Bullet Setback, Multiple Chamberings

[ar15barrels]

Correction: Just checked my rejects again. The worst was Hornady critical defense with one seated .60 deeper.

0.60mm?

[Donny1]

I didn't skip anything.
I responded to the first post.
I didn't GET to your correction until today...

A 31,100psi load at 1.120" becomes a 37,047psi load when the bullet is seated 0.040" deeper.

Thank You!

[Donny1]

The question is : Is .040 enough set back to be dangerous?

I just went and measured 6 mags I had loaded with factory defense rounds ( Sig, Hornady and Federal). and seperated them by brand. Some had fluctuations within .010-.030 plus or minus. Some were right on. Sig V crown was the most consistent. It was hard to find OAL info. From now on, I will measure OAL when I buy and write it on the box. All oddballs were set aside . Most, sorted by brand were within .020-.030 of average. The worst were .080 short.

What is the depth below average that set back becomes dangerous?

I realized how inconsistent factory ammo can be when I started reloading. Not just seating depths, powder as well.

[JoyfulJoker]

Yes. The one on the left is out of a newly opened box .

These bullets have a red blob on the tip (Hornady critical defense) which has a slight variation making them a little tough to measure. This one bullet was noticeably deeper with the naked eye and my eyes popped when I measured . They are steep cone shape bullets. There is a transition between the cylinder part of the bullet and the cone. The bullet was deeper than that transition.

[BajaJames83]

Not max

Xtreme XDEF 124gn HP
5.4gn CFE Pistol
1.120
1050fps

Light crimp with FCD, just enough to straighten the case

That is hardly any crimp...
I Would suggest going heavier. While you dont have to go crazy just a nice firm crimp will stop that.

[Sandspider500]

Same concept

[ngnrnlo]

I don't have CFE pistol in Quicjkload, but using Unique, a 31,100psi load with a 124gr plated hollowpoint seated to 1.120" oal will become a 73,000psi load when the bullet is seated to 0.980" oal.

Wouldn't the bullet start moving much before the pressure reaches 73000, thereby increasing case volume and preventing overpressure?

[pacrat]

Wouldn't the bullet start moving much before the pressure reaches 73000, thereby increasing case volume and preventing overpressure?

Not enough to matter. It isn't just a "pressure" issue. It is a "pressure/time" correlation issue.

With rifle cartridges and SLOW burning powders. Peak pressure is reached with the bullet a few inches ahead of the chamber in the barrel.

In pistol cartridges and REAL DAMN FAST powders. Bullet barely moves at all before peak pressure is reached.

There just isn't enough TIME for the bullet to get ahead of the pressure curve.

[ar15barrels]

Wouldn't the bullet start moving much before the pressure reaches 73000, thereby increasing case volume and preventing overpressure?

I would never bet my face on such an assumption.
Maybe the barrel would vent and take out the slide before the bullet moved enough to relieve the pressure.

[tabascoz28]

Speaking only on 9mm, I've never had issues with seating depth until I got into the cheap coated bullets. I've noticed that they need to be seated to minimum length just to seat properly in my glock. Today I just did a test, 1.12 works in my AR pistol and M9 just fine. Sticks a little in my CZ p01 once chambered but will always fire. 1.09 is still not good enough for the glock but it is an aftermarket barrel.

I've used Berry's, Hornady, brass jacketed and different brands of coated. Bayou is what I'm using now and it is really round, ogive is really up front. Now I have to seat to like 1.05 and download just to get the glock working...

[JoyfulJoker]

Brass that fly out of my CZ’s dribble out of my G19. These were FMJ 124 grain. Increased my load to see the difference. Haven’t tested yet.