Loaded some 175smk with the with 10g of trailboss. To make a long story short these are still supersonic...about 1565fps. From my calculations. In have a 100 yard zero with 175 FGMM...according to my shooter app that has a velocity of 2380fps at 100yds. My subsonic impacts were 12" low. I calculate it at about 1590fps. I basically used the shooter app and went out to about 875yds...where I would add about 11.5 - 12MOA. My question is does that sound about right. Also...I can't remember the rule of when to switch to mag primers...isn't any loads below 85% case volume. My barrel is 20", 1:10. Anyone else run into this with trailboss?
- Thread starter gaowensjr
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That seems really high velocity wise for only 10gr of trail boss. I am currently using 10.5gr under a 200gr bullet and am right around 1045 FPS out of a 20" barrel. The load for the 180 gr bullets was right around 10gr as well with similar velocities.
I use standard primers and do not open the flash hole up like some do, I've never found it to be necessary with my personal testing. That being said, I've used Trail Boss exclusively for subsonic loads. If I were using another powder that wasn't so bulky then I might look into messing with other primers, but I still couldn't say whether or not they are necessary as I simply have not played with anything else.
I use standard primers and do not open the flash hole up like some do, I've never found it to be necessary with my personal testing. That being said, I've used Trail Boss exclusively for subsonic loads. If I were using another powder that wasn't so bulky then I might look into messing with other primers, but I still couldn't say whether or not they are necessary as I simply have not played with anything else.
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I wonder what cartridge is being discussed?
I wonder if you chronographed the load if it would agree with the app?
I wonder if you chronographed the load if it would agree with the app?
Based on the lack of detail in the original post and the fact he is likely using the 175 gr SMK because he already has them on hand, I would assume 308 by the 20" barrel and 1:10 twist he specified.
Please tell me were 1565fps is subsonic? A 175SMK pushed at 1070 will need between 8-10moa of up over your full power load and many will need up to 12 or better depending barrel harmonics. If I read your post right you will never get to 875 yds with 12 more moa either. I shoot a lot of subs and 175smks suck past 200yds,(most past 140yds) my best load takes 55moa + 2.5mils over my base 100yd zero to get to 400 yds.
Remember all programs are dependent on correct input, if the input is faulty the output will be as well.
I've pushed many a 175SMK with 10.4 grs of trailboss over the years and have only broken the sound barrier once, but it was not in the S/E USA
If your really going to shoot a lot of subs go with a semi pointed, they fly better than a round nose and do more damage when they arrive.
Remember all programs are dependent on correct input, if the input is faulty the output will be as well.
I've pushed many a 175SMK with 10.4 grs of trailboss over the years and have only broken the sound barrier once, but it was not in the S/E USA
If your really going to shoot a lot of subs go with a semi pointed, they fly better than a round nose and do more damage when they arrive.
Sorry..it was 308 and the 175's is heaviest I have at the moment. Very late when I posted..lol....might want to reread the post. I never said I was shooting past 100 yards. I am just seeking advise because I loaded the 10g trailboss and had 12in drop at 100 yards.
A 12 inch drop at 100 yds is almost 12 moa. That is usually what the drop would be for a subsonic load. I believe you calculated wrong. You may still be supersonic, but only by a small amount, like 50 fps or less. Try 9.5 gr and see if that gets you there.
I don't know how you did you calculation, or if the shooting program allows you to do it from the data you have. To reverse engineer a velocity based on poi, you usually have to measure zeros from at least 2 different distances. To calculate velocity from a single poi, the only way I can think of doing it is to accurately measure the time of flight, and plug numbers into a kinematic equation. It will give you an average velocity, not muzzle velocity, because it does not account for drag/negative acceleration.
Shoot a zero at 100 yds, then 200 yds, take the difference between elevation and plug that into the program. Only way to do it outside of a chronograph.
I don't know how you did you calculation, or if the shooting program allows you to do it from the data you have. To reverse engineer a velocity based on poi, you usually have to measure zeros from at least 2 different distances. To calculate velocity from a single poi, the only way I can think of doing it is to accurately measure the time of flight, and plug numbers into a kinematic equation. It will give you an average velocity, not muzzle velocity, because it does not account for drag/negative acceleration.
Shoot a zero at 100 yds, then 200 yds, take the difference between elevation and plug that into the program. Only way to do it outside of a chronograph.
I should have asked in my above statement, but do you know for sure that they are supersonic? Do you hear the sound barrier crack, or are you just going by your numbers? Reason I ask is because you may have the load you are looking for already, and I wouldn't want to see you drop your powder charge needlessly and risk a squib. I am confident that ½ to 1 grain less wouldn't cause a squib, but that is just my assumption, and the 1% time I am wrong, I create a potential hazard.
So shoot again, and listen for the cracks. If you hear cracks, lower by .5 gr, and repeat as necessary. But I think you are already very close, and as it gets warmer outside, a load that is supersonic by a margin will become subsonic.
Instead of using your imaginary numbers, a 70 dollar chronograph will save you a lot of time, components, and hair pulling. Empirical data trumps paper every day of the week.
I see now what your are trying to do but you are comparing apples to oranges. Besides trying to guesstimate velocity of one compare to the trajectory, not drop of another is futile. Another problem is that you are assuming that the BC of the bullet is the same. It's different at 1000fps and 2500fps.
Compare your 10.0g Trailboss load to itself at 2 different ranges and you will have the data you need to give a reasonable guesstimation at the velocity. You could even do it at 50 and 100yds
i know something is off with your app or data, because EVEN IF you were doing 1500fps, at 500 yds you would have a 35 MOA adjust to stay on target. 12 MOA adjust at 875?? I wish my 2800fps 168s were that good.
I see now what your are trying to do but you are comparing apples to oranges. Besides trying to guesstimate velocity of one compare to the trajectory, not drop of another is futile. Another problem is that you are assuming that the BC of the bullet is the same. It's different at 1000fps and 2500fps.
Compare your 10.0g Trailboss load to itself at 2 different ranges and you will have the data you need to give a reasonable guesstimation at the velocity. You could even do it at 50 and 100yds
i know something is off with your app or data, because EVEN IF you were doing 1500fps, at 500 yds you would have a 35 MOA adjust to stay on target. 12 MOA adjust at 875?? I wish my 2800fps 168s were that good.
