My interest in the subject of how long it takes different bullets to leave a gun barrel led me to research the somewhat related question of action lock time. Both the bullet in the barrel transit (or dwell) time and the lock time can affect shooters’ practical accuracy.

As this is a firearms related discussion forum, some of this may also interest others. First, though, a disclaimer: The figures I cite as examples were obtained via an Internet search using the AI Gemini. Some of the values seem to have been obtained from manufacturers’ marketing information. As with any source of information from ancient scripture to the latest LLM, any questions should be investigated and confirmed further through whatever sources you trust.

My first question about bullet transit time, i.e., how long it spends in the barrel between ignition and exit was prompted by wanting to know if it had an effect on accuracy due to the shooter’s small, involuntary movements while holding a rifle. Those movements include heartbeat and small muscle tremors. That time can be roughly calculated from the bullet’s muzzle velocity, and one that travels twice as fast as another will spend one-half the time in the same length barrel. That in itself puts 22 Long Rifle cartridge shooters at a disadvantage when the rifle cannot be held perfectly still (i.e., never).

Lock time is the delay between when the sear releases the gun’s firing pin or hammer and when the firing pin strikes the cartridge primer. Minimizing lock time also helps a skilled shooter’s accuracy by reducing the effects of involuntary movements during that delay. That’s why top tier 22LR competition rifles that are commonly fired from unsupported positions such as kneeling and offhand (standing) have mechanisms that reduce lock time as much as possible.

As a reminder, a millisecond (ms) is one one-thousandth of a second; 10 milliseconds is one one-hundredth of a second, and is the shortest time interval most hobby shot timers like the Kestrel KST1000 can resolve.

Another caveat before going further is the question of how much do a few milliseconds one way or the other matter to us? The answer for most shooters is none. If you can’t imagine how it could matter to you then the obvious answer is that it doesn’t. If, however, you’re a shooter who strives for maximum accuracy when shooting from realistic positions or you’re just interested in what guns do and how they do it, read on.

Some lock times as provided by my Gemini friend:

Tikka T3 / T3x (centerfire): ~1.3 ms*
Anschütz 2000 Series (Olympic/Match Rimfire): ~1.5 ms
Tikka T1x (rimfire): ~1.5 – 2.2 ms* (According to Gemini, “This is exceptionally fast for a factory production rimfire rifle.”)
Savage 10/110 Series, AccuTrigger (centerfire): ~1.6 ms
CZ 457 (rimfire): ~2.5 – 3.0 ms
Remington 700 Short Action (centerfire): ~2.6 ms
Winchester Model 70 Short Action (centerfire): ~2.6 ms
Remington 700 Long Action (centerfire): ~3.0 ms
Ruger M77 Hawkeye (centerfire): ~3.4 – 3.6 ms
Mauser 98 / Mil-spec Surplus (centerfire): ~4.0 – 5.0 ms
Geissele Hi-Speed National Match trigger (AR-15): ~4.4 ms
Ruger 10/22 (rimfire): ~5.0 – 6.5 ms
Mil-spec AR-15: ~8.0 – 10.0 ms†

The response to my questions stated that the reasons for the longer lock time of a typical AR-15 trigger is the weight (inertia) of the hammer and the long distance it must rotate through to contact the firing pin.

* The responses about the T3/T3x centerfire and T1x rimfire mechanisms stated that Tikka specifically strives to reduce lock time by reducing firing pin weight, shortening the firing pin movement distance, and increasing firing pin spring power.

† It’s often reported that gas-operated rifles like the AR-15 and variants are more difficult to shoot accurately than bolt actions. That’s usually blamed on the reciprocating mass of the bolt carrier group, but could action lock time have an effect as well?

quote:

That time can be roughly calculated from the bullet’s muzzle velocity, and one that travels twice as fast as another will spend one-half the time in the same length barrel. That in itself puts 22 Long Rifle cartridge shooters at a disadvantage when the rifle cannot be held perfectly still (i.e., never).

Acceleration down a gun barrel is not linear, you might could derive a closer estimate of barrel time from the barrel length vs muzzle velocity at Ballistics By The Inch.

I used to hear it said that an expert smallbore shooter could do better with a target .22 from prone with sling, glove, and jacket than off a bench.

I have also read that the Remington 788 was known for its accuracy not only because of its 9 rear locking lugs, but its low lock time.

Did your research indicate anything regarding the lock time of the Remington 788 to add to your list?

PC

quote:

Originally posted by PCWyoming:
Did your research indicate anything regarding the lock time of the Remington 788 to add to your list?

It was not on the sample list I got, but a separate query answer said it was 2.4 – 2.5 ms, which is shorter than that of many bolt action rifles and believed to contribute to its accuracy.

The AI answer did point out that bullet acceleration is not linear, but for rough comparisons of bullet transit times muzzle velocity is not too bad.

With the exception of sling shooting with an uber-tight cuff, I don't think heartbeat in and of itself has any effect on accuracy. The old adage of breaking a shot between heartbeats is virtually impossible. If one's heartrate is so fast from exercise that it is causing the sights to move, rifle movement is more likely coming from heavy breathing and/or muscle fatigue.

I agree that involuntary movements are issues. My personal nemesis is relaxing my squeeze on the rear bag right as I break the shot. And sometimes relaxing my neck muscles as I break the shot. Both of these flaws in technique send rounds high.

IMO shorter lock times help reduce the time that flaws in technique effect the POI. A common flaw is trigger press. It isn't easy to press the trigger straight to the rear without disturbing the sights. It's why dry firing is so important, for any type of firearm. Many shooters don't press the trigger straight back and line with the rifle bore. Many shooters impart a slight left or right bias to the trigger press, which is transmitted to the entire rifle. A faster lock time may reduce the POI effect of a flawed trigger pull, as the movement has less time to affect the disturbance in bore direction. As an example, let's say that a shooter's trigger press moves the rifle 1/64" laterally. That's not much. Assuming there's 2 feet between the trigger and the end of the barrel, and assuming the trigger press causes only the center of the rifle to move laterally, the potential POI shift is 150/64" at 100 yards. A fast lock time might reduce that POI shift and a slow lock time might increase that POI shift.

Another primary shooter's flaw is not controlling the rifle's recoil all the way through the cycling process. The cycling process is short and minimal with a bolt action rifle, however it's longer and more complex with a semi-auto. Controlling recoil means that the rifle only recoils directly backwards along the bore's axis -- no vertical or horizontal deflection. Such movement is very noticeable with a optic, however few shooters accept that it occurs, nor understand its effects on accuracy. Recoil management becomes more of an issue with high-recoiling calibers, but all calibers produce some recoil. Many shooters feel their crosshairs never move from the POA during the recoil cycle. As electronics advance to the point that our in-scope sight pictures are available to view again later, such analysis will be revealing to many.

The bottom line is that many shooters don't put in the tedious training it takes to develop a quality trigger press and solid recoil management. IMO this is a primary reason so many rifle shooters emphasize great trigger action, light trigger pulls, and mechanical rests for bench shooting. They're essentially trying to mitigate flaws in shooting technique.

This message has been edited. Last edited by: fritz,

Yes, trying to break shots between heartbeats is certainly fantasy for me. I first heard of the notion just a few years ago from someone who claimed to have been a military sniper. He may have been, but if so I can only wonder about his actual abilities and experiences unless his heartrate was 20 BPM or so.

When I’ve read some stories by former military snipers, I’ve gotten the impression that a literary agent told them to add as much impressive-sounding stuff to their tales as possible. I still remember one thriller which was supposedly written by one that had the protagonist dodging bullets from an M14 that were totally silent because the weapon was equipped with a suppressor.

Heartbeats have a significant effect on my rifle accuracy. Long ago when I competed in small bore three-position shooting (offhand, kneeling, prone), I used a very tight sling around my support arm biceps to not only provide support but also to reduce the pulse effect on my lower arm. A tight shooting coat also helped a little.

These days I can’t shoot from the prone, and most is from kneeling or standing with a tripod for support, plus a little from the bench with a rest or bipod. When shooting from any position, a major factor I need to deal with is the effect of my heartbeat. It moves the gun horizontally, back and forth with every beat.

I shoot many drills with bolt action rifles (~7K rounds thus far this year), such as the 100+ rounds yesterday with my T1x trying a new kneeling position. Seventy-five of the shots were at 1.5 MOA dots at 50 yards and the results were pretty good for me (eight misses). But most of the shot-to-shot points of impact deviations were horizontal, and I see that all the time with my drills, and even when shooting for groups seated at a firm bench.

All my practice and focusing on things like proper breath control and trigger press have greatly improved my marksmanship over the past two years, but heartbeat is still definitely my nemesis.

I’ll first say that I’m not an expert. However, I have put some rounds down range through various firearms.

I’m going to say that this is a non-issue for most. UNLESS we’re talking about ELR stuff.
We’re talking about thousandths of a second between trigger break and round leaving the muzzle.
Thousandths of a second in modern day firearms.

Unless the shooter is already in motion…
Take handguns- let’s say the shooter is using too much finger on the trigger, and pushing the gun low and left.
Shooters hand (and gun) are already in motion. I don’t think that the thousandths of a second we’re discussing is going to affect the point of impact from the time of the trigger break.

Fritz mentioned something- sling shooting.

So there you are, nice tight cuff around your support bicep, laying in a perfect prone position…
The front sight / crosshair is still going to do that little dance.
Slow steady inhale, the sight / crosshairs dip-
*** you crack the shot as the crosshairs are southbound ***

Here’s the Trigonometry Problem:

***IF*** the gun moves >< that much here at the muzzle during the thousandths of a second we’re discussing, we know what point of impact is going to be > < that much depending on distance to the target.

quote:

Originally posted by sigfreund:
When shooting from any position, a major factor I need to deal with is the effect of my heartbeat. It moves the gun horizontally, back and forth with every beat.

I shoot many drills with bolt action rifles (~7K rounds thus far this year), such as the 100+ rounds yesterday with my T1x trying a new kneeling position. Seventy-five of the shots were at 1.5 MOA dots at 50 yards and the results were pretty good for me (eight misses). But most of the shot-to-shot points of impact deviations were horizontal, and I see that all the time with my drills, and even when shooting for groups seated at a firm bench.

All my practice and focusing on things like proper breath control and trigger press have greatly improved my marksmanship over the past two years, but heartbeat is still definitely my nemesis.

We all have different physical attributes, strengths, and weaknesses. We all should learn how our bodies interface with firearms.

My POI errors are consistent with the common issues that are spelled out in Rifles Only courses. My vertical dispersion is generally a result of breathing, cheek weld, or rear bag. Horizontal dispersion is almost always a trigger pull issue. Outside of funky barriers, I generally contact a rifle only with my clavicle bone, right-hand palm, and a light brush of the stock on the cheek. I don't experience a heartbeat effect.

The one exception to the heartbeat effect for me is a test done at Rifles Only. Students were asked to get in a stable prone position -- relax and get comfy. Initially look away from the optic, hold your breath for 30 seconds, then look through the optic while still holding your breath. Most of use could see fluttering in our vision, generally consistent with the timing of our heartbeat. We repeated the test by staying in the scope for the full 30 seconds. It was an "eye opener" of why we shouldn't hold our breath while shooting, but instead break shots at the normal pause at the bottom of the respiratory cycle. But of course that concept goes out the window if one has just run some distance between stages....