RUN TOO FAST?

Get or give advice on equipment, reloading and other technical issues.

Moderator: Mod

Message
Author
John T
Posts: 192
Joined: Sat Jan 07, 2006 5:42 pm
Location: Brisbane

RUN TOO FAST?

#1 Postby John T » Sun May 03, 2020 10:36 pm

Hello.

Why do we shoot high B.C. bullets at Limit velocities? To run against the wind, of course. But to what purpose? Is it to crank on 5 minutes in a 10 mph wind instead of maybe 6 1/4? I don't think so.

You want something up your sleeve to cheat the bastard when it plays its cunning tricks. Has it changed or hasn't it, or has it changed more. Bastard.

CHANGE. That is what defeats us. And why would we bother if it were not so?

11.00 at Belmont. The "Slop". Anyone who has shot on Duncan knows what that means. Is it 1 mph right or 1 mph left or zero?

Let's pause, and take a walk in the ball park, where facts and figures are flimsy.

I use the "Ballistic Explorer" program, and apply the following assumptions;
Range 1000 yds
7 REM SAUM
BER 180 VLD. Radius 0.013 MOA/0.142"
Powder is 2209
57.0 of 2209 delivers 2960MV
Standard Conditions, with a 1mph wind from 9.00
Limits. MV2960. ME3500
Target radii. "X", 0.239 MOA. "6", 0.479 MOA. "5", 0.959 MOA
2209 is rated at 35 fps per grain for the 180 in the RSAUM
Minimum load, 50.0.

The bullet at 3004 MV (Limit +44) will drift 0.492 MOA (the same as the "6" radius 0.479 + bullet radius 0.013 = 0.492) under the influence of a 1 mph wind. In the perfect scenario, it will touch the "6" ring on the water line 3.00. But, with the legit MV of 2960, you get drift of 0.504 MOA. You have missed the "6" by 0.012 MOA/0.125". The score is a "5".

At a legal velocity, you will not "cheat" a 1 mph wind. You will miss the "X" and the "6".

Let's lower the MV to 7715. Why? The recommended minimum load is 50.0. What MV will 50.0 of 2209 deliver?
Say 57.0 delivers 2960MV. 7 grains (57 - 50) @35 = 245. 2960 - 245 = 2715.
1 mph drift is 0.578 MOA/6.052".
You miss the "6" by 0.086 MOA/0.900".

There is 0.074 MOA/0.775" difference between the 2960 and the 2715 in a 1 mph wind.

The ME's are 3503 and 2947.
Very crudely, that's a reduction in recoil of about 16 %.

Add what you see as advantages from lower MV"s.
And disadvantages.

The only one I will mention for now is, should I dust off the 284W? The minimum load is 47.0. Which is the more accurate case for loads below 2800?

Maybe another, MV goes down by about 20 fps in a 28" barrel and by about 60 fps in a 26"; easier tuning.

If I get back to the mound, this could be my first project.

Regards,
John Tracey.
3.5.20

UL1700
Posts: 338
Joined: Sat Sep 16, 2017 5:39 pm

Re: RUN TOO FAST?

#2 Postby UL1700 » Mon May 04, 2020 10:12 am

John T wrote:The bullet at 3004 MV (Limit +44) will drift 0.492 MOA (the same as the "6" radius 0.479 + bullet radius 0.013 = 0.492) under the influence of a 1 mph wind. In the perfect scenario, it will touch the "6" ring on the water line 3.00. But, with the legit MV of 2960, you get drift of 0.504 MOA. You have missed the "6" by 0.012 MOA/0.125". The score is a "5".


The marker has just watched someone hit every corner of the 5 ring with the occasion 4 and finally here you are grouping well in the 6 with a good number of centers, they put in a white spotter in and realise that the 6 ring has broken so quickly change it for an orange. Irritating as the target took a little while to appear but now the 5 is a 6 and you are still in the f open competition. Even on Hexta you are within the radial error so it might go you way!

A poor argument I know but its how my head works :oops: As a 10KG 7mm SAUM isn't a particularly hard recoiling rifle I don't see that a reduction of 0.7 ft/s or 3J as necessarily worth it especially if some time is invested in reduction of felt recoil and ensuing accurate and repeatable tracking. Personally I take every point something if an MOA I can whilst never sacrificing the group. For us as relativity new shooters so far it appears to be working :D

James

AlanF
Posts: 7078
Joined: Wed Jun 15, 2005 8:22 pm
Location: Maffra, Vic

Re: RUN TOO FAST?

#3 Postby AlanF » Mon May 04, 2020 11:24 am

I devised a score simulator a few years back, and its interesting to see how scores vary with muzzle velocity. The following figures are for a National Queens shoot (10 ranges between 300 and 1000yd) and pitched at the level of someone near the sharp end of the field i.e. accurate rifle, good shooter skills. This is for a 7mm 180VLD.

MV---------Score
2750------593.67
2800------594.70
2850------595.72
2900------595.73
2950------596.74
3000------597.75
3050------597.77

Note that none of the performance disadvantages of high velocity such as extra recoil, barrel heating etc. are factored in to this.

In my own situation, that says that my 7 Shehane running at about 2870fps gives only about 1 point away to the SAUMs over the course of a Queens. Not a lot when you look at the additional cost to maintain a SAUM. The fact that SAUMs are currently the most successful 7mm chambering in Australia, is I think more about the skills of the shooters using them (and the quality of their equipment) than about performance superiority of that chambering over the likes of the Shehane and even the standard 284.

pjifl
Posts: 768
Joined: Fri Jun 17, 2005 12:15 pm
Location: Innisfail, Far North QLD.

Re: RUN TOO FAST?

#4 Postby pjifl » Mon May 04, 2020 11:56 am

I think the SAUM Cartridge is a tad more accurate and consistent than a 284 apart from a higher Velocity.

But, OTOH, a good 284 in the right hands does not give much away to a SAUM.
I run my 284 at about 2820 f/s with 180s.

Peter Smith.

AlanF
Posts: 7078
Joined: Wed Jun 15, 2005 8:22 pm
Location: Maffra, Vic

Re: RUN TOO FAST?

#5 Postby AlanF » Mon May 04, 2020 12:46 pm

Yes, I should have said "ballistic" rather than "performance superiority". Not having used a SAUM, I'm not in a position to compare the inherent accuracy. They do liken the shape of the SAUM to the 6BR, so I suppose its not surprising that its very accurate.

BATattack
Posts: 1045
Joined: Mon Dec 29, 2008 10:29 pm

Re: RUN TOO FAST?

#6 Postby BATattack » Mon May 04, 2020 2:08 pm

At the world's in 2017 Rod was running a SAUM in the upper node at about 2960 from memory and took out the gong. I was running a SAUM at around 2910 and placed 3rd about 4 points behind from memory?!. There were plenty of other variables and velocity isnt king but at the end of the day it may be another .001% to help get you over the line. . . . . . .literally . . . . .in a tight comp.

It all depends on the individual. What is their brass prep, how do they clean their barrel, what is their tolerance to recoil / muzzle blast.

williada
Posts: 920
Joined: Wed Jul 22, 2009 12:37 am

Re: RUN TOO FAST?

#7 Postby williada » Mon May 04, 2020 2:49 pm

It is important to look at the decay of BC over distance. Too many programs look at the average figure. It is misleading. Ask yourself which would perform better at 1000 yards - a .223 or a .308W? They both have a similar BC written on the boxes. Experience will tell you it is the .308W.

Much like the transonic range, but it is not, there is a velocity zone that is better for similar BC bullets in free flight. Keeping in the right speed zone as long as possible is desirable. Maintaining the velocity in that zone on a higher node is a safe bet if conditions are variable. Of course a projectile that spends less time in the air is less subject to the wind effects and aerodynamic yaw effects at long range. It can also punch through turbulent air more readily where high pressures and eddies exist at times over mounds causing the nose of the bullet to re-orient to wind flow direction. VLD bullets have a high BC and can be twitchy in turbulent conditions despite perceived gyroscopic stability.

Such bullets come with the requirement of a fast twist rate. This exacerbates throat wear and has fouling issues and are harder to keep in tune. All of these have to balanced in a time frame for getting the most out of the barrel in a competition window.

In my humble experience, BC does not determine how well a rifle will group. That comes back to tune.

williada
Posts: 920
Joined: Wed Jul 22, 2009 12:37 am

Re: RUN TOO FAST?

#8 Postby williada » Mon May 04, 2020 3:14 pm

I would add that general observations I have made with a number of calibres over time, is that close to 3000 fps things seem to come together in free flight for group, particularly in TR and FS. In FTR, guys run with high BC but they are also trying to max out their bullet velocity. The energy limits IME have restricted the grouping potential of the SAUM. Recoil is less of an issue with small calibres and velocity is the thing that makes them competitive.

Gyro
Posts: 543
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: RUN TOO FAST?

#9 Postby Gyro » Mon May 04, 2020 3:33 pm

Don't the top F Standard shooters get very close to the F Open shooters in the Oz comps, despite giving away a HUGE amount of wind drift ?

williada
Posts: 920
Joined: Wed Jul 22, 2009 12:37 am

Re: RUN TOO FAST?

#10 Postby williada » Mon May 04, 2020 3:55 pm

Yes Rob, for a few reasons. Carmichael back in the 1970's came up with a figure of advantage of scope shooters over aperture sights was 15% in the scores at the time in the USA. But he said that advantage disappeared at 1000 yards. He put it down to the fact aperture sights still centre a hazy target at 1000 yards and that scopes have difficulty in seeing the actual point of aim.

Today, the use of Eagle eyes or front lens has refined the sighting ability of TR shooters. I think Alan would agree that a cross hair enables the eyes to balance a blurry black aiming picture in much the same way particularly in mirage conditions on reduced power. I know surveyors prefer a crosshair for this reason. Using a dot or a fine crosshair on high power in dense mirage may not be advantageous.

On permitted ranges, TR shooters use high nodes in the order of 3030 to 3070 fps. This certainly reduces wind drift in the hands of a skilled operator using a window of wind strength and direction in which to shoot so they are never outside 1 MOA change. Of course the can now tune their gear with scopes at short range and use rifles capable of similar accuracy. The rest is technique.

Many F standard shooters have a sound TR background where the skill lies in condition reading and refinement of position and can confidently shoot when the sight picture is not as clear. Then when a bad picture arises IMO they can adapt more readily by winding back scope power and quartering the aiming mark with the cross hairs and dialling rather than aiming off. Another skill learner from TR. Now put them behind good gear with projectiles travelling in excess of 3000 fps, they can match it with FO shooters who do not possess those skills.
Last edited by williada on Mon May 04, 2020 11:51 pm, edited 1 time in total.

GSells
Posts: 629
Joined: Sun Aug 13, 2017 11:04 pm

Re: RUN TOO FAST?

#11 Postby GSells » Mon May 04, 2020 8:57 pm

Gyro wrote:Don't the top F Standard shooters get very close to the F Open shooters in the Oz comps, despite giving away a HUGE amount of wind drift ?

Wow Rob are you trying to start a Fight ! :mrgreen:
Last year Wilddog won at Muckadilla and beat open I think it was , defiantly beat me he was in standard . I was using a poor man's saum! Best I've seen him shoot in a while .

ben_g
Posts: 254
Joined: Sun Apr 24, 2016 7:37 pm

Re: RUN TOO FAST?

#12 Postby ben_g » Tue May 05, 2020 6:43 am

Gyro wrote:Don't the top F Standard shooters get very close to the F Open shooters in the Oz comps, despite giving away a HUGE amount of wind drift ?


In calm or in steady conditions an F-standard shooter sure can run with the F-open guys and beat them.
But if the level of wind reading and shooter skill is equal the calibre with the best combination of wind drift and grouping will win.

I will use Canberra Queens grand agg last year as an example as I was there and the conditions were pretty bad for the whole shoot except the last day.

https://www.results.nraa.com.au/the-can ... t-results/

Look at the grand aggregate, the F-standard winner (who trounced the rest of the F-standard field BTW) would have finished 9th in F-open (31points down). The 2nd place getter in standard would have finished 12th at the bottom end of the field in open (52points down)

Put shooters of the same capability behind equally accurate grouping rifles the better wind performance will win out over the course, particularly in rough conditions just Alan’s statistical modelling shows.

pjifl
Posts: 768
Joined: Fri Jun 17, 2005 12:15 pm
Location: Innisfail, Far North QLD.

Re: RUN TOO FAST?

#13 Postby pjifl » Tue May 05, 2020 8:02 am

The difference in the Canberra Queens results is far greater than a simple comparison of 'scores' because people are willfully ignoring the number of Xs. Add them in and see what happens.

Despite this, I have huge respect for the top FSD shooters. They are also probably the most disciplined group when it comes to having their Rifle Range Tables spot on. Probably derives from many having shot TR in competitions and teams.

Another Group of Shooters to admire are a few FTR shooters using standard FS bullets - and still winning.

We should not be pitting one discipline against another. Move any of the top shooters into another discipline and, after a running in period they will make their way into the top group of shooters. Talent and a bit of luck at times.

We should never forget that there is some element of luck involved in shooting. BUT when the top shooters are lucky enough to see an easier patch of wind, they know exactly what to do to make the most use of it.

Peter Smith.

ben_g
Posts: 254
Joined: Sun Apr 24, 2016 7:37 pm

Re: RUN TOO FAST?

#14 Postby ben_g » Tue May 05, 2020 8:16 am

I was simply comparing whole scores to compare the differing ballistics of the two disciplines.

Add in the X count and the difference is even more apparent.

The reason why it’s interesting to compare F-standard to Open is really the only difference between them is ballistics.
The top standard guys have open level setups and can shoot as well as the F-open guys, their rifles are just as capable as grouping as an F-open rifle.

The difference in scores between the two disciplines (I’m talking the top end of each field) can almost wholly be attributed to ballistic advantage. Look at Grand Aggs across most events and the F-open guys generally have higher scores and X-counts.

I’m not even remotely suggesting the difference is because the open shooters are better than standard shooters. But the comparison does highlight the advantage that superior ballistics (namely wind drift/deflection) does hold.

Rich4
Posts: 185
Joined: Sun Feb 24, 2019 2:33 pm
Location: Chinchilla

Re: RUN TOO FAST?

#15 Postby Rich4 » Tue May 05, 2020 8:16 am

Gyro wrote:Don't the top F Standard shooters get very close to the F Open shooters in the Oz comps, despite giving away a HUGE amount of wind drift ?

Are you suggesting the gap is a bit wider in NZ? :lol:


Return to “Equipment & Technical”

Who is online

Users browsing this forum: No registered users and 10 guests