A little cocking cam mod. advice please

Boyd, I have no 100% way, but soaking some in Kroil might work. At any rate, measure the fall on
only the ones that don't go off. If the primer does go, it will certainly drive the pin back out some.
At any rate, I would rely on the max depth, as the worst case scenerio
 
I would use a sized case. That's what you have in the chamber when you pull the trigger to shoot a target. You could use a junk case with a split neck or other damage and drill out the flash hole so there is less pressure produced in the primer cavity. Light oil "should" kill the primer.
 
Boyd Allen said:
One issue, that has not been discussed, sort of a tangent to a tangent, is that with a smaller firing pin tip, mine is an .062, it may be that less kinetic energy is required to do the deed optimally . . .
Click to expand...
Or it could mean more is needed. Maybe area counts?

The moment we (well, the shooting gunsmiths) figured out ignition is not a binary proposition, as far as I know, the only measuring system became statistical, namely, group size.

As far as getting measurements goes, why not do it each way? Sized/unsized, no primer, spent primer, "dead" primer, and full load. You'll get different numbers, which may be useful someday. But not, I think, today.

I've always thought that ignition, and the building of the pressure curve (slope), is the most important part of "tune." It is not the MV. MV is the only convienient measurement we can take, and it has not proved terribly useful -- with the possible exception of Jim Borden's test on charge weight versus MV when loading on several different days, proved out by shooting groups.

Anyway, am I right? Probably not. It's a gut feeling, and there have been a lot of them disproved over the years.
 
Charles,
I have a friend who tends to over complicate projects and then not do them because they are. I think that what I have outlined will be more than adequate for the intended purposes. BTW in the past, one manufacturer, used a strain gauge to plot pressure curves with various spring weights over a much larger range than anyone has discussed in any forum that I have read. It was done with a .062 pin, and the results were uniform down to a surprisingly low spring weight. I point this out, not to discount the idea that different spring weights might show different results on the target, but as information about the usefulness of pressure curves as a predictor of target performance.
Boyd
 
Good idea. Do you think that one would change the other? BTW on the whole firing pin thing. I have a friend (who is all about the details) who sets his Savage firing pin protrusions at .035, with no problems. I know that my testing may not be the nth degree, but it reflects the questions that I currently want answered. Perhaps, after I have the results in hand, I will think of other questions and then come up with appropriate tests. Perhaps you could save us some time and share test procedures and results. So often, on this board, posters get into arguments about how things work, one fellow's theory against another's. Most of the time, they (myself included) lack the facilities to actually directly observe the thing that is being discussed/argued, but it goes on and on, back and forth. I have a more limited goal, I want to know what happens, possibly at the most superficial level, when I do something. Right now, I don't know if the primer dent that will be created when I set one off in a fired empty case will have a different depth than the dent in the primer that was fired normally with powder and bullet. If there is no difference, I may try to kill some primers, and retest. Who knows,at some point I may glue a shim to the front of the front spring shoulder , to limit firing pin protrusion, and see how short I can go before problems show up. Or I might do the test on a factory rifle to save rounds on a match barrel. The PPC is working really well, at the target. I am just curious.
Boyd
 
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Have at her Boyd. I haven't conducted actual tests on strike depths but have had a few misfires over the plinking years and the depths are dramatically deeper. I would guess different types/brands of primers would give slightly different results. We have talked about killing primers before, they are easy to ruin but not kill. I doubt killing them would have any effect on depth when no charge is used but this is what tests are for.

Any way you could test using different spring weights? This thread started with bolt operation effort and spring weight plays a big role in that. If inconsistant ignition results from "weak" spring weights, it might show better from an accurate rifle.
 
I have tried a spring that was as light as 19#, with a .062 firing pin tip, and steel pin, with no problems evident. I think that when we start modifying striker assemblies to improve accuracy, the range of modifications generally fall within a range that produces reliable ignition. I became interested in using the heavier spring, with the steel pin, was a conversation that I had with a well known benchrest smith about the modifications that he does to BATs. Having a slick bolt is great, but there is not slick bolt trophy at matches. I would trade an easy bolt for smaller groups. We shall see. It may make absolutely no difference, but I will have to shoot it a while to see, and there is always the chance of "placebo effect". On the other hand, if it makes me shoot smaller....
 
Quick Test

Boyd,

I pulled the bullet from a loaded round and fired it "primer only" and did a visual comparison with a fired case from the same batch of 223.

There is a definite visual difference:
1) The fired primer from the loaded round has the normal amount of flattening and the FP indentation is obviously more shallow.
2) The primer from "primer only" has little or no flattening and an obviously deeper indentation.

I don't think I learned anything we didn't already know from experience. The rods on my depth mic's won't fit into the FP indentations and I don't know any other ways to make this measurement.

Maybe you or someone else will know how to measure this.

A. Weldy
 
This works on a BAT to check primer peircing depth
1. Unsized case - un-loaded case - safe area
2. kill primer with WD-40 or kroil
3. place case in chamber and slowly close bolt while depressing trigger
4. measure bolt shroud/firing pin fall while firing pin resting on primer using caliper with "wire" style depth
5. Zero calipers
6. Lift bolt to re-cock
7. Fire
8. Re-measure firing pin drop and subtract your numbers........you have your peircing number.

I have measured two Bat 3 lugs with Fed 205M killed primers......results were 0.018" penetration and quite consistant. I got this from a very good shooter, its not my process, I simply stole the wheel. I works good.

I also had a Farley that was shooting inconsistant. This same test revealed .011 penetration. I made a new Nitrided firing pin (was bent slightly and rubbing the 0.062" diam) and re-installed and checked. Now has a much louder click and penetrates .020" to .022" and shoots great! Maybe someone can comment on what penetration is correct. I have heard a number that Federal suggests, however, I dont know if it is correct and wish not to publish false or misleading info. Anyone have info here for proper firing pin penetration to consistantly ignite various brands of primers?
 
Just got in from the range. I need to do some more measuring, but the difference between a loaded round and a primed case is approx. .006. In the case of the primed case, the whole primer looks somewhat caved in with the firing pin dent in the middle. The loaded round primer has this overall caving in brought flush. This with a .062 firing pin tip and a nominal 25# spring. After I get a little dinner, I will get the cases out and do some more measuring to see how much of the total fall was used on the primed case. It may be that we are wasting some of the total fall because of excess firing pin protrusion.

OK... supper inside me...brain function more or less back to normal...a relative thing. With the rifle cocked, the back of the cocking piece sticks out of the shroud .040, and when the trigger is pulled it falls to a point that is recessed .187, giving a total pin fall of .227. .020 of this is due to reversing the trigger bracket. The depth of the back of the cocking piece, after closing the bolt while holding the trigger, on a case that was only primed, is .167, so the total fall to where the primer apparently stopped the pin was .207. The same measurement using a regular fired case, is .158+, so it would seem that the difference between a loaded case and one that was only primed, using reinserted cases, is .008+". I should mention that the discrepancy between this figure and the difference measured at the range, where the measurements were taken without opening the bolt, may be attributed to differences in an imprecise technique, or assuming that I am perfect,:rolleyes: discrepancies in firing pin centering in the previously fired cases, due to their not being indexed.

Ease of bolt operation was not an issue. While at the range, I played with settings of a Beggs tuner, and I am here that the differences on the target were not subtle. When I decided to try a different tuner location, eight turns forward, about flush with the muzzle, my first setting gave me a vertical line that was about 3/4" out to out. I was able to make this disappear, with a quarter turn. After trying a few more refinements, I returned to may previous location, and since the day had gotten warmer, dropped the load. My intent being to find the best combination of tuner location and conventional tune, and then leave the tuner alone, ala Buckys. It seemed that in tune points are a turn apart, and I have read that although this may solve the vertical issue, that different in tune spots may exhibit differences in horizontal. On my next trip to the range, I plan of looking at how the rifle shoots at one turn intervals, over some range. The other thing that I worked on was my front stop and rear bag positions, as well as pinning vs. free. It was a good day to test. Conditions were good.
 
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