Blowing primers query

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timothi3197
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Blowing primers query

#1 Postby timothi3197 » Sat Dec 19, 2009 10:23 pm

Giddsay, blew four primers in a row today(lucky I had safety glasses on for the last one) before the last one blew some crap down the firing pin hole, jammed the pin and it was broken on extraction.
The load is 25 grains of 2208 behind an 80 grain AMAX with a .010 jump. The cases have been neck sized twice and are fire formed to the chamber. The primers are PMC(russian) small rifle, the cases are remington.

This is a .223 conversion on an Omark action, I have always thought the firing pin fit was a bit loose and the spring a bit weak but was told by the gunsmith it was ok?. Even with the light running in loads(25 grains 2208 behind 50 grain noslers) the primers seemed to have a raised crater.

I remember reading somewhere here that the .223 bolt heads didn't match the old firing pins that well, does anybody have the dimensions or any advice?

I have pulled the remaining rounds and weighed all the charges they are all 25 grains or a smidgin less.

Kind regards,
Tim

Simon C
Posts: 422
Joined: Wed Jun 22, 2005 9:43 pm
Location: Adelaide

Primers

#2 Postby Simon C » Sun Dec 20, 2009 5:32 am

Gday mate,

Sounds like the firing pin hole may need to be bushed.

I'm sure the 223 experts will chime in though. I know that many people also choose 2206 for this cal too. Maybe it is powder related?? Or u got a bunch of soft cupped primers
"Aim small, miss small"

Simon

Malcolm Hill
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Joined: Fri Aug 25, 2006 9:40 pm
Location: Mid North S.A.

#3 Postby Malcolm Hill » Sun Dec 20, 2009 7:51 am

Tim
Your problem is quite common with the Omark converted to 223. There are a few issues that cause it. The original firing pin diameter is not always the culprit, it is more so the actual clearance of the pin in the hole. If it is a sloppy fit it will usually cause cratering of the primer. This can be reduced by using either the Remington 71/2 or CCI br4 primer which have a thicker cup and handle the higher pressures better as well as making sure the firing pin spring is in good condition. Bushing the bolthead and reducing the pin diameter back to around .060 thou is another option and the later production boltheads already have the smaller hole. The other thing is don't just assume that a load of 25 gns of 2208 will be ok in your rifle because other people use it. With the tight spec chambers and bore dimensions that are being used these days that load can be on the warm side in some rifles. I have two rifles that are happy at 24.8 gns for around 2950 fps and going up to 25 gns gives just over 3000 fps (30 inch barrels) but also gives measurable case head expansion with Lapua brass. Other rifles are quite happy to digest over 25gns without problems so I would suggest you try and chronograph your load to see what it is getting. From my experience anything over about 2950 will result in reduced case life or problems with sticky extraction in Omarks.
Regards Malcolm

david262
Posts: 5
Joined: Sun Jan 08, 2006 3:54 pm
Location: north coast nsw

pmc primers

#4 Postby david262 » Sun Dec 27, 2009 7:55 pm

From what I have read on US forums the standard PMC primer is too soft.You need to use the magnum version as it has a thicker cup. The standard is good for 222's and hornets.

timothi3197
Posts: 191
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Location: Australia

#5 Postby timothi3197 » Sun Dec 27, 2009 8:59 pm

Thanks Fellas, I bought 100 BR4 primers and will try them shortly, I have had a look at some fired .222 cases that had a mix of winchester primers and these PMC ones and with the same load the PMC ones are flattened but the winchester ones still have a rounded edge- definately points to soft primers. I am also waiting on a new firing pin spring as well, the old one is very weak compared to the one out of my .308.

I will let you all know how I go, if I don't get a good result I will send the whole rifle to one of the mainland firms to have a look at.

I am resurrecting my .308 for the club prize meet just in case(just have to put another scope on it and load a few rounds)

Kind regards, this is a good place for sensible advice. :D

timothi3197
Posts: 191
Joined: Thu Oct 16, 2008 9:46 pm
Location: Australia

#6 Postby timothi3197 » Sun Jan 03, 2010 8:48 pm

Update- I made some up with BR primers and then couldn't get consistant ignition. Finally put my old .308 spring in the .223 bolt (3/4" longer for the same count and wire diameter- 4.997") and most of my problems are now gone.
I have a spring on order from MAB and when the season is over will get the bolthead bushed to .060", it is currently a light clearance fit to a .072" firing pin, same as my .308.

Now the trigger is being painful and I have to run excessive sear engagement due to wear on the surfaces so it is very creepy.

I will get a two stage Davies on the way tomorrow.

Woody_rod
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#7 Postby Woody_rod » Mon Jan 04, 2010 10:04 am

For the amount of money you will spend on getting your bolt head bushed, I would recommend changing the bolt head, firing pin and spring as a system to new units made by Total Solutions Eng. (MAB is their barrel brand)

This way, you get the latest version of the bolt head, smaller pin diameter and a new spring - and they fit together nicely unlike the originals. Of course, if you change the bolt head, the headspace may not be the same.

Oh, and most people in WA use CCI 450 Magnum primers for 2208 or 2206 powder. We have used up to 26 grains of 2208, and others using 25 grains 2206 with no problems with primers or extraction (or case life), but I would not recommend it for an Omark.

Malcolm Hill
Posts: 328
Joined: Fri Aug 25, 2006 9:40 pm
Location: Mid North S.A.

#8 Postby Malcolm Hill » Mon Jan 04, 2010 12:31 pm

Rod
The CCI 450 also gets a bit of use in the 223 over here and I currently use it in one rifle. Surprisingly though I've found that the Remington 71/2 gives higher velocities in the same loadings. I don't know that I"d like to be too close to anyone using 25 gns 2206 behind an 80 grainer in any rifle, not just an Omark. ADI lists 22.5 as a maximum and I'd be sure case life would suffer regardless of what action it was used in.
Regards Malcolm.

timothi3197
Posts: 191
Joined: Thu Oct 16, 2008 9:46 pm
Location: Australia

#9 Postby timothi3197 » Mon Jan 04, 2010 5:47 pm

Just a quick note, and I will copy as well to a proper thread in the technical section for others future reference:

Just got a new Omark firing pin spring fron TSE today,

New length is 5.364", 33 turns of 0.055" wire with an OD of .395" (average)

Older but still functioning length is 4.997" same turns, outside diameter and wire thickness.


Old (definately doesn't work properly) length is 4.829" , same turns and .400" average outside diameter.

Big question is at what length should they be changed?

Woody_rod
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#10 Postby Woody_rod » Mon Jan 04, 2010 10:30 pm

Malcolm Hill wrote:Rod
The CCI 450 also gets a bit of use in the 223 over here and I currently use it in one rifle. Surprisingly though I've found that the Remington 71/2 gives higher velocities in the same loadings. I don't know that I"d like to be too close to anyone using 25 gns 2206 behind an 80 grainer in any rifle, not just an Omark. ADI lists 22.5 as a maximum and I'd be sure case life would suffer regardless of what action it was used in.
Regards Malcolm.


I certainly don't recommend the load either, but that's what this guy uses. Not sure about case life, probably not that great I agree.

The action won't be harmed by this load, it has another few dozen tonnes + to go before it gets anywhere near its maximum pressure rating. The barrel and/or case would probably let go a lot sooner.

timothi3197
Posts: 191
Joined: Thu Oct 16, 2008 9:46 pm
Location: Australia

#11 Postby timothi3197 » Sun Jan 10, 2010 7:42 pm

Update, I fired 37 shots yesterday using a new firing pin spring spring, BR primers and 24.8 grains of 2208. No misfires, craters or blown primers, I will still get the bolt head bushed when I finish for the season(next week is the last shot I will have I reckon) but it got me through yesterday with respectable scores (under the conditions) which is all I was after.
:D
Thanks,


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