Hammer Strike Strength and Precision?

[FaRKle!]

So a couple weekends ago when I tested the ELF-AR10 trigger in my PWS my groups were absolutely awful. I brought a friend to the range with me and we were both shooting 4-5MOA 5-shot groups with 175gr match ammo of various manufacture. I couldn't believe how terrible we were doing. Of course, we were also experiencing many failure to fire malfunctions due to the ELF trigger causing light primer strikes (we only went through one five round group that didn't have any light primer strikes, the others all had at least one).

This past weekend I took a different friend to the range with me to test MechArmor's new "Rough Justice" trigger. Same rifle, same ammunition as before, but we were now shooting just under MOA-2MOA groups with zero light primer strike malfunctions.

I know the USAMU says that weaker hammer springs affect precision, but I never realized just how much it did. Anyone else have experience with this phenomenon?

[mrmackc]

I experienced very poor accuracy with a new .243 Remington 700 in 1980. I had been a gunsmith for 4 years and though I had "it all knowed up". Changed scope, mount, ammo no change. Checked with an old shooter that asked about the trigger. I told him "can't be the trigger" ...but it was, installed a Timney and the rifle became a 1 minute grooper. Weak springs not only cause light primer strikes and slow powder burn but slow down hammer and fireing pin speed. which spoils accuracy. One of the most accurate rifles I ever had was a Remington 788 .308, the 788 has a very fast lock time out of the box.

Edited May 11, 2015 by mrmackc

[survivalshop]

 You may have been altering or breaking your concentration with the miss fires . The trigger may have been having varying disengagement pressures ( trigger pull #'s ) & that also may have had an effect on your grouping .

 

 Light Hammer strikes causing less than normal accuracy , well, if the primer ignites , its pretty much out of your hands , so I'm not sure how it could or would matter . <dontknow>

 

  A good consistent trigger pull , will help anyone be a better shooter . 

[FaRKle!]

You may have been altering or breaking your concentration with the miss fires . The trigger may have been having varying disengagement pressures ( trigger pull #'s ) & that also may have had an effect on your grouping .

 

 Light Hammer strikes causing less than normal accuracy , well, if the primer ignites , its pretty much out of your hands , so I'm not sure how it could or would matter . <dontknow>

 

  A good consistent trigger pull , will help anyone be a better shooter .

I was getting high variability even with consecutive shots (no malfunction in between).

I also tested my consistency this past weekend. My friend and I loaded up the rifle with 10rnds. He shot one round, then I got behind the gun and shot one round, and then we continued to switch off after every single round till we each had a 5rnd group. I was actually very surprised at our performance. Both of us shot within 1.5MOA, and on mine I had 4 shots making one large hole.

Edited May 11, 2015 by FaRKle!

[98Z5V]

I know the USAMU says that weaker hammer springs affect precision, but I never realized just how much it did. Anyone else have experience with this phenomenon?

 

Yep.  When we'd get consecutive light strikes, we'd notice accuracy drop.  Turn the rifle in to the Armorer, and tell him what was up - like, leave the range and hit up the Armorer right then.  Return to the range, fire up the rifle, and everything was fixed.  He'd $hitcan all the springs in the lower. Replace with new Colt springs.

 

Weak hammer springs aren't going to move the hammer as fast (as well as cause light strikes).  That's Lock Time.  Extra strength hammer springs will make the hammer even faster, and decrease Lock Time a little more, but there is a trade off.  Lock Time is the time it takes for the hammer to ignite the primer, from trigger release. 

 

The longer the Lock Time is, the more chances you have to fuk with the rifle - move it off target, fidget, sneeze, $hit some britches, whatever. The faster the Lock Time is, the less chance you have of influencing that rifle in the wrong way. 

[survivalshop]

    How slow are the Hammers dropping to give a weak primer strike & ignite the primer ? What are we talking about , Micro milliseconds ? I just don't buy the explanation for the poor grouping .  Lock timing & its speed has to do with action speed, on how the FCG & BCG resets or locks back into battery , from shot to shot . In theory , a heavier Hammer spring can slow the process down , because of resistance . I don't see how any of that can effect pulling the trigger to drop the hammer on a primer. 

 

  No offense & I mean it , how do you know what your Armorer did to the rifle ? Did you watch him work on it ? Just how much were you into Gunsmithing back then or at that time ?  Really .

[planeflyer21]

My understanding is Lock Time has evolved to include the entire action.  Originally it was the time from pulling the trigger to the ignition of the charge.

 

How does that relate to accuracy?  Compare shooting a single-action revolver (about 1/10th of a second lock time) to a striker-fired SR9 (with a lock time of about 7/1000ths of a second).  For the S/A revolver that is a window of time over 100 times longer than the SR9 in which heeling, pushing/pulling the trigger, flinching, etc., can affect the Point Of Aim (POA) prior to the ignition of the cartridge.

 

At 5 yards it is hardly noticeable.  Push the targets out to 50 yards and the differences will be exponential.  

 

The same is so with rifles.  Most people would agree that an inline muzzle loader is more accurate than a flintlock. all other factors being the same except for lock time (meaning use the preformed propellant pellets, conical saboted bullets, fancy fiber optic sights on both rifles).

 

On 1911s lock time is reduced dramatically with the installation of titanium firing pin, hammer, hammer strut, and mainspring cap.  Less weight = shorter lock time.  It made a noticeable difference on my Springfield 1911A-1.

Edited May 12, 2015 by planeflyer21

[mrmackc]

If you have any doubts about any factor that effects "lock time" (old definition)  having to do with accuracy, please talk to Mr. Geissle or David Tubb both of these men have practical experience, and I consider them experts.   I certainly am no expert, I just have read a lot and learned from my mistakes.  David's dad Geroge Tubb was a good friend and shooting mentor to me when I was really into NRA competition shooting, of which I wasn't ever very good at.

Edited May 12, 2015 by mrmackc

[98Z5V]

     No offense & I mean it , how do you know what your Armorer did to the rifle ? Did you watch him work on it ? Just how much were you into Gunsmithing back then or at that time ?  Really .

 

Helped rip it apart while he was digging the parts out and reinstalling them.  He knew what was going on right away.  He's what got me into looking at these things deeper, and figuring out not just what the problem was, but why it was a problem in the first place.   Nobody liked the two Armorers we had - they were awesome.  If I had free time, i'd go shoot the $hit with them, just to do it.  I still talk to one of them today, and he's a hell of a good friend.  <thumbsup>

 

If you have any doubts about any factor that effects "lock time" (old definition)  having to do with accuracy, please talk to Mr. Geissle or David Tubb both of these men have practical experience, and I consider them experts.   I certainly am no expert, I just have read a lot and learned from my mistakes.  David's dad Geroge Tubb was a good friend and shooting mentor to me when I was really into NRA competition shooting, of which I wasn't ever very good at.

 

I was going to mention David Tubb.  Glad someone else did.  He's put out quite a bit of into on how Lock Time has an affect on accuracy.  Yes, we are talking about milliseconds, too.  <thumbsup>

[survivalshop]

    I agree with the Lock time measurements & their effects on accuracy , as a system !

   Trigger release, hammer travel speed & firing pin travel to primer & its ignition , but we are talking about the first two of those factors ( on this rifle ) , with changing out a Trigger/Hammer module , the only factors that are different.  <dontknow>

 

   Unless you have the proper measuring devices to tell if the speed of the Two Different Modules Hammers and the first Trigger pull/release  #'s , that was showing poor grouping , its all conjecture . Even the ammo could cause poor grouping ,from lot to lot , box to box .

 

  Just too many factors effect how a rifle will shoot , even temperature ,to put all that on a Hammer spring , I just don't buy it  , just too many other contributing factors .

 

  I say its just a better working trigger Module , more consistent , etc , etc  <thumbsup>  

[98Z5V]

There's a bunch that could be done to these rifles to better them, as far as Lock Time goes.

 

Heart of the Action

by David Tubb   |  September 23rd, 2010

http://www.rifleshootermag.com/shooting-tips/shooting_tips_rs_heartaction_200811/

 

In the search for the ultimate in match rifle accuracy, faster is better.

 

 

Tubb’s redesigned bolt for the Remington 700 is all about reducing lock time and increasing accuracy. It incorporates a lightweight firing pin, smaller firing pin hole, smaller ejector and a more efficient extractor design.

 

The Remington 700 action is popular and in use by many competitive shooters, as well as tactical professionals, and for years I’ve been striving to make it better.

 

It’s unrealistic to criticize a reasonably priced factory rifle for not including some of the re-engineered system components I and others have come up with.

 

The ignition system is a good example. I am adamant about attaining an extremely fast lock time (the time between trigger break and primer ignition).

 

Shooting offhand, for instance, there’s always more movement than we want. I believe that there is a connection between rifle accuracy and lock time, and without a doubt there is a connection between lock time and score when shooting at targets on a windy day.

 

So every time we can reduce the time between trigger break and cartridge ignition, we have effectively improved accuracy. If the shot fires closer to the time the sight or crosshairs are on target, then the bullet will hit nearer to the position of the sight or crosshairs. Can’t ask for more than that.

 

So the first product I created many years ago was the SpeedLock lightweight firing pin for the 700. After that, and realizing that no amount of custom gunsmithing could accomplish what a clean sheet of paper could, I came up with a new, complete bolt assembly.

 

The components included an efficient, small extractor; a smaller firing pin hole diameter; a small diameter ejector; precision manufacturing techniques that eliminate the need for truing and squaring; and, of course, fast lock-time. I also wanted to offer interchangeable bolt knobs so shooters could change them to suit their needs.

 

I incorporated every lock-time reduction trick I know—light-weight aluminum bolt shroud, lightened cocking piece, chrome silicon spring and a SpeedLock firing pin with an 0.062-inch diameter pin tip to go along with the smaller hole diameter into this part—and it provides a little better than 40 percent faster ignition over standard bolts. That means the bullet leaves the muzzle before the firing pin tip on a stock 700 action has even hit the primer. That’s big.

 

Reducing the firing pin hole diameter to 0.065 inches (a Remington bolt’s firing pin hole is normally 0.078) also makes for far fewer pierced primers when striving to attain maximum velocities from a load. Additionally, increased striker energy is imparted onto the primer for more reliable ignition.

 

The reason for reducing the ejector diameter was to help minimize brass flow into the ejector hole, and with a smaller ejector plunger hole in the locking lug the bolt is slightly stronger. Remington stock size is 0.135 inch; ours measures 0.110.

 

The extractor design is another part I developed years ago. Shooters have long been replacing the stock Remington extractor with a Sako-style one to improve function. I believe an extractor should be as small as possible to increase the effective bolt face integrity, but it must also work 100 percent. Additionally, I increased the bolt body diameter to 0.699 inches, so that bushing the front and rear for a close fit in the action—as we often do on stock bolts—isn’t necessary. Adding flutes to the bolt body decreased weight and changed its appearance. A custom rifle should look custom.

 

 

NOTE: We, on this board, will have an option for a Titanium firing pin coming up soon.  <thumbsup>

[ChaseFan9]

Wow, how has all of that not had it's own thread before? Everything you ever wanted to know about lock time...

[survivalshop]

  The name on this thread is " Hammer strike strength & precision " , not lock time , the issue was hammer strength , light primer strikes with out ignition . Lock time of course probably was increased , more so because of a binding Hammer or inconsistent trigger sear release , both of those will effect group size , with out a doubt .

Of course, we were also experiencing many failure to fire malfunctions due to the ELF trigger causing light primer strikes (we only went through one five round group that didn't have any light primer strikes, the others all had at least one).

 

  All the precision shooters are big on lock time , Mostly your Target , Match & Long range shooter's , most of us ( unless you are one of them ) will not even realize the one or two Milliseconds or fractions of them , in our shooting experiences .

  The speedy Pistol shooting matches now a days are won by fractions of a second , so any advantage to the speed to which they can get round to round time , the more advantage they may have .

  All of these precision firearms have to be tuned for all this to come together , they also don't have to take these firearms in a combat or Hunting conditions. Yes ,you are going to bring up precision sniper rifles , they are not the same as a competition only rifle .

   There is a fine line to draw when setting up for decreasing lock time , a heavier hammer spring to take a fraction of a Millisecond off lock time , effects trigger pull/release , a lighter Firing pin ( Titanium ) may need the heavier Hammer spring or lighter & on & on . Its a system, all components working together to make a difference .

  The OP's situation & maybe even 98's , could have been effected , just by removing the components & that could have dislodged something or corrected a bind that could have been the caused the issues . Its hard to tell in hinds sight ,with no controlled measuring to compare the effects to. <dontknow>

 

  On the subject of light primer strikes , if the primer ignites , its not light strike . A pierced Primer will rob the ignition of the main charge in the Cartridge & that will also alter group size & your past lock timing when the Primer ignites . 

we were both shooting 4-5MOA 5-shot groups with 175gr match ammo of various manufacture.

 

  The above could also contribute to grouping . 
 

   

[planeflyer21]

Oh yeah.  Shooting two or more types of ammo when chasing accuracy is a big no-no.  May as well pull your hair out with a Zippo lighter.

[FaRKle!]

Let me clarify, each group was shot using the same ammo. Each group independent of any others was bad. It'd be plain stupid to try to claim something about group consistency while using two different brands/types of ammo. I'm very far from incompetent when it comes to DOE.

Ammo used was SSA 175gr OTM and HSM M118LR. I've shot sub-MOA with the HSM out of this rifle with a Geissele SD-E.

Edited May 13, 2015 by FaRKle!

[survivalshop]

  I didn't mean that you mixed them , I know you know better than that ,that wasn't my intention with bringing it up . Different ammo will print differently & some ammo could foul a barrel & cause grouping problems with other ammo tested also.  <thumbsup>  I normally swab the barrel in-between test loads & clean with copper type solvents if my groups get out of hand as yours did . Not saying that was your issue , but its something to think about when your groups go crazy.  

   I have had , very good ammo or bullets show flakes of copper on the patch , when swabbing in-between load testing.

 

  You just had a bad Trigger Module, you proved that , to me , the Trigger is one of the most important components in the firearm for bringing out the capabilities of the rife & shooter for Accuracy . Yes ammo ,barrel/chamber , shooter has a lot to do with it also , but a bad trigger system will keep the firearm & shooter from it full potential.

 

  Since most of us know how the MilSpec triggers are & they can be cleaned up , but offer little compared to what is available now a days & after my 870 incident while hunting , I will not have a Trigger smith tune any factory trigger of any type.

   

 

 

[breastroker]

OK, I want that Titanium AR 308 firing pin, who and when???

 

So if Geissele were to make a SSA trigger with titanium hammer, with the same strength springs lock time would be reduced???

[survivalshop]

  MechArmor Defense Systems was coming out with a Titanium Firing pin & there may be others .  

  Any weight reduction of a moving component like the Hammer will increase its speed & lower its lock time , One would assume . 

[98Z5V]

So if Geissele were to make a SSA trigger with titanium hammer, with the same strength springs lock time would be reduced???

 

Yes, lock time would be reduced.. 

 

And would it work?  Maybe No.  Because of Mass...

 

Mass in motion. 

 

How much does a standard hammer weigh, and how much does a Titanium hammer weigh?  That needs to be known, very first.

 

If you have a steel 3-ounce hammer being energized by that hammer spring, what is the final energy of that mass-in-motion at the end of it's travel, when it impacts the firing pin?  For $hits, lets call it 30-lb/ft of energy.

 

Grab up a high-speed combat-fighting super-badass Titanium superhammer that weighs 0.5oz, and guarantees faster lock time.  Proven, it'll lock faster, with the same spring - physics says it has to.  However, that faster hammer weighs 2.5oz less than the stock hammer, and it only imparts 5-lb/ft of energy on the firing pin, and leaves you with misfires because of that.

 

How's that hammer speed working for you now?...  It's a balance, man, and more than that, it's a science - faster lock time might not be all that, if it imparts less energy, to the level that it's not reliable.

 

What you're talking about is Golf.  You can swing a lighter 3-Iron faster than you can swing a 9-Iron.  Is that lighter 3-Iron gonna knock the ball further, or is the 9-Iron gonna knock the ball further?... Mass in motion...  you need to balance it.  There's no shortcut.

[Robocop1051]

To make it worth it, the velocity of the lighter mass has to increase exponentially. I don't know all the math, but just picture popping a squirrel with your .45ACP, launching a 230gr at 850 fps.... and then popping another with a 4k+ fps 35gr .22cal varmint grenade. The proof is in the mist.

[survivalshop]

  Yes, Mass has a lot to do with functionality , as far as striking the firing pin to ignite the Primer . There is a give & take with respect to decreasing lock time , some things work with certain actions & some don't work so well  .

Edited July 25, 2015 by survivalshop

[EngrBob]

Kinetic energy is one-half mass times velocity squared.  Changes in velocity have a greater effect on energy than mass.  It is a balance but doubling mass only doubles the energy (with a constant velocity) but you only need to increase velocity about 40% to get the same result (with constant mass).

[survivalshop]

 A Mechanical Engineer among us , now all we need is the weight of the Titanium Hammer & a Geissele or std Hammer to see if it will work . <dontknow>  <laughs>  <munch>

[ironmonster]

Kinetic energy is one-half mass times velocity squared.  Changes in velocity have a greater effect on energy than mass.  It is a balance but doubling mass only doubles the energy (with a constant velocity) but you only need to increase velocity about 40% to get the same result (with constant mass).

 

I was gonna say that,  But you said it a lot better than I could have. ^-^

[jtallen83]

Kinetic energy is one-half mass times velocity squared.  Changes in velocity have a greater effect on energy than mass.  It is a balance but doubling mass only doubles the energy (with a constant velocity) but you only need to increase velocity about 40% to get the same result (with constant mass).

:ugone2far: but will it shoot?? Sometimes I wish I was better at math....

but then someone else does it for me :hail: