Fecked up

[auquhollie]

Last week i made up some new rounds with new lapua brass (243AI). After uniforming the primer pockets and chamfering the necks i primed and filled the cases as usual. I used a new primer this time as i can no longer get the 210 match. I am onto cci Magnum primers, are these ok in 243 AI ?????

 

Well i went out to the farm and fired off a few. I was really just going to fire form some new brass. After a few rounds i was getting missfires. The primer had a very small indent on it. i assumed it was the firing pin or pin spring that was buggered so i ordered and fitted it today. I decided to get out to the farm and finish fire forming the brass. The gun would not fore off some of the rounds.

 

So what is going on ?.

 

The only things i can think of is either :-

 

A, I pushed too hard (used a battery drill) when uniforming the primer pockets and have made the pockets too deep. There fore now the primer sits to low and the pin isnt stricking it hard enough.

 

Or

 

B, The spring / firing pin i just fitted is faulty ?.

 

Or

 

C, The new primers i have just bought CCI Magnum are not suitable for 243 AI.

 

Has anyone ever uniformed primer pockets and gone in too far causing missfires ?. I really did push when i was milling out the pockets .

 

I await your reply's

 

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[ejg223]

If you take the bolt apart and drop the firing pin in, how far does it look out.

Had a friends ruger that was just caked up and the firing pin just didn't

protrude out enough.

edi

[auquhollie]

Cheers mate,

I will have to go have a look see.

 

The pin was out wednesday as i replace the firing pin and spring so it was all cleaned then. It is strainge how it fired half the rounds but not the other half.

 

Is it ok to use a magnum primer in a 243

 

Im convinced that when i reemed out the primer pockets i really pushed in with the uniformer tool and im thinking i took out too much brass. It shouldnt have though as the tool has a no go shoulder to stop this happening.

 

Having a look earlier you can feel the difference between the shot and missfired primer heights.

 

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[Guest varmartin]

A tolerance of up to 0.010 ( 10 thou ) below the case head is acceptable.

 

I doubt very much they are seated too low as the firing pin protrusion of up tp 60 thou will set off the primer reliably.

 

I had this exact same problem a while ago....try lifting the bolt handle just off its seat and fire a dummy round with just a primer in the case.

 

you do not need to load rounds with powder and bullets to fix/trace your fault..

[John MH]

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Since you are using LAPUA my only advice to you would be not to bother with primer pocket uniforming as it is probably not necessay given the expected quality of the virgin brass. I doubt that you would see any tangible gain in accuracy by uniforming already pretty uniform primer pockets although I can understand the logic for doing it on lower quality brass.

 

John MH

[Guest wireviz]

[i would just like to add i once had a similar problem when i first started and it was put down to contamination by my own hand touching and picking up the primers can make them useless .Or the primers could have got damp some were else try some new primers it don't cost much for that test ps don't finger them it always gets you in trouble and leaves a nasty smell on your paws.

[craigyboy]

Could it be you havent got the bullet jammed into the lands? Therfore with the ackley chamber the case head is not pushed against the boltface? I dont know if the bullet needs to be jammed when forming brass for a .243 ai but it could be the cause the light strike and I do know some wildcats need it to ensure proper forming.

[Vermincinerator]

It sounds to me as if you have a headspace problem caused by your ackley chamber being cut to deep.

An Ackley chamber should be cut .004"-.007" shallower then the standard chamber, when done correctly you should feel some resistance on closing on the bolt.

If this resistance is present you will not need to jam the bullet hard into the lands.

The fact that your rifle fails to fire many of the cartridges tells me that the firing pin is pushing the case further enough forward for it to not have any effect on ignition.

Take your rifle to a competant smith and get him to check the headspace with a set of 243 Ackley headspace gauges.

 

Ian

[eldon]

Besides what Ian said the CCI primers are known to be harder.

When I started loading for my 222 the factory ammo had no misfires yet the first homeloads with CCI primers had about 8 out of 24 misfires. I replaced the spring and all was well.

Maybe the harder primers are just showing up other weaknesses in your system.

[auquhollie]

Cheers for the rplys lads.

 

I dont think it is a head space problem. after speaking to a forum member today i made up some un-formed cases with the tip right out into the lands. I also primed up some cases with just a primer and no powder. When i tested them i had 1 missfire out of five with the empty cases. And 1 missfire out of five with the loaded cases (tip well into the lands).

 

I also swapped the firing pin and spring from a mates rifle into my bolt and tried firing the miss fired cases. They still miss-fired.

 

I am completely stumped. It is something to do with either the new batch of cci magnum primers and the new un-fireformed cases.

 

This is the only thing that has changed in the set-up, both rifle and ammo.

 

I keep coming back to the fact that when uniforming the pockets i used a battery drill and really pushed hard maybe taking a bit too much brass out. When i spoke to Martin today he thought this shouldnt be a problem as the fire pin protrudes out of the bolt face a fair bit. Maybe combined with the un-fireformed cases not touching the sholder (ie) too much head space and too much brass taken out of the primer pocket is causing it to strike light. Like whats been said itspushing the case forward instead of striking the primer.

 

Who knows, sertainely not me.

 

Off to order some new brass and rule that one out. Will try some softer primers as well.

 

All the best.

 

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[Andrew]

Have you checked to make sure there is no drag on the firing pin/striker? One of my rifles was acting up in a similar manner and I found that the over-travel adjustment was set too fine. The sear was dragging as it was coming off. I don't know what rig you're shooting but it might be still be in the ignition system.~Andrew

[craigyboy]

In my experience with over seating primers I found with some cheap soft brass and some serious hamfisted work on the priming tool I was able to push primers as deep as 0.013 when I got to the range and tested the ammo misfires happened on all primers seated over 0.011, the pin still struck and looked like it struck just fine but obviously not enough, of course I had done this as an experiment, it wasnt just a combination of inexperience and my iron grip . Just thought this may have been some use to you.