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Position sensitive.

Discussion in 'Handloading and Reloading' started by Furncliff, Mar 20, 2009.

  1. Furncliff

    Furncliff Well-Known Member

    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?
  2. Steve C

    Steve C Well-Known Member

    The following quote was taken directly from Hodgdon's TightGroup product description:
    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.
  3. kestak

    kestak Well-Known Member


    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
  4. Walkalong

    Walkalong Moderator

    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.
  5. Furncliff

    Furncliff Well-Known Member

    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?
  6. Walkalong

    Walkalong Moderator

    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.

    The back of the case is where you want the powder for best, most consistent ignition/burn.
  7. MCMXI

    MCMXI Well-Known Member

    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.

  8. TimRB

    TimRB Well-Known Member

    "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.

  9. Jim Watson

    Jim Watson Well-Known Member

    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.
  10. Walkalong

    Walkalong Moderator

    Those results should prove interesting, when you get round touit. :)
  11. RidgwayCO

    RidgwayCO Well-Known Member

    You mean like this?


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

    D. Manley Well-Known Member

    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.
  13. Walkalong

    Walkalong Moderator

    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. :eek: 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.
  14. Casefull

    Casefull Well-Known Member

    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.
  15. Walkalong

    Walkalong Moderator

    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)
  16. DBR

    DBR Well-Known Member

    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.
    Last edited: Mar 21, 2009
  17. Walkalong

    Walkalong Moderator

    Was Clays tested along side Green Dot?
  18. DBR

    DBR Well-Known Member

    I did not test clays. To the best of my recollection I tested:
    Red Dot
    Green Dot
    Blue Dot
    WAP (now Ramshot Silhouette)
    VV 320

    All loads were for approx 750-800 fps from a 3 1/16" revolver barrel (Ruger SP101).
  19. 1SOW

    1SOW Well-Known Member

    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.


    Need to rechrono....crap

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

    DBR Well-Known Member


    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.

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