Make sure your ammunition has the legs...

[Stalker62]

I post this thread is the vain hope, that it may help another poor soul who has decided that reloading is a good thing.

The rifle is an AI AX in .308 - nothing wrong with that.

The ammunition (home grown) is:

Lapua brass - nothing wrong with that.
CCI LRPs - nothing wrong with them.
Powder Swiss RS 50 - nothing wrong with that (46gr weight - quite possibly something wrong with that)
Bullets - 155gr SMK -nothing wrong with them.

I made these up about three years ago, with the intention of building a DOPE card for this rifle.

It is a slow process, which is not a problem, I am not in a hurry to be anywhere.

However, the last two outings on the 1,000 yard range and I was having a mare. I could not get on paper.

I will share a little secret with you, in the sure and certain knowledge you will hold it close to your breast. After the last wasted day on the 1,000 yards, and as I was packing up, I noticed that my windage was dialled in for 2 milliradians (mils) when I had assumed (fatal) that it was a zero. Consequently I had been (in all probability) hitting the target three across. Schoolboy - and a wasted afternoon.

Back there yesterday. Firing off magazines of ammunition. Nothing. I dragged in a couple of sensible members of the club to 'spot' for me. Nothing.
I gave them the rifle to have a go. Nothing.

One guy then thought he saw a 'splash' at about 900 yards.

I went back to the Zero Range and sent three. It all seemed to be in order.

Back to the point. More nothing.

"Have you tried it with factory ammunition?"

Someone past me three rounds of factory. I went back to the Zero Range and chucked a couple down range.




Back to the point and loaded with factory ammunition, the first round was in the 4 ring. This was cause for some celebration. After 'two days', and much wasted time and bullets, are on.

Quite simply the rounds I had built are good to about 600 yards - after which they just run out of steam. The interesting fact (for me) is that you would not know this just by looking at the Zero Range target.

I bought nearly 300 rounds of factory (I am up in Scotland in the summer) and mentally put my home loads to one side for 'short range'.

Finally able to fill in another line on the DOPE chart.


So just a tip for anyone else who is about to make the same mistake, (of course no one would). Make sure your ammunition has the 'legs' to get out there.
Such a frustrating time and so easily resolved.

Any hoo.

Just to put things into perspective.

Whilst I was dicking about on the 1,000, and 1,200 yard point, I saw a memorial bench which overlooked the range. I thought it rather poignant.







I never knew Mr Evans, but I could not help wondering what he would have made of my efforts...

 

[rustypigeon]

I’m not really sure what to say other than buy a chronograph. You could have saved a lot of wasted ammunition with a few shots through a chronograph. I’m not sure I agree that your homeloads don’t have the legs to get to 1000 yards either. You could be pushing them at 2000fps and still get impacts on target if you know what you are doing

 

[Stalker62]

You could be pushing them at 2000fps and still get impacts on target if you know what you are doing

Bless you for that...

 

[Smellydog]

Get some powder in there.
It's like everyone is **** scared to wind (wined) anything up these days....
Thanks for sharing and glad your better.

 

[Bavarianbrit]

I tent camped for a few days once in the early 80s at Bisley camp on a small bore comp, one of my happy memories.

 

[Dalua]

My TR load is 46.4gr RS50 with Dyer HBC 155gr BTHP. That seems to get to 1000yds OK.

I were shooting a target at 1000yds and the POI was 900yds I would conclude that although more powder might help (if safe), more elevation would probably be the practical thing to go for as being possible to do on the firing-point...

It's like everyone is **** scared to wind anything up these days....

Nothing scary about winding up the elevation

 

[Robs]

Agree with rusty pigeon, chronograph will give you the answers you need, the load data seems good.

 

[Cottis]

On the plus side, the guy two lanes next to you is wondering how on earth he managed to shoot the best 10 shot group ever when he only let 5 shots go himself

 

[Donkey Basher]

From hands on experience shooting AI rifles with 26” factory barrels…

I have found that even when shooting factory (GGG & before that RUAG) 155gn through a (relatively speaking) short barrel in a wind there is a strong possibility that you will struggle to consistently be on target at 1000 yards. In basic terms the velocity starts to drop to around the transonic region where the bullet becomes unstable, then add in the wind as an external factor & that instability becomes an issue.

Have a look at Quickload (or whatever software you’re using) & see what your down range velocities are from 800 to 1000 yards. There’s a reason why the TR community use rifles with 30” barrels and non standard bore dimensions to ensure their bullets are still supersonic at 1000 yards.

I have overcome it reliably by only using 175gn ammunition for 1000 yards & longer.

 

[Stalker62]

I have overcome it reliably by only using 175gn ammunition for 1000 yards & longer.

What's the science?

 

[Foxyboy43]

From hands on experience shooting AI rifles with 26” factory barrels…

I have found that even when shooting factory (GGG & before that RUAG) 155gn through a (relatively speaking) short barrel in a wind there is a strong possibility that you will struggle to consistently be on target at 1000 yards. In basic terms the velocity starts to drop to around the transonic region where the bullet becomes unstable, then add in the wind as an external factor & that instability becomes an issue.

Have a look at Quickload (or whatever software you’re using) & see what your down range velocities are from 800 to 1000 yards. There’s a reason why the TR community use rifles with 30” barrels and non standard bore dimensions to ensure their bullets are still supersonic at 1000 yards.

I have overcome it reliably by only using 175gn ammunition for 1000 yards & longer.

Hmmm. From what I read on this and all many a few of his posts there is more than the bullet at risk of becoming unstable!
Just saying….

 

[xavierdoc]

What's the science?

Higher ballistic coefficient so not going transonic before reaching 1000yds

 

[Stalker62]

Higher ballistic coefficient so not going transonic before reaching 1000yds

Forgive me - I have a real mental block with this.

Why does a heavier bullet have a better BC?

 

[xavierdoc]

I had a similar experience several decades ago. My club had booked some lanes on Stickledown and we worked back to 1000yds.

My 308Win 155gr Scenars were drilling the centre out to 900yds but at 1000yds they were all over the place or off target. The butt marker radio'd back that they were going through sideways.

Not enough velocity for that BC bullet.

I've had the same since at Orion, out to the mile with a 284Win in an ELR comp. Good accuracy to 1500yds but misses all over the place thereafter. Luckily my team mate was shooting 300Norma and carried us for the win!

A chrono, coupled with a ballistic calculator using the true/tested BC (typically G7 BC for boat-tail bullets) will give you a good idea of where transonic zone will be.

Some bullet designs tolerate transonic transition better than others, so it's not always going to result in instability but wherever possible try and stay supersonic at the max distance you want to shoot.

 

[xavierdoc]

Forgive me - I have a real mental block with this.

Why does a heavier bullet have a better BC?

Essentially because, for a given shape, it will be longer and more aerodynamic.

There are other factors though: ogive and boat-tail shape being a big part. Furthermore, lighter bullets can be driven faster so sometimes the equation can tip the other way if the lighter bullets faster velocity can offset its lower BC.

In 6.5mm the Lapua 123Scenar punches above its weight (compared to 136 and 139Scenars) as it has the best form factor of these three and can be pushed faster. It won't hold true for all applications but when you run the numbers you sometimes find drop/drift doesn't always favour the heavier option (but usually does.)

 

[Stalker62]

Essentially because, for a given shape, it will be longer and more aerodynamic.

Thank you; that makes sense.

I have just tried to order :-

Modern Advances in Long Range Shooting by Bryan Litz, but that is proving harder than a hard thing.

While you are on fire, have a look at this thread:-

Zero Targets​

and see if you know the answer to another great ballistics mystery...

 

[Smellydog]

Isn't part of the coefficient equation calculus the weight. Changing the weight and length increases the coefficient which manifests itself down range.

 

[bowji john]

This is a grand topic

Partly science and partly witchcraft

If I shoot and study for the rest of my life, I’ll still know little to nothing

I read and re-read Brian Litz,s books in the hope that someday I might gain an iota of understanding

J

 

[paul o']

You do make I smile with you trails and tribulations .

 

[Rory]

What's the science?

This is why the US snipers moved from 168gr to 175gr for .308.
The 175gr will stay supersonic to 1,000yards.