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bullet velocity variation / scales accuracy.


bob roberts

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Evening all, my trusty Dillon d terminator has recently conked out and I have been looking into a replacement.

Dillon have quite nicely offered me another one at a reduced price, but since I have been looking into long range shooting I’d like to read up on all my options.

The Dillon worked very well, as long as it had between fifteen and twenty minutes to warm up and I didn’t put the light on. (exasperated sigh) Seriously it’s zero would wonder if I did. :blink:

I like the look of the automatic RCBS scales, it looks quick and far more pleasant to use, but I think I would be happier with something that accentuates accuracy and absolute consistency i.e. makes it that little more perfect :)

Has anyone any experience of how a more precise scales, a Sartorius GD503 or even a Prometheus, effects the velocity variation of your ammo? How does this affect your group size too?

 

I quite like the idea of the loads truly being accurate to one kernel of powder, it looks fun like any another intricately detailed precise hobby. :blush:

http://www.youtube.com/watch?v=gfl9C0-5zYw

 

Far less irritating than the Dillon, where you knew the reading was to the degree of ish or thereabouts.

http://www.youtube.com/watch?v=6scLPhkT-8w

It looks like it has been assimilated. :)

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Hello

I haven't gone down the auto measure route yet but

Over 5 shots I dribbled into my pan, and then chronometer I had 5 percent difference between top and bottom velocity

How does that compare to your loads

Ps the five shots went into 15/16 of an inch

Regards

Alan

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  • 2 weeks later...

Jasus lads, almost embarrassed to tell ye this ... but ...

 

The scales I use is a €12 jobbie including postage from Hong Kong .... Yes I know their rubbish and a waste of money and magnetically dampened and ... and ...

 

BUT ... I said I would try one just to see... I use it to load for my F-Tr rifle which is holding 0.2moa @ 1000 yards with an extreme spread of 6 fps ... now I may have been lucky and gotten the 1 in a million but thats whats working for me and I don't have to plug it in 4 hours before hand to settle.

 

I think the most important thing about a scales in consistency.

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Sounds to me like you need a scale that measures to one hundredth of a grain instead of a tenth. I got one off ebay for £50 and I find myself adding or removing single grains of varget! I'll add a link when I get some decent reception.

Alternatively, you could work up a sweet load using the ladder method. This will find a load that has more powder weight latitude meaning the weighing accuracy of an automated powder scale becomes more acceptable.

I use a lee thrower which gives better than 1/10gr fairly consistently, then trickle up to weight. With practice I reckon its a lot faster.

Swamp D. is using my old scale - he neglected to mention the need to position the powder in exactly the same place to get any consistency :-P

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Jasus lads, almost embarrassed to tell ye this ... but ...

 

The scales I use is a €12 jobbie including postage from Hong Kong .... Yes I know their rubbish and a waste of money and magnetically dampened and ... and ...

 

BUT ... I said I would try one just to see... I use it to load for my F-Tr rifle which is holding 0.2moa @ 1000 yards with an extreme spread of 6 fps ... now I may have been lucky and gotten the 1 in a million but thats whats working for me and I don't have to plug it in 4 hours before hand to settle.

 

I think the most important thing about a scales in consistency.

 

2" group at 1000yds. Really? I think the benchrest world record is 3.5" for a 10 shot group, so well done.

 

The accuracy of scales is not really the issue here. What's important for reloading is that the zero of the scales doesn't drift during a reloading session and also that the scales are designed to accurately respond to small changes in weight. There are many types of lab balance out there but they are designed to do different jobs.

 

If you want to measure powder charges down to 1 kernel of powder (approx. 0.01 - 0.02 of a grain) then you need scales such as the Sartorius GD503 (that model isn't sold in the UK, BTW) which is designed to measure small changes and won't drift.

 

You could spend £25 - £250 on an electronic balance, choose the wrong type and get worse results than a RCBS mechanical powder balance.

 

You could also make sure you have found the right load for your barrel by ladder testing or the OBT method and then small variations in charge weight won't affect velocity and elevation much anyway.

 

It's all down to how accurate you need to get your load, how much time and money you want to spend doing it and whether you think it's worth checking every measurement to get that 'edge'.

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Jasus lads, almost embarrassed to tell ye this ... but ...

 

The scales I use is a 12 jobbie including postage from Hong Kong .... Yes I know their rubbish and a waste of money and magnetically dampened and ... and ...

 

BUT ... I said I would try one just to see... I use it to load for my F-Tr rifle which is holding 0.2moa @ 1000 yards with an extreme spread of 6 fps ... now I may have been lucky and gotten the 1 in a million but thats whats working for me and I don't have to plug it in 4 hours before hand to settle.

 

I think the most important thing about a scales in consistency.

Indeed,it is good to have consistency-but to what level?The test of consistency is to measure the same charge of powder say ten times,and see if you get the same weight indicated.That will need rather precise sales,you just can't tell by eye on many beam scales.

 

Small groups don't confirm consistency,though they are even more important.They might just indicate that the rifle is tolerant of minor charge weight variations.6fps does support a high level of consistency.

Even so,I'd be very surprised if .2 moa at 1000 was shot consistently,even for 2 shot 'groups',let alone 5 shot groups.It's inconsistent with one off world records,but you probably mean .2 moa of vertical dispersion,which is very good consistency.

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Just to clear up a point the rifle and load are holding 2" @ 1000 yards .... that is to say 2" of vertical the horizontal is down to me and thats a different story as my wind reading could improve, but as to grouping I holding about 4.5" to 6" ... i.e. 2" high by 4.5 -6" wide...

 

Although the scale is cheap it does weigh to 0.02 of a grain.

 

Germán A. Salazar wrote a very interesting article about velocity for 1000 yard shooting .... LINK

 

​This is definitely worth a read as are many of his articles.

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Just to clear up a point the rifle and load are holding 2" @ 1000 yards .... that is to say 2" of vertical the horizontal is down to me and thats a different story as my wind reading could improve, but as to grouping I holding about 4.5" to 6" ... i.e. 2" high by 4.5 -6" wide...

 

Although the scale is cheap it does weigh to 0.02 of a grain.

 

Germán A. Salazar wrote a very interesting article about [/size]velocity for 1000 yard shooting .... LINK

 

​This is definitely worth a read as are many of his articles.

Indeed,he advises not to listen to what others say about their pet loads.-because you need your 308 sorted for 1000-thus:

 

"The most important point to keep in mind is that additional velocity (ie beyond that which gives accuracy,safe pressures and velocity above the transonic 1.2 mach value) does very little to increase wind drift resistance" .Note,crucially,Mach 1.2 is what you need,and it varies altitude,atmospheric conditions and so on.

You need that 1.2 mach.Anything more is likely to simply increase pressure etc and be an increasing danger to all round,with no gain.

Well,that's what one of the top shooters and ballistically and generally savvy guys says.Absolute velocity is not the holy grail.

Gbal

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Very interesting read,, My self I use a Lyman ohaus beam scale,

I will not use electronic scales as I think that they are to temperamental,,

 

For low volume competition rounds I will always use this scale,

and for field work I will throw with a Harrell powder thrower,

one point that I would like to make is that I will load the pan in the same place

every time??

Also case preparation and a constant neck tention has a very big part to play in the

equation?? plus the biggest of all the bloody wind,,,

 

You that know me will know that I have done ok using this setup.

 

Darrel

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I still think that it will be very satisfying to know that the first step of the f class experience will be quantifiably perfect.

The rest of the steps, well only the group size and scores can attest to those!

I’ll probably find myself loading the maximum I am allowed to hold, labelling their exact load weight then sorting them in groups of twenty two.

Just for the fun of it. :blush::D

I don’t mind having to import it, rare and perfect is better than that rarely perfect dam silly Dillon. ^_^

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