Help calculate muzzle velocity and drop

[sasquatch]

You should always test drops at least out to the maximum range you're wanting to shoot, or farther. Shooting at 300 and extrapolating to 500 is not the best way to go.

I’m not that far into it yet, it’s for discussion

I can’t even see that far where I hunt.


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[sasquatch]

The only way Im aware of is if a barrel is brand new and its chamber isnt firecracked enough yet to increase pressure and speed up the MV.

So the question is, is the OPs gun brand new?

Close, prob only 60-70 rounds through it


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[Harvey_NW]

The only way Im aware of is if a barrel is brand new and its chamber isnt firecracked enough yet to increase pressure and speed up the MV.

Well now you're aware of another.

 

[Koda_]

Close, prob only 60-70 rounds through it


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In my experience I would run at last another 100rds of cheap ammo thru the gun before working on drops and zero.
My 280ai sped up and leveled off after about 120rds. Yeah, its kinda frustrating, ammo isnt really cheap for this caliber.

 

[hereinaz]

Yes, barrels speed up between 100-120 rounds, but not that much. I don't sweat it that much as long as I have confirmation and don't shoot more than 20 before I hunt again.

If you aren't hunting close to 500 yards, I'd just confirm drop and go kill stuff.

Chalk it up to unknows, like whether Sasquatch is real and aliens exist.

 

[EdP]

New barrels are slow until the bore roughens up some

Taperpin, did your really mean to say that a new barrel roughens up some with shooting?? That wasn't what I was expecting to read. I thought shooting smoothed out the roughness left from machining on a barrel that had not been lapped.

 

[EdP]

Another possibility is that what is printed on the box is wrong because the mfg has changed powders. I read recently that some factory loads are not as fast as in the recent past due to powder shortages resulting from international conflicts. The mfgs are using less optimal powders because the powders they were using are not available. They may have changed powders but not what is printed on the box.

 

[Koda_]

Taperpin, did your really mean to say that a barrel roughens up some with shooting?? That wasn't what I was expecting to read. I thought shooting smoothed out the roughness left from machining on a barrel that had not been lapped.

Its actually the chamber throat that roughens up, increasing pressure and velocity.
The bore smooths out but ive never heard that makes for any practical effect on pressure or velocity.

 

[Harvey_NW]

Its actually the chamber throat that roughens up, increasing pressure and velocity.
The bore smooths out but ive never heard that makes for any practical effect on pressure or velocity.

The firecracking that increases pressure and resistance is in the first couple inches of the grooves in the barrel, not in the throat. If the throat gets carbonized enough to have an effect that would be a "carbon ring".

 

[TaperPin]

Taperpin, did your really mean to say that a new barrel roughens up some with shooting?? That wasn't what I was expecting to read. I thought shooting smoothed out the roughness left from machining on a barrel that had not been lapped.

Yep, the bore from the throat forward a bit, gets so hot it fire cracks the metal surface, which is rougher than the new barrel surface.

Brian Litz has some bore scope pics showing fire cracking and shows his cleaning method in this video (I’m not a Litz fan boy, but it has some useful bits):

 

[TaperPin]

I should have said I’m not going to start cleaning with JB to smooth the bore - simple carbon and copper remover used without scrubbing much is much simpler. I can’t get over the feeling he’s managing velocities with the smoothness of the bore as if it’s commonly done, which while it obviously works for him, seems to add needless complexity, and many of us burn out barrels without an issue JB needs to solve.

 

[GoatPackr]

Where do you live. Maybe someone around you has a chronograph that you can shoot over and see what you get?

 

[sasquatch]

Where do you live. Maybe someone around you has a chronograph that you can shoot over and see what you get?

I have a chronograph stored away that I got for archery. I just have to dig it out, i originally didn’t just due to wanting to see the true proven drop.

Now that it seems very slow I’ll shoot it through one to see what I’m getting. Prob be a week or two

I’ll report back. When I do shoot I’m gonna have a few diff rounds to test out also


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