I have heard that holes through a primer without any other pressure signs is called blanking. I built a 6.5 Creedmoor, 24" Ballistic Advantage Barrel and a Trybe bolt carrier group. It shot all the S&B ammo fine, no problems. But when I tried my reloads, which were several grains under the max. load, the primers blanked. Then I heard you have to use magnum primers (I'm using Lapua brass small rifle primers) but hadn't seen that in the reloading manuals. I could not get any of the Varget loads to not blank. 135 grain at first, then the 140 grain. Sierra 135, Barnes Match Burners for the 140 grain. No adjustable gas block yet. Thinking that might help. Also, the hole for the gas was too small, researched it, and drilled it out to the proper specs. as per several manufacturers. Works great now for bolt hold open etc. but still blanking. What do you think caused this? I also heard if the firing pin hole is too large, that causes this. Pin looks good, a bit of powder on it of course, but no pitting or damage. Anyone cured this problem before? Thanks for your help. Oh, and when it first happened I stopped, took all that ammo home, pulled the bullets, and checked the powder and it was correct according to published specs. Would loading them to 2.775 instead of 2.800 cause this as well?
Blanking 6.5 Creedmoor
- Thread starter writerman
- Start date
Normally moving away from the lands with all else being equal won't cause that much difference in chamber pressure.
All the brass I have is Lapua, which has a small rifle primer hole. And I bought a lot of it, not knowing. You mean use brass 6.5 that has large primer hole would solve it? You think this condition is dangerous?
It's very undesirable. Gas escaping back into the bolt is always undesirable and a potential safety risk for bl;owing out ionto the shooter's face/eyes, even if that risk is slight in most modern actions. Safety aside, it will eventually erode the firing pin tip and enlarge its hole in the bolt making the problem even worse. From the bolt, it might also be vented into the trigger group carrying fouling and soot and if still travelling fast enough could damage a finely built match trigger assembly.
Also, ask yourself where the little brass disk that's now missing from the primer cup has gone to. Nine times out of ten it follows the firing pin as it retracts into the bolt body. Collect a few inside there and they affect firing pin fall and the strength of its blow onto other primers potentially leading to mis or hangfires - very undesirable.
Been there, got this teeshirt. In my case, it was a rifle rebarrelled to 6.5X47L whose brass is only available in SP form. At that time nobody turned pins down and bushed bolts in the UK, so I had to pay for rechambering to 260 Rem in order to return to large primers.
First, what primers are you using?
What is the reason you drilled out the gas port on the barrel?
It is a 24" barrel with a Rifle length gas system so you have excessive Dwell time already.
You drilled the port to get more gas now you are looking for an adjustable gas block to reduce the gas.
What is the reason you drilled out the gas port on the barrel?
It is a 24" barrel with a Rifle length gas system so you have excessive Dwell time already.
You drilled the port to get more gas now you are looking for an adjustable gas block to reduce the gas.
The gas wasn't enough, and I researched the hole size and found out for 6.5 Creedmoor the hole should be a certain size, which this one was too small. After drilling it out, the bolt locks back perfectly every time on an empty magazine. Hole was definitely too small. Drilled for .223 I think. I don't need an adjustable gas block, I was just ruminating that it might help with the blanking. Everything else works fine. I am using small rifle primers CCI, the number is 400 I think. I wanted to switch to CCI small rifle magnum primers, but no primers are available right now anywhere. I guess S&B factory ammo uses magnum primers, this is why they did not blank and worked perfectly, 40 rounds worth. And you are right, the reason I wanted to make sure the blanking does not happen anymore is to keep everything on the safety up and up. Just trying to figure out why the factory ammo didn't blank and worked perfectly. I was told by Hogdon to use magnum primers.
CCI 400 primers are not intended for your application.
Use CCI450 or Military 41 primers or switch to large rifle primer cases
that have a thicker cup.
Use CCI450 or Military 41 primers or switch to large rifle primer cases
that have a thicker cup.
Your issues with blanking are caused by your using CCI-400 primers which are dangerous to use in AR guns due to slam fire risk, and in your case too thin of cup for the pressures you're running.
You can:
A) reduce your charges to a safer level that does not blank
B) Switch to CCI-450, BR-4, CCI #41, or FGG 205M.
C) Use LRP brass as large rifle primers have the thickest cup material
D) Bush your firing pin to reduce excess gap in the firing pin hole
Because rampant component hoarding is making buying difficult, the quickest way to solve this is to reduce your charges to a level that won't blank and then find a node that works.
You can:
A) reduce your charges to a safer level that does not blank
B) Switch to CCI-450, BR-4, CCI #41, or FGG 205M.
C) Use LRP brass as large rifle primers have the thickest cup material
D) Bush your firing pin to reduce excess gap in the firing pin hole
Because rampant component hoarding is making buying difficult, the quickest way to solve this is to reduce your charges to a level that won't blank and then find a node that works.
You need a "high pressure" bolt and firing pin. AR-10's are known to blow, blank, and crater primers on higher pressure cartridges like the 6.5 CM and 260. This issue is compounded by the use of SRP brass.
Thank you. I think you are right, that was it. If only I had read that in the reloading manuals before I started reloading all these Lapua, and then of course buying them. I will just have to wait until I get some small rifle magnum primers at a reasonable cost. Oh, they're going for what now? A buck apiece? Not likely I will be shooting my 6.5 soon. I will try reducing loads though. Might work. I think the Lapua would be fine with the magnum primers. Have to save it for when sanity returns to buying reloading components. I appreciate the advice and help.
It’s a function of fp hole size, that’s it, done. Trust me. Measure your firing pin tip diameter.
I once built a 6.5x47 on a FN SPR action. Fp diameter on that was .080+. With even mild starting loads I blanked any and every primer. DID NOT MATTER whether mag primer or 7 1/2’s, 450’s, etc. bushed bolt and turned fp to .065”, done....problem solved.
to FIX your problem, either swap out your bolt and firing pin with a smaller fp hole version, or have someone bush the bolt face and turn your pin down.
OR shoot LRP brass.
As an aside, I have also built many custom AR10’s in many calibers to include the 6 and 6.5 creed, 6x47 Lapua, 243, 260, 7-08, 308, 338 Fed, and even a 358 Win. Used Armalite parts on most, and by luck they were the proper one to use for the 6x47 Lapua as they have a smaller diameter firing pin and hole. No issues with blanking.
I once built a 6.5x47 on a FN SPR action. Fp diameter on that was .080+. With even mild starting loads I blanked any and every primer. DID NOT MATTER whether mag primer or 7 1/2’s, 450’s, etc. bushed bolt and turned fp to .065”, done....problem solved.
to FIX your problem, either swap out your bolt and firing pin with a smaller fp hole version, or have someone bush the bolt face and turn your pin down.
OR shoot LRP brass.
As an aside, I have also built many custom AR10’s in many calibers to include the 6 and 6.5 creed, 6x47 Lapua, 243, 260, 7-08, 308, 338 Fed, and even a 358 Win. Used Armalite parts on most, and by luck they were the proper one to use for the 6x47 Lapua as they have a smaller diameter firing pin and hole. No issues with blanking.
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Old Navy
Gold $$ Contributor
Exactly!!!! Been there and done that. Installed a JP high pressure bolt and never had another problem.
Attachments
Snap! That was exactly the rifle model I referred to in my earlier post, also same cartridge. I always use magnum/BR small primers in any mid to high pressure application and changing make/model did not provide a cure. 260 Rem and large primers - mild 'cratering' at the worst with maximum loads; small magnum primers: serious cratering and maybe 10% blanking at starting load charges and pressures.
Rem 7 1/2 BR/magnums in the SPR with 6.5X47L starting loads
Exactly what my primer blanks look like. Some do it, some don't. Today I went out to the range and for 130 gr. Sierra TMK at 32 grains Varget at 2.775 OAL no blanks, 140 Grain Barnes Match burners XBR 8208 29.9 and 31.5 grains 2.790 OAL no blanks, and then 140 Grain Match Burners with 32/33 grains Varget 2.790 OAL no blanks. But I'm still going to get that JP high pressure bolt because I think you are right, it would certainly help. Also, since they're reloads and I bought the ONLY RCBS 6.5 Creedmoor die set I could get, it's for bolt guns, and I need to get the smaller one for semi-autos. Any idea how to do that? LOL! And drilling out the gas tube hole in the barrel was also exactly the right thing to do. Now the bolt holds back, and each round re-chambers, except for the ones still slightly too large in diameter, due to the die set being incorrect. I will correct that. I wonder if the die set specs were also partly to blame for the blanks? Holding the spent case in there too long? Maybe not I guess, because then it would also happen in bolt guns? This is what I love about precision reloading, so many variables, it really teaches you something.......I wonder what? LOL! Oh, and by the way, I love all the info. really appreciate your experience and help. Thanks!
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Ha! If only I could get any of those primers. Have to wait I guess.
205mAR primers for CM and u will solve ur problem and cci 41 will work also .
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