Flattest shooting database

[Greatgrandad]

I have a 30 inch 300 RUM, and a new "club" where I can actually shoot it for the first time in about 6 years. I relocated about 2000 miles and the "club" is newish. It would be a hoot to see how fast I can make it go. It's bench rest setup and it never occurred to me to give "speed" a go with it.

Elevation would have to be another thing to standardize on. DA, density altitude, effects actual trajectory significantly but if allowed to be manipulated... That is why submissions would need some validation.

If you wish to see something really fast -
300 RUM, 30-06 and 308 with sabot 22 caliber loads. The 300 RUM 52 grain has broken 5,300 fps and the 30-06 52 grain has broken 5,000 fps.

 

[fseaman.js]

Anyone know of a chronograph that can do muzzle velocity and velocity at a 300 yard target?

LabRadar? Garmin?

 

[fseaman.js]

If you wish to see something really fast -
300 RUM, 30-06 and 308 with sabot 22 caliber loads. The 300 RUM 52 grain has broken 5,300 fps and the 30-06 52 grain has broken 5,000 fps.

I was just looking at them on E Arthur Brown. $15.95 for the sabots, $15.95 for the seater and $16.95 for the case mouth expander. Though I can make one of those on my lathe. All in all, cheap for such an experiment.

but

It doesn't have to be me to get valid numbers and that's not the point of the project.

 

[HRM Johnny]

I have read that the Sabots make a horrible mess in your barrel. Has anyone tried them?

 

[hemiford]

Just for doing simple calculations, you could compare expansion ratios. One "index number" would be
cartridge volume divided by barrel volume, where barrel volume is Pi x Bore squared x barrel length all divided by 4.
(I can't type math symbols). Powder weight varies of course, but brass capacity is a bit more constant.
These are not Gnat's *** numbers but will definitely show a trend.

You can set all these "index numbers" equal by varying the barrel length for each cartridge.

For example, 30-06 brass is say 66 grains capacity. A 22-inch 30 caliber barrel is 1.639 cubic inches.
66 / 1.639 = 40.3
Don't worry about units. 40.3 is the comparator "index number".

So 7-STW is say 99 grains capacity. Set 40.3 equal to 99 / X, so X = 2.456.
2.456 is the cubic inches of barrel volume for a 7-STW that will give the same expansion ratio as a 30-06 with a 22-inch barrel.
2.456 x 4 divided by Pi divided by .284 squared = 38.8 inches.

38.8 inches is the barrel length for a 7-STW that gives the same expansion ratio as a 22-in 30-06 barrel.

Surprising, isn't it ?

You can do this calc for any cartridge. The cartridges that yield the longest barrel requirement are the most overbore,
and therefore the best candidates for a flat shooter (I would say).

6.5-300 Wby, 7RUM, 30-378, 338 SnipeTac (Allen Magnum), these are about the most common super overbore cartridges.

 

[fseaman.js]

38.8 inches is the barrel length for a 7-STW that gives the same expansion ratio as a 22-in 30-06 barrel.

The coffee hasn't kicked in yet.

I think I will look at muzzle pressure for a 22" 30-06 vs a 38.8" 7 STW. QL calculated.

 

[Victor3Ranger1]

Seems "big". Of course any standard is better than someone saying a PBR with no reference to the "Vital Zone Radius" and making claims that their PBR is 500 yards.

Go with a 6"
That way it can only drop 3" from center to miss

 

[Victor3Ranger1]

The coffee hasn't kicked in yet.

I think I will look at muzzle pressure for a 22" 30-06 vs a 38.8" 7 STW. QL calculated.

I'm interested in what you find on this.
My next 7STW is supposed to be 28"

 

[Victor3Ranger1]

I have read that the Sabots make a horrible mess in your barrel. Has anyone tried them?

I have used them off and on for years.
I really haven't seen anything bad

 

[HRM Johnny]

Thanks

 

[skipglo]

All I can offer....is Good Luck Sir on your pursuit! Verifying folks submissions would be an endless endeavor.....it's the old adage..."..FIGURES DON'T LIE...BUT LIARS CAN SURE FIGURE" !!!!

 

[fseaman.js]

All I can offer....is Good Luck Sir on your pursuit! Verifying folks submissions would be an endless endeavor.....it's the old adage..."..FIGURES DON'T LIE...BUT LIARS CAN SURE FIGURE" !!!!

Yeah, kinda the thing with such databases.

We will see how it goes. Like I said, I could change my mind.

 

[tomcat818]

Anyone know of a chronograph that can do muzzle velocity and velocity at a 300 yard target?

LabRadar? Garmin?

LabRadar claims 200yds with larger projectiles with mine I get 100yd velocities for 150gr and up out to 125yds with 215gr. This is Berger's doppler radar setup for BC testing out to 1500yds:

https://bergerbullets.com/wp-content/uploads/2020/06/AB-Doppler-RADAR.gif

Looks expensive

The Garmin is good for near muzzle only.

 

[skipglo]

Yeah, kinda the thing with such databases.

We will see how it goes. Like I said, I could change my mind.

Knitting....try knitting!!