Several primers not showing much pin strike

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bolster55
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Re: Several primers not showing much pin strike

#61 Postby bolster55 » Mon Nov 06, 2017 6:40 am

hello Johnk
primers weighed between 3.68 and 3.70 grains, no relationship between the two types of primers.
The large radius primers had the same variation in weight as the small radius primers.
regards
Phil

johnk
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Re: Several primers not showing much pin strike

#62 Postby johnk » Mon Nov 06, 2017 6:40 am

Ta.

bainp
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Re: Several primers not showing much pin strike

#63 Postby bainp » Thu Nov 23, 2017 10:19 am

See attached photo of normal strike on left and light strike on right
Normal and light strike primers.JPG

There was no appreciable difference in the feel when I ejected the spent primers from the cases using a Wilson spent primer punch under a small arbor press. There also was no appreciable difference in the feel of seating new primers in the two cases. I use a Lee hand primer so difference in feel is very obvious. I also have gauges for primer pockets to tell if the pocket has expanded. The primer pocket of both cases would not let the "no go" gauge enter
What is causing this???
Regards _ Philip
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jasmay
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Re: Several primers not showing much pin strike

#64 Postby jasmay » Thu Nov 23, 2017 10:26 am

You sure your firing pin isn't getting hung up?... "light strike" looks almost like no strike....

Brad Y
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Re: Several primers not showing much pin strike

#65 Postby Brad Y » Thu Nov 23, 2017 1:49 pm

If these cases have been fired before and not excessively fl sized I agree with Jason. Firing pin assembly needs attention

KHGS
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Re: Several primers not showing much pin strike

#66 Postby KHGS » Thu Nov 23, 2017 4:42 pm

bainp wrote:See attached photo of normal strike on left and light strike on rightNormal and light strike primers.JPG
There was no appreciable difference in the feel when I ejected the spent primers from the cases using a Wilson spent primer punch under a small arbor press. There also was no appreciable difference in the feel of seating new primers in the two cases. I use a Lee hand primer so difference in feel is very obvious. I also have gauges for primer pockets to tell if the pocket has expanded. The primer pocket of both cases would not let the "no go" gauge enter
What is causing this???
Regards _ Philip


Phill, I believe you have two problems in the same area.
1) It is a no no to put grease on the firing pin assembly, firing pin assemblies should be saturated with a WD40 style spray & them blown off with an air hose. Cocking cams should be lubed with a "saturated" Mos2 grease.
2) Your spring is weak & needs to be replaced.
Keith H.

bainp
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Re: Several primers not showing much pin strike

#67 Postby bainp » Fri Nov 24, 2017 8:08 am

I don't think it is any of the problems mentioned.
The problem first appeared in August at the South Australian MR Championships. On my return from there, I started the thread, asking for advice. Following some questions to me, I disassembled the bolt mechanism, thoroughly cleaning it in solvents and reassembled with a light sewing machine oil. then blew all excess oil away with compressed air.
I checked spring tension, I cannot turn the cocking piece from uncocked to cocked with bare hands, I need the supplied special tool to give the added leverage. The action is a Maddco which is a Remington style action and should cock easily with bare hands if the spring is too weak.
Following this work I competed at the Coonabarabran Ultra Long Range, where just a 7 of the 130 or so shots fired showed signs of a light pin strike.
On my return from Coonabarabran I did the same cleaning regime again on the bolt. Have now returned from the Australian MR Champs, and found that 4 of approx. 300 rounds have the light strike on the primer.
I don't own a bore scope so I cannot have a good look inside the bolt body to check if there is a fleck of brass stuck in there somewhere, but I have been through a fairly rigorous cleaning regime and liberal use of compressed air to 130PSI.
I also said in my early posts that these cases are at least several times fired in this chamber, but are very old.
I have tried to identify if there is a problem in my case preparation, primer seating technique etc. etc. but cannot find anything.
I did notice that the heavy (normal) strike primers are still ever so slightly set below the case base, but the light strike ones are flush with base of the case, hence the check of the primer pockets mentioned in my previous post. I use either a Sinclair or Lee priming tool. This batch were prepared using the Sinclair and the lever comes to an abrupt stop when the primer bottoms out, so I am doubtful if there was a problem with my primer seating.

The light strike rounds fired exactly like any other of the 300 rounds and I won the most recent competition so at this stage it is not causing me any obvious accuracy problems. However I would like to find the cause, as who is to say if it won't cause future problems.
Regards - Philip

johnk
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Re: Several primers not showing much pin strike

#68 Postby johnk » Fri Nov 24, 2017 8:35 am

Philip,

Have we been missing something here?

Were you saying that the ones that you designate as being light strike nevertheless fired normally and weren't misfires or hangfires?

if that is the case, then Keith is probably correct. The firing pin spring has lost a small degree of its strength allowing the primer, subsequent to ignition to force the firing pin back flattening the pin crater. That it occurs only occasionally suggests that there might be marginal differences in primer pocket dimensions allowing the occasional looser one to expend more of its energy moving rearward during combustion rather than being restrained against the pocket wall, the consequence of which is it has remaining energy to push the crater flat again.

John

Matt P
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Re: Several primers not showing much pin strike

#69 Postby Matt P » Fri Nov 24, 2017 10:39 am

Have you contacted Maddco ??

bainp
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Re: Several primers not showing much pin strike

#70 Postby bainp » Fri Nov 24, 2017 10:58 am

I have been trying to contact Neville Madden to buy a new spring. He is not answering his phone today but I will continue trying.
I have now photographed inside of the primer that was in my post from yesterday. It looks on the verge of blanking up the firing pin hole.
Inside primer.JPG

Can a weak firing pin cause this?
I would have thought excess pressure would be the most likely cause. But I am not losing cases to primer pocket expansion and 296 cases didn't show any problems out of 300 fired at the last matches.
Philip
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Barry Davies
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Re: Several primers not showing much pin strike

#71 Postby Barry Davies » Fri Nov 24, 2017 12:05 pm

G'day Phil.
I would check your firing pin fall. This is a function of where the trigger picks up the cocking piece. You can have sufficient protrusion and spring tension but if the fall is a bit short misfires occur due to the firing pin not having sufficient energy to detonate the primer. The fall as such may be right on the minimum and coupled with a few thou variations here and there you get misfires some of the time.
I am not totally familiar with the Maddco but would think the fall should be around 5 to 5.5 mm ( guess )
Barry

Jase PTRC
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Re: Several primers not showing much pin strike

#72 Postby Jase PTRC » Fri Nov 24, 2017 12:21 pm

Does your trigger assembly have any free play where it mounts to to the action? I have seen where trigger assemblies are able to move forward under pressure from cocking which reduces the travel of the firing pin and reduces the spring tension causing light strikes.

Jase PTRC
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Re: Several primers not showing much pin strike

#73 Postby Jase PTRC » Fri Nov 24, 2017 12:28 pm

The other thing i have seen is with firing pins that thread into the cocking piece is that over time the firing pin winds its self out and reduces the amount of pressure due to lengthening of the section where the spring sit effectively reducing spring pressure when cocked. In the action i saw this on i was not able to cock this action by hand in either instance.

bainp
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Re: Several primers not showing much pin strike

#74 Postby bainp » Fri Nov 24, 2017 1:31 pm

I think people are getting off the track here.
I have never said I am having trouble with misfires. Other posters have mis-read what I have said and made posts that I am having misfires.
Just a few in every hundred shots show what appears to be a light firing pin strike on the primer, but all fire without any hint of hang up or misfire.
If you look at my photos in previous posts, you can see that normally there is more than adequate strike. It just a few that appear a bit light.
In the last photo I posted, the primer almost got pierced by blanking the primer up the primer pin hole in the face of the bolt. This particular primer that almost got blanked is one of the primers that appears to have a light strike because it is extruding into the firing pin hole.
Does a soft firing pin spring or too short a striker fall cause this?
Philip

Jase PTRC
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Re: Several primers not showing much pin strike

#75 Postby Jase PTRC » Fri Nov 24, 2017 1:53 pm

Bainp See Johnk's last post. I agree that yes insufficient spring tension either from a weakened spring or due to the seated length of the spring changing mechanically as i suggested in my posts could cause this. I have seen it with my own rifle from both issues i listed and easily rectified, Check the things that i suggested regarding your trigger assembly and firing pin where it threads into the cocking piece as you can do this without spending any money and little time.


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