bullet length.

[MJR]

Following a dismal performance at the egg shoot i started looking at all my kit for an explanation (couldn't possibly be down to shooter error lol). Mechanically everything was fine, tight scope screws etc so i looked at my ammunition. To cut a long story short the bullets i'd loaded are 20 thou longer from base to ogive than the previous box and im wondering if this would explain the unexpected vertical rise of poi especially at 500 yds? Load is 43.7gn 4831sc, lapua brass,br2 primers and 105gn vld.

[Laurie]

It could be down to several things, most likely a combination of them. Unless you're running very close to the lands, under 10 thou' jump, even more so under 5 thou', the bullet lot difference shouldn't affect your MV to any great extent. It may well bugger your group sizes up mind you. That's why most handloading authorities don't recommend using less than 10 thou' jump unless you're going to measure and batch bullets, and check the COAL (case-head to ogive using a comparator) for each finalised round. Too small a jump allied to bullet variations can see some touch the rifling, others jump - never a happy situation.

 

Otherwise ..... Different powder and primer lots as well as bullets, ambient temperature, and less dense air compared to wherever you got your scope settings. Diggle is somewhere around 900 ft ASL and that knocks nearly an inch of mercury off the atmospheric pressure reading compared to a range at sea level for any given pressure applying on the day. In itself, it shouldn't make that much difference at 500 yards (it does for a ballistically top-notch 308W F/TR rifle and load combination at 1,000, there being around an MOA difference between Diggle / Blair Atholl and Bisley settings.)

 

Then there are lighting, mirage etc factors .... not that mirage is usually a Diggle problem. Nevertheless, this and other factors can cancel each other out and your scope settings are spot-on, or if you're unlucky they all go one way and your settings become a half-MOA or more out. Half-MOA at 500 yards is approx. 2.5 inches / 63mm and what's the size of a hen's egg? (I wonder .... does Vince B buy 'extra large organic', or supermarket cheapskate small eggs for the Egg Shoot?)

[The Gun Pimp]

Then there are lighting, mirage etc factors .... not that mirage is usually a Diggle problem. Nevertheless, this and other factors can cancel each other out and your scope settings are spot-on, or if you're unlucky they all go one way and your settings become a half-MOA or more out. Half-MOA at 500 yards is approx. 2.5 inches / 63mm and what's the size of a hen's egg? (I wonder .... does Vince B buy 'extra large organic', or supermarket cheapskate small eggs for the Egg Shoot?)

 

It's down to one thing - NO SIGHTERS!! Without sighters, we are rubbish!

 

Six shooters didn't hit the groundhog at 300 yds despite scoring well at 100 yds. At 500 yards - a third of the field didn't hit it - which is normal! It's all down to the wind - which was very light on the day but we had mirage to contend with so difficult to see shot-holes at 300 yds.

 

The eggs were British Standard kitemark specification from free-range hens living a stone's throw from Diggle! They made a nice omlette this morning.

[gbal]

It's down to one thing - NO SIGHTERS!! Without sighters, we are rubbish!

 

Six shooters didn't hit the groundhog at 300 yds despite scoring well at 100 yds. At 500 yards - a third of the field didn't hit it - which is normal! It's all down to the wind - which was very light on the day but we had mirage to contend with so difficult to see shot-holes at 300 yds.

 

The eggs were British Standard kitemark specification from free-range hens living a stone's throw from Diggle! They made a nice omlette this morning.

Gordon Benedictine! Amen to that.

This should be food for thought to all shooters in a civil or uncivil relationship with small animate or inanimate targets at these sorts of distances.

Even hard boiled hillbillies.

 

Gbal

[MJR]

''It could be down to several things, most likely a combination of them. Unless you're running very close to the lands, under 10 thou' jump, even more so under 5 thou', the bullet lot difference shouldn't affect your MV to any great extent. It may well bugger your group sizes up mind you. That's why most handloading authorities don't recommend using less than 10 thou' jump unless you're going to measure and batch bullets, and check the COAL (case-head to ogive using a comparator) for each finalised round. Too small a jump allied to bullet variations can see some touch the rifling, others jump - never a happy situation."

Laurie, thanks, I wasn't aware of that recommendation and the load is 5 thou off the lands.

 

Vince, i've no doubt you are right, sighters are bliss! But I did feel something was not as it should be even with my poor shooting on the day. My wind reading needs to improve but it was the vertical that had me puzzled.

 

Gbal, oddly enough I didn't spot any hillbillies keen to demonstrate their shooting prowess, funny that?

 

Gents, thanks for all the replies, very informative.

[Scotch_egg]

Mike,

 

I put it down to myself letting you down and not accompanying you. We did rather well in cz with no sighters and the quart was spot on.

 

If you want to get out to 500 let me know we can get out this week.

 

 

 

 

 

[Offroad Gary]

Perhaps its those funny chart things i saw you looking at.... Get yourself a decent ballistic app!

[Scotch_egg]

Perhaps its those funny chart things i saw you looking at.... Get yourself a decent ballistic app!

 

Ouch!

 

I was on the app in cz and matched the charts for .308 metre for metre. Can't fault the charts. I loaded my rounds to martch velocity and as lucky they grouped.

 

Might have been an off day.

 

 

[MJR]

I'm not a ballistic app kinda guy but out of interest isnipe matchs my charts at the ranges the egg shoot is shot over, after that the app gets optimistic but the charts still work, well they did with the original bullets. Bottom line is the charts work. I will need to verify with the new bullets and recheck zero/group size and velocity.

Scotch, this week is very busy but could make it one evening?

[Ronin]

G bal makes an excellent point,

 

we read of people taking shots at long range on live quarry, even with "race guns" (highest spec rifles you can get and experienced reloading / shooting) we dont always hit what were aiming at.

 

The rifle I was using shot a .276" group at 100 from cold bore scoring highest possible marks on the prairie dog target.

 

At 300 my drop chart was spot on and I shot a reasonable group ..

 

At 500, I missed a wind call by a couple of mph and found my elevation was 1.5 MOA out (although I was on paper and shot a 2 inch group) it was out of the scoring area by a long way - which, if shooting at live quarry, would equate to a wounded or missed animal......depending on size of course.

 

No sighters of course.. a great leveller and true test of abilities.......