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Question for 50 Cal shooters

 
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  #1  
Old 06-11-2010, 08:36 AM
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Question for 50 Cal shooters

I am interested in the performance of the 50 (.510) BMG after it goes Sub Sonic.

I know that most bullets really lose there accuracy when this happens and was wondering
if anyone had done any comparisons between lighter bullets and heavy bullets at sub sonic
velocities.

Question: Are the heaver bullets less effected by the transition to sub sonic or they
essentially the same.

The old Black powder rifles are capable of outstanding accuracy at long distance and most
go sub sonic soon after they leave the bore.

They usually use 500 to 600 grain bullets and the modern LR rifles use 250 to 400gr bullets
at much higher velocities and with much better BCs.

With the better 50 cal bullets(BCs over 1) and muzzle velocities over 2800 ft/sec they go
through the transition at well over 2000 yards with 750 to 800 grain bullets.

So I was wondering if heavy projectiles were less effected during Sub Sonic flight.

All opinions are welcome but also anyone with facts and figures are what I need .

J E CUSTOM
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Old 06-11-2010, 01:22 PM
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Re: Question for 50 Cal shooters

I think you'll just have to try shooting them at very long range and see how they perform. I've shot both 750 and 800 Barnes solids at up to a mile from my 40" McBros single shot but at that range they're both well supersonic.

Computer programs (McGyro and McTrag) can calculate the stability of spinning projectiles and the drag, but they don't calculate the difference in loss of spin and forward energy. They can't really calculate long range stability correctly.

With sufficient initial velocity heavier VLD bullets will typically travel further before going transonic then lighter but faster VLD bullets. It's not obvious which bullet will be more accurate even up to the point where the lighter bullet goes transonic though wind deflection and velocity sensitivity for both can be calculated. Precession effects related to stability are generally too complex to calculate. Really, the only way to know for sure is to do shooting tests at those ranges with various bullets.

Personally I don't attempt to shoot at distances which give transonic velocities. Sure, you can shoot transonic to at least twice as far transonic as supersonic, but the chance of obtaining decent accuracy (limited by wind deflection and muzzle velocity variation) becomes small rapidly after bullets become transonic even it the bullet does remain stable. Time of flight is a big part of both drop and wind deflection. Slow bullets simply cannot compare well for accuracy to supersonic bullets at ranges over a mile whehter they remain stable or not. For subsonic only shooting where the bullet has no stability problems practical hunting ranges can't be over about 600 yards for any known cartridge/bullet combination.. Sure, a heavy subsonic bullet can kill at over a mile, but it cannot be very accurate limited by wind deflection and muzzle velocity variation (usually the latter).

It's practical to build shoulder fired rifles which can reach 2500 yards supersonic. The Cheytacs and similar can do it. They're still too wind sensitive to assure reliable hunting accuracy. 50 BMGs can't do as well. They have too much bore area to case capacity regardless of bullet selection. That is, low drag 50 cal bullets are too slow.
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Old 06-11-2010, 01:58 PM
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Re: Question for 50 Cal shooters

Try jd jones @ ssk ind. He has the 510 whisper that sends 700 grain slugs down range @1050 or less to be truly suppressed.
Robster
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Old 06-11-2010, 03:39 PM
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Re: Question for 50 Cal shooters

at 1050 fps it is subsonic. The point is to stay below the speed of sound to avoid the transonic stage.
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Old 06-11-2010, 05:38 PM
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Re: Question for 50 Cal shooters

Robster, is it leaving the muzzle at 1050fps and if so any idea at what range it essentially runs out of gas?
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Old 06-11-2010, 06:13 PM
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Re: Question for 50 Cal shooters

Chas,
I`m not sure on the .510 I shoot a 338 whisper with 300smk`s sighted in at 200yds i`m 15 high at 100yds and 51 low at 300 yds at aprox 950 fps.Works great for woodchucks and coons.
robster
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Old 06-11-2010, 06:51 PM
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Re: Question for 50 Cal shooters

I guess what I am trying to find out is if your going to shoot out past the super sonic are
the heaver bullets effected less because of mass.

With all the talk about 2700 yard kills/hits it looks like it would be more likely with a heaver
projectile. The MI Abrams battle tank was making hits in excess of 2 miles and I know/think
the velocity is below the speed of sound at that distance.

There is no hidden agenda just curious.

When I can find a place to shoot far enough I will test it out my self unless someone comes
up with real data.

Thanks
J E CUSTOM
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Last edited by J E Custom; 06-12-2010 at 07:17 AM.
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