Position sensitive.


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Furncliff
March 20, 2009, 01:24 AM
I've been testing Tite Group and W231 in a S&W 15-3. Last go round I thought to test for position sensitivity by tilting the barrel up to the vertical then back to the rest for the next shot. The load was for a .38 special using 3.3 g of TiteGroup and a 125gr LFP at Col 1.45.

First target saw 10 rounds go into 2 inches (10yds)

Second target tilting the gun before each shot saw 6 rounds go into .925 in..

Are TiteGroup and W231 particularly position sensitive? Is this a function of too light a load?

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Steve C
March 20, 2009, 04:13 AM
The following quote was taken directly from Hodgdon's TightGroup product description:
Unlike pistol powders of the past, powder position in large cases (45 Colt, 357 Magnum and others) has virtually no effect on velocity and performance.

TightGroup's claim to fame is that its supposed to be position insensitive, believe it or not.

W231 makes no such claims.

Better accuracy could have come from powder position by tilting the pistol up or it could have come from shooting slower and concentrating better.

kestak
March 20, 2009, 07:43 AM
Greetings,

I reload for plinking .500 S&W with 14 grains of Unique over 350 grains berry.

I noticed the powder fills that huge case only to about 1/3 and I made a point to put the muzzle up to send the powder to the back of the cartridge. Does that mean I could not do that safely? :banghead:

Thank you

Walkalong
March 20, 2009, 07:54 AM
Titegroup claims to be position insensitive, but my results don't bear that out. I have done a good bit of testing of powder forward and powder back with light loads in .357 cases, and a little bit in .45 Colt as well. The results can be disturbing.

For instance. SR 4756 is severely position sensitive. It needs to fill the case pretty well. With a load that will push a 125 Gr plated pill around 900 FPS powder back, it will stick a 125 Gr pill powder forward with the same charge. That is one that stuck in my mind. I had to beat out the bullet with a brass rod. Very good powder, but only if it fills the case well.

Maybe I will do some testing with Titegroup this weekend and get some numbers.

Furncliff
March 20, 2009, 11:05 AM
Steve C "or it could have come from shooting slower and concentrating better."

mmm. nope. I was in the groove by the time I did the test. The difference in the groups was so extreme I thought I was shooting a different load. I'll retest and see how it goes.

Any thoughts on this and UNIQUE?

Walkalong
March 20, 2009, 11:31 AM
Any thoughts on this and UNIQUE?

Unique is much bulkier and will fill the case much better. That in itself will help consistency. It won't be the cleanest burning at that low pressure .38 target load level.

If you have Clays, 700X, or American Select, or Red Dot, try one of them. All very clean in .38 Spl, and not quite as position sensitive as many others. AA #2 works very well too, (Not too position sensitive and gives great ES & SD numbers), but has to get up to more pressure to burn clean, unlike those other 4. It wil leave little half burnt balls of powder until the pressure gets up a bit.

Every senario is different. (different neck tension/crimp/bullet weight/powder/pressure level/etc, etc.You just have to try it and see.

I noticed the powder fills that huge case only to about 1/3 and I made a point to put the muzzle up to send the powder to the back of the cartridge. Does that mean I could not do that safely?
The back of the case is where you want the powder for best, most consistent ignition/burn.

1858
March 20, 2009, 01:56 PM
Despite TightGroup's claim, how can the position of the powder in the case (particularly in situations where there's a fair amount of free space in the case) NOT affect the burn characteristics and therefore the pressure.

Here's some information from VihtaVuori's reloading guide:


2) Free space in the case

When using charges which leave large amount of free
space in the case, the shooting characteristics may vary
largely depending on where the powder is located in the
case. If the powder lies totally in the bottom of the case
(i.e. in the end where primer is), the muzzle velocity and
especially the maximum pressure become much higher.
The maximum pressure may even be doubled when
same powder charge is moved from the bullet end to the
primer end of the case. This can simply be demonstrated
by shaking the revolver barrel upwards or barrel downwards
just before turning it smoothly in horizontal
position, aiming and shooting. Also the recoil may
transfer the powder in either end of the case. This is
sometimes seen as a velocity change between the first
shot and the following shots.
The shot to shot deviations in velocity and pressure
are normally increased when using load which leaves
the cases half empty. For this reason such loads are not
recommended for target loads. The data below is tested
in a way that the powder is as much as possible in the
primer side before firing, and therefore, the pressures
and the velocities represent the maximum values which
were obtained using our test equipment and cartridge
components indicated in the table.


3) Risk for underload detonation

This risk is always present when using highly reduced
loads of any smokeless powder. The large free space in
the case may generate a pressure wave which can cause,
in the worst case, powder to burn as a shock wave, i.e.
to detonate, instead of normal fast burning process. The
extremely sharp pressure peeks involved in detonation
can destroy the weapon and may lead to serious injury.
All these loads given here are extensively pressure
tested and no sings of underload detonation were found.
We strongly recommend everyone to follow strictly
these tables to minimize the risk for underload detonation.

:)

TimRB
March 20, 2009, 02:10 PM
"First target saw 10 rounds go into 2 inches (10yds)

Second target tilting the gun before each shot saw 6 rounds go into .925 in.."


Doing a little modelling of this in Excel, I have concluded that it's easily possible for that scenario to happen completely at random. You're going to need to fire many more rounds than even ten to make any sort of meaningful decision about this variable.

Tim

Jim Watson
March 20, 2009, 02:18 PM
I did a little chronograph work on position sensitivity when Titegroup was new on the market. In .44-40, I found it to be less sensitive than 231 but more sensitive than 700X, based on velocities with muzzle up before firing versus muzzle down. I have some .38 Special loaded with a variety of powders for a wider comparison, one of those Round Tuit projects.

I would expect good performance in that regard from Trail Boss which is so bulky as to leave little airspace. Of course black powder, which is commonly loaded compressed, is well known for very low velocity variations.

Walkalong
March 20, 2009, 02:21 PM
I have some .38 Special loaded with a variety of powders for a wider comparison, one of those Round Tuit projects.Those results should prove interesting, when you get round touit. :)

RidgwayCO
March 20, 2009, 04:11 PM
You mean like this?

http://img12.imageshack.us/img12/4899/roundtuit9829561.jpg

My neighbor in England (fishing buddy and best friend) gave this to me several years ago. I have no idea why...

D. Manley
March 20, 2009, 05:01 PM
First target saw 10 rounds go into 2 inches (10yds)

Second target tilting the gun before each shot saw 6 rounds go into .925 in..

Were these benched or off-hand? I certainly don't have the credentials to determine the effects of sensitivity as it translates to accuracy, but...I'm inclined to believe that when 10-rounds don't group tighter than 2-inches at 30-feet then, something else is responsible. Most loads that literally "pattern" at 25 yards will still cut ragged holes at 10.

Walkalong
March 21, 2009, 10:18 AM
I have my log book in front of me.


.357: Midrange loads.

9.1 Grs N340 - 125 Gr Zero bullet ***

Powder Back - Avg 1351 FPS

Powder Forward - One shot = 1261 FPS (90 FPS difference)(6.67%)

----------------------------------------------------------------------

7.5 Grs SR 4756 - 125 Gr Zero bullet

Powder Back - Avg 1149 FPS

Powder Forward - One shot = 678 FPS! (471 FPS difference)(41%)

----------------------------------------------------------------------

7.3 Grs Universal Clays - 125 Gr Zero bullet

Powder Back - Avg 1215 FPS

Powder Forward - One shot = 1054 FPS (161 FPS difference)(13.25%)

----------------------------------------------------------------------

8.1 Grs N330 - 125 Gr Zero bullet

Powder Back - Avg 1280 FPS

Powder Forward - One shot = 1128 FPS (152 FPS difference)

I forgot to shoot one Powder Forward with the Unique load. :o I'll do that today. I am 100% sure it will be good.

I have also logged some data like this with light loads in .38 &.357 brass, but am tired of typing. :)

Use these loads at your own risk.

Casefull
March 21, 2009, 10:56 AM
The reason I came up with the name caseful is just what your post is about. The longer I have reloaded the more I have gotten away from powders that leave the case half full. A 40sw will chrono more consistenly than a 10mm with the same load and same bullets in the same pistol...cause the case is stuffed full of powder.

Walkalong
March 21, 2009, 05:48 PM
I forgot to shoot one Powder Forward with the Unique load. :o I'll do that today. I am 100% sure it will be good.
I was wrong. 7.6 Grs and a Zero 125 Gr bullet gave an Avg 1261 FPS with one shot powder forward giving 1040 FPS. (221 FPS difference)(17.5%)

Unique dissapointed me. N340, as well as Unique, fills the case about 90% with those loads. 9.1 & 7.6 Grs. Giving around 1325 FPS and 1275 FPS, but the N340 was a better load. I was hoping Unique would match it, since Unique is cheaper. I still need to bump up the Unique charge to get around 1300 to 1350 FPS and see if it does better. It may redeem its self.

Anywhere from 8.9 to 9.2 Grs of N340 shot great with Low ES & SD numbers, and a very good powder forward number. (9.2 Grs ES & SD numbers were better than 8.9 Grs-duh)

DBR
March 21, 2009, 07:56 PM
I tested a number of powders in 38spl 148gr DEWC several years ago for position sensitivity. The best (least sensitive) by a fair margin was Alliant Green Dot. Also, a longer barrel does tend to even things out a bit. Titegroup was nothing special. Ball powders were worse than flake powders.

Edited to add: Position sensitivity has some serious implications for self defense ammo. The first round is likely to be from a holster draw muzzle down. If you carry a short barreled gun and the velocity of the ammo is marginal for expansion this is most likely going to be the lowest velocity the ammo is capable of. I chrono all of my carry ammo muzzle down and make sure that velocity is within the expansion window of that particular bullet. Manufacturer's specs do not usually consider the worst case.

Walkalong
March 21, 2009, 08:45 PM
The best (least sensitive) by a fair margin was Alliant Green Dot.Was Clays tested along side Green Dot?

DBR
March 21, 2009, 10:00 PM
I did not test clays. To the best of my recollection I tested:
Red Dot
Green Dot
Blue Dot
Unique
231
Bullseye
WAP (now Ramshot Silhouette)
VV 320
Titegroup

All loads were for approx 750-800 fps from a 3 1/16" revolver barrel (Ruger SP101).

1SOW
March 21, 2009, 10:00 PM
As a new reloader, this thread is no fun at all!
I was so proud of my 9mm 231 @ 1060 from a first shot draw.

THE 1ST TIME I SHOT MY AMMO, I WON MY LEAGUE PRODUCTION CLASS SHOOT ALSO FOR THE FIRST TIME.

Need to rechrono....crap

Getting ready to try N320 aiming for 1035ish....I'll remember this thread.

DBR
March 21, 2009, 10:16 PM
1SOW

Chrono at least 5 rds (10 is better) muzzle up and then muzzle down. For each shot tap the gun against something solid before the shot to positively settle the powder. If you make power factor with the worst shot velocity and you are going to be shooting at about the same ambient temperature you are good to go.

Added: 9mm will be less position sensitive than 38spl I tested.

Walkalong
March 22, 2009, 10:10 AM
Added: 9mm will be less position sensitive than 38spl I tested.
Bigtime. :)

Need to rechrono....crap
You will be OK. Let us know the results though.

Walkalong
March 23, 2009, 08:58 PM
.357: Light loads - Today: 72 Degrees and overcast.

4.3 Grs Titegroup - 125 Gr Berrys bullet

Powder Back - Avg 854 FPS

Powder Forward - One shot = 619 FPS (235 FPS difference)(27.5%)

Nothing special here as far as being position insensitive.

----------------------------------------------------------

4.7 Grs AA #2 - 158 Gr Berrys bullet

Powder Back - Avg 769 FPS (too light)

Powder Forward - One shot = 772! Tried it again = 738! (+3 & -31 FPS difference)(.96%)

Potential here if it is accurate. I did not load enough to check.

DBR
March 23, 2009, 10:05 PM
Walkalong:

I did my tests with plated 148gr DEWCs seated flush with the case mouth and medium roll crimp over the end of the bullet. I used new Starline brass, same lot of primers, same day.

I did this back in 2002 I think (could have been a bit more recent) and at this moment I can't lay hands on my notebook. I only remember the best (Green Dot) and worst (WAP) and the fact that Titegroup was unimpressive.

The DEWC reduces case volume and should give the most "optimistic" results. I don't think you can compare a 125gr bullet to a 158gr bullet. For one thing case volume is not the same and the heavier bullet has a longer burn time.

Interesting results though huh! This is not a subject I see written up much but I think it matters.

1SOW
March 24, 2009, 12:06 AM
In 9mm, Vit made me nervous when "Wobbly" mentioned how close 4.0 grains of n320 come to the fmj bullet on a light load.

There is very little airspace at 1.12 or less.

Walkalong
March 24, 2009, 08:49 AM
I don't think you can compare a 125gr bullet to a 158gr bullet.That is a good point. I should have picked another 125 Gr load to post with the first one. (AA #2 does like the heavier bullet better, much better, that's a fact)

I think more important is how close the pressures are. The ES, SD numbers almost always get better as pressures go up. Sometimes the powder forward number does too, but not always. Some powders just hate being away from the primer.

There is very little airspace at 1.12 or less.That is a good thing. :)

Walkalong
April 15, 2009, 03:15 PM
Based on this thread I picked up some Green Dot and ran a simple little test today. 6 shots with the powder back and 6 shots with the powder forward. Not a big sample, but enough to show what I wanted to know. It was obvious even without the chrono.

6" Trooper MK III
------------------
CCI Cases@ 1.140....CCI 550 Primers....Berry 125 Gr TrFP....1.550 O.A.L.....4.1 Grs Green Dot....67 Degrees
---------------------------------------------------------------------------------------------------------------

Powder Back

Hi-826
Lo-754
Avg-799
ES-62
SD-23

Powder Forward

Hi-516
Lo-246
Avg-415
ES-268
SD-96

DBR
April 15, 2009, 06:47 PM
Your results are totally different than mine.

Some possible reasons:

1) The Flush seated wad cutters I used are heavier and substantially reduce case volume.
2) I was crimping over the bullet nose so crimp was likely tighter.
3) I think I was using 3grs of powder.
4) I used WSP primers (1995-96 manufacture) which are pretty hot.
5) Last but not least; the Green Dot I used was manufactured around 1995. I am pretty sure Alliant reformulated all of the "Dot" powders around 2000 for cleaner burning. Who knows what that means.

Sometime in the next month or so I will do a repeat. I still have some of that lot of powder.

Walkalong
April 15, 2009, 06:51 PM
It may do just fine with deep seated wadcutters. It should better anyway. It might improve a little at 4.3 Grs as well, but I don't see it improving that much.

I have yet to do some testing with various primers to see if one does better than another in this application.

I have used WSP and CCI 550's with good results with other powders.

HKGuns
May 17, 2009, 05:29 PM
I can't remember where I read this, but I seem to recall selection of powder should be done while considering the size of the case you are loading and how much it will fill the case when filling your cartridge with powder. This being one of several considerations of course.

It was in one of my reloading manuals. Speer perhaps.....

DBR
May 17, 2009, 11:10 PM
I have been doing the things that must be done as the snow melts and spring comes, also testing buckshot patterns. I have not yet retested the powder position results, but I will eventually.

I "think" the crinkled flake powders that have low bulk density should be less position sensitive if the primer is hot enough. Further testing will tell.

Add: Higher pressure loads also seem to be less sensitive to powder position probably because the burn is more complete.

fguffey
May 18, 2009, 11:31 PM
http://www.leverguns.com/articles/taylor/blowups.htm

F. Guffey

DBR
May 18, 2009, 11:46 PM
The navy had some problems with guns in the 4" size (estimate from memory) blowing up for unknown reasons. They did extensive experiments to try and reliably recreate the problem. They did manage to recreate the problem but they never could do it "on command".

Later research with modern, fast, pressure sensing equipment has shown that in some situations a harmonic pressure wave can be reflected back down the bore from the base of the projectile and add to the existing pressure of the propellant creating a pressure spike while the projectile is part way down the barrel.

This may explain the unexpected blow ups. The slower the projectile is moving down the barrel the more time such a transient event has to occur.

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