it out at.
Also, remember when we push a bullet out at 2400 fps, that also means it left the barrel doing 2400 revs per second. Because the bullet is turning once each foot. And each second of 2400 RPS (now that it's out of the barrel) it's moving at 2400 feet. (2400 fps.)
But, the second bullet also fired from the 1-12" barrel, except this time it's at 3000 fps. It is rotating at 3000 rev's per sec. Because we pushed it out at 3000 feet per sec. So now once that bullet leaves the barrel it is turning 1 1/4 times as fast as the 2400 fps fired bullet.
Again, in a vacuum, the bullets would both turn 3000 times to get to 1000 yds. and 5280 times to get to one mile. BUT WE ARE NOT IN A VACCUUM! The bullets slow down much faster than the rate they turn slows down. And since the barrel doesn't hold them at that rate of one turn every foot, they continue to spin at about the rate they left the barrel at. If the bullet is moving fast enough and spinning fast enough it will remain stable. If the balance between the two goes out of a given ratio or one or the other falls below a threshold the bullet will become unstable.
ALL of the above comments are more or less correct but if you had as much trouble deciphering the information above as I did this may help. I firmly believe you can figure this out yourself if you learn the basics. It's always easier to fix something if you know how it works when it's not broke. (This by no means a complete list of what's available on the net but they are my favorites.) I recommend you save the following links and use them to learn how, not just why, the previous posters came to their conclusions:
Barrel Twist Formulas:
It's been alluded to here but never defined. For your personal use it may come in handy: The correct rifling twist rate for a particular bullet can be calculated by using a formula originated by Sir Alfred Greenhill during the late 1800s. Not being the quickest shot on the block, I had to translate it to something I could use easily:
1). Take Bullet Length (l) and divide it by Bullet diameter (d). = RATIO (r)
2). Take Bullet Diameter (d) and divide that by the RATIO (r). = (Q)
3). Take that sum, (Q) and multiply by 150 (or 180)
4). Sum equals Recommended Barrel Twist For that Bullet.
IOW: l/d = r
d/r = Q
Q times 150 (180 for velocities in excess of 2800 fps) = Twist
If you notice I added "Q" to make things a little easier.
ANOTHER SOURCE:
This is from the McGyro program developed by Bill Davis and Robert McCoy. This program takes into consideration:
1). O.A.L. of projectile
2). Nose length
3). Meplat diameter
4). Nose shape
5). Boattail length
6). End diameter
7). Twist rate
A stability factor of between 1.25 and 1.75 or so will serve you well.
http://www.lascruces.com/~jbm/ballistics/drag/drag.html
MORE....
All About Barrels
RECOMMENDED* RIFLING TWIST RATES
http://www.rifleshootermag.com/gunsmithing/RS_allaboutbarrels_200902/index.html
Again, alluded to here but this is the process:
Bullet RPM = MV X 720/Twist Rate (in inches)
Calculating Bullet RPM - Spin Rates and Stability ? AccurateShooter.com Bulletin
http://accurateshooter.wordpress.com/2008/06/03/calculating-bullet-rpm-spin-rates-and-stability/
ALSO OF INTEREST:
SWAT Article BARREL LENGTH
http://www.tacticaloperations.com/SWATbarrel/
BARREL LENGTH AND THE PRECISION RIFLE
Why shorter barrels may often be better
by Eugene Nielsen Copyright c 2000
SWAT Article BARREL LENGTH
http://www.tacticaloperations.com/SWATbarrel/
Fast, accurate and easy!
quickload quicktarget software
http://www.neconos.com/details3.htm
I downloaded the "Demo". The program costs $149.95
How to Calculate MOA and Bullet Drop:
Dexadine Ballistics Software - ballistic data for shooting and reloading
http://www.dexadine.com/qgeneral.html
Another New Ballistics Program: A suite of ballistics programs:
Custom Tactical Rifles - Rifled Barrel - Rifled Barrels - Border Barrels - UK
http://www.border-barrels.com/index.htm
External Ballistics form
http://www.border-barrels.com/external_ballistics.htm
HOME PAGE:
Custom Tactical Rifles - Rifled Barrel - Rifled Barrels - Border Barrels - UK
http://www.border-barrels.com/index.htm
An in depth discussion of Rifling Twist Rates By Chuck Hawks:
RIFLE BARREL
http://www.chuckhawks.com/rifle_barrel.htm
There you go. Measure your bullets length. Measure the speed at which you fire it. Then do the math. You'll see if you up your chamber you will stabilize the bullets you were firing before. And now you may even stabilize a little bit heavier (longer) bullet.
-JD
That's just some stuff I found when I too was looking for a new caliber long-gun. I fail to understand how firearms manufacturers get away with producing rifles that only meet general criteria and accommodate only minimal or a limited choice of bullet weights. I know that is not the case with your question but I came to the conclusion from my research that, when looking for out-of-the-box accuracy and a larger range of bullet weight stability without buying numerous firearms of the same caliber, Savage is the only logical choice.
Then came the disparity of barrel lengths (which you inquired about) offered and what affect that would have related to the caliber and twist rate. It certainly explains WHY a different choice in bullet design or bullet weight can make accuracy good, better, best or just plain lousy. Have you ever heard a shooters say, after many boxes of expensive ammo, how their rifle loves a certain bullet, load, factory ammo or whatever?? That seems to be a function of buying a name-brand rifle and then finding something it was designed to shoot well. I have numerous rifles of the same caliber that all shoot differently with the same factory load. That's why reloading is fun.
Now I've taken a different route and decided what range of bullet weights and type of bullets I can easily find, like, and perform well and then find a gun that will accommodate them with the best out-of-box accuracy. My next new rifle will be a Savage. I also found there aren't may used ones available, as is the case with the more popular name brands, which also tells me something.
Anyway, I hope things work out with your .358. Have you gotten your Arisaka yet???
Sandwarrior, or anyone else:
Do you have any thoughts on my reasoning above???
Got the arisaka. It is a type 99 made in Nagoya. I am absolutely pumped!!!!! I'm almost 100% positive that it is NOT a last ditch rifle. I had a gunsmith check it out, and it is goooooood to go. I am sooo stoked to squeeze the trigger. But i have a while. I need reloading dies, .312 pills, brass, powder. Load finding.
I have to save up for a wedding...... but until then i'm pretty pumped to add it to my collection!
I'm getting 358 tips here soon, 180 hornady's. I have extra powder (that the load's recipe that i found calls for)and primers so I will update everyone when i breakdown my reloading table and bring it to my new home (just moved) so yea, that will be a while too.
Thanks for all your help and again, you guys are amazing for knowledge and experiences. I am glad to be part of gun broker community and learn all this new material for a newbi re loader (only 23 years old) Thanks!
-JD
I like your thinking. I just wish sometimes I could get someone on Madison Avenue to actually think that way. Think about what shoots great bullet-wise first. Then build the rifle around that. What we always see is a compromise. Never a full-on specific task dedicated rifle...except Savage. It always seemed like in the past when Winchester and Remington were into building a very few heavy barrels they were more interested in them becoming some kind high grade/collector type rifle instead of a long range work-horse, like the 700 and 70 were to the every day crowd.
Even still there are improvements manufacturers could make. Time will tell.
quote:I had a gunsmith check it out, and it is goooooood to go. I am sooo stoked to squeeze the trigger. But I have a while. I need reloading dies, .312 pills, brass, powder. Load finding.
I can't help with the dies because I need mine. I have two sets of RCBS dies (not for sale). I also have two of the Lee Classic Loaders, (not for sale either) which I finally found on E-Bay. I have those Classic Loaders for every caliber weapon I own and whole heartedly recommend getting one, if you can find one. Being portable and packed in a small box makes them very versitile. All you need is a 16 oz. mallet. The dippers are accurate enough if used properly but a small (jewellers) electronic scale also works well as long as the batteries last.
As for load finding, no problem. This is a basic article about the Arisaka but it does include Load data with a range of powders and bullet weights. It also addresses some safety issues and describes how to form cases from 30-06 brass.
The 7.7 Arisaka
This World War II classic is efficient, accurate and a heck of a lot of fun to load for.
By Bob Forker Posted: 2008-09
Categories: Reloading, Reloading, Rifles, Ammo,
Source Page:
The 7.7 Arisaka | Reloading
http://www.gunsandammo.com/content/the-77-arisaka
I highly recommend you have a good manual so:
My Hornady manual has 7.7 Jap load data for powders NOT found on the above list. And, my 1966 Speer #7 (and #8 -1970) Manual has load data for a 100 gr. plinker, 150 and 180 gr. Bullets, again NOT found on the above list. The New Speer has NO Data 7.7 Jap and neither does the Nosler. The Sierra and Lee Manuals also have 7.7 Jap load data.
quote:I have to save up for a wedding...... but until then I'm pretty pumped to add it to my collection!
Ahhhh. to be 23 again. (And know what I know now about life and other stuff.) Congratulations, when's the ceremony??
-JD