drag, twist, and transonic flight.

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mdeland
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Re: drag, twist, and transonic flight.

Post by mdeland » Thu Apr 22, 2021 12:10 pm

Also, aircraft are spinning at a hundred thousand RPMs ! As most of our bullets flight is in transonic then the gyro stability must be the biggest factory in overall accuracy,No?

bruce m
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Re: drag, twist, and transonic flight.

Post by bruce m » Thu Apr 22, 2021 4:27 pm

good observations kenny.
there are probably at least 2 issues with finning.
one is the potential for it to make the centre of mass of the bullet fail to align with the geometric axis of the bullet.
in this case spinning the bullet faster to achieve stability will only make matters worse.
the other is airflow.
even with even finning, airflow would be seriously affected compared to a perfect base.
with uneven finning the situation would be even worse.
combine that with how it affects shockwaves and life is starting to look like more difficult than it needs to be.
tighter chambers will minimize the problem, as will harder alloys, but some form of support for the bullet base as you have shown, would also have to be on the agenda.
i remember dan talking of trying high density polyethylene wads in an attempt to support the bullet bases, but never heard of a conclusion on that one.
loose chambers can even give bullets a slight cupped base as they swage down to fit the barrel and this itself could put the bullet off balance.
my recovered bullets that were breech seated have had perfect bases.
one thing about shooting at 1 mile is that there is no room for poor verticle.
good vert at 1 mile must accompany better vert at 1000 yds as long as velocity is very consistent.
bruce.
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bruce m
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Re: drag, twist, and transonic flight.

Post by bruce m » Thu Apr 22, 2021 4:30 pm

mike,
i would not like to be in an aircraft spinning at thousands of rpm :shock:
i might get giddy :lol:
bruce.
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Kenny Wasserburger
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Re: drag, twist, and transonic flight.

Post by Kenny Wasserburger » Thu Apr 22, 2021 4:49 pm

Shot HDPE wads in my 38-50 good enough to win a midrange Scope National title in 2015 2.5 months after getting out of a wheelchair.

I am going to try them in my 40-70 this season, .062 thick, also going to revisit them in my long range guns this next month at Alliance Neb and Byers Colorado Creedmoor match and midrange Nationals.


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Distant Thunder
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Re: drag, twist, and transonic flight.

Post by Distant Thunder » Thu Apr 22, 2021 4:53 pm

bruce and Kenny,

I used HDPE wads in my .45-90 Shiloh with it's tight standard GG chamber and bore diameter paper patch bullets and with them accuracy was great. Same bullet I now shoot in my .45-70 Hepburn, after some minor modifications to the diameter and length.

Accuracy was quite a bit better with the HDPE compared to the LDPE. I don't know what the harder wads did but they sure worked.
Jim Kluskens
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bruce m
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Re: drag, twist, and transonic flight.

Post by bruce m » Thu Apr 22, 2021 5:00 pm

now i have to get some hdpe to make wads :!:
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bruce m
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Re: drag, twist, and transonic flight.

Post by bruce m » Thu Apr 22, 2021 5:04 pm

i often wonder about finning when using a chamber for bore diameter bullets.
the base of the bullet in the case could never bump up to bigger than groove dia.
has anyone recovered bullets fired in such a chamber and observed finning, or lack thereof.?
bruce.
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powderburner
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Re: drag, twist, and transonic flight.

Post by powderburner » Thu Apr 22, 2021 5:22 pm

Bruce i have a 2&7/8 with a bore sized chamber and built a wad stack so my bullet bases look as shot. it took a bit and was an interesting trip. i did see am improvement in accuracy when i had the right stack.
Got lucky and had some snow one winter to be able to check bases.
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desert deuce
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Re: drag, twist, and transonic flight.

Post by desert deuce » Thu Apr 22, 2021 7:04 pm

Looks like Kenny and Dean have cracked the lid on Pandora's Box when extolling the virtues of HDPE wads in WAD STACKS.
AND, both of you worthy's mention WAD STACKS, and in particular the use of HDPE wads in WAD STACKS.
Yes, I remember Kenny talking about some of his wad stacks but not in combination with HDPE.
Please, that is just not enough information for inquiring minds.
WAD STACKS (plural) and a (singular) HDPE wad do not agree.
Please share the remaining components of your wad stacks and how you control compression/coal when you seat those stacks in the case?

I recall Dan was insistent that the base of the bullet steered the bullet in flight. Conceptually I am not sure how to describe that accurately.
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Re: drag, twist, and transonic flight.

Post by GrumpyBear » Thu Apr 22, 2021 7:30 pm

desert deuce wrote:
Thu Apr 22, 2021 7:04 pm
Looks like Kenny and Dean have cracked the lid on Pandora's Box when extolling the virtues of HDPE wads in WAD STACKS.
AND, both of you worthy's mention WAD STACKS, and in particular the use of HDPE wads in WAD STACKS.
Yes, I remember Kenny talking about some of his wad stacks but not in combination with HDPE.
Please, that is just not enough information for inquiring minds.
WAD STACKS (plural) and a (singular) HDPE wad do not agree.
Please share the remaining components of your wad stacks and how you control compression/coal when you seat those stacks in the case?

I recall Dan was insistent that the base of the bullet steered the bullet in flight. Conceptually I am not sure how to describe that accurately.
Maybe like a rudder on a boat, simplistically speaking ?

Kenny Wasserburger
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Re: drag, twist, and transonic flight.

Post by Kenny Wasserburger » Thu Apr 22, 2021 8:01 pm

DD,

In my 38-50 I used a thin card wad .023 to compress the powder then seated the .062 HDPE wad won in it with a dowel tool I made. I will use the same in the 40-70 this season.

In the 45-110 I use a .062 vegetable fiber wad to compress, then the .062 LDPE or HDPE wad seated with a dowel tool, lastly a Sagebrush 1/8 felt wad is seated. Bullet is seated slip fit down on the felt wad. This same wad stack was used with my NASA bullet in 2006 @the Creedmoor Nationals to win Scope class, was 9th overall also. I took 6 individual gold’s that Championship, and the big one. I beat Michael Jackson by over 50 points the 2005 Champion. I use wad stacks, and primer wads, and shoot a 45 2-7/8ths. I am told wad stacks don’t work or not necessary, I hear the same about primer wads, also told a 45-110 won’t shoot. Yet loads with wad stacks, a primer wad out of a 45-110 has exhibited 18 inches of vertical at 1 mile, with a PP Bullet. And hold the record for top score, and 8/10 in a single relay, actually was 9/12 counting sighters.

I have been using wad stacks for years, rubber Cellulose gasket material can be substituted for the LDPE or HDPE material, as can .084 cork material for the felt. I do not believe they are as accurate though.

The wad stack is discussed at length in my up coming book on BPTRA shooting.

Kenny Wasserburger

Dan T was right about the base, we discussed at length one evening in Phoenix after the day at 800-900 doc and Michael Rix and myself were tied for first going into the 1000 yard line. Dan had recovered one of my bullets and questioned me at length about the wad stack, and no finning on my bullet’s bases.

It is my belief, no proof but evidence says so, that The HDPE wad material is acting much like a gas check completely protecting the bullet base and keeping the lead from flowing back and being displaced by the rifling past the bullets base.
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bruce m
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Re: drag, twist, and transonic flight.

Post by bruce m » Fri Apr 23, 2021 12:17 am

how much better than 16" vert at 1 mile can some of those 338 lapua guys get :?:
especially with irons.
not much i bet, and also bet some of them can't do it.
bruce.
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bruce m
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Re: drag, twist, and transonic flight.

Post by bruce m » Fri Apr 23, 2021 12:38 am

just reread kenny's post and should have said 18" vert.
still excellent.
back to the wadstack.
it would be interesting to know haw hard that felt gets at full pressure.
felt is amazing stuff. the byzantines used it for armour on their heavy calvary soldiers and horses up till around 1500 a.d.
bruce.
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Re: drag, twist, and transonic flight.

Post by bruce m » Fri Apr 23, 2021 1:08 am

powderburner,
thank you for that.
have you ever recovered any with just single wads?
my old paul jones money greaser, original design, shoots better with veg wads than ldpe, but i have never tried hdpe for comparison.
unfortunately none have been recovered to check bases.
the 40/72 on the other hand shoots ddpp better with ldpe than veg.
those veg wads are quite hard compared to ldpe.
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semtav
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Re: drag, twist, and transonic flight.

Post by semtav » Fri Apr 23, 2021 7:01 am

bruce m wrote:
Tue Apr 20, 2021 12:34 am
just watched brian's video.
the first thing that comes to mind is the guy is a denier of spin decay.
by now we know that aberdeen proving ground found quite a bit of spin decay in 308 bullets and could measure it.
it does not matter if you start the bullet spinning fast enough to still have stability when spin has decayed.
his talk of the effects of airflow on planes IS relevant to bullets entering and leaving the transonic zone.
all these thing are forces on the bullet, and it will try to change its attitude in flight to compensate and balance the forces.
while it is doing this it is steering itself into a bigger group, and in extreme cases wobbling and even tumbling.
0ur bullets are flying for 3 seconds, which is a fair while, and a lot more can happen in that time than the 1 second of a 308 at the same range.
we need enough spin to resist all the hostile things that happen to a bullet in flight for maintainance of stability.
maintainance of stability helps maintainance of accuracy.
and with current technology it is all but impossible to overspin a bullet but easy to give it less than optimum spin.
bruce.
Bruce,
I missed this post.
Just wondering, would it be fair to compare his bullets at 2000 yds to our bullets at 1000 yds

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