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Subsonic bad?

 
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  #1  
Old 03-18-2010, 12:22 AM
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Subsonic bad?

So what exactly happens to a bullet as it goes subsonic that makes it no good for shooting/hunting?

I'm wondering because I just ordered me a nice .308 and I'm trying to figure out my max effective range for coyotes. It should still have the knockdown power beyond 1000yds, but I'm just wondering what else factors in?

Looking at my ballistics program looks like it will stay supersonic (in this weather) to about 875-900.

I almost can't wait to shoot out my 7mm so I can re-barrel that rig and get serious!

Shane
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  #2  
Old 03-18-2010, 02:14 AM
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Re: Subsonic bad?

I belive most bullets become unstable when they go transonic. In other words instead of a ''spiral'' they fly more like a ''wounded duck'' just like a good throw vs a not so good throw with a football.(with alot less speed involved).
Someone correct me if Im wrong. This is waht Ive been led to belive for years.
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  #3  
Old 03-18-2010, 05:37 AM
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Re: Subsonic bad?

What happens to the bullet as it transitions from supersonic through transonic to and then into subsonic flight depends on the bullet design. A rounded nose bullet that is short for it's weight will do just fine but it's performance in supersonic flight will be dissapointing because the BC won't be very good. A bullet with a long secant ogive and real high BC, (SMK and VLD for example), will not do as well in transonic and subsonic flight, but they will go a lot farther before they get into that speed range because of their high BC.

My buddy has a .300 Whisper. He was having trouble with bullet stability shooting the heaviest SMK he could find - it was going sideways through the target at 100 yards. His timing was good - I'd just finished reading the chapter on stability in Litz's excellent book. Based on what I read in the book I suggested he go to the heaviest round nose bullet he could find. He did. It made nice round holes at 100 yards. Problem solved.

A .308 is used a lot on paper at 1,000 yards - I don't see that cartridge as a 1,000 yard hunting round although it might work for coyotes.

You mention a 7mmMAG. I havent' hunted with one ... yet. I just got one. Studying the ballistics for that cartridge has been interesting. It looks to me like it's a viable 1,000 yard cartridge for whitetail and smaller game with the right bullet. 7mm bullets have higher BC for their weight than .308 bullets. 7mm seems to a caliber where it "comes together" for long range shooting of high BC bullets out of a viable walk around hunting rifle with out a muzzle brake (a feature). Another one seems to be .338 but almost always with a muzzle brake unless the rifle weighs 20 lbs or more.

Fitch
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  #4  
Old 03-18-2010, 06:39 AM
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Re: Subsonic bad?

I agree with fitch , i tried subsonic loads in my 308 and couldn't get match bullets to group so in desparation i tried some 180g flat base round nose over 7g of unique and voila instant inch groups at 100m ?
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  #5  
Old 03-18-2010, 08:12 AM
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Re: Subsonic bad?

Quote:
Originally Posted by Fitch View Post
What happens to the bullet as it transitions from supersonic through transonic to and then into subsonic flight depends on the bullet design. A rounded nose bullet that is short for it's weight will do just fine but it's performance in supersonic flight will be dissapointing because the BC won't be very good. A bullet with a long secant ogive and real high BC, (SMK and VLD for example), will not do as well in transonic and subsonic flight, but they will go a lot farther before they get into that speed range because of their high BC.

My buddy has a .300 Whisper. He was having trouble with bullet stability shooting the heaviest SMK he could find - it was going sideways through the target at 100 yards. His timing was good - I'd just finished reading the chapter on stability in Litz's excellent book. Based on what I read in the book I suggested he go to the heaviest round nose bullet he could find. He did. It made nice round holes at 100 yards. Problem solved.

A .308 is used a lot on paper at 1,000 yards - I don't see that cartridge as a 1,000 yard hunting round although it might work for coyotes.

You mention a 7mmMAG. I havent' hunted with one ... yet. I just got one. Studying the ballistics for that cartridge has been interesting. It looks to me like it's a viable 1,000 yard cartridge for whitetail and smaller game with the right bullet. 7mm bullets have higher BC for their weight than .308 bullets. 7mm seems to a caliber where it "comes together" for long range shooting of high BC bullets out of a viable walk around hunting rifle with out a muzzle brake (a feature). Another one seems to be .338 but almost always with a muzzle brake unless the rifle weighs 20 lbs or more.

Fitch
Interesting. So maybe the best thing to do (instead of relying on a ballistic calculator) would be to walk some paper out there and see when they start keyholing?

I hear you on the 7mm. I've been shooting rocks out to 1000 with 162gr Amaxs. Next bullet I'm trying is going to be the Berger 180gr match hunting. BC is .659 and it's suitable for big game (Not that I'm to that level yet)

Last edited by shaneman153d; 03-18-2010 at 08:15 AM.
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  #6  
Old 03-18-2010, 08:32 AM
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Re: Subsonic bad?

Shooting at 300yards or less a FB is the best choice period. To make a very long story that would take too long to type----why do you think the BR guys such as myself use them exclusively and for my 1k rifle boat tails. This topic has been addressed numerous times so do a search on the topic and ye shall find the information that you seek.
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  #7  
Old 03-18-2010, 10:58 AM
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Re: Subsonic bad?

Quote:
Originally Posted by Boss Hoss View Post
Shooting at 300yards or less a FB is the best choice period. To make a very long story that would take too long to type----why do you think the BR guys such as myself use them exclusively and for my 1k rifle boat tails. This topic has been addressed numerous times so do a search on the topic and ye shall find the information that you seek.
Wrong thread?
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