If ballistics is a science ....

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AlanF
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Re: If ballistics is a science ....

#31 Postby AlanF » Sun Mar 10, 2019 6:29 am

Gyro wrote:....if you release shots at a target with the rifle not on its NPOA ....

NPOA = natural point of aim?

wsftr
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Re: If ballistics is a science ....

#32 Postby wsftr » Sun Mar 10, 2019 6:56 am

Gyro wrote:
wsftr wrote:this is well worth a read. In particular the conclusion.
https://blog.ammolytics.com/2018-12-12/ ... ocity.html
I found it fascinating that he measured a forward motion before recoil that he attributed to the firing pin.

Conclusions
When shooting a precision rifle, preloading your bipod is an incredibly effective technique for managing recoil and getting your sights back on target to watch for impact or prepare for your next shot. However, if you expect it to have an effect on your muzzle velocity, you're going to be disappointed.

Here's what I learned and observed based on the experiment I described above:

I measured no change in muzzle velocity with either technique.
Due to huge differences in mass, the bullet has left the barrel before the rifle moves under recoil.
Chamber pressure readings verified that some of the rounds shot with a preloaded bipod were slower by coincidence, not correlated to or caused by recoil technique.
The median velocity is more robust than the mean (average) and is better suited for ballistic calculators.
My reloading practices need improvement, likely around bullet sorting.


The real problem for me here that's not mentioned in the conclusion is that as many of us know : if you release shots at a target with the rifle not on its NPOA then the bullets will go everywhere. This is a fundamental to accurate shooting and plays out in all kinds of ways across all shooting classes. For an F Class rifle, of either class, the guns relatively higher inertia value compared to say a carry-around sporting rifle may perhaps lessen this dynamic, but believe me if you handle an F Class gun incorrectly/inconsistently you will not shoot well. And I suggest if you are shooting a cartridge/bullet combo that generates a relatively higher "gun upset" during recoil then the problem just get worse.

Whether the velocity is affected or not I have no idea ( despite many saying it is ) but I would presume it would be, just from basic physics theory.


Yeah recoil management is huge in this sport...asks the boys that want to shoot 230s in FO sure there are stories out there of it being achieved, they are the exceptions that prove the rule.
I thought it was interesting that this approach brought as much "science" to the process as what seems possible.

bruce moulds
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Re: If ballistics is a science ....

#33 Postby bruce moulds » Sun Mar 10, 2019 7:16 am

it seems there are 2 areas involve in starting all bullets the same.
one is ammunition consistency in all its forms, combined with barrel condition, and the other is hold, for want of a better term.
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

Gyro
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Re: If ballistics is a science ....

#34 Postby Gyro » Sun Mar 10, 2019 7:21 am

AlanF wrote:
Gyro wrote:....if you release shots at a target with the rifle not on its NPOA ....

NPOA = natural point of aim?


To be sure to be sure cobber

Gyro
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Re: If ballistics is a science ....

#35 Postby Gyro » Sun Mar 10, 2019 7:47 am

But Bruce it just aint that simple. If it was we would all be top shooters.

And the experiments the guy put forward about recoil and velocity are surely just another guy trying his best to test stuff. Many have done this over many years. Some do it with Rail guns in a tunnel or a warehouse. It's all bloody interesting stuff.

That guy RDavies ( who has done a bit of shooting ) says it well with "ya need to look out for everything". The everything part I reckon includes some tricky stuff too and ya really need to involve a top gunsmith to make sure everything is OK too.

I chamber my barrels and went with a 284AI this year. I borrowed a PTG throating reamer to lengthen the chamber throat for the 180 Lapua Scenars. The gun went bloody well in parts but kept throwing the odd bad vertical shot. I knew I hadn't done it.

Turns out the Lapua bullets measured about .2844 and the throating reamer cut to about that size too. So to cut a long story short I ended up lapping out the throat with a bullet ( 9 of them actually ) with some 400 grit ally oxide, to provide more clearance around the bullet. Then gun came right. Much better ES and no wild elevation shots. And no I didn't butcher it with that method as I was really worried I would. I was desperate to cure what I believed was killing my accuracy.

I'm getting off track here but just shows how many things there are that can compromise your accuracy and only with discussion with some other experienced guys did I find a solution.

bruce moulds
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Re: If ballistics is a science ....

#36 Postby bruce moulds » Sun Mar 10, 2019 8:34 am

gyro,
you need to start from a foundation, or all else is wasted.
as an aside, congrats on doing a successful lapping.
my experiences doing this with bullet moulds have not always been happy ones in terms of roundness.
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

Gyro
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Re: If ballistics is a science ....

#37 Postby Gyro » Sun Mar 10, 2019 9:16 am

bruce moulds wrote:gyro,
you need to start from a foundation, or all else is wasted.
as an aside, congrats on doing a successful lapping.
my experiences doing this with bullet moulds have not always been happy ones in terms of roundness.
bruce.


Yes Bruce damn right u need the foundation, which perhaps suggests there are things that need to be controlled or managed. No arguement here.

I'll start. I reckon weighing cases is a waste of time.

I just sort the bullets on weight and BTO, mostly just to identify any outliers.

I seem always to end up with a jammed bullet.

I also begin to suspect pointing bullets does more harm than good.

Seems today its wise to err on the side of extra clearace ( than was previously thought ) on the neck of a loaded round ......

williada
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Re: If ballistics is a science ....

#38 Postby williada » Sun Mar 10, 2019 11:28 am

Bruce your comments are spot on, the bullet does have to start right. I am also reminded of the Houston Warehouse. The last comments the old man gave goes something like,"... its all in the neck". Also visits to the Geelong Winchester factory by self and PP to seek "Palma" ammunition improvement for an Australian team when we still used factory stuff, it was demonstrated specifically how to measure neck tension of factory ammunition by batch sampling on both seating and extraction and tested the ammunition in their underground 100 yard range. Winchester certainly knew the value of neck tension and also changed their compound to seal necks in order to prevent fouling. They went through the experiment of no compound at all which saw groups open up and I saw for myself the value of what they did. Old wives tales of cracking the seal are great entertainment but miss the mark based on what I saw at Winchester who used controlled experiments and equipment beyond the means of the average Joe.

If people are going to anneal then it has to be done properly. Its all work, in the short term, but offers long term gain financially and on the target because it extends case life and once sorted the batches are more consistent over time. I now anneal after every shot. That in itself adds to accuracy because you are holding a variable constant over time by not having to break in new cases which may vary between batches. Annealing is pretty fail safe using an AMP induction method. In case manufacture, a case is probably annealed nearly a dozen times. The brass quickly work hardens as it is formed hence the need to anneal to form it without failure. Best factory brass is finally neck annealed by induction, not in drums in an oven. Here lies the proper use of an expansion iron in the neck. It does two things. One, it opens the junction of the neck and shoulder up because that shrinks on annealing and is a vulnerable place for donut formation with further reloading. Also if necks are not turned and even if they vary a tad in thickness, the firing will harden the necks at different rates and give variable neck tension over time. If people seat the projectile body below the junction of the neck and shoulder, they are asking for trouble in this scenario. Two, with the expansion iron thrusting in an out a couple of times it also work hardens the brass sufficiently for greater consistency and neck tension. The case neck has to be lubricated to do this effectively. I use powdered moly. I like the ideas of Barry's and Gyro's with graphite. If brass is annealed and as I mentioned before when turning necks, then the cutting tool will turn more accurate necks and case culling is reduced.

By reducing the variables where possible through better gunsmithing or stock design then nuances at the elite level can become significant in aggregate scores over a few ranges but particularly at 1000 yards which Rod has commented upon which very few people shoot regularly or keep records of what they do for analysis. In keeping to the thread topic, I might close by saying which I have documented before in regard to lapping the throat area. You have to wreck a few throats to learn how to do it. Yes, we have lapped throats with a projectile mounted on a rod Gyro. These days I do it with a lapping tool made on the lathe cut to the lead angle of the reamer which I design these days to be an angle that is tangent to the ogive of the bullet at contact point. This method is not so much about bullet clearance in modern barrels, where the groove should match the bullet diameter more precisely but gives relief to any chambering that is not concentric or yes, the reamer throat diameter is a mismatch with the bore diameter perhaps creating a step that needs removing for a smooth transition. It also relieves the cross grooves created by the reamer and reduces run in time for copper fouling in the throat. I also use the tool to polish out carbon fowling rather than scrubbing to prevent dimensional change. I am not talking about neck clearance here and carbon build up to vary case seal

Speedy Gonzales advocates full length sizing fired cases which obviously are longer than virgin brass. This does not overwork the brass if custom dies match the chamber and gives consistent wall grip essential to accuracy. Virgin brass is approximately .006" under go gauge headspace. Australian team members used to use a crush fit of .002" on factory brass. Perhaps the real lesson is in the consistent wall grip. Now how many people bump the shoulder back .006" on fired brass? Not me! We know results with virgin brass can be great, but can we duplicate it? I know I can reload for accuracy with fired brass time and time again. One swallow does not make a summer. Seems to me the suppleness of the virgin brass is a big factor in gas seal. We can't fully recover the brass suppleness over the length of the case because we can only safely anneal the neck. So I think Speed Gonzales full length sizing with custom dies is the next best thing to approximate better gas seal.

I don't weigh cases, but measure volume. Do all my charge testing with a jam setting to make sure the bullet is concentric and start up pressures are consistent. Final check with seating depth test determines the group I want for different ranges. With regards pointed bullets, I have conducted controlled tests at 1000 yards which has convinced me of the benefit gained from pointing bullets.

Gyro
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Re: If ballistics is a science ....

#39 Postby Gyro » Sun Mar 10, 2019 6:17 pm

Handbrake wrote:If ballistics is a science why is it so difficult to get consensus on issues relating to reloading?
I am a relative newbie to F Open using 6.5x47 Lapua and having bought another box of new cases checked the neck thickness which ranged from .0125 to .013. I have tried to get clear advice on whether neck turning is necessary prior to first loading, after first loading, when the differences gets to a certain percentage, not to bother as there will be minimal benefit, etc., etc.,
From what I have been able to understand so far in broad terms consistent tension and thus release is a critical component to good loads. Any thoughts?


Just to direct some suggestions to Handbrakes original question : I suggest dont get hung up on having cases with perfect necks. The modern thinking on that is dont bother and just leave plenty of room around the nk on a loaded round. It used to be fashionable to turn necks to within an inch of thier lives. Been there done that. Its actually bloody hard to get really accurate necks. Even after very carefully massaging them so they are consistent in thier wall thickness today, then likely a bunch of them wont be tomorrow after being fired.

The best way I've used is to first run the new unfired cases over a tight fitting "tapered lead-in" machine reamer in the lathe WITH THE REAMER RUNNING IN REVERSE. I just ran the reamer in the lathe chuck at about 200 rpm and held the case in the tailstock in a drill chuck and drove it over the reamer with some oil. Just leave the lathe running and keep changing the cases in the keyless drill chuck. Real easy and quick to do a batch : say just over an hour to do 300 cases. And i ended up with cases that had a very nice even inside surface. Believe me they aint otherwise !!!

So now after turning those cases on a tight fitting mandrel on the lathe they are VERY uniform. But the only way I now know how to keep them remotely consistent is to set up a reaming die to continue making cuts after every firing, or at least for a few more firings while the brass settles down. Did it help ? Helps my headspace anyways. Ya could just be like most others these days and dont get hung up on it and just leave plenty of room around the loaded rounds neck for the inevitable neck wall variances. Seems that works just fine.

Sooooo much of what we do has zero science. It just makes ya feel like you've done all u can.

My personal fetish is drilling down into what the system does during recoil. Has been for years. Cheers Rob.

John T
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Re: If ballistics is a science ....

#40 Postby John T » Sun Mar 10, 2019 8:11 pm

Hello Handbrake.

Did you earn that name at your golf club?

Can I suggest that at this early stage of your F Open career, you keep to the basics and take developments slowly. Neck turning is an acquired skill. There is much more to it than ripping a few thou off a case neck. Ruining 1 in 3, $2.50 cases is expensive education.

Only an experienced neck-turner could improve on cases which have only 0.0005 variation. So, forget about neck turning, for now.

Your loaded necks should measure 0.289 to 0.290.

Your chamber neck should be no more than 0.293.

I guess that you have a Full Length resizing die with the standard de-capping rod with an expander ball. That assembly is not likely to deliver necks which are in-line, a serious no-no.

Buy a bushing die, a 0.286 bush and an "expander" from Barry Davies that will give you your desired neck tension, say, 0.262/0.002.

Regards,
John T.
10.3.19

Gyro
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Re: If ballistics is a science ....

#41 Postby Gyro » Mon Mar 11, 2019 4:40 am

John T wrote:Hello Handbrake.

Did you earn that name at your golf club?

Can I suggest that at this early stage of your F Open career, you keep to the basics and take developments slowly. Neck turning is an acquired skill. There is much more to it than ripping a few thou off a case neck. Ruining 1 in 3, $2.50 cases is expensive education.

Only an experienced neck-turner could improve on cases which have only 0.0005 variation. So, forget about neck turning, for now.

Your loaded necks should measure 0.289 to 0.290.

Your chamber neck should be no more than 0.293.

I guess that you have a Full Length resizing die with the standard de-capping rod with an expander ball. That assembly is not likely to deliver necks which are in-line, a serious no-no.

Buy a bushing die, a 0.286 bush and an "expander" from Barry Davies that will give you your desired neck tension, say, 0.262/0.002.

Regards,
John T.
10.3.19


Great advice John, especially with attaching some numbers/measurements/clearances to your story.

It's not complicated stuff really, but still takes experience to get properly familiar and comfortable with.

Handbrake
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Re: If ballistics is a science ....

#42 Postby Handbrake » Mon Mar 11, 2019 6:49 pm

Thanks guys for the varied responses - I believe a cautious approach is required and will concentrate to n to he basics as He run these new cases in

bruce moulds
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Re: If ballistics is a science ....

#43 Postby bruce moulds » Sat Mar 16, 2019 10:42 am

lubing inside case necks.
I have found that seating bullets into lubed case necks in an arbour press offers far greater consistency of feel than in unlubed ones.
this suggests a more similar grip on the bullets.
in my case I used graphite, and have never tried grease, but might.
I wonder how any of these lubes will affect friction of the bullet in the barrel, which might not matter if it is consistent.
I have avoided moly for the above reason.
obviously some of the measuring devices available for measuring seating pressure are better than feel, but all these things cost money.
one thing becomes apparent when lubing case necks.
the amount of jam attainable becomes much more limited than using unlubed necks.
bullets push back into the case when you close the bolt much more easily.
again this might not matter if it is consistent, but can it be?
as fouling accumulates in the leade angle, bullets could easily be forced further into the cases.
jumping bullets is another thing.
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

Bigtravoz
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Re: If ballistics is a science ....

#44 Postby Bigtravoz » Sun May 05, 2019 8:20 am

Handbrake wrote:If ballistics is a science why is it so difficult to get consensus on issues relating to reloading?
I am a relative newbie to F Open using 6.5x47 Lapua and having bought another box of new cases checked the neck thickness which ranged from .0125 to .013. I have tried to get clear advice on whether neck turning is necessary prior to first loading, after first loading, when the differences gets to a certain percentage, not to bother as there will be minimal benefit, etc., etc.,
From what I have been able to understand so far in broad terms consistent tension and thus release is a critical component to good loads. Any thoughts?


Simple answer is does the neck of the chamber cut in your rifle require you to turn your neck to give sufficient release of the projectile? Usually unless the chamber has a neck that requires neck turning little if anything is achieved by doing it unless there are large variations in the brass to begin with.

Chrisjan
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Re: If ballistics is a science ....

#45 Postby Chrisjan » Mon May 06, 2019 3:37 am

On the topic of lubing case necks before bullet seating. My biggest concern is to apply the lubricant evenly and the same across all brass. I have once mixed some Lyman white graphite into nutmeg tumbler media. It had a great effect in reducing and creating consistent seating pressure. The trade of is that I had to thoroughly whipe all the loaded cases to clean the outside of the cases.

I however with great success and no bad effect at the time stopped using it because of the concern of the graphite eventually create a buildup or alter barrel velocities.


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