How High ES will shoot a clean in 500 yard F-class?

[Keith Glasscock]

I shot my 284 in a 500 yard F-class match this weekend. On the last string (testing loads) I was able to use a friend's Labradar (Thanks Pat!). The load opened up more than a little. The group had a total vertical of 3.8 inches. Conditions were extremely blustery to say the least.

I shot a 200-11x with a shockingly high ES that I won't disclose just yet.

So, what do you think is the maximum 20 shot ES that will allow a clean in F-class at 500 yards?

 

[Alex Wheeler]

Es and vertical at long range have limited correlation. 0 es may show more vertical than 20 es. Thats a fact. Obviously at some point you will see that es on the target. I bet you could shoot clean at 500 with 40fps es

 

[Ned Ludd]

It's fairly easy to calculate a [theoretical] value for this solely based on velocity using a ballistic program, such as JBM. The following is for a .308 Juggernaut load with avg MV of 2750 fps. You raise/drop the velocity until the drop is +/- 0.5 MOA at 500 yd for a 1 MOA 10-ring (i.e. - find the max/min MV that will give a total 1.0 MOA vertical change at 500 yd). For the above 185 load, the ES comes out to be 114 fps (+/- 57 fps)

 

[savagedasher]

I can say that with low ES at 300yd You can clean 5 - 5 shot targets .
250 with 25x All under .750 Larry

 

[Keith Glasscock]

It's fairly easy to calculate a [theoretical] value for this solely based on velocity using a ballistic program, such as JBM. The following is for a .308 Juggernaut load with avg MV of 2750 fps. You raise/drop the velocity until the drop is +/- 0.5 MOA at 500 yd for a 1 MOA 10-ring (i.e. - find the max/min MV that will give a total 1.0 MOA vertical change at 500 yd). For the above 185 load, the ES comes out to be 114 fps (+/- 57 fps)

If you look closely, the two examples you show have a different launch angle 4.469 MOA vs 4.278 MOA. If you turn off Elevation Correction for zero range, then the answers are a little less generous.

Fortunately for me, one end of the velocity spectrum was in the node and demonstrated positive compensation.

If I had been shooting at 1k, I have no doubt that I would have been struggling to keep it in the 9 ring...

 

[Ned Ludd]

Yes - I was in a hurry and that was just a quick and rough estimate to get total MV spread that would give you approximately 1 MOA vertical at 500 yd. You're right, it's better not to correct for zero at 100 yd, but realistically, a ~50 fps change in velocity isn't going to change the 100 yd zero very much as indicated. However, the total velocity spread for 1.0 MOA vertical at 500 yd for that load would actually be slightly less than 114 fps. Corrected, it comes out to +/- 48 fps, rather than 57 fps, or 96 fps ES. In the grand scheme of things, that difference is really irrelevant because it's still almost 100 fps ES, a much larger value than some might have expected. That same ES would give somewhere in the neighborhood of 2.6 MOA vertical at 1000 yd. The more interesting question is...exactly what was the ES value you measured?

 

[Alex Wheeler]

If you look closely, the two examples you show have a different launch angle 4.469 MOA vs 4.278 MOA. If you turn off Elevation Correction for zero range, then the answers are a little less generous.

Fortunately for me, one end of the velocity spectrum was in the node and demonstrated positive compensation.

If I had been shooting at 1k, I have no doubt that I would have been struggling to keep it in the 9 ring...

you get it

 

[pat fulghum]

I would think that to be clean you need to hold closer to .6 MOA not 1 moa vertical. You could get by with 1 MOA vertical *IF* you had a perfect horizontal control.

114 fps was calculated above to hold 1 MOA.

Take that number and multiple by my .6 MOA (to give you some horizontal wiggle room) and you get something that is VEry very close to the real ES recorded.

Keith was just jealous of my little 6BR's ES OF ~15 (over 22 shots).
Now if I could just hold the same horizontal as his .284 I might win won of these. Keith beat me by one point (again) but I had him in x count.....Someday!!

 

[DRNewcomb]

Do you have statistics for the same ammo fired through an optical chronograph and/or under less blustery conditions? Some people have reported that the accuracy of the LR can be affected by stuff (e.g. grass, dust, etc) moving around in it's field of vision. I don't have any personal experience, it's just what I've read.

 

[billlarson]

Es and vertical at long range have limited correlation. 0 es may show more vertical than 20 es. Thats a fact. Obviously at some point you will see that es on the target. I bet you could shoot clean at 500 with 40fps es

This above....is the correct info....also google Jerry Tiereny... he used to post on here....... terrific shooter/tester/scientific fact finder........ he proved it......
bill

 

[Keith Glasscock]

Do you have statistics for the same ammo fired through an optical chronograph and/or under less blustery conditions? Some people have reported that the accuracy of the LR can be affected by stuff (e.g. grass, dust, etc) moving around in it's field of vision. I don't have any personal experience, it's just what I've read.

No, this was a shockingly high ES for a 284. I have no intention of repeating the experiment.

The air was pretty clear of particles when the readings were taken, and the results on paper appear correctly correlated to my accepted norms of 284 behavior. Before I forget. The range in question has an elevated shooting position. The bullets are about 15-20 feet in the air from the muzzle out to 300+ yards. LRs work really good here. Many of my friends use them at every match.

 

[Keith Glasscock]

OK, enough suspense (like there really was any), the ES was 63 for those 22 rounds.

 

[Keith Glasscock]

Keith was just jealous of my little 6BR's ES OF ~15 (over 22 shots).
Now if I could just hold the same horizontal as his .284 I might win won of these. Keith beat me by one point (again) but I had him in x count.....Someday!!

15 fps including the clean, cold bore shot! The next 21 shots had an ES of 9. I saw it myself at the prior match.

Pat is the reason I have to shoot a Dasher at MR. I need all the help I can get to stay ahead of him - for now.

 

[rardoin]

I shot a clean at 600 (MR1-F) this weekend with both sighters in the ten (22 shots). Last time I ran the Labradar at a match the ES was 51 for 46 rds. with the current load. A 9 shot verification 2 weeks ago showed an ES of 18. The 9 shot group was .260" at 100yd with the higher V shots hitting a little lower so I am likely on the edge of a node with the load but it is working for now.

 

[Berger.Fan222]

It's fairly easy to calculate a [theoretical] value for this solely based on velocity using a ballistic program, such as JBM. The following is for a .308 Juggernaut load with avg MV of 2750 fps. You raise/drop the velocity until the drop is +/- 0.5 MOA at 500 yd for a 1 MOA 10-ring (i.e. - find the max/min MV that will give a total 1.0 MOA vertical change at 500 yd). For the above 185 load, the ES comes out to be 114 fps (+/- 57 fps)

To do this properly, you need to set the elevation (in MOA) as constant rather than the zero range.

You really want to know how impact changes with velocity without the scope being rezeroed.

 

[4xforfun]

Not"F" class, but, my Dasher load with the 108 BT had a TERRIBLE ES....over 40fps. But it shot so well on my own 1000 yard range I took it to the 2011 IBS 1K Nationals in WV and cleaned up!!

The end,

Tod

 

[zx10mike]

this thread just made my day,my 284 is shooting very well but no matter what es is around 20fps.i came quickly to the conclusion i was wasting a new barrel and i'm just shooting it.despite a higher es than some i'm the weak link in this set up and that is all a man can ask.