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Proper Twist 300 WM ?

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  #8  
Unread 04-06-2010, 08:09 AM
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Re: Proper Twist 300 WM ?

I'm going to need a little bit of help here to make sure I don't screw this up.

I'm building a rig that will be a good bench rifle and a good hunting rifle. So ideally not perfect for either.

I've had success with the Nosler Accubonds so I figured I'd set it up for those. They are also semi-reasonable in price. I want a flat shooting cartridge which is why I'm leaning towards the lighter bullets 165 and 180gr. I hear the 208gr Horndady A-Max have a really high BC so figured I'd try to see if I could squeeze those in there as well.

Yesterday I set up some dummy cartridges with an OAL of 3.85" so that I can seat the bullets in the magazine. I did this with 165gr and 180gr Accubonds.

I was very surprised with something that I learned. Both dummies measure the same to ogive. I was very surprised since they have the same oal. I always thought the variance among different weight bullets was from the ogive to the tip. Not the ogive to the base.

I'm really not sure of the true impact of my discovery. I know now that the 180gr bullet is stuffed further into the case. It almost seems to me that in order to take advantage of a cartride case capacity that one would want to use a magnum action with the larger magazine well so that bullets can be loaded to where just the caliber is in the case neck.

I'd really appreciate it if folks could chime in.

Thanks

Tom
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  #9  
Unread 04-06-2010, 11:15 AM
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Re: Proper Twist 300 WM ?

Quote:
Originally Posted by MontanaRifleman View Post
Tom,

What is your shooting goal? If LR shooting is your goal, it is best accomplished with high BC bullets. High BC bullets require a faster twist. High BC bullets have high BC because of their shape which is long and pointy, which is why they require a tight twist. If you gi to the Berger site, you will see that a 210 Berger requires an 11 twist (minimum) The 208 Amax has a very similar BC as the 210 Berger which means, that at the same weight, they are about the same length and probably require the same twist.. IMO, trying to decide between a 10 and 11 twist or 12 twist is the same as straining at gnats. This is something that BR shooters do and they are usually shooting a different type bullet (flat base often) than LR shooters, and different type of rifels.

If you go with an 11 twist, you will be able to shoot all of the common comercially available bullets but you wont be able to shoot the LR friendly, high BS bullets.

-Mark
Mark is correct! that is why I kept asking if you were sure that you would never want to shoot heavier bullets which he also correctly pointed out that length is the real determining factor...........Mark, you must want to shoot some of my new 250-260 grainers if you are going to an 8 twist
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  #10  
Unread 04-06-2010, 11:28 AM
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Re: Proper Twist 300 WM ?

Quote:
Originally Posted by statjunk View Post
I'm going to need a little bit of help here to make sure I don't screw this up.

I'm building a rig that will be a good bench rifle and a good hunting rifle. So ideally not perfect for either.

I've had success with the Nosler Accubonds so I figured I'd set it up for those. They are also semi-reasonable in price. I want a flat shooting cartridge which is why I'm leaning towards the lighter bullets 165 and 180gr. I hear the 208gr Horndady A-Max have a really high BC so figured I'd try to see if I could squeeze those in there as well.

Yesterday I set up some dummy cartridges with an OAL of 3.85" so that I can seat the bullets in the magazine. I did this with 165gr and 180gr Accubonds.

I was very surprised with something that I learned. Both dummies measure the same to ogive. I was very surprised since they have the same oal. I always thought the variance among different weight bullets was from the ogive to the tip. Not the ogive to the base.

I'm really not sure of the true impact of my discovery. I know now that the 180gr bullet is stuffed further into the case. It almost seems to me that in order to take advantage of a cartride case capacity that one would want to use a magnum action with the larger magazine well so that bullets can be loaded to where just the caliber is in the case neck.

I'd really appreciate it if folks could chime in.

Thanks

Tom
The reason the bullets seated the same is because they are both an 8s spitzer design so the ogive is the same. The difference in the two is the shank length that contacts the lands. You are correct in assuming that best case scenario is to seat the longer bullets to the base of the neck for more case capacity and sometimes better accuracy. I should have been more clear why I was pumping to see exactly what bullet you planned on sticking with. It seems you are not quite sure at this point so I would in that case go with the 10 twist (as Mark suggested) and I would have it throated to accomodate the A-MAX or what ever is the longest you decide on. Be aware that if you do that, the 165's may barely go into the neck if you want them near the lands which "usually" equates to better accuracy. This is why you need some idea of what you want to accomplish in the long run. Also be aware that you can always cut the throat out a little further but you can't put it back if you cut too much unless you set the barrel back. Hope this helps......Rich
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  #11  
Unread 04-06-2010, 11:50 AM
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Re: Proper Twist 300 WM ?

Quote:
Originally Posted by elkaholic View Post
You are correct in assuming that best case scenario is to seat the longer bullets to the base of the neck for more case capacity and sometimes better accuracy.

Rich,

The problem here is that if I were to do this the cartridge wouldn't fit in the magazine. Should I have bought a magnum action to get the longer magazine well?

I'm going to load up a dummy 208gr Hornady A-Max to oal 3.385" to see where that puts me with regards to the ogive on the 180gr Accubonds. Maybe there I will see that this is a moot point.

The one thing I know is that seating to the base or caliber isn't going to happen if I want to be able to load to the lands and fit the magazine well.

Thanks

Tom

Last edited by statjunk; 04-06-2010 at 12:01 PM.
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  #12  
Unread 04-06-2010, 12:34 PM
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Re: Proper Twist 300 WM ?

This is a common problem with many manufacturers and is also the reason why a lot of guys end up shooting single shot. It's part of the growing pains that we ALL go through and sometimes regret our first choice. RESEARCH and ASK just like you are doing and then make the best decision for your particular need. I make my own bullets and I still have trouble deciding some of these things at times......Rich
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  #13  
Unread 04-06-2010, 09:48 PM
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Re: Proper Twist 300 WM ?

To my surprise when I seat a 208gr Hornady A-Max to an oal of 3.385, the ogive is inside the case.

While I'm excited about this project I'm at a stage where I can back up with minimal cost. I'd have to sell my rifle and pick up another. Should I find a magnum action?

Tom
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  #14  
Unread 04-06-2010, 10:09 PM
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Join Date: May 2008
Location: South of Canada and North of Wyoming
Posts: 6,068
Re: Proper Twist 300 WM ?

Quote:
Quote:
Originally Posted by statjunk View Post
To my surprise when I seat a 208gr Hornady A-Max to an oal of 3.385, the ogive is inside the case.

While I'm excited about this project I'm at a stage where I can back up with minimal cost. I'd have to sell my rifle and pick up another. Should I find a magnum action?

Tom
In most LR hunting situations, you are not going to need the speed of a repeater. You can eject and eject and load single shot fairly quickly if you have too. I have my 300 RUM configured with one in the chamber and one down in the mag. The point of the top bullet in the mag is above the mag wall, so it does not have to fit in the mag box. I have a two shot configuration in my rifle which is a Rem 700 Sendero LA.

I'm not sure what action you have, but with a Wyatts extended mag for a 700 LA you can seat the longer bullets out to the lands usually. Or you can just go custom action if it's in your budget.
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