JUMP!

Over the years I’ve shot a variety of revolvers and most of them have been stamped as being a .357 Magnum.  I don’t play games that require “Magnum” loads so I generally shoot something shorter with a reduced power loading that is easier on the hands and the wallet.  Lately the go to loads have been in Short Colt cases.  The cases are just a bit bigger than a 9mm with a rim on it and they go in and out of my S&W 627 easily.  So far I haven’t noticed any problems but I have heard many a wise old sage posit that there will be a deleterious impact upon accuracy due to the vagaries of “bullet jump.”  Bullet jump is the bullets leap across the vastness of the cylinder as it leaves the case and makes its journey towards the chambers throat.  I picture Evel Knievel attempting to jump the Snake River Canyon when I think of this.  There is my bullet poised upon the precipice, eager, ready to face an uncertain future.  It didn’t work out for Evel Knievel, I’m hoping my bullets have better luck.

short v special
38 Short Colt case and cartridge next to 38 Special case and cartridge

Okay, enough dramatic humor.  It’s pretty obvious that I think “bullet jump” is a bunch of hooey.  At least as far as accuracy out of my revolver is concerned.    I understand that there may be different forces at play when we are discussing rifle accuracy and the distance off of the rifling.  For this test we are talking about a .38 Special at 1.155” vs. a .38 Short Colt at .765 case length.  Sure the Short Colt is visibly shorter but we are talking about .39 of an inch and I just don’t think it is going to make a vast difference in that minuscule amount of time that the bullet is in the cylinder making it’s way towards the throat.

The plan is to load the same projectile over the same sort (but not amount) of powder and the same kind of primer but in the appropriate cases for each cartridge.  I’ll use a .38 Short Colt and .38 Special for the test.  Each one will be fired at 15, 25 and 50 yards from sandbags.  Each load will be using published data.  According to the manuals these loads should yield similar velocities from each of the 2 different loaded rounds.

sw686
S&W 686 6″ bbl

The gun I am using in the test is a no dash S&W 686.  It is an awesome gun but it does have that factory front ramped sight that I have a hard time seeing (this marks the end of the excuse making section).  The 686 has had an action job and has been cut for full moon clips.  For this test I did not use the moon clips.

First up I tried a batch of .38 Specials loaded into Starline Brass and topped with an Armscor 158gr fmj.  I set my target at 15 yards and shot the gun from sandbags.  After the shooting was done I had a 2” group with a flier.  Without the flier it was 1.5”.  Then I loaded the 686 with 38 Short Colts and fired 6 rounds at 15 yards.  This time I had ANOTHER FLIER that bumped my group size up to 2.5” but without that flier I had a nice 5 shot group inside of 1.5”.  I also notice that at all distances my Short Colt rounds did string sort of diagonally whereas the Specials were more of a cluster.

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At 25 yards the 686 kept all 6 of the .38 Specials in a nice 2” group with no fliers.  The .38 Short Colts, or the guy pulling the trigger, fell a bit short here and came in with a group of about 3.25” with a lot of diagonal stringing.  This is still well within the A zone of the USPSA target I was using but the stringing may be due to the “bullet jump” from the .38 Short Colt cases.  At least there were no signs, at any distance, of key holing or other deleterious results.

50 yards is where the “bullet jump” crowd seems to feel that the Short Colt will reveal its weakness.  I hate to tell you that for me, on this trip to the range, it didn’t happen.  At 50 yards with my crummy eyesight and the hard to see factory front sight (please refer to paragraph 4, sentence 2 for my excuse making section), the 38 specials went into a 6” group.  At that distance I can’t really call anything a flier.  I’m sure better shooters than I could shrink that group with the same gun and ammo but I think I’m seeing the results I want from this.  Then I shot the .38 Short Colts at 50 yards and had to chuckle.  I got a 5” group with 5 of the shots in or touching the A zone.  I don’t think “bullet jump” is hurting me on that one.

So a couple of hours at the range and a little time at the reloading bench and I have the answer that I was looking for.  If I’m not hitting what I’m aiming at I can’t blame “bullet jump.”  Maybe the “trigger nut” is to blame?

One final note, I did drag the chronograph to the range just to make sure I was comparing apples to apples velocity wise.  I didn’t record the data but both cartridges made USPSA minor with a little room to spare.  Now, from looking at those pictures I need to adjust my rear sight just a smidgen.  I’m also getting some unburned powder in the .38 Special (note the suet on the fired cartridge in the picture up above) so I’ll have to work on that too.  Oh well, that’ll have to happen on the next trip out.

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