Gunsmithing 300BLK misfires on CCI BR4 & Rem 7 1/2

st1650

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Long story short I started in the 300BLK bolt game with the AAC Remington SPS 700 which was a mediocre experience (inaccurate, misfires, etc) and since apparently it was a semi-common issue, I switched my handloads to using Fed 205m/CCI 400 only.

then I sold the barreled action and got a Defiance anTI with a prefit thinking it would resolves the issue which I felt was caused by excessive headspace and Remington firing pin size.

the new build actually has a tight chamber and I had to bump the shoulder back on my new brass so that it wouldn't be stiff to close the bolt. Out of habit, I kept using Fed 205m for my loads both subsonic and supersonic and it's been 99.9% reliable.

This week I ran out of Fed 205m so I decided to experiment. I cleaned and dried the bolt, made sure the striker spring had good tension and no debris in the channel.
I tried some 7 1/2 and and CCI BR4 and sure enough I got a good 20% failure rate on the BR4 and 5% failure rate on the 7 1/2. Most of them would ignite on 2nd try but few BR4 did not ignite at all. All rounds were primed by hand and I made sure the primer was all the way in. The primers look like they have a really good dent.

So is this a sign that there could be potentially something to investigate ? It's not so hard to just buy a few Ks of 205m and be done but I did notice that the "magnum" primers tend to have tighter SD with subsonic load so would have been nice to be able to use them. Not sure what else could be done beside a stronger striker spring but then it comes at the cost of a heavier bolt lift.

Trigger is a TT 2 stage set at 1.5 lbs, I use the same trigger on my Nukes and RimX without any issues.
 

st1650

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I may have the same issue with BR4s.
What caliber ?
I’ve cleaned my firing pin and retuned my headspace and set up my hand primer to prime deeper and now have almost no issues with REM 7 1/2 but the BR4s are still problematic.
 

SABuzzard

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Long story short I started in the 300BLK bolt game with the AAC Remington SPS 700 which was a mediocre experience (inaccurate, misfires, etc) and since apparently it was a semi-common issue, I switched my handloads to using Fed 205m/CCI 400 only.

then I sold the barreled action and got a Defiance anTI with a prefit thinking it would resolves the issue which I felt was caused by excessive headspace and Remington firing pin size.

the new build actually has a tight chamber and I had to bump the shoulder back on my new brass so that it wouldn't be stiff to close the bolt. Out of habit, I kept using Fed 205m for my loads both subsonic and supersonic and it's been 99.9% reliable.

This week I ran out of Fed 205m so I decided to experiment. I cleaned and dried the bolt, made sure the striker spring had good tension and no debris in the channel.
I tried some 7 1/2 and and CCI BR4 and sure enough I got a good 20% failure rate on the BR4 and 5% failure rate on the 7 1/2. Most of them would ignite on 2nd try but few BR4 did not ignite at all. All rounds were primed by hand and I made sure the primer was all the way in. The primers look like they have a really good dent.

So is this a sign that there could be potentially something to investigate ? It's not so hard to just buy a few Ks of 205m and be done but I did notice that the "magnum" primers tend to have tighter SD with subsonic load so would have been nice to be able to use them. Not sure what else could be done beside a stronger striker spring but then it comes at the cost of a heavier bolt lift.

Trigger is a TT 2 stage set at 1.5 lbs, I use the same trigger on my Nukes and RimX without any issues.

Have you tried the same loads in a different 300 Blackout rifle? Just to confirm it's the rifle and not the round? I ran into something that sounds similar to what you are experiencing...I worked up a single load to use in a 300 BO SBR AR and SBR T/C Contender and a SBR Rem 700 barreled by SSK/JD Jones. The SSK chamber was tighter (inside SAAMI minimum, but tight). With Lee dies, I ended up oversizing the brass to get the basses to fit the SSK chamber. This caused the same light primer strikes in the SSK 700. Primers looked like they took a good hit, but didn't go off. I tried the same rounds in the T/C and AR. AR ran with no problems. The T/C had a few light primer strikes, not nearly the same as the 700. Dropped the rounds in a LE Wilson case gauge and realized that I had introduced too much headspace and the cases were sliding too far into the chamber to let the firing pin get that last little reach it needed. I switched over to Hornady dies and used the LE Wilson gauge double check. No problems since. I could clearly and definitively tell which rounds were going to miss-fire by looking at the Wilson gauge prior.

Primers were Remington 7 1/2 BR and CCI 400. Same primers that had issues before, now work fine.

Not sure if that's helpful info for you or if I'm describing a different problem.
 

st1650

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Have you tried the same loads in a different 300 Blackout rifle? Just to confirm it's the rifle and not the round? I ran into something that sounds similar to what you are experiencing...I worked up a single load to use in a 300 BO SBR AR and SBR T/C Contender and a SBR Rem 700 barreled by SSK/JD Jones. The SSK chamber was tighter (inside SAAMI minimum, but tight). With Lee dies, I ended up oversizing the brass to get the basses to fit the SSK chamber. This caused the same light primer strikes in the SSK 700. Primers looked like they took a good hit, but didn't go off. I tried the same rounds in the T/C and AR. AR ran with no problems. The T/C had a few light primer strikes, not nearly the same as the 700. Dropped the rounds in a LE Wilson case gauge and realized that I had introduced too much headspace and the cases were sliding too far into the chamber to let the firing pin get that last little reach it needed. I switched over to Hornady dies and used the LE Wilson gauge double check. No problems since. I could clearly and definitively tell which rounds were going to miss-fire by looking at the Wilson gauge prior.

Primers were Remington 7 1/2 BR and CCI 400. Same primers that had issues before, now work fine.

Not sure if that's helpful info for you or if I'm describing a different problem.
I think you’re 100% right
 
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Oldloser

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My headspace on the cases is perfect. There is no difference between those that fired and those that did not. The misfires have deep imprints that match the fires cases. All my ccis fired just fine. I plan to disassemble the rounds tomorrow and look at a couple on the inside to make sure it’s not moisture or something else.

Next step is to put them in an indentical rifle and test as well as put ccis in some of the misfire cases and test. Right now I have a 20% failure rate in the last 200 rounds since I started using BR4s.
 

Oldloser

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What caliber ?
I’ve cleaned my firing pin and retuned my headspace and set up my hand primer to prime deeper and now have almost no issues with REM 7 1/2 but the BR4s are still problematic.
6.5x47. 4th fire lapua brass. Brand new pin btw. But issue began before new pin when I got into my br4 supply
 

Alabama556

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    I had the same experience on my 300blk bolt action built off of a 700. I don’t use anything but fed primers.

    Cci or rem are not reliable.