Get your head round this

[kent]

Ok, becoming a bit obsessive now about the .22 Hornet. getting some strange results working loads though. This is what happened today working on a new extended over mag length / spec. 40 grn v-max load. Powder was Hogdens LilGun primer cci 400 small pistol (primer that produces the lowest SD historically for me). I have found this low load velocity gain thing happening before in the hornet, just cannot figure out why other than load density- though the top load listed here is a full case it is not truly compressed.

 

11g= 2940 fps

11.2=2890fps

11.4=2830 fps

11.6=2824 fps - steady decrease in speed to this point

11.8=2844 fps - starts to rise again

12= 2927 fps- blip?

12.2= 2912 fps

12.4= 2923 fps- 1.4 g extra to give a lower velocity?

 

now I should point out these are not average velocities, each was a single shot recorded and the barrel was clean, de-greased by meths patching, chamber cleaned and all dry patched also aired gun and inspected bore before starting the test

 

so notice how the lowest charge produces the highest velocity and reduces for the next three incremental gains in charge weight before staggering (yeah it has a blip but SD isn't fab in a hornet) up to a similar level.

 

If you look at this as it is being one load varying the SD from those velocities is 41.37 fps, in some respects about to be expected from the hornet ( though I can get it down to sub 20 ) and not by any standards unusable at the upper end of its most effective range window of say 200 ish. Makes me wonder if I should just forget about weighing the charge at all as even a full to the brim case wont overpressure.

 

 

Personally I am thinking its the use of such a low pressure powder, but in what way is this acting and can it be controlled any better?

 

Any ideas?

 

 

BTW these are fire formed cases from Hornaday factory rounds ( the SD of which was around 80 fps)

[DaveK]

Very nice but how did each shot perform accuracy wise. All very nice knowing how fast it's going if it doesn't hit the spot.

 

I load my 40 grainers with 21.2gn H110. My last shot was 190 yards on a hare. Haven't a clue on the ballistics and with that sort of accuracy, who cares?

 

21.2? where did that come from? naturally I meant 12.2.

[gbal]

Ok, becoming a bit obsessive now about the .22 Hornet. getting some strange results working loads though. This is what happened today working on a new extended over mag length / spec. 40 grn v-max load. Powder was Hogdens LilGun primer cci 400 small pistol (primer that produces the lowest SD historically for me). I have found this low load velocity gain thing happening before in the hornet, just cannot figure out why other than load density- though the top load listed here is a full case it is not truly compressed.11g= 2940 fps11.2=2890fps11.4=2830 fps11.6=2824 fps - steady decrease in speed to this point11.8=2844 fps - starts to rise again12= 2927 fps- blip?12.2= 2912 fps12.4= 2923 fps- 1.4 g extra to give a lower velocity?now I should point out these are not average velocities, each was a single shot recorded and the barrel was clean, de-greased by meths patching, chamber cleaned and all dry patched also aired gun and inspected bore before starting the testso notice how the lowest charge produces the highest velocity and reduces for the next three incremental gains in charge weight before staggering (yeah it has a blip but SD isn't fab in a hornet) up to a similar level.If you look at this as it is being one load varying the SD from those velocities is 41.37 fps, in some respects about to be expected from the hornet ( though I can get it down to sub 20 ) and not by any standards unusable at the upper end of its most effective range window of say 200 ish. Makes me wonder if I should just forget about weighing the charge at all as even a full to the brim case wont overpressure.Personally I am thinking its the use of such a low pressure powder, but in what way is this acting and can it be controlled any better?Any ideas?BTW these are fire formed cases from Hornaday factory rounds ( the SD of which was around 80 fps)

 

The standard deviation is the average amount by which a shot deviates from the average of a set of shots,all using the same powder charge.

One shot tells you very little,especially as independent

testing tends to show the Hornet does produce somewhat high SDs.But you find this a

out by eg looking at the velocities of ten shots with the same powder charge,and working out the aberage amount that each deviaes from the ten shot average.

 

You can then do this with ten shots at a different powder charge.The SD might very well be a bit different for that powder charge.

You can not work out a standard deviation from one shot at each of ten different charges.

,so any anomalies this produces,as in your figures,are spurious.

That said,the hornet does not have a reputaton for very great consistency.But your one shot velocities differences are the very reason that SD is needed-there is just

quite a lot of variation likely at each charge level.

In a nutshell,one shot at each powder charge is just not enough to base anything on....especially in the likes of the hornet..the next shot might be plus or minus 40 fps (you say 20 fps)-on average,so you can add 20/40 fps and subtract the same from each of your single shot figures-that is what SD means in practice-does anything really remain?

My apologies if this is not what you did,but it seems to be what is reported.

SD can only come from variations within a sample eg 10 shots at 11.4 g,and shows how consistent that load is in velocity.

gbal

[kent]

People, I totally know how SD works I was pointing out its not a lot different on hornet levels for different load levels (you could get a 40 SD with an equal load in this particular case).

 

Firing one shot is actually how I like to start developing a load. The aim is to look for pressure without having to pull a stack of rounds when you find out its at a lower point than you suspected, I will often go a fair way over just to find out how much is too much, often the lower start loads are treated with little respect by many so why waste a stack of bullets shooting the groups at low start levels. Also putting more powder in doesn't always mean more speed- it has to be burnt! hundreds of shooters put more powder down their tubes totally oblivious to the fact it is doing nothing for them - maybe a bit more muzzle flash. many never chrono their loads or only start once they have a load shooting, greater than expected velocity in itself is a good enough indicator something is amiss- hence I like to start this way

 

Once I am done with single round testing I will run multiple groups looking for the best, its quite easy to use up a full box in early testing and then have to toddle back to the shop for another box just to test them further against other loads at extended ranges etc

 

Heck, I never realised you had to fire more than one shot to find out if a load was accurate- I thought it was nearest the bull wins. Been doing it wrong all these years then wondered why all my groups were 0.224" and other people got different, thought their bullets were doing strange things. It all much clearer now

 

Point is " why does this case seem to produce low load peak velocity levels?" I am still swapping and testing different primers / primer types and it still comes back as cci small pistol being the lowest SD and best groups. What is happening is the barrel actually too long? is the ignition being retarded via density, if so why should it reduce then clime? This is not the first Hornet load that this has occurred with.

 

H110 will no doubt behave differently but at 10,000 greater CUP for 100 fps less and shorter brass life its not a road I wish to tread at present. I have some good shooting loads already but I am really trying to learn more about the why bit here