Myth Busting Neck Tension and Bullet Setback

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Adding to previous measurements. Measurements #6, #7 and #8 were done with Everglades 115 gr FMJ (concave base .354"), RMR 115 gr FMJ (.3555") and Zero 115 gr FMJ (.356").

Measurement #6 with Everglades 115 gr FMJ (Concave base sized .354" average) at 1.130" OAL - http://www.evergladesammo.com/bullets/handgun-bullets/ac-9mm-115gr-fmj-bullets-340.html

NOTE: Everglades does sell other 115 gr FMJ (flat base) advertised as .355" - http://www.evergladesammo.com/bullets/handgun-bullets/9mm-115gr-bullets.html

- Frankford Arsenal dial calipers verified with .355"+ pin gauge - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10523549
- Lee dies were used
- Finished OAL used was around 1.130"
- Bullets were sized .354" on average and .377" taper crimp was used - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10567453
- Dummy rounds (no powder, no primer) were measured before/after they were fed/chambered in Glock 22/23 using KKM/Lone Wolf 40-9 conversion barrels and 9mm magazines without riding the slide

These headstamp cases did not experience bullet setback:
  • CBC
  • GECO
  • GFL
  • PMC
  • PPU
  • RP
  • Tulammo
  • WIN

These headstamp cases experienced bullet setback
(After Glock 22/KKM barrel, After Glock 23/Lone Wolf barrel):
  • Aguila: .000", -.001"
  • BLAZER: -.001", -.001"
  • BLAZER: -.001", -.003"
  • BLAZER: -.002", -.046" (This is not a typo)
  • .FC.: -.001", -.001"
  • .FC.: -.001", -.001"
  • .FC.: -.002", -.002"
  • Perfecta: -.001", -.001"
  • Starline: .000", -.001"

Measurement #7 with RMR 115 gr FMJ (sized .3555" average) at 1.130" OAL:

- Frankford Arsenal dial calipers verified with .355"+ pin gauge - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10523549
- Lee dies were used
- Finished OAL used was around 1.130"
- Bullets were sized .3555" on average and .378" taper crimp was used - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10567453
- Dummy rounds (no powder, no primer) were measured before/after they were fed/chambered in Glock 22/23 using KKM/Lone Wolf 40-9 conversion barrels and 9mm magazines without riding the slide

NOTE: Since CBC, GECO, GFL, PMC, PPU, RP, Tulammo and WIN headstamp cases did not experience bullet setback with .354" sized Everglades bullet, they were not tested for .3555" sized RMR 115 gr FMJ.

These headstamp cases did not experience bullet setback:
  • Perfecta
  • Starline

These headstamp cases experienced bullet setback (After Glock 22/KKM barrel, After Glock 23/Lone Wolf barrel):
  • Aguila: -.001", -.001"
  • BLAZER: .000", -.001"
  • BLAZER: -.001", -.001"
  • .FC.: .000", -.001"
  • .FC.: -.0005", -.0005"

Measurement #8 with Zero 115 gr FMJ (sized .356" average) at 1.130" OAL:

- Frankford Arsenal dial calipers verified with .355"+ pin gauge - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10523549
- Lee dies were used
- Finished OAL used was around 1.130"
- Bullets were sized .356" on average and .378" taper crimp was used - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10567453
- Dummy rounds (no powder, no primer) were measured before/after they were fed/chambered in Glock 22/23 using KKM/Lone Wolf 40-9 conversion barrels and 9mm magazines without riding the slide

NOTE: Since CBC, GECO, GFL, PMC, PPU, RP, Tulammo and WIN headstamp cases did not experience bullet setback with .354" sized Everglades bullet; and Perfecta and Starline headstamp cases did not experience bullet setback with .3555" sized RMR bullet, they were not tested for .356" sized Zero 115 gr FMJ.

These headstamp cases did not experience bullet setback:
  • Aguila
  • .FC.

These headstamp cases experienced bullet setback (After Glock 22/KKM barrel, After Glock 23/Lone Wolf barrel):
  • BLAZER: .000", -.0005"
  • BLAZER: .000", -.001"

Summary/Conclusion: As demonstrated by various measurements of bullet setback and case wall thickness, I think I could state there is a correlation between bullet setback and case wall thickness measured .200" below case mouth where case wall thickness is greater (and where most neck tension is applied on the bullet base, with some exceptions).

Based on bullet setback test results with various headstamp cases, I am now inclined to believe all future accuracy testing should be done with brass that won't produce bullet setback with particular bullet I am testing; which should reduce reloading variables of bullet setback and "chambered" bullet seating depth that should result in more consistent chamber pressures and hopefully smaller groups.


FYI, here are averages of bullet setback and case wall thickness from various measurements:

Average Bullet Setback from Measurement #2 with X-Treme 100 gr plated RNFP at 1.040" OAL:

.0000" - CBC
.0000" - GECO
.0000" - S+B
.0000" - Starline
.0000" - WIN
.0003" - GFL
.0003" - PMC
.0004" - PPU
.0004" - R-P
.0004" - Tulammo
.0006" - AGUILA
.0007" - PERFECTA
.0012" - FC
.0013" - .FC.
.0016" - SPEER
.0020" - BLAZER


Average Bullet Setback from Measurement #3 with Hunting Shack Munitions 115 gr plated RN at 1.130" OAL:

.0000" - GECO
.0000" - R-P
.0000" - WIN
.00008" - CBC
.00008" - Tulammo
.0001" - PERFECTA
.0003" - GFL
.0006" - PMC
.0008" - BLAZER
.0010" - .FC.


Average Case Wall Thickness .100" Below Case Mouth (Thickest to thinnest):

.0129" - PPU
.0126" - S+B
.01256" - CBC
.0125" - HRTRS
.0124" - Tulammo
.0121" - GECO
.0120" - PERFECTA
.0119" - AGUILA
.0116" - R-P
.01158" - GFL
.0115" - PMC
.0111" - WIN
.0110" - Starline
.0108" - .FC.
.0105" - SPEER
.0104" - BLAZER


Average Case Wall Thickness .200" Below Case Mouth (Around Bullet Seating Depth for 115 gr FMJ/RN loaded to 1.130" OAL):

.0144" - CBC
.0138" - PPU
.0137" - GECO
.0135" - HRTRS
.0135" - Tulammo
.0133" - S+B
.0132" - WIN
.0131" - GFL
.0130" - AGUILA
.0130" - PERFECTA
.01225" Starline
.0122" - PMC
.0121" - R-P
.0115" - .FC.
.0111" - SPEER
.0110" - BLAZER
 
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