Lock Time

In it’s simplest terms ‘Timing’ in a locked breech pistol is the period during which the barrel and slide remain together after the ignition of the cartridge relative to the point at which the barrel starts to separate from the slide. At the instant of ignition, the slide and barrel will start rearward travel and cartridges with a lot of ‘horsepower’ and high impulse (such as the original Norma 10mm or real hot 45 ACP) can sometimes accelerate the slide so rapidly that the barrel will start to unlock before the bullet is in free flight. This is commonly referred to as ‘opening early’ and there are varying degrees and indicators of the malady depending on a wide variety of circumstances. The result in its lesser form is that the pistol or ammo is ‘apparently’ inaccurate and groups tend to 'string' (which was one of the early criticisms of the S&W pistol in 40-caliber.) As the problem escalates there’s a potential that the cartridge case will bulge, and in extreme circumstances actually rupture, because of the residual pressure in the case that is no longer fully contained by the chamber.

To help explain this further we'll use the S&W 5906 (original platform for the 4006) as an example. The 5906 is timed to react to the physics of the 9mm and introducing a cartridge into the chassis that has substantially greater bullet weight and larger piston diameter, with very similar velocity will tend to hyper accelerate the slide both from a standpoint of initial thrust and terminal impact velocity. In fact the slide velocity almost doubles - perhaps even higher at times. This is part of the reason why the Colt Delta Elite was less successful than anticipated. The original Norma 10mm cartridge overpowered the pistols geometry and ability to contain the energy. Engineers either ignored, or were oblivious to geometric lock time and attempted to control the increased energy with recoil springs alone. This did little to retard the timing and nothing to decrease load on the frame and slide.

Part of the solution in situations such as this is to extend the amount of time the barrel and slide remain together which aids in absorbing the increased energy generated by cartridges of high impulse. A proportionally heavier recoil spring is required to dampen the increase in free slide velocity but can’t be relied upon exclusively to retard timing. The effect of the two modifications limits the tendency of the gun to open early and brings the free slide velocity down to a manageable level while offsetting the potential of damaging impact of the slide against the frame. It also reduces the amount of effective recoil the shooter has to absorb, which is the energy that is so uncomfortable to many shooters.

Unlike the S&W 5906, the Colt 1911 was designed and timed for 45 military ball and any caliber short of that (with the exception of the original Norma 10mm and to a lesser degree the 40 S&W) will tend to retard the timing of the pistol making it necessary to deal with the lack of operating energy generated by the cartridge. The effects of this are well illustrated in the fact that in order to make a 1911 work with ‘sub calibers’ engineers sometimes reduced slide and barrel mass, reduced recoil spring rate and increased ejector lengths to compensate for short cycling. This is the least effective method of designing around the situation. What is required is a fine balance of the above and to mechanically advance the timing so that the slide stop dwell time is matched to the peak energy of the cartridge.

While some mistakenly discount, or even refute the fact that ‘timing’ is an issue in the 1911 pistol, there is some validity to the statement that “A properly built 1911 is automatically timed if it is built right”. As confusing as that quote may be at first glance, the point is made and well taken, but it only holds true if the gun is intended to perform within the confines of traditional 45 ACP ball, a caliber that emulates those levels, or is “built right” with due deference to a lesser caliber because one may have to build it differently to “build it right”. Considering that nowadays there are a large number of 1911’s being manufactured and modified in calibers other than 45 ACP and that the range of available 45 caliber ammo in itself is endless, timing has become a HUGE issue.

At Pistol Dynamics we are extremely conscious of barrel lock time because it relates to ultimate performance and accuracy. During my Bianchi days I spent a lot of time and energy developing what are arguably the most accurate 1911 based pistols ever built. They were remote bushing modular guns that had the barrel supported by the frame through spherical bushings and wide links. The slide had nothing to do with the accuracy or timing of the pistol; its sole purpose was to facilitate the feed and ejection cycle. There was little retard effect through mass because the slide was independent of the barrel and sight plane. The only way to the keep the gun closed was to retard the lock time.

Our method of adjusting lock time is different to most traditional methods. While we use John Browning’s original geometry as the benchmark and the basis to our practical guns, most other calibers and applications of the handgun is controlled by our leg and link geometry. If we build a dedicated IDPA gun for a serious competitor for instance, it will be timed for a somewhat reduced load to optimize accuracy and performance. The leg and link will almost produce a constant arc as it relates to travel on the slide stop as opposed to mechanical dwell on the slide stop pin that is required for heavier loads. The system relies on resistance generated by the link being set ‘past dead center’ of the barrel in battery relative to the link pin and bore axis angle. There’s no effect on function and reliability if the parameters of the intended use is exceeded within reason. But like many other things there’s a sweet spot and all we’ve done is develop a method of controlling and adjusting that sweet spot.

Will a 1911 work perfectly if it’s not timed correctly? Probably, and maybe most of the time. It’s that gray. All you have to do is go to your local club and watch the frequency of poor handgun performance on the line. Even if only one third of those glitches are timing related there’s a lot to be said for taking heed of it. Most of the cynicism, skepticism and rejection of this concept is generated by those who work on ‘tactical’ or ‘fighting’ 1911’s exclusively chambered for 45 ACP. These individuals are operating within the confines of the original design intent and are therefore exempt from having to deal with it. They’re not looking for accuracy that rivals cartridge capability in calibers that were never intended to operate in the pistol (most of which didn’t even exist back in 1911). Quite frankly there is no voodoo in making a 1911 work with factory equivalent 45 ammo, literally anybody can do it. The real challenge is similar to that faced by race car engineers; squeezing out every ounce of performance potential through reduction in tolerance and an increase in efficiency and still have it work within the confines of the ultimate intended use and ammunition compatibility.

PSL