Help Diagnosing Misfires

[scyzer]

Hi All,

I'm looking for some advice on how to start diagnosing a very high proportion of misfires (most recently 5 out of 20 rounds) with, unfortunately, a very high number of variables that have changed.

In summary:

• I've received my re-barreled rifle back from my gunsmith
• My bolt and firing pin assembly have been micro-slicked
• I'm using virgin 223 brass (ADI), unsized but I have expanded the necks to make them more uniformly round
• I'm using a new batch of CCI BR4's (hoping this isn't the issue as I've got almost 1000 left)
• I'm using the K&M Deluxe Priming tool and have been priming with 2 thou crush - calibrated each time
• I used a K&M small primer pocket uniforming tool - I have not changed the depth setting from factory which is currently at 0.1210-0.1215" measured using my Mitutoyo (seems like it's within spec)
• I'm seating VLDs with 5-10 thou of jam

I've worn gloves every time I've primed so I don't think my issues been caused by contamination.

I had initially thought that the seating depth would largely avoid headspacing issues with the new brass (please let me know if this is an incorrect assumption).

I have cleaned the firing pin assembly and bolt and I have included pictures of the misfired primers (please let me know if these seem like light primer strikes).

Factory ammunition exhibits no issues.

I am thinking that I'll need to go test each variable but where should I start?

Any guidance would be very much appreciated!

Collin

(Links below rather than enormous pictures)

http://i.imgur.com/ErEe4Aj.jpg
http://i.imgur.com/tSBcaH7.jpg
http://i.imgur.com/EVWXdjM.jpg
http://i.imgur.com/QVGnT7E.jpg

 

[ab_bentley]

Those are good solid hits, I would put the primers in suspect. By chance are you running a lightweight fringing pin?

 

[243winxb]

What action? Check firing pin protrusion. Maybe replace firing pin spring with a factory one.?

Low velocity of the firing pin causes a lot of misfires.

 

[Mikemci]

I would press those primers out and do the hammer test on them.

 

[scyzer]

Thanks all for the help so far.

Tikka action - stock firing pin. Is there an easy way to measure protrusion of the firing pin? Currently thinking I'll measure the gap to the bolt face and deduct the gap to the firing pin from the front of the lugs.

 

[243winxb]

I'm seating VLDs with 5-10 thou of jam

Factory ammunition exhibits no issues.

Try reloads without a jam. The firing pin strike can be absorbed as the bullet is pushed into the case. Light neck tension makes it worse.

Savage actions - The firing pin strike can set the 223 shoulder back .006" The new brass will be stopped by the extractor.

 

[chop house]

I'm using a new batch of CCI BR4's (hoping this isn't the issue as I've got almost 1000 left)

first, i am not pointing to the br-4s, i am simply pointing out there was recently an extensive thread on the site about them specifically. don't have the link, sorry

second, when i start to get cratering on loads that i know are not too hot, with certain rifles, i switch to br-4s because the cup is thicker (thus 'harder')

lastly, there were comments on referenced thread about contamination occuring by the reloader, and seemed they leaned toward - ya almost gotta spray em with wd-40 to screw em up - to paraphrase.

have you checked the datum lenth of your virgin brass?

 

[spclark]

Start with verifying re-chambered headspace against your brass length. New brass is often way short of spec, you need to know where it sits in your chamber once you close & lock bolt, otherwise everything else you check will have no relevance to the problem.

 

[JLT]

Those are good solid hits, I would put the primers in suspect. By chance are you running a lightweight fringing pin?

I'm with ab_bentley on this one. The strikes appear to be more than adequate to light a primer. A weak spring would not leave such an impression on a BR primer cup. Bad lots sneak by QC now and then.

 

[243winxb]

• I'm using the K&M Deluxe Priming tool and have been priming with 2 thou crush - calibrated each time

• I used a K&M small primer pocket uniforming tool - I have not changed the depth setting from factory which is currently at 1.210-1.215" measured using my Mitutoyo (seems like it's within spec) I'm using virgin 223 brass (ADI),

 

[scyzer]

Whoops - typo.

0.121" - 0.1215"

 

[243winxb]

No Shoulder, & it still Fired - Shoulder not needed to fire a primer. Savage Axis 223- TEST- Cut case off behind the shoulder. Install new primer in fired case. Load into rifle using a cleaning rod to place case head in bolt face & under the extractor. REMOVE CLEANING ROD BEFORE FIRING. Did this 2 times. Both primers fired when the trigger was pulled. 1 case ejected normal, the other did not. Some firearms will need the shoulder, some dont. The extractor must keep the case head from moving forward to much.. Firing pin protrusion can be as much as .055" Its going to reach the primer. If you bulge the neck or shoulder by over crimping, 2 things may happen. 1.A Misfire from a bulge in the neck/shoulder junction.. This will cause the firing pin strike to be absorbed, as it pushes the neck deeper into the chamber,but only if the cartridge head clearance is large/loose.

 

[scyzer]

Start with verifying re-chambered headspace against your brass length. New brass is often way short of spec, you need to know where it sits in your chamber once you close & lock bolt, otherwise everything else you check will have no relevance to the problem.

Thanks - I might deprime the two rounds tomorrow and do a relative comparison of the shoulder/case head measurements (using the LE Wilson tool so I can't get exact readings) and will compare it against fired brass for reference.

 

[NorCalMikie]

First thing I would be looking at is the BRASS!! Jam those bullets maybe .020 + to hold the case head back against the bolt face. Once fired, make sure you're not pushing the shoulders back too far to cause the same problem again. Forget the primers or firing pin spring till you get the brass length sorted out. Not going to cost you anything that way.

 

[HTSmith]

So I will take a guess, and I'm keying off the fact that you are having no issues with factory ammunition. I suspect it is related to uniforming the primer pockets and the seathing of the new primers. I'm of the opinion that primers should be seated by feel--seated until they reach a firm stop and no further. By using too much force/crush you can render the primer useless. On the other hand seating to an arbitrary depth may not be bottoming the primers. It is also possible that the uniformer is cutting too deep. You might try loading several without touching the primer pockets and seating the primers by feel and see how they work.

 

[dkhunt14]

I would believe it to be headspace on the case is short. Yes that primer hits look good but they also were not hit with big psi and flattened some. That would make them look deeper them they are. Anytime a primer doesn't fire, the hit looks deeper. The BR4 is the hardest thickest cup of all primers so it is harder to ignite when things aren't right. Matt

 

[Webster]

Hi All,

I'm looking for some advice on how to start diagnosing a very high proportion of misfires (most recently 5 out of 20 rounds) with, unfortunately, a very high number of variables that have changed.

In summary:

• I've received my re-barreled rifle back from my gunsmith
• My bolt and firing pin assembly have been micro-slicked
• I'm using virgin 223 brass (ADI), unsized but I have expanded the necks to make them more uniformly round
• I'm using a new batch of CCI BR4's (hoping this isn't the issue as I've got almost 1000 left)
• I'm using the K&M Deluxe Priming tool and have been priming with 2 thou crush - calibrated each time
• I used a K&M small primer pocket uniforming tool - I have not changed the depth setting from factory which is currently at 1.210-1.215" measured using my Mitutoyo (seems like it's within spec)
• I'm seating VLDs with 5-10 thou of jam

I've worn gloves every time I've primed so I don't think my issues been caused by contamination.

I had initially thought that the seating depth would largely avoid headspacing issues with the new brass (please let me know if this is an incorrect assumption).

I have cleaned the firing pin assembly and bolt and I have included pictures of the misfired primers (please let me know if these seem like light primer strikes).

Factory ammunition exhibits no issues.

I am thinking that I'll need to go test each variable but where should I start?

Any guidance would be very much appreciated!

Collin

(Links below rather than enormous pictures)

http://i.imgur.com/ErEe4Aj.jpg
http://i.imgur.com/tSBcaH7.jpg
http://i.imgur.com/EVWXdjM.jpg
http://i.imgur.com/QVGnT7E.jpg

Not sure what you mean by .002" primer crush. There is no spec to seat primers .002" below the case head. That number just insures the case head touches the bolt face so you don't get slam fires. I have no problem with BR4 primers. A year ago I solved a FF by carefully adjusting my priming tool. I was pushing to hard and damaging the primer. The primer cup did not look flattened but I was pressing very hard. I must have damaged the thin wafer of priming compound. Not sure but I think the priming compound is brittle and you can crack it. I use a RCBS pocket uniformer and seat by feel. The push rod on my LEE priming tool protruded about .040" as it comes from the factory. It's adjusted now so it protrudes about .025" No misfires since this change with about 1000 shots Rem 7 1/2 and BR4 primers. It's difficult to measure pin protrusion with a caliper. The actual setting depends on shell holder dimensions and clearance to insert the sell.

 

[MGYSGT]

I had a similar problem with new unfired LC brass. Turns out the shoulders were too short. Try it without expanding the necks prior to loading the new brass.

 

[fyrewall]

Those primers looked like they were wacked real hard and deep having a normal looking firing pin dent; this would indicate a normal firing pin force and protrusion beyond bolt face; this would also indicate normal head-space. You did say factory ammo worked OK? I have never seen new factory brass that had grossly excessive head-space.

What's with the "2 thou crush"? Does this mean the little primer anvil was pressed back .002 into the primer body? What about seating depth - bullet or primer? Webster got this out while I was working on this post.

Possibly, upon primer seating the primer's explosive body was gently pushed aside leaving no explosive lead whatchamacallit between the inside primer cup and top of anvil and thus nothing to hit/explode upon a firing pin dent - this is pure speculation. Every miss-fire that I have ever had with uncontaminated primers was caused by inadequate concussion like shallow or weak firing pin hits. Any chance of oil or some type of glop inside primer pockets.

Another possibility is the "sweet spot" that CCI talks about. What this apparently means is that the primer anvils are shaped to allow off-center pin hits/detonation but your firing pin dents look like they are centered real good.

Possibly you might try randomly selecting 20 or so primers out of the brick of 1000 and seat these not as deep but still slightly below flush and trying them. If another rifle that uses small primers is available try the primers in that. Occasionally, I call and talk to CCI people about stuff and despite my dumb questions they treat me nice.

My priming operations compared to yours are crude and hasty but the primers go off with a 99.999 probability. Possibly, you might try omitting a different separate detail step while priming lots of 10 or so and ID those with a felt tip pen.

You are to be commended on wearing gloves (nitrile?) during your ammo production ops. Best to keep those nitrates and explosive lead whatchamacallit traces off your hands for any number of reasons.

 

[scyzer]

Couldn't resist doing an experiment before going to bed (it's 2am in Australia) - to all those who said headspace: well done!

The two rounds were 20 thou under the shoulder/case head length versus the fired brass. I'll sort my new brass a little better going forward.

Fingers crossed this resolves everything - if not, many tests ahead...