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9/23/2020 3:47:02 PM
Posted: 2/21/2016 7:56:45 PM EDT
I reload 150 gr fmj hornady for my AR10 short barrel. Have allot of 168 A-Max bullets I would like to reload but want the same POI at 100 yards. Is there a program that will be able to tell me how much powder to use to get the 168 gr to match the 150 gr bullets? I chrono my reloads so do know what the 150's are doing. Also have a ballistics ap on my iphone but not sure if that would be time consuming or won't work at all. Only worried about max of 300 yards.
Link Posted: 2/21/2016 10:16:56 PM EDT
I was with you until your last sentence where you mention 300 yds.

Load both and bench them at 100 yds. Adjust load(s) to match point-of-impact.

Now, shoot them at 300 yds and see where you are.
Link Posted: 2/21/2016 11:04:29 PM EDT
Its a 10.5 inch barrel. Yeah, already considered that but waste allot of powder. Considered going off the reload book and loading to same velocity for the different bullets and adjust from there which would probably be the only way. Then use my ballistics ap to see how it does going down range. Thought to check if by chance there was specific software able to do this. Thanks for the suggestion though.
Link Posted: 2/21/2016 11:13:15 PM EDT
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Originally Posted By Bearcat24:
Its a 10.5 inch barrel. Yeah, already considered that but waste allot of powder. Considered going off the reload book and loading to same velocity for the different bullets and adjust from there which would probably be the only way. Then use my ballistics ap to see how it does going down range. Thought to check if by chance there was specific software able to do this. Thanks for the suggestion though.
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Not sure "waste" is a good word here, i feel load work ups are most of the fun.  To my knowledge the only way to do it would be to match them up at 100 then see

what happens at 300, just going by the advertized velocity my be a good starting point but lighter bullets should take longer to drop and then you have to factor in

The coefficient.
Link Posted: 2/22/2016 11:34:45 AM EDT
[Last Edit: 2/22/2016 11:45:47 AM EDT by DakotaFAL]
In my experience,shooting national match with an M14, you need 2-3 clicks to go from 100 yards to 200 yards
200 yards to 300yards = 3 clicks
300 yards to 600yards = 12 clicks

That's pretty much the case for M59, M80, M118, M118LR, where you won't find more than 1/4 MOA difference in their trajectories.  It also applies to M1 and M2 Ball ammo as well as M72 match ammo in the M1 Garand.

It works for the most part with M852.   M852 is loaded slow, at only 2550 fps, and it will be about a half MOA lower at 300 yards, about 1 MOA low at 400 yards and 2 MOA low at 600 yards.  However, increase the load to get a 168 gr SMK to 2700 fps and it will match M118 and M118LR within 1/10th of an MOA out to 600 yards.  

In essence, what is happening is that the higher velocity of the 149-150 grain rounds offsets their lower BC, and the 150, 168 and 173 and 175 grain rounds have fairly similar trajectories out to 600 yards.

In your specific case, a Hornady 150 gr FMJ-BT at 2750 fps and a 168 gr A-max at 2700 fps will be pretty well matched out to 400 yards with nearly identical trajectories, with the A-max going about 1 MOA flatter at 600 yards.  

Whether the zero will be the same is another matter as the recoil impulse and angle of departure also changes a bit with the different loads.

Your best bet is to zero one of them as your primary load, set it up on your rifle with 100 yard basic zero, confirm it at 300 and 400 yards,  and then shoot then other load with the same zero and adjust as needed to get a new 100 yard basic zero and corresponding 300 and 400 yard zeros.   Then all you have to do is note the change in zero going from your primary load to the secondary, and add that to the scope when you switch from the primary to the secondary load.
Link Posted: 2/22/2016 1:11:39 PM EDT
[Last Edit: 2/22/2016 1:16:32 PM EDT by borderpatrol]
I'm a veteran of over 200 high power rifle tournaments (NRA/DCM/CMP). There is no such thing as getting two different bullets to print at the same point of aim. You might achieve this at 100 yards, but after that ballistics own the range.

I had a friend that made me laugh. He would tighten the crap out of his M1-A sights once zeroed because he never wanted them moved. The fact is all ammo needs to be zeroed and records kept of how they print on target. Adjust your sights as needed.

The reasons sights are adjustable is so you have the flexibility to adjust as needed. I would zero for the 168 grain ammo if your not willing to make adjustments and let the crap FMJ's go wherever they go.  

edited to add: My M1-A ammo needs 3.5 moa going from 100 to 200 and 200 to 300. My chronograph reads 2500 fps shooting my hand loads.

40.5 grains of IMR-4895

41.5 grains of IMR-4064

40.0 grains of H4895

41.5 grains of Varget

43.0 grains of WW-748

All seating Sierra 168 grain Match Kings @ 2.800", Winchester standard large rifle primers, Lake City 7.62x51mm brass. I consider these maximum loads and you probably should too. Start a little lower and work up to them. Shoot the load that groups the tightest, velocity is secondary to accuracy.
Link Posted: 2/22/2016 4:03:04 PM EDT
Great info. May do as suggested on setting up the 168's and let the 150's land where they will. Another good point is set one and see how the other does and record the difference. Thanks
Link Posted: 2/22/2016 7:25:33 PM EDT
[Last Edit: 2/22/2016 7:26:47 PM EDT by Motor1]
Don't be surprised to find that the 150s will likely shoot lower at 100 yards than the 168s.

I understand your initial question but truthfully those 2 bullet weights are too close to try using ballistics calculator and load data to obtain a single POI for both at 100 yards. Simple barrel harmonics could make as much difference as any load changes.

Motor
Link Posted: 2/22/2016 11:00:53 PM EDT
As long as I select one bullet for my accurate shot the other can be close but not to far off. Pretty much my short range plinker. My bolt 308 is my reach out and touch something. Thanks again.
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