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Splitting Ballistic Hairs

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Post by Bigtrout Mon Feb 04, 2019 2:08 pm

Just a check on my sanity which is sometimes questioned.  It's too winter to shoot so I pulled out the ballistic tables and load data to get an idea what I need to load for 9mm 125's and 147's.  It seems intuitive that going transonic early in flight would would be less accurate than late in flight.  All 115 load data indicate a transonic condition during 50 yards for temperatures from 35 to 80 when checking my muzzle velocity chrono data.  Assuming a 10" twist, would subsonic loads for the 125/147 projectiles give me better accuracy at 50 yards?  I've received a free sample from Zero of 50 of each 125 & 147 JHP and want to make the most out of my next range session with them.  By the way I weighed a 10 piece sample of each and they only had a spread of 0.5 gr.
I know folks here say to push the 115 1100 fps or more.  Even at 1250 the 115 will go transonic before reaching 50 yards.  Thanks for any comments.


Last edited by Bigtrout on Mon Feb 04, 2019 2:26 pm; edited 1 time in total (Reason for editing : Clarity)
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Post by David R Mon Feb 04, 2019 2:33 pm

You have to shoot them out of your gun.  
I found 115 HAP shooting well with 5 grains of CFE pistol.   I chornied the load and got 1025 fps from a 5" gun with a 100 fps spread.   Went to Tite Group trying from 3.6 to 4.2.  Ended up at 4.0 which was most accurate and happened to be 1025 fps with 30 fps spread.  

My wife has been shooting them all winter at a 50 foot match.  I get a little better accuracy with 5.0 WW 231 behind a 115 FMJ for 1100 fps. Best with 6 grains unique for 1225 fps.  


I have had spotty luck with 147 coated lead.  Sometimes it amazes me how well they shoot then other times....

This is off the bench.

Good luck in your search.
David
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Post by robert84010 Tue Feb 05, 2019 6:40 pm

They say 1100 with a jhp and no more because that is considered sub sonic and will never be trans- sonic. Nobody in bullseye does a 147 over 1100 fps, don't even know if you can get there with a 9mm, because you might as well shoot 45 at that point. Known good 147 ammo is generally around 900fps, well into sub sonic range. If you don't believe me tell the Army because this is what they use.

https://atlantaarms.com/9-mm/

these guys know things and this is why i'm saying "known good ammo".

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Post by lablover Tue Feb 05, 2019 7:56 pm

robert84010 wrote:They say 1100 with a jhp and no more because that is considered sub sonic and will never be trans- sonic. Nobody in bullseye does a 147 over 1100 fps, don't even know if you can get there with a 9mm, because you might as well shoot 45 at that point. Known good 147 ammo is generally around 900fps, well into sub sonic range. If you don't believe me tell the Army because this is what they use.

https://atlantaarms.com/9-mm/

these guys know things and this is why i'm saying "known good ammo".
So the army is using 146 Atlanta arms ?  I’ve yet to find a good load for my XDM 5.25 then again I’ve not done lots of load development with it either.  Focus is on my 45
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