Related to the latest Stopped Muzzle posts...

B

Boyd Allen

Active member
Rather than risk an inappropriate intrusion into Bill's thread, I make this comment in a separate thread of my own. Feel free to comment.

In looking at various causes and effects, I think that a distinction needs to be made between momentum and kenetic energy. The formulas are different. For example,I have an aftermarket firing pin assembly that has a slightly heavier than stock firing pin spring, and a striker assembly that is significantly lighter. While the momentum (that seems to be what moves the rifle) is decreased, the kenetic energy (that seems to be what is important to primer ignition) is maintained at factory level due to increased velocity, and lock time is decreased (not a consideration, within the range of this comparison, for shooting from the bench). I think that for my rifle, accuracy is slightly improved. The obvious signs of change from the stock configuration are a decrease in reticle movement and sound level when dry firing.

I have always maintained that there are significant differences between rimfire and centerfire, and for that reason, what works for one, may or may not work for the other. Similarly, there are significant differences between position and rested shooting, that dictate different design priorities.

This is not new. Those of you who are old enough may remember that the match performance of '03 Springfields were improved by the substitution of so called speed locks for the factory parts. firing pins were lightened and striker spring rates increased. I mention this because the stock configuration had a very heavy striker and a light spring, something that evidently is desirable for rimfire bench shooting.
 
Physics

One of our more educated posters has already given us a formula to determine acceleration, a=F/M, which he has equated to lock time, given a fixed length of firing pin movement.

Remington 37 gunsmiths would lighten firing pins in the hope of improving lock times. These firing pins were 540-550 grains and had plenty of metal that was easy to remove. These same gunsmiths said this modification "quieted" the rifle.

Calfee is going in another direction. He is, I think, trying to increase the strike of the firing pin with the equivalent formula, Force=Mass x Acceleration.

Since the Turbo firing pin weighs more than the 52 firing pin, he is adding weight to the firing pin and possibly using a stronger spring to maintain acceleration numbers, given the firing pin movement cannot easily be changed. This will increase lock time but provide the "hammer" he believes is best for ignition.

The question is, will the increased mass of the firing pin induce vibration that may unsettle things as the bullet exits?
 
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frey said - I believe the "dimple" philosophy was intended to help "pin" the case in the chamber just before ignition to reduce the possible vibration of the heavier strike.

I think what Calfee was actually trying to do with the pre-dimple was to create a shape under the pin that acted like the big dimple in Federal cases. Comparing the size of the two dimples, and considering how burning proceeds across the priming compound shape, you would have to come to the conclusion that Calfee is a little in error with this idea. That's not say his shape is wrong, he's just wrong in his analysis of what's happening.

If you compare the actual shape of the priming compound in rim fire and center fire primers, and then study how burning has to travel through these different shapes, you will see why it is more difficult to get good ignition in a rim fire as compared to a center fire. This difference in "burn time" also explains the difference in uniformity between large and small center fire primers.

We know that it is energy, rather than momentum, of the pin strike that determines how well ignition will occur. Assuming that you can't have too much energy (forgetting vibration for the moment), then it makes some sense to add weight to pins, as long as, at the same time, you also increase the spring load. Probably Calfee's approach (I guess this is his approach!) of adding weight and then testing to determine if accuracy is better, is a good approach. He is simply testing to determine what combination of energy, vibration, and lock time is best for the different shooters; position and bench rest. How he describes what he is doing is sort of odd but I guess we are all "kinda odd".
 
In the case of the Viper action, I believe that preproduction tests were done with the standard steel firing pin assembly down to about half the spring weight of a Remington 700. I should mention that the .062 firing pin diameter is thought to require less spring than the larger pin tips due to higher unit loading. The thought was to see what limits could be observed by looking at pressure curves using a strain gauge glued over the chamber area and connected to an Oehler (sp?) 44. There was no discernable problem at the lightest weight that was tried.

On the other hand when Greg Tannel was testing his light firing pins he found that he needed a 25# spring because there were problems associated with lighter springs. (probably .072 tip dia.) Also, I have heard from gunsmiths that told me of ignition problems associated with using light pins with standard weight springs, this with .072 firing pin tips, which probably made the issue more critical.
 
Boyd Allen

Boyd
At the Sacramento club we have an engineer who is a NBRSA 600 and 1,000 Yard National Champion plus he reset 19 National High Power records in 2008 alone.
He adds a weight to the firing pins in his BAT actions and has posted pictures of it on www.6mmbr.com
Lynn
 
hulk said:
One of our more educated posters has already given us a formula to determine acceleration, a=F/M, which he has equated to lock time, given a fixed length of firing pin movement.

Remington 37 gunsmiths would lighten firing pins in the hope of improving lock times. These firing pins were 540-550 grains and had plenty of metal that was easy to remove. These same gunsmiths said this modification "quieted" the rifle.

Calfee is going in another direction. He is, I think, trying to increase the strike of the firing pin with the equivalent formula, Force=Mass x Acceleration.

Since the Turbo firing pin weighs more than the 52 firing pin, he is adding weight to the firing pin and possibly using a stronger spring to maintain acceleration numbers, given the firing pin movement cannot easily be changed. This will increase lock time but provide the "hammer" he believes is best for ignition.

The question is, will the increased mass of the firing pin induce vibration that may unsettle things as the bullet exits?
Click to expand...

___________________
The great RF Smiths Bob Hart & Walter Womack would also shorth OAL of pin
And grind rear barrel of bolt for a clearance.
They made the 37 into a real shooting machine.:)
 
Fred J

Fred
Its not an article but a thread about BAT actions not firing primers.In it the Moderator posted some pictures of the fix and where it can be found.I headed to work right now but hen I get home in about 10-12 hours I will try and get you on it.
Most of last year my shooting had slumped very badly.I read the thread made the correction and then placed second then first at our last two matches with the very same gun and barrel.I am pleased.

When I read about the 37's am I reading dated material or are they still winning against the turbos?
Lynn
 
Friend Boyd

Friend Boyd:

Thank you for allowing me to post....

I quote from you: "I have always maintained that there are significant differences between rimfire and centerfire, and for that reason, what works for one, may or may not work for the other. Similarly, there are significant differences between position and rested shooting, that dictate different design priorities."

Boyd, If I were to build two identical rifles, save for the quality of ignition, both with the exact same accuracy potential otherwise, the one with the most uniform ignition will always shoot better.

I think I work harder at ignition than any other aspect of my work.

In a centerfire cartridge the priming mixture istelf has but a very small influence on the total combustion process, that drives the bullet....

In a rimfire cartridge, the priming mixture itself has a major influence on the total combustion process, that drives the bullet, as we have a very small amount of powder and a very large primer.....

In a centerfire cartridge the primer lights the powder from the center of the case and most usually lights straight against the powder....

In a rimfire cartridge the primer lights the powder on the side of the case, and on most guns, lights at the beginning, in an air space.....

On a centerfire cartridge, the firing pin compresses against a thick, brass cup which rests against a fairly soft brass anvil....with the compound between..

On a rimfire cartridge, the firing pin compresses against a very thin brass surface, .008" or so, and has for its anvil the STEEL breech face of the barrel.....

Making extremely uniform rimfire ignition is a major challenge.....we must somehow cause the firing pin to penetrate far enough to compress the priming mixture, EXACTLY THE SAME EVERY SHOT, but not penetrate so far as to compress violently against that steel anvil, (breech face) as the pin will bounce and we've then lost all accuracy....

I have found that a heavier firing pin with the correct spring can be made to meet the above requirements much better than an ignition system that relies on the spring only to do the bulk of the work...

Your comment on position shooters and benchrest requirements being different......if one thinks about it, quick lock time should be a major requirement for someone shooting offhand, at least that's what I've always been told, and it does make sense....

But if better accuracy can be produced with a heavier pin, could there not be a possibility that a good position shooter could score better, even with somewhat less lock time? ......I just don't know......I always think back to Sir Philip Sidney's quote: "Nothing is achieved before it is thoroughly attempted"

Thanks again for allowing me to post..

Your friend, Bill Calfee
 
Bill,
Good post. A very long time ago, I asked a local rimfire prone shooter why he didn't test his ammunition from the bench. He told me that top shooters in his sport had not been able to get reliable results that way, that based on that experience, they did their testing shooting prone.

Lynn,
I have seen several posts that described ignition problems with BAT actions that were ultimately fixed with a stronger spring. The literature is full of accounts that advise shooters to replace striker springs every so often to maintain accuracy. I am not suggesting that your results are not real, but that there may be more than one way to achieve the goal of optimizing striker energy. I would point out one thing however, your 1,000 yard guns are built to a much heavier weight limit than a short range sporter, and because of that may be less influenced by the increased momentum of a heavier firing pin. Also I would like to know how heavy the spring is on the action that you added weight to the firing pin on. It may be that it was on the low side, and that simply replacing it with one of greater strength may have gotten the same result....just conjecture
 
Spring does the work.

The spring does ALL of the work, regardless of the weight of the firing pin. There is no other driving force, only the spring.

SteveM.
 
The spring is ALL?

That might be one way of looking at it but it's not the complete way. You could have the very best spring available, of the best materials, correctly designed, but if the rest of the components in the bolt don't allow you to turn spring force into the right amount of work, then you will not get good ignition. You have to have a pin of correct weight traveling at enough velocity to overcome case strength and crush the priming compound quickly enough to detonate it. It has to be recognized that all components in the bolt are important, and everything has to be right to make the system work as it should.
 
To Calfee...

I understand what you are trying to do, and the questions you have. You wonder which is best: a heavier pin at low velocity or a light pin at high velocity? Energy of the striking pin is related to the weight of the pin times the velocity of the pin squared. Its important to note squared - this means when you double the velocity ,you have 4X the energy!

If energy of strike is same with both conditions then probably ignition will be same. If energy is set higher with one condition or the other then probably the ignition will be better at the higher energy. Consistency can not be determined from pin weight alone so this has to be looked at from some other property of the system, such as friction, or distortion.

Vibration or pin bounce with the weight or spring changes we're talking about here probably should be of little concern. However a point you might consider is that adding weight to the far end of the pin does make a rather "springy" assembly. It's one that would be more apt to bounce than one with the weight up near the point of the pin. The idea that bounce is influenced by the anvil or breech may miss the point.

Lock time will be greater at low pin velocity. You also wonder which this would affect more; a benchrester or a position shooter. Put simply; long lock time will have a lesser affect on the shooter which has the firmest hold on his gun - normally this would be the position (especially prone) shooter. As the position gets less steady such as offhand then long lock time will become more detrimental.
 
Dated

Lynn said:
Fred
Its not an article but a thread about BAT actions not firing primers.In it the Moderator posted some pictures of the fix and where it can be found.I headed to work right now but hen I get home in about 10-12 hours I will try and get you on it.
Most of last year my shooting had slumped very badly.I read the thread made the correction and then placed second then first at our last two matches with the very same gun and barrel.I am pleased.

When I read about the 37's am I reading dated material or are they still winning against the turbos?
Lynn
Click to expand...
----------------
Lynn,it is dated. The Smiths passed on and shooter who had rifles with that work on them...just keep on shooting.
Jerry Graves had a Womack 37 last wimeter that was a thing of beauty. I had one and sold it to Gene Davis.
I picked this all up when I shot LR prone. These rifles got every trick in the book,1000 is a long way off and a fast fall was needed.:)
 
FWIW
Not long ago I spoke with Kelbly’s about questions I had concerning timing and ignition. I figured since most of my personal custom actions are Panda’s I would go straight to the horse’s mouth so to speak for answers to my questions. I also felt that what applied to Kelbly’s actions would probably apply to Remington's and Remington clones.

I wanted to know how and why they set up their actions as far as timing, firing pin drop, spring weight, pin weight, etc. I was told that they generally follow what Remington and Mike Walker tested and developed in the 60’s. Supposedly Remington spent about $100K in 1960’s dollars testing all of this. I was told that Remington specs have slipped and the dimensions and tolerances on the factory Remington’s are not what they originally were (not a surprise as most already know that).

Some recommendations and parameters from Kelbly’s for their actions:

Pin fall should be between .240”-.280” and the norm they shoot for is generally .260”.

Do not recommend altering the spring weight or pin weight.

Recommend changing springs after ~3K rounds.

Pin tip is very important and needs to be very smooth and round.

If pin fall is less than .240” inconsistent ignition can result. The more it is shortened the more likely ignition will suffer.

They know some of their actions have been altered (cocking piece to sear hand off for smoother bolt operation) to where the pin fall is .220”-.230” or less and still shoot well but they have fixed some inconsistent rifles with that short of a fall by increasing it back into the .240”-.280” range.

Anyway just some notes that I thought might be interesting to add to this discussion.
 
If I may be so bold........................!

As to attempt interpret what another man thinks or says. I may get blasted for my effort but here goes.

The way I understand of what Mr. Calfee is saying: I hope I can express this correctly.

100% ignition, 100% of the time, no more no less! Or maybe said another way, the ignition system is to produce 100% of the energy needed to produce 100% ignition with each and every shot. Less than 100% energy will produce inconsistent ignition and poor accuracy. More than the required 100% of energy needed will be transferred back to the firing pin as bounce and accuracy will suffer. Mr. Calfee feels the Turbo action as he tunes them achieves this. Therefore, he is building his 52 ignition system to mimic his Turbo system. I think it would be hard to argue that he has not or will not achieve this. Is there more than one way to achieve this 100% ignition? Yes, no, maybe/probably so! Mr. Calfee feels he has found the best way. Add to that, I would think Mr. Calfee believes his way produces the least upset to the rifle.

Off-hand or position shooting is in itself a dynamic process. The question is can perfect ignition at a slower lock-time offset the benefit of faster lock-time and perhaps less than perfect ignition? Then he suggest that it be put to the test!
Sounds as though Mr. Calfee may be wanting build a position rifle to prove/disprove the argument. To that I say, build the rifle Mr. Calfee and it will be shot!

D R
 
Friend DR

Friend DR:

Per your post just before this one.....

My friend, you've described the challenge perfectly, what I'm attempting to do.....?

DR, in this age in which we live, (accuracy), one would think that everything that could possible be done, has been done, tested, re-tested, a dozen times.......a thousand times.....to produce ultimate accuracy..

No my friend......we accuracy folks are a conserative lot.....change comes slow........so slow that, sometimes, we will defend things, that we've been taught, just because "it's always been done that way",....to the death......

Bill Calfee is dumb.......but I've already discovered, in spite of myself, that we've got so much to learn about accuracy.....

I'm now into ignition........we're, (me alone if it takes it), are going to solve this ignition thing...FOREVER......

Then we can look at the rest of the puzzle......

Your friend, Bill Calfee
 
Kathy said:
Friend DR:

Per your post just before this one.....

My friend, you've described the challenge perfectly, what I'm attempting to do.....?

DR, in this age in which we live, (accuracy), one would think that everything that could possible be done, has been done, tested, re-tested, a dozen times.......a thousand times.....to produce ultimate accuracy..

No my friend......we accuracy folks are a conserative lot.....change comes slow........so slow that, sometimes, we will defend things, that we've been taught, just because "it's always been done that way",....to the death......

Bill Calfee is dumb.......but I've already discovered, in spite of myself, that we've got so much to learn about accuracy.....

I'm now into ignition........we're, (me alone if it takes it), are going to solve this ignition thing...FOREVER......

Then we can look at the rest of the puzzle......

Your friend, Bill Calfee
Click to expand...

Mr. Calfee,
Please know that I feel honored to be considered among your friends.
It's also nice to know I got it right!
It seems without me knowing just why, been working in the same direction.
First, let me say, I'm no BR shooter but I do shoot from a bench to check accuracy improvements.
I'll say this, if you "Bill Calfee is dumb" then I am dumber then a fence post with two knots
missing!
I have been taking 'hammer spring' out of revolvers, lever guns as well as bolt guns for years. Damn the lock time, I guess I'm just sensitive to the hammer fall or pin strike. Never considered what it may be doing to ignition with the exception of too light a strike.
I did it and it seemed to work for me. However, I don't feel myself to be cutting edge shooter so I can not tell you how much it helped in scores. My silhouette and prone scores have improved but that could from better triggers as well as lighter strikes, better ignition plus and practice, practice, practice! Still I hear, fast lock time is so important with position shooters. I hope you will try one of your BR sporter rifles in a position stock with a top-notch shooter behind the trigger to prove/disprove once for all time the argument.

Your friend,
D R
 
You can say what you want about Kathy, but the man is a perfectionist. Look at the picture of his modified firing pin and springs; everything is high polish bright and shiny. I have taken apart the bolt on my 52D and put it back together with the same parts in basically the same condition, dull, tool marks and far from shiny. When you see pics of his rifles, the attention to detail is unequalled, jeweled, bolt, even jeweled scope bases. That kind of workmanship takes dedication. Thanks, Douglas
 
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