Piece 3, Firing pin impact and accuracy

[joeb33050]

Charlie Dell's test is the only test I've found to date.
As before, I'm looking for data.

A number of single shot shooters have reported that accuracy has gone to pot and that this was traced to a broken-but-still-working firing pin.
A number of other shooters have reported that firing pin or striker spring force-that the force with which the firing pin hits the primer-is an important determiner of accuracy.
There are springs and firing pins for sale in the gun magazines, said to increase accuracy.
Yet others say that this increased accuracy has to do with other things happening, lock time reduction among them; and that it ain't the primer strike force that increases accuracy.
I don't know, all I know is the Charlie Dell test. It seems to me that we/you could devise and perform a test using one of the adjustable pressure firing pin Savages. I don't know how to do this test with any rifle I own.
Still looking for data.
Thanks;
joe brennan

[44man]

I like the idea to try and confirm this problem and hope a bunch of us will really work on it. I have to find a gun to borrow that will work.
It raises a lot of questions;
Was there a difference between old primer composition and new ones?
Does how a primer is seated change things, in other words, what happens between a primer that just touches and one that is seated to push the anvil up into the compound?
Does firing pin travel along with a weakening spring effect anything?
How about firing pin or hammer drag?
I really have to wonder if improvements in priming compound just made the problem go away?
What about the powder charge itself? Will a fast powder do different then a slow powder?
Have I been hanging on to this idea all of these years when it no longer applies?
I know it used to because of all the work I did and improvements I had over the years so I have stuck hard with the idea. If things have changed for the better with primers, I will be the first to admit I am now wrong.
Looks like we have a lot of work now instead of looking for stuff written many years ago that might no longer apply.
Maybe I am just too durned old! But then again, I am glad I brought this up because anything we learn will benefit all of us.

[Trailblazer]

I recently replaced the mainspring in my Model 70 264 Win Mag. I meant to test it with both springs at one range session. It was so cold and windy at the range that I did not bother changing it there. I shot about a 2" group with the weak spring. After changing the spring I shot about a 1" group at the next range session under much better conditions. To many variables to draw any conclusions, but I am still curious about it and will probably will do a proper test one of these days.

The reason I was suspicious of the spring is that primers were always cratered even with mild loads. I did a crude test on the bathroom scale and the old spring had about 17 lbs. pressure when at the approximate length when cocked. The new spring is a Wolf 24 lb. spring. Primers are not cratered with the new spring. The load I used for testing was 60 grains RL-25 with Federal 215's and the 120 Sierra. It may be that firing pin strike has more effect on large charges of slow burning powder and with magnum primers.

[44man]

There seems to be a lot more to it then can be predicted and is the reason I have stuck to it all these years. I figured more is better then less and it just was not worth reducing tension.
It is just too easy to remove any problems that might occur, whether real or imagined.

[fourarmed]

It would be easy to do a test with a Ruger BH. Just unhook one leg of the hammer spring - which I have heard called a "Ruger trigger job."

[Bullshop]

It would be easy to do a test with a Ruger BH. Just unhook one leg of the hammer spring - which I have heard called a "Ruger trigger job."
Thats not the hammer spring its the trigger return spring.
BIC/BS

[fourarmed]

Well, poo!

[KCSO]

Although it is easy to do in a SAA the short barrel and crude sights don't lend themselves to meaningful data. When I redid my 1886 from the rebound to a straight coil i was curious so I tried a couple of weaker springs. I found no difference in accuracy until I got to the point of an occasional mis fire, then groups strung badly. I think consistancy has more to do with accuracy than how strong or weak a spring is. Where the extra power sprinigs come in is in lessening lock time and to tell a difference there you would need a super accurate platform a good bench and lots of test ammo. I don't think you would prove anything unless the gun was 1/2 miniute capable and you were shooting from a perfect bench in perfect weather. The tests I did with the 1886 certianly proved only that groups string when you get misfires. the fact that a 22 pound spring shot a 3" group and a 18 pund spring shot a 3 1/2" group is really pretty meaningless. However when you go from 8" strung to 3" round you have a definate indication something is amiss.

[Dale53]

Charlie Dell was a personal friend of mine and I spent a number of evenings (and full days) with him discussing various "issues". Charlie was a tireless experimenter and taught many of us many helpful things.

His primer test was set up with a test fixture that shot pellets over a chronograph screen driven entirely by the primer force. The fixture had adjustable firing pin striking force. He learned that if the primer went off, the velocity was constant. His conclusion was that if the primer went off, accuracy would not be effected by "light" firing pin springs.

However, the process did not take into account "brisance"(sp?) . That is, the "shattering effect" of a lightly struck primer compared to a "properly struck" primer. It may well be that brisance is affected by light firing pin blows and THAT affects accuracy.

In other words, his experiment was fine as far as it went, but it may needed to be taken to the "next level".

I agree, that it would take a REALLY accurate rifle in a tunnel to really get some meaningful data. However, it is possible that the primer manufacturers already have good data on this matter.

Bill Calfey, master .22 bench gunsmith, has written a great deal in Presision Shooting on ignition. He believes, very strongly, that "killer" ignition makes possible "killer" groups. He makes a very good case...

Dale53

Dale53

[leftiye]

So, D53, we may be looking at the possibility that lightly struck primers burn more slowly? Might be. I'm not really well into primer material chemistry, but I know that the basic things used like fulmiate of mercury, potassium chlorate and such are very unstable, almost like nitro, and are true explosives, detonating under shock. Modern primers are made out of other stuff, but I suspect the same characteristics are necessary in a primer. It may not be possible to attribute a "burn rate" to these, as they do degrade instantly in no pressure situations. I hesitate to say it, but it does look like if you can get it to go at al, it all goes already. One possible way out is the volume of the primer pocket might vary as we crush the primer indifferent ways, thus affecting the pressure of the primer's shock wave.

[Ricochet]

It's true that explosives in general have variable detonation velocities, that is, rate of propagation of the explosive shock wave front through the energetic material, depending on several variables including how the explosion was initiated.

How that translates into effects on powder ignition by gas from the combined explosion of the explosive components of the primer mixture and rapid combustion of the solid fuels and oxidizers in the mix, followed by the flaming mass of gaseous and liquid products of these reactions expanding out of the primer pocket through the flash hole into the powder chamber, is another matter. I would guess that the velocity of detonation becomes fairly unimportant after going through this multistage process. There might be some effect of a fast, deep indentation of the primer cup compressing the volume of the primer cup/pocket space and increasing the pressure inside of the primer cup that way. Don't know if that would result in a hotter ignition of the powder, though, as that hot gas would give up some heat to the primer cup, anvil and pocket at the higher temperature, and it would then expand and cool more as it flowed through the flash hole into the powder chamber.

My basic expectation is that the primer either goes bang or it doesn't, and that any effects of different firing pin blows will have a relatively small effect on the cartridge's ballistics.

[leftiye]

I think that's what you've got to get to in the end. The primer explosive material can't be ignited a little at a time- unless you measure time in extremely fine increments. I suspect said increments are too small to matter, even on the time plane of a cartridge's ignition. It either goes or it don't.

It also looks to me like the primer space volume issue wouldn't make too much difference either. The amount of flame/ heat would still be the same, and the difference in volume would be miniscule even in this scope of size.

Another thread dealing with flash hole size of the ctg. case however provides another way that this could be varied, and it would be nice to know just how this could be manipulated usefully for maximum ignition, but let's assume here that flash holes were uniform. Assuming, of course that the actual amount of explosive in the primer were correct, not too much nor too little, it either works or it doesn't

[MtGun44]

My 1886 Win Extra Lite (modern, rebounding hammer) was a misfirer about
1 in 5 or 10 shots, AND strung shots very badly, some as much as 18" vertical.
After cutting the rebound leg on the spring guide and eliminating the misfiring,
the groups are MUCH better, with no vertical stringing altho it is still not the
tack driver that my Marlin is.

One more data point in favor of weak ignition = poor accy.

Bill

[joeb33050]

Dale;
We're talking about two different tests here. The test I posted is with a real gun and real groups shot in the tunnel rig.
joe b.





Charlie Dell was a personal friend of mine and I spent a number of evenings (and full days) with him discussing various "issues". Charlie was a tireless experimenter and taught many of us many helpful things.

His primer test was set up with a test fixture that shot pellets over a chronograph screen driven entirely by the primer force. The fixture had adjustable firing pin striking force. He learned that if the primer went off, the velocity was constant. His conclusion was that if the primer went off, accuracy would not be effected by "light" firing pin springs.

However, the process did not take into account "brisance"(sp?) . That is, the "shattering effect" of a lightly struck primer compared to a "properly struck" primer. It may well be that brisance is affected by light firing pin blows and THAT affects accuracy.

In other words, his experiment was fine as far as it went, but it may needed to be taken to the "next level".

I agree, that it would take a REALLY accurate rifle in a tunnel to really get some meaningful data. However, it is possible that the primer manufacturers already have good data on this matter.

Bill Calfey, master .22 bench gunsmith, has written a great deal in Presision Shooting on ignition. He believes, very strongly, that "killer" ignition makes possible "killer" groups. He makes a very good case...

Dale53

Dale53

[Char-Gar]

Dale mentioned the "brisance" of a primer and spoke of it as "shattering effect". I understand brisance to be the rate or speed a primer releases 100% of it's energy. Brisance does not measure the amount of energy, nor the tempreture of the energy, but the rate of it's release.

Thus a low brisance primer has a longer "burn" which can be helpful with small charges of powder in cases without undue increase inv pressure..

So just what is brisance?

[Ricochet]

Brisance is a French word for "breaking." It does refer to the shattering power of a high explosive, and is measured by firing a small amount of an explosive in a cavity filled with a measured amount of sifted coarse sand, sifting it again and measuring the fine sand and dust produced by the explosion. It's not really applicable to primers and shouldn't be used, IMO. I've never seen a primer test that actually measured it in any way, and it's usually misused as a term for the force of the primer's explosion, as in how far it drives a weighted pendulum or how fast it launches a projectile. That's improper terminology.

There is a shattering effect of primers on powder grains near the flash hole. Highly variable depending on the powder, its age and condition, conditions of loading, flash hole size... It'd be very difficult to quantify.

[KCSO]

Read "The Muzzleloading Cap Lock Rifle" by Roberts. They went all through this with caps in the 1870's with some favoring a weak cap some a strong cap and various hammer sprinig issues. This is not a direct comparison as a hammer has to have enough spring tension to not only set off but contain the explosion. I don't have a gun capable of giving me a firm answer so I will continue to err on the strong spring side. I have used a cap tester and I went with the most uniform rather than the hottest or coldest cap.

[PineTreeGreen]

Years ago,my nephew and I reloaded 12 ga. for trap. We had used "700X" powder. Someone told Steve that"Red Dot"was the Hercules(at the time)eqivalent. So he bought an 8 pounder of Red Dot and started to reload. I was in Oklahoma and in a phone conversation told him to be sure to check the powder bushing. He had already loaded about 600 rounds. When I returned from Oky land I was informed that these Red Dot loads were some sweet to shoot. He was shooting a "Model 12"and I had a KS-5 Kreighof. The Model 12 would digest this stuff great. The k-gun would pierce Win and Fed primers and the firing pin would not retract which hung the gun up from opening. I don't remember if it poked holes in any other brands. This was definatly a LOW pressure problem. May not be on the subject just my .02 worth.