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  #46  
Old 11-02-2019, 07:42 PM
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Quote:
Originally Posted by Bigbore View Post
Snarky is fine, I was hoping someone would ask.

Of all the ignition schemes I've seen, 6 o'clock is the one that intuitively makes sense to me, I think I read about it in Bill Calfee's book. The theory is that there may be empty space in the cartridge at 12 o'clock, 6 o'clock insures the ignition occurs at a location guaranteed to ignite the maximum amount of powder.

I don't know how much of the case volume is empty in the different brands and styles of rimfire cartridges but 6 o'clock ignition makes it unnecessary to even consider.

Good to see you posting, you've been scarce lately.
Just happened to see this thread and it was interesting. I'm not a target shooter, just a plinker. If you have access to a chrono and want to see if theres a difference try this. Pick several brands of ammo you use. Shoot them and record the info. Now try this. Flip your gun upside down in the rest and repeat. Yup thats what I said. Your powder will now be on the "bottom" of the case at 12:00 O,clock in front of the FP with no modifications.. Should be easy its a semi auto. See if theres more consistency. Ok start laughing. I have to go find my bulk ammo and soup cans for the range tomorrow. Soda and beer cans have deposits.
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  #47  
Old 11-04-2019, 07:51 PM
Bigbore
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Originally Posted by MKnarr View Post
Not really. As I mentioned, some of the rounds have no primer at all and my opinion is a 6 o'clock firing pin won't solve anything if the primer is getting knocked off by the pin strike. In many thousands of rounds of match ammo, Lapua Midas, Eley 10x or Match, I've never had a misfire. I don't shoot any bulk ammo but as I said, most of the rounds I pick up are Federal, Remington and a few CCI. There is a post that a guy pulled the bullets on a few different rounds and showed the pictures of the primer. See post #58

Someone else was going to try firing a rifle upside down but I never heard any results.

We did our vibration study on the cheap but the results were very enlightening. Unfortunately all the data was in 123 format on an old computer so I have no data anymore. But I remember from the time the trigger was released until the vibrations started was in the milliseconds. And just the pin hitting a fired case lasted about a half second or so. BTW both my rifle and the friend had triggers in the 2 ounce region and the stethoscope was taped to the bottom of the stock which had free floating barrels.

I remember Benchmark did a study on barrel harmonics with a tuner. They used a device on the sides of the barrel, not touching, to study the wave pattern of the barrel with different tune settings. The proved that the barrel was not stopped as Calfee says but was at different elevations depending on the velocity. The theory posed by Varmint Al was a slower bullet was released at a higher elevation of the barrel muzzle while a faster round was released at a lower elevation when the tuner was tuned correctly. Their study pretty much proved that theory was correct. Unfortunately the study has been deleted from the Benchmark web site.

I'm guessing from your handle Bigbore, that you are or were a high power shooter. I started out my competitive career as a high power competitor in 1964 to 1972. I started smallbore from 1968 to 1978 and benchrest from 2004 to 2015 at which time it became a job again so I quit and only shoot for fun now.
A lot of good information here. I do searches and rarely stumble on the gold that people can link to from distant discussions. It is getting harder and harder to see good data in posts.

I don't shoot high power, "Bigbore" is derived from sloooow and huge to develop FPE. Quite the opposite of today's popular shooting sports.
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  #48  
Old 11-04-2019, 07:54 PM
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Quote:
Originally Posted by scooter22 View Post
Just happened to see this thread and it was interesting. I'm not a target shooter, just a plinker. If you have access to a chrono and want to see if theres a difference try this. Pick several brands of ammo you use. Shoot them and record the info. Now try this. Flip your gun upside down in the rest and repeat. Yup thats what I said. Your powder will now be on the "bottom" of the case at 12:00 O,clock in front of the FP with no modifications.. Should be easy its a semi auto. See if theres more consistency. Ok start laughing. I have to go find my bulk ammo and soup cans for the range tomorrow. Soda and beer cans have deposits.
Yes, I seem to be one of the few who admit to being in possession of a chronograph. I think if I experiment with this I'll start with the upside down firing.

Last edited by Bigbore; 11-04-2019 at 08:29 PM.
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  #49  
Old 11-04-2019, 08:22 PM
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Originally Posted by JGR_LV View Post
but unless you've just flat run out of other things to fix...
If you checked out my "CAD" post I eluded to "running something by the forum". This was it.

I'm always tinkering with something. I have straightforward projects that have a goal, and then there is tinkering which I may or may not finish, or even start.

I just finished my first rimfire bolt gun last week. The project was clearly defined and completed inside one month. The accelerometer project, which I have almost working, is stuck on the output for one axis, and there is a high speed video project which I haven't started, a brand new Casio Exilim sitting unused for two years. I made a mount for the camera which affixes it to the rear of the scope pretty efficiently but I'm already churning another design around in my head for the 3D printer. These are just the rimfire related projects, I have a few other hobbies I rotate in and out of.

The firing pin idea was inspired by a CAD program upgrade and was swimming around in my head so I thought I would get some input. It was opportunistic as I was using the bolt drawing to try the CAD upgrade, I wanted to test my skill at importing separate drawings and combining them to confirm the accuracy of each. It worked. So far it's just a fun intellectual exercise that the forum seems to be enjoying. As stated there has been work done on it already and I found visiting it interesting.

Last edited by Bigbore; 11-04-2019 at 08:44 PM.
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  #50  
Old 11-05-2019, 12:47 AM
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HI all, I don't post here very often, I just watch.
This thread got my atention.
Is this something like you're thinking about. It's a trick that I believe Bullseye shooters have done for years.
The idea of the hits below the rim is because of the softer surface of the brass and because of the possible no primer compound in the rim
Attached Images
File Type: jpg 4- Marvel Modified firing pin hits.jpg (144.6 KB, 224 views)
File Type: jpg 1- Marvel Modified Firing Pin.jpg (126.7 KB, 223 views)
File Type: jpg 3- Marvel Firing Pins.jpg (142.6 KB, 223 views)
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  #51  
Old 11-05-2019, 07:22 PM
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Quote:
Originally Posted by jg-biker View Post
HI all, I don't post here very often, I just watch.
This thread got my atention.
Is this something like you're thinking about. It's a trick that I believe Bullseye shooters have done for years.
The idea of the hits below the rim is because of the softer surface of the brass and because of the possible no primer compound in the rim
These are a 12 o'clock position strike on the left and a 6 o'clock position strike on the right if the bottom of the case were the face of a clock. It will be struck at the top of the case(12 o'clock) for 99% of guns.



Last edited by Bigbore; 11-05-2019 at 07:27 PM.
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  #52  
Old 11-16-2019, 04:21 PM
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has anyone had the time to get a firing pin made up yet?
i have been thinking about the idea of taking two stock pin and
connecting them together, to test
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  #53  
Old 11-18-2019, 10:25 PM
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this is what i was thinking
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  #54  
Old 11-19-2019, 03:14 AM
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I'd think you would have ignition problems with such a wide FP. I doubt the stock spring would have enough force to flatten the whole head of the case and crush the rim. IIRC there were some guns that had a dual faced FP with two strike tips. Like if you filled the middle away and left the top and bottom to hit the rim. I don't see those around anymore. Plus if the head of the case was deformed that much there may be exstraction problems. jmho in the middle of the night.
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  #55  
Old 11-19-2019, 04:00 AM
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It will have two points on it.i 12 and 6 . will have to fit it to the bolt.
And yes the center will machine down.
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  #56  
Old 11-19-2019, 04:55 PM
Bigbore
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Quote:
Originally Posted by 22/silencer View Post
has anyone had the time to get a firing pin made up yet?
i have been thinking about the idea of taking two stock pin and
connecting them together, to test
I've been gone for a week and won't have rimfire shooting time for at least another week.

I want to try the up side down test before I invest any time with prototypes but admittedly, if I miss an 11/27 window for that test it will be a while.
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  #57  
Old 11-22-2019, 09:52 AM
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What a great thread! I think though the firing pin position you are trying for is the wrong way round. Think about it; ideally if you want consistent ignition, the firing pin would have to impact at the 3 o;clock and 9 o;clock position! Anything at 12 o'clock may be trying to ignite an empty space.

I'm not trying to rain on anybody's parade, but with 3 and 9 o'clock impacts, any amount of powder in the case would be sitting parallel to ground and be ignited evenly from both sides(increased velocity)?..................................
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  #58  
Old 11-22-2019, 11:13 AM
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Originally Posted by Ray1946 View Post

but with 3 and 9 o'clock impacts, any amount of powder in the case would be sitting parallel to ground and be ignited evenly from both sides(increased velocity)?..................................
In theory any of the ignition locations can be tested as a single strike by simply canting a stock rifle ninety or one hundred eighty degrees. At this point, if any numbers are going to be produced to take this from a fun, anecdotal discussion to the lab, it looks like it is going to have to be me. With the demands of my personal life and the holidays upon us it is looking like the new year.
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  #59  
Old 11-23-2019, 12:18 PM
Bigbore
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This outstanding experiment was brought to my attention:

http://www.geoffrey-kolbe.com/articl...firing_pin.htm

I feel like I had run across it at some time in the past, maybe others will recognize it. I'm surprised this and Calfee's book are the only work that has surfaced so far.

This should interest and provoke some questions.
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  #60  
Old 11-25-2019, 08:57 PM
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well i am almost done with firing pin
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Last edited by 22/silencer; 11-25-2019 at 09:35 PM.
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