Can the SIG Sauer\u00ae P320 fire enough out-of-battery to induce case failure with proper ammunition? With the meteoric rise in popularity of the P320 amongst serious, high-volume shooters, we’ve seen reports of blown cases.<\/p>\n
So, here’s a series of firing tests and factual analysis to put these reports into proper perspective.<\/p>\n
We ask that you do not copy and paste this post to online forums, as we may update it with additional information in the future. Most of the content from this post – and a discussion – is available on Facebook and other platforms.<\/em><\/p>\n <\/p>\n Table of Contents<\/strong><\/p>\n The factory-spec P320 barrel has more than adequate case wall support to contain SAAMI-spec chamber pressures, even when fired so far out of battery that further slide-barrel retraction prevents primer strike. This is far out-of-battery beyond any mechanically plausible scenario for a normal P320 to fire by its design.<\/p>\n My tests should demonstrate this to anyone’s reasonable satisfaction. The pistol was designed to function safely with proper spec ammo, and we increase our risk when we shoot remanufactured ammo, reloads, and the cheap stuff.<\/p>\n Blown cases result from out-of-spec, faulty ammunition.<\/p>\n Would more case wall support yield more of a margin for defective ammo? Yes, perhaps, but our goal should be to shoot quality ammo and be particularly careful in making reloads.<\/p>\n\t\t\t\t Do not try this at home or the range. The pistol was modified (as described) for testing, and we completed the testing in a safe environment. Do not<\/strong> defeat or remove any safety systems or components on your pistol.<\/p>\n I set up this pistol to release the striker with enough energy to detonate a primer throughout the entire locked travel<\/em> of the barrel and slide.<\/p>\n We set up this P320 parts gun to represent a worst-case scenario<\/strong> far exceeding a factory-spec pistol’s most extreme out-of-battery condition. I paired an early 4.7″ Full-Size barrel with a light 3.9″ Compact slide. I fitted a short recoil spring that did not exert enough force<\/strong> to hold the slide closed.<\/p>\n The 4.7″ Full-Size barrel selected for this test is from early commercial P320 production. It exhibits the substantial chamber-mouth bevel typical of most P320s.<\/p>\n I defeated all internal safety functions<\/strong>, including the following components.<\/p>\n The point in slide travel where the disconnector drops the trigger bar from engaging the sear in a standard P320 is typically between .085 and .125 back from full-battery.<\/p>\n A standard P320 striker assembly lacks the energy to ignite primers with the slide retracted after a certain point<\/strong>. The factory striker spring is engineered not to yield adequate ignition force unless the slide and barrel are sufficiently in battery to contain chamber pressure safely. To compensate, I installed two inter-wound striker springs to deliver enough force to ignite primers.<\/p>\n We then marked datum lines on tape at the following points.<\/p>\n The total locked travel from 0 (at which the barrel is adequately engaged with the locking shoulder to permit the striker to impact the primer) to fully in-battery is approximately .226″. As noted, modifications were needed<\/strong> to get the P320 to fire in the 75% and fully out-of-battery positions, including defeating the internal safety functions.<\/p>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n The Speer Gold Dot G2 LE 9mm Luger 147 grain duty rounds measure .3881″ at the base.<\/p>\n At approximately 150 power factor, these loads well exceed<\/strong> typical 115gr or 124gr ball ammunition and most other standard commercial loadings.<\/p>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n\t Round 1 – using the specified ammunition – was fired from fully in-battery<\/strong>.<\/p>\n The fired case max diameter measured .3892″. (This represents a case expansion of about 1.1 thousandths.)<\/p>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n\t Round 2 – using the same ammunition – was fired at 50% in-battery, with the slide retracted .113″ from fully in-battery, and held in place using a wedge.<\/p>\n This case measured .3887″ at its greatest diameter.<\/p>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n\t Round 3 – using the same ammunition – was fired at 25% in-battery (75% out-of-battery), with the slide retracted .163″ from fully in-battery and held in place using a wedge.<\/p>\n This case also measured .3887″ at its greatest diameter. (The same as Round 2.)<\/p>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n\t Round 4 – using the same ammunition – was fired at 0, or at that point in slide-barrel travel at which further retraction will pull the barrel out of engagement<\/em>.<\/p>\n This case measured .3901″. (This represents a case expansion of about 2.0 thousandths.)<\/p>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n Our second set of testing used a variety of ammunition, including the following. (Left to right in the photo.)<\/p>\n All rounds were fired at 0, or at that point in slide-barrel travel, at which further retraction will pull the barrel out of engagement. <\/em>The measurement at this point is approximately .226″ out-of-battery<\/strong>.<\/p>\n Despite doubling<\/strong> the striker springs, ignition at this slide position (0-0 lockup) was unreliable<\/strong>. As shown in the photos of the primer strikes, most rounds required multiple hits<\/strong> before igniting.<\/p>\n The off-center primer hits further show the marginal out-of-battery condition in the test pistol.<\/p>\n None of these cases exhibit signs of excessive expansion. They compare well with rounds fired from fully in battery.<\/p>\n <\/p>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<\/a>\n We cut off the locking shoulder of the barrel and set it up to where it could fire at any point – or at least drop the striker at any point – at which the striker could possibly reach the primer. The pistol was set up similarly to a straight blowback design, where the breach is not locked during primer ignition.<\/p>\n\t\t\t\t Do not try this at home or the range. The pistol was modified (as described) for testing, and we completed the testing in a safe environment. Do not<\/strong> defeat or remove any safety systems or components on your pistol.<\/p>\n\t\n
TL;DR<\/h3>\n
\n\t\tConfiguring a P320 for testing\n\t<\/h2>\n\t
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\n\t\tTesting with Speer Gold Dot G2 9mm Luger 147 grain ammunition\n\t<\/h2>\n\t
The Ammunition<\/h3>\n
Test Round 1<\/h3>\n
Test Round 2<\/h3>\n
Test Round 3<\/h3>\n
Test Round 4<\/h3>\n
\n\t\tA second round of testing with various factory new ammunition\n\t<\/h2>\n\t
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\n\t\tExtreme Testing Video – Cutting Locking Shoulder OFF\n\t<\/h2>\n\t