Opposite of setback?

[email protected] · October 27, 2009, 09:39 PM

Testing some 357 loads from S&W 686. Checked my COL of remaining rounds for setback after firing a few rounds. I got measurements that were between
.002-.004 LONGER. I measured each COL individually before and after firing the other rounds. Is this a crimp issue? I'm using 125g Rainiers and a Redding taper crimp die set very light but I expected setBACK not forward. Is this a revolver vs pistol phenomenon? If so, why?

LHB1 · October 27, 2009, 09:57 PM

Yes, bullet protrusion/creep occurs in revolvers due to recoil pushing gun backwards while inertia tries to hold bullets still. Setback occurs in semi-autos due to bullet strike on feedramp during feeding. We typically use firm roll crimps on revolver loads and taper crimps on semi-auto rounds since many of the latter supposedly headspace on front of case. Would suggest you get a roll crimp die for your .357 revolver loads and use bullets with crimping cannelures.

Sport45 · October 27, 2009, 10:01 PM

There's nothing going on in a revolver to cause setback. When it fires recoil pushes the gun back. The mass of the bullet doesn't want to move back quickly so it tries to stay where it is as the case is yanked back by the rim.

A Ranier bullet is probably about as slick as a lead bullet and at 125gr there isn't a lot of length seated for neck tension to hold on to. Try using a little more crimp and if that doesn't work polish a bit off the expander for more neck tension.

All that said, I wouldn't worry too much about .004" after being in the gun for five rounds fired. As long as it stays in the crimp groove and doesn't jump far enough to tie up the cylinder they should work fine.

October 27, 2009, 09:39 PM	#1
[email protected] Member Join Date: November 27, 2007 Posts: 18	Opposite of setback? Testing some 357 loads from S&W 686. Checked my COL of remaining rounds for setback after firing a few rounds. I got measurements that were between .002-.004 LONGER. I measured each COL individually before and after firing the other rounds. Is this a crimp issue? I'm using 125g Rainiers and a Redding taper crimp die set very light but I expected setBACK not forward. Is this a revolver vs pistol phenomenon? If so, why?

October 27, 2009, 09:57 PM	#2
LHB1 Senior Member Join Date: March 25, 2005 Location: Houston, TX Posts: 1,545	Yes, bullet protrusion/creep occurs in revolvers due to recoil pushing gun backwards while inertia tries to hold bullets still. Setback occurs in semi-autos due to bullet strike on feedramp during feeding. We typically use firm roll crimps on revolver loads and taper crimps on semi-auto rounds since many of the latter supposedly headspace on front of case. Would suggest you get a roll crimp die for your .357 revolver loads and use bullets with crimping cannelures. __________________ Good shooting and be safe. LB Last edited by LHB1; October 28, 2009 at 08:55 AM.

October 27, 2009, 10:01 PM	#3
Sport45 Senior Member Join Date: May 25, 1999 Location: Too close to Houston Posts: 4,196	There's nothing going on in a revolver to cause setback. When it fires recoil pushes the gun back. The mass of the bullet doesn't want to move back quickly so it tries to stay where it is as the case is yanked back by the rim. A Ranier bullet is probably about as slick as a lead bullet and at 125gr there isn't a lot of length seated for neck tension to hold on to. Try using a little more crimp and if that doesn't work polish a bit off the expander for more neck tension. All that said, I wouldn't worry too much about .004" after being in the gun for five rounds fired. As long as it stays in the crimp groove and doesn't jump far enough to tie up the cylinder they should work fine. __________________ Proud member of the NRA and Texas State Rifle Association. Registered and active voter.