Twist to stabilize a bullet

[patw]

This is in regards to reloading the 300-221.  I have a barrel that has a 1-10 twist.  I have used it with light bullets for deer hunting, 125 grains.  My YHM phantom suppressor finally came in after five long months of waiting for the paperwork to clear, and I am now working up some subsonic loads.  I have always read that to stabilize a heavy bullet you needed a barrel with a 1-7 or 1-8 twist.  I have started to play with some loads according to some of the recipes, and for sure the heavier bullets start to tumble at 25 or 50 yards, but I did not have the chrono set up so I have no idea of velocities.  Then I started wondering, I can understand that with a heavy bullet you may not be able to get the velocity that would give you enough RPM of bullet spin to stabilize it, but if I am trying to keep the loads subsonic say at 1050 fps, any bullet will spin at the same rate whether it is 150 grains or 220.  What am I missing?

[gypsyman]

Kinda like the difference between throwing a football, and a knuckleball. Put spin and speed on a football, and you get a straighter line. Slow it down, and it ends up wobbling like a knuckleball. And can't be thrown as accurately. With projectile's,(bullets) accuracy depends on weight and bullet diameter. A bullet out of a 45-70, can be stabilized with a 1400-1500 fps, and a 1-35 to 1-45 twist. A smaller bullet, faster spin. gypsyman

[martineta]

Careful, careful, careful.  I have Three 300 whispers and a 300-221.  First one was a Thompson barrel 1 in 10 twist.  It is deadly accurate with 125 and 150 ballistic tips.  I have since bought a 300 whisper from SSK with the 1 in 8 twist to shoot the big 220 and 240 SMK's and 225 outlaw state bullets.  I believe JD Jones in that you need the faster twist to stabilize the heavy bullets plus the faster twist is also great for the 125's and 150 grain bullets.

Before you try the big bullets thru your can.  Shoot of bunch of subsonic rounds at white paper at 50 yards not trying to get the great group but trying to see if the bullets are punching perfectly round .308 holes though the paper.  What you absolutely don't want is a wobbley bullets leaving your barrel resulting in a baffle strike in your suppressor and ruining an expensive can.

What I would do is buy another barrel in 1 in 8 twist for the heavy subsonic rounds and use the 1 in ten twist dedicated to supersonic in lighter bullets.

You can also just sell the 1 in 10 barrel and apply the funds to a new 1 in 8 barrel and accurately shoot both.  The 1 in 10 barrel will be snapped up here or on Gunbroker lickety split.

Good luck.  I love shooting the subs and supers both and the deer definitely fall down when I do my part.

What gun do you have it on?

A great source for info on the 300 whisper and its varients is www.quarterbore.com 300 whisper pages.  They are in the process of moving their server and the site is down.  Should be up though in a week or less.

[patw]

Martineta, I have it on an ar15. 

I actually had a 1 in 8 upper at one time, but it did not seem to shoot as well as the one in ten.  I found I was not using it, so I traded it for a pistol (I am finding that I am not using the pistol either....wish I had kept the 1 in .  I have been shooting the whisper/300-221 for five or six years.  Started out building the rifle for my daughter who was seven at the time.  Turned out she was afraid of the noise, but since I had the rifle, I put it to good use.  I have hunted with it several years, and it has been wonderful.  Little noise, no kick to speak of, and I am not sure how dead the deer are supposed to be, but it seems to kill them dead enough.  All of this has been with the 125 grain bullets with 17.5 gr of H110 at around 1850 fps , which seems to be the max in my rifle.  Any more powder and I start to blow primers and ruin the brass. 

As I mentioned since I got the can, I found renewed interest in heavy bullets.  I started playing around with a bunch of different loads and bullet weights.  I test fired them and of course the heavy bullets were starting to tumble at 25 or fifty yards, but I did not check the fps.  Last time out I did set the chrono up and found some 180 grains that seemed to behave.  I have found that my rifle likes 8.7 grains of Lilgun with the 180 grain bullets, pushing them at 1015 fps.  That was what got me wondering why, at around 1000fps, a 180gr bullet would be more stable than a 220 grain bullet, when both would be spinning at the  same rate.

In any case, it seems you have some experience with shooting the heavy bullets at animals, so if you would not mind sharing your experience, it would help me.  Running the OGW calculator, I get 150 lbs for the 125 at 1850, but only 50 lbs for the 180 at 1015.  That had me a little leery of shooting any animals with the heavy bullets, so your real life experience would be helpful.

[martineta]

The long pointy 220's and 240's are heavy at the rear of the bullet which makes them prone to want to wobble unless a fast rate of spin is put on them while in the barrel.  The lighter the bullet, they behave better.  I have not tested but read over on quarterbore that the 190's and lighter perform fine out of 1 in 10 twist barrels.

Hunting question,  I use the Outlaw State bullets to hunt with but due to their design, I think I read they don't feed well out of an AR style clip.  A call to Outlaw State would be your best bet before buying any bullets.  $65 I think for 50.  Expensive but they work for me.  They are supposed to expand under sunsonic velocity but so far every deer I have shot has been a pass thru and I wasn't able to recover the bullet to look at it.  I will say, all the chest shots made a mess of the lungs and exit hole was good size and the two run offs left plenty of blood for me to find them. 

I loaded 100 220 sierra matchkings subsonic but have not hunted with them.  Supposedly they also tumble on impact.  I like my Outlaws so far and will probably continue using them to hunt until I read where somebody has something better.  As far as downrange muzzle energy and suitability for hunting,  I think the pass through of the chest area of the deer is evidence that the round has enough juice to get the job done.  Good luck.

[patw]

Finally understand about the problem with longer bullets being harder to stabilize after reading this article  http://members.shaw.ca/cronhelm/SubsonicBullet.html
Looked up the outlaw bullets and it seems like the solution.  They say the 225gr .308 will stabilize in a 1-10 twist barrel and the 210gr .308 will stabilize in a 1-11.25 twist barrel.  What weight do you use? 

I think I would rather get a 210 than take a chance on getting bullets that do not stabilize since as you say, they are not cheap.  I am not sure a pig would know the difference between a 210 and a 225 anyway.  Also sent them an email to see if they will feed in an AR.  They look like the 30-30 Berry plated bullets, and those did not feed in my AR.  Too bad because they shot well.

[martineta]

I use the 225 grain outlaws.  Outlaw State Bullets is a great company to buy from.  Small and customer focused.  I bought 50 bullets from them in 225 grain.  They shipped lickidy split to me.  A couple of weeks go by and before I had a chance to load them, another package of 50 arrive with a note from the owner telling me the first 50 probably would not expand at subsonic velocities.  Please mark and use the first 50 for "load development, and hunt with the new ones.  Wow!  I was impressed and a loyal customer ever since.  Thank you Outlaw State.  Call them up.  The guy that owns the company will answer all your questions. 

[RaySendero]

This is in regards to reloading the 300-221.  I have a barrel that has a 1-10 twist. ..... but if I am trying to keep the loads subsonic say at 1050 fps, any bullet will spin at the same rate whether it is 150 grains or 220.  What am I missing?

Well for
1) your missing the effect of bullet length - The heavier bullets in a given caliber will most usually be longer.
and 2) it takes more RPM to stabilize these longer bullets.

You can increase RPM with a faster twist barrel and/or you can increase RPM with faster velocity.  In your case, faster velocity is not an option when trying to keep the bullet sub-sonic.

If I were you, I'd use the Greenhill formula to get an estimate of the max bullet length your barrel twist would stabilize.  Then choose the heaviest bullet just below this max as a starting point.