40 cal. bullet setback


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glockky
September 13, 2012, 09:42 PM
I know i have been kind of burning this site up with threads here lately but i have ran into some things that i havent ever had trouble with.

I started loading 40 for the first time and have always heard one of your biggest enemies is bullet setback. Well i bought some 180gr RNFP jacketed bullets and was trying to set me dies up. I loaded a few and then cycled them through my pistol. I was suprised to see that in 5 chamberings i lost .030 . I then tightened my crimp up to where i could actually see the taper crimp and am still getting around .003 to .005 bullet setback with every cycle. Is this normal?

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bds
September 13, 2012, 10:08 PM
You do not get neck tension from the taper crimp. You get neck tension from resized case neck applying friction pressure on the bullet.

I would make sure you are full-length sizing the cases (bottom of sizing die barely kissing the top of shell holder/plate). If you are loading on a progressive press, the top of the shell plate may be thicker, not allowing the die to come all the way down.

If you have a single stage press, try sizing the same case along with some other cases and see if the neck tension improves. If it does, you may need to grind the top of the shell plate some.

beatledog7
September 13, 2012, 10:16 PM
Some setback is normal, but that sounds like a lot. I agree with bds--sounds like you might be getting less than adequate neck tension.

Have you cycled and measured some factory rounds for comparison?

jjjitters
September 13, 2012, 10:22 PM
A couple thou is normal,sometimes even .01"(at the extrem).with the crimp just a little less than your last setting does it set back more than a couple thou?

bds
September 13, 2012, 10:38 PM
Bullet setback does occur (to a certain extent) due to several factors and thankfully most of us chamber our rounds only once.

IME/IMO, bullet setback is more of an issue for 40S&W because unlike 9mm FMJ bullets which are pointed RN that feed/chamber with less bump on the ramp. With 40S&W TCFP/RNFP, the blunt point of the bullet seems to bump the ramp more to seat the bullet deeper in the case neck. And if you have work hardened case wall that experiences spring back after resizing, the bullet will seat even deeper when the bullet nose bumps the ramp.

If you are at mid-to-high range load data, you may have some "head room" from chamber pressure increase from deeper seated bullet. If you are loading at near max/max powder charges with mixed range brass with unknown reload history as to how many times the case base was stretched (thinned) and "fixed" by push-through sizing dies like Lee FCD/Redding G-Rx dies, you may be working on a recipe for weakened case wall that may lead to case rupture/case failure aka KaBoom.

I reserve "known" once-fired brass (ones I saw go from factory new boxes into the pistol) for 40S&W max charge loads. For mixed range brass with unknown reload history (even though they may "look" shiny from wet tumbling with SS pins), I use mid-to-high range W231/HP-38 load data with wider start/max ranges). For this reason, I really prefer not to use Titegroup for 40S&W and do not suggest Titegroup to new reloaders, even at mid-to-high range load data as I only have 0.5 gr swing between start to max charge. ;) Be safe. YMMV

40S&W 155 gr Hornady XTP Titegroup Start 5.4 gr - Max 5.9 gr 31,700 PSI

40S&W 165 gr Sierra JHP Titegroup Start 4.6 gr - Max 5.1 gr 33,600 PSI

40S&W 180 gr Hornady XTP Titegroup Start 4.2 gr - Max 4.7 gr 33,300 PSI

jjjitters
September 13, 2012, 10:57 PM
Thats why often when you see a .40 cal KaBoom, you also see Titegroup listed as the powder, and an unhappy gun owner usually asking if it was a double charge. .03 setback in my Quickload added 8300PSI to a just under max load.

glockky
September 13, 2012, 11:22 PM
Well i have got it doing better. My loading manual show a COL or 1.250 and my pistol and magazine will handle 1.350, so i am gonna use that as a cushion. I am loading 6.5 gr of power pistol, I didnt want to go with a fast burning powder to start out with.

I am still getting around .005 and i guess i am gonna have to live with it, and just not cycle rounds a bunch which shouldnt be an issue. Thanks for the info

bds
September 13, 2012, 11:25 PM
glokky, recheck your manual. It should say 1.125" OAL.

As to what OAL to use, you should conduct the barrel drop test to determine the Max OAL (www.thehighroad.org/showthread.php?t=506678) and feed/chamber from the magazine to determine the Ideal OAL.

Then conduct the full-powder work up to determine the charges that will reliably cycle the slide and produce accurate shot groups.

glockky
September 13, 2012, 11:32 PM
thats my bad its 1.125 and i went 1.135. thanks for the correction.

murf
September 14, 2012, 02:28 AM
suggestions: mount a 40 cal brush in a drill and clean the carbon out of the inside of the case (it's really slick), clean any lube, oil, etc. out of the case.

may help, may not.

murf

44junkie
September 14, 2012, 03:15 AM
I got the Lee undersized .40 cal sizing die and have had no set back issues since. It probably shortens case life due to overwork, but for me it's not much of an issue since .40 brass is relatively inexpensive and plentiful.

gamestalker
September 14, 2012, 09:19 AM
The more crimp you produce for auto loading pistol brass, the less neck tension produced. The taper crimp die for these type cartridges is not intended to increase, nor produce, additional neck tension, at all! I have not crimped a single auto loading pistol cartrodge in more tha 30 years and have yet to experience bullet set back, not once.

How it's done:
Stop belling the case mouth completely, chamfer the inside of the case mouth, and seat the bullets with the die backed out to the point the crimp does not touch the case mouth at all. That's it! You now have as much neck tension as can be produced.

Don't be confused though, it is still necessary to use a crimp for revolver brass. that type of brass is reliant upon a good crimp to hold the bullet, thus preventing it from jump / setback.

GS

918v
September 14, 2012, 12:40 PM
You are overexpanding the case. Less bell = more case tension. More case tension = less bullet setback. Less bell requires greater precision when starting a bullet in the case, but it's worth the effort.

glockky
September 14, 2012, 05:00 PM
I am just belling the case enough to where the case wont wrinkle when i seat the bullet. I will try not crimping during the bullet seating stage, then crimping after and see if that makes a difference.

rcmodel
September 14, 2012, 05:08 PM
Your expander may be too big.
If it measures .398" or more it is too big and is over-expanding the case when you bell.

It should measure no more then .397" - .3975" tops for proper neck tension.

It won't hurt to chuck it up in a drill and wear off a couple thousandths with emery cloth.

rc

918v
September 15, 2012, 11:40 AM
Lemme ask, are you lubing your brass by shaking it in a bag sprayed with HOS?

glockky
September 15, 2012, 12:16 PM
no not any lubing. I have gotten it down to .003 to .005 now and it think thats good. I should not be chambering ammo 4 or 5 times before shooting.

Bovice
September 15, 2012, 05:20 PM
I load my .40s at 1.130 to 1.135. No need to load at minimum length, most .40s are happy with SAAMI max length.

bds
September 15, 2012, 05:24 PM
1.135" OAL may work for your pistol/barrel/magazine but working OAL for other pistols/barrels/magazines should be determined individually by function testing the feeding/chambering from the magazine. I typically load TCFP nose profile bullets at 1.125" OAL to work in many pistols.

BTW, factory Golden Saber 165 gr JHP is loaded at 1.127" OAL while Winchester Ranger-T 165 gr JHP is loaded at 1.125" OAL.

YMMV

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