Author Topic: 40 S&W Bullet Tension and Setback  (Read 1029 times)

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Offline tdogg

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40 S&W Bullet Tension and Setback
« on: January 14, 2018, 12:51:24 AM »
So I was shooting at my local USPSA match today and had a failure to feed.  The cartridge hung up on the feedramp and I got an opportunity to practice a jam drill on the fly.  After the string I picked up the cartridge that hung up and it was setback ~1/8 inch.  I'm really glad it didn't chamber after it got hung up.  It would have been pretty exciting had it got shot.

I didn't think about it at the match but when I got home I pulled other cartridges out of that batch and tested them for setback by pushing them into my bench.  To my surprise they would seat deeper with moderate pressure!  This sparked an investigation to see what in my process is causing the low bullet tension.

My Lee sizing die was just shy of the shell plate, so I turned it down to touching and locked it down.  I pulled my PTX expander plug out and inspected it.  While out I cleaned it up and polished it with some varying grit sand paper and my drill.  I figured if I made it smaller it would only help.  I then put it all back together and adjusted the expander to do less flare.

I then tested the new adjusted setup with some of the same brass and bullets and made some dummy cartridges.  They all still setback and fail the bench test.  I even just sized a case and seated a bullet without expanding.  It was more difficult to setback but still would. 

Equipment:
Hornady Lock N Load AP
Lee Dies with a separate taper crimp

Components:
Pull Down plated RNFP 165 and 180gr, both are just over .400 inch (not sure on brand)
Win brass (all sorted same headstamp)

I am at a loss as what I should do?  Should I invest in a small base sizing die?  I don't want to switch brass or bullets as I have plenty of them.  Do any of y'all have any experience with the EGW or Lee small base dies?  Are there any other options I am missing?

Cheers,
Toby

Offline M1A4ME

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Re: 40 S&W Bullet Tension and Setback
« Reply #1 on: January 14, 2018, 07:39:50 AM »
You can seat a bullet without using the case mouth expanding die? 

I can't.  If I tried I'd crumple/tear/destroy the case mouth.  BTDT when I ran across a piece (or several, over the years) of brass that I missed when running a batch through the expander die.

Either your brass has very, very thin walls or the resizing die doesn't have the proper ID to resize the cases.
Better to have it and not need it, than to need it and not have it.  So, if you see me walking the dogs with my SIG 556R, its okay.

Offline jeep45238

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Re: 40 S&W Bullet Tension and Setback
« Reply #2 on: January 14, 2018, 10:41:54 AM »
Either your brass has very, very thin walls or the resizing die doesn't have the proper ID to resize the cases.

The second seems to be a more likely candidate.  Every manufacturer makes a lemon occasionally, but it seems the higher priced ones do it far less frequently.  I never had that issue with Hornady or Dillon.



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Offline jameslovesjammie

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Re: 40 S&W Bullet Tension and Setback
« Reply #3 on: January 14, 2018, 11:20:28 AM »
Toby,

What is the thickness of the brass and what is your crimp diameter?

Also, did you measure the bullets to ensure their size?  Pulled bullets could be swaged down to a smaller diameter (ESPECIALLY plated or lead).

Offline dave33

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Re: 40 S&W Bullet Tension and Setback
« Reply #4 on: January 14, 2018, 11:30:27 AM »
Definitely a problem with your sizing die if you can seat a bullet without flairing the brass.  Some brands of brass are thinner than others and are more likely to have setback issues if not resized properly, especially using FMJ or plated rounds.  I use a Lee U die on all calibers I load with FMJ bullets for a little piece of mind.  The U dies do a great job, I can almost stand on my rounds without fear of setback, I highly recommend using one.  I was a little concerned about needing extra effort on the press handle while reloading since the resizing is going a little farther than a standard resizer but I don't really feel much difference.  I do use Hornady one shot case lube though.

Offline tdogg

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Re: 40 S&W Bullet Tension and Setback
« Reply #5 on: January 14, 2018, 12:54:06 PM »
So after sleeping on it, I think this is a a combination of things.

1. The wall thickness on the Win brass is slightly less than spec (~0.010-0.011 as best I can measure with calipers).
2. The pulled plated bullets are slightly swaged down (just over 0.400) and should be 0.401
3. Possible that my brass is work hardened and not sizing properly anymore

I have a hard time believing that my brass is over worked.  I have a quite a bit and most of it was once fired range brass (some mine, some purchased) that is fairly new but I couldn't tell you how many reloads.  I try to load it first in first out, I have a return bin and a supply bin so I keep all of it in circulation and don't just reload the same pieces over and over.  Plus you would think I would see split case mouths if the brass was work hardened I haven't seen any during loading 40.  I have had a couple with my 45 brass.

I took some measurements of the case mouth diameter through the loading cycle.

Sized:  0.419
Expanded: 0.421
Seated Bullet: 0.422
Crimped:  0.421-0.422 (tried different amounts and none leaving crimp mark in bullet)

I've set my expansion to the minimum amount that would easily accept the bullet so it doesn't teeter on the case mouth.  it's much less than I was using prior as you have to get the bullet just right for it to sit on the case mouth.

I think I'm going to try the EGW small base die for these pulled plated bullets.  I don't think I need the Lee U die as it is 0.003 smaller, it would just work the brass that much more.

So now the million dollar question, what should I do with the ~500 loaded cartridges that could potentially setback?  It does take moderate force to get the bullet to move.  Should I run them through the crimp die again?  I don't think it will do any good.

I've shot maybe 1000 of these without issue.  I'm leaning toward just shooting them.  Knowing they may setback, I won't just hammer the slide if I encounter a jam.  What do y'all think?

Thanks to everyone for their input.

Cheers,
Toby

Offline jameslovesjammie

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Re: 40 S&W Bullet Tension and Setback
« Reply #6 on: January 14, 2018, 01:13:39 PM »
0.422 should be perfect, as long as the case wall thickness is .011 and your bullet is .400.

Offline painter

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Re: 40 S&W Bullet Tension and Setback
« Reply #7 on: January 14, 2018, 01:18:01 PM »
I wouldn't run them through the crimp die again if they're measuring the .422 you reported. If you crimp smaller, it will do nothing to prevent setback, and might even exacerbate the problem.
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Offline IDescribe

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Re: 40 S&W Bullet Tension and Setback
« Reply #8 on: January 14, 2018, 01:18:50 PM »
Taper-crimping with straight wall pistol cases doesn't increase neck tension or help.  So don't bother.  Over-crimping with a straight wall pistol case can actually reduce neck tension.

Your problem is most likely under-sized bullets.  Lots of people would go right ahead and shoot those.  I don't know what I'd do.  Best practice is to break them down.  If I'd shot 1000, I might have the confidence to do the wrong thing and shoot them.  But I wouldn't advise someone else to.  And I'm fond of using opportunities like that to teach myself lessons.  Breaking down 500 cartridges with an impact puller will stick in your memory. ;)


Offline IDescribe

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Re: 40 S&W Bullet Tension and Setback
« Reply #9 on: January 14, 2018, 01:24:40 PM »
Also, on single-stage presses, in 9mm, I seat jacketed bullets without expanding as a standard practice.  It's not an indicator that the sizing die is wrong.  It's an indication that the bullet base has a slight bevel to it.  ;)   And it knocks out two dies. 

I wouldn't do it with plated, lead, or coated lead, though, because I wouldn't want to damage the bearing surface.

Offline M1A4ME

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Re: 40 S&W Bullet Tension and Setback
« Reply #10 on: January 14, 2018, 01:50:48 PM »
I made a fairly large powder mistake one time due to a shadow (not enough light) on my scale.  I had 5 more grains of powder than I wanted/needed.

I did the tear downs 100 rounds at a time over a week.  Just sit down with the kinetic bullet puller, a jar lid to dump the powder/bullet into and then just went at it.  Didn't get to work on them every evening but got done in about a week.

You can tell when you don't have enough of a "bell" on the case mouth.  You feel the clunk/chunk as the bullet is forced past the case mouth/rim and you get little pieces of bullet jacket all over your shell holder and press.  I've seen it on .223's (55 grain FMJBT) when I forgot to chamfer the case mouth.

ID's right about the lead, coated and plated bullets.  Probably so soft that seating them against a sharp corner/edge would just gouge them up.  I was wondering awhile back if part on an issue I had with lead bullets was the bullet being squeezed down in a very tight case mouth.  Lead can be pretty darn soft, easy to deform.
Better to have it and not need it, than to need it and not have it.  So, if you see me walking the dogs with my SIG 556R, its okay.

Offline tdogg

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Re: 40 S&W Bullet Tension and Setback
« Reply #11 on: January 14, 2018, 04:07:54 PM »
So I pulled out some old SD cartridges I made in 2014 using the same dies and checked them for setback.  They take considerably more force but I can still get them to shorten.

These were made on my single stage Lee if I recall correctly. 

They are 165 GR gold dots over Viht 3n37. 

I think I'm going to shoot these and replace them when I get my smaller die.

Maybe my die is a little over sized too?

Given the amount I have and the force it requires to move them I'm not that concerned shooting what stock I have.  I definitely won't be making any more until I get a new die though.

Cheers,
Toby

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Offline Wobbly

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Re: 40 S&W Bullet Tension and Setback
« Reply #12 on: January 14, 2018, 09:47:13 PM »
It can only be a couple of things....

• Expander too large (should be about .002" smaller than a jacketed bullet)
• Bullet diameters too small
• Sizing die not reducing the case OD far enough
• Bad brass (bad alloy, cases damaged, etc)
• Too much taper crimp buckling the case

 ;)
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Offline tdogg

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Re: 40 S&W Bullet Tension and Setback
« Reply #13 on: January 14, 2018, 10:08:40 PM »
Here is a picture of the setback cartridge next to a normal length cartridge.



I measured my expander plug after polishing and it was about 0.398 in the flat spot.  Really hard to measure though as it isn't really flat.  Obviously the flare section is larger.

Given I can setback my old sd reloads I'm leaning toward it being a die issue.  Maybe the swaged pulled plated bullets are amplifying the issue.

Once I get a small base die I will post up my bench test results.

Cheers,
Toby



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Offline Sundang

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Re: 40 S&W Bullet Tension and Setback
« Reply #14 on: January 14, 2018, 10:13:12 PM »
I agree with I Decribe. I think the bullets are undersized. I'm not sure how you can get around that.
Have you tried new projectiles?

 

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