224 Val 24grs of IMR 8208 XBR behind 80.5 Berger Full Bore. This load was producing 3/4 MOA single-digit S-Ds Virgin Starline brass. I blew a couple of primers out of 15. How much should I drop the charge "?
224 Valkarie Blowing primers
- Thread starter Ironworker
- Start date
If this is an AR you really need to check the firing pin well... I'd replace it for good measure.
Piercing primers in an AR generally damages the firing pin.
Piercing primers in an AR generally damages the firing pin.
Yep drop the charge it's already a bit past max in one book I checked. So drop it at least 1 full grain as max if primers are sometimes blown, and it could be worse on hot days or hot chambers. Also look for other factors that cause high pressures....like seating into the lands. Recommended max charges in loading manuals are not always achieved in our chambers...so as soon one primer is blown...Stop...pull bullets, lower the charge for that powder, and investigate for other causes also.
I was cratering primers in a 6 arc, even in the lower end of powder charges. Eventually I switched to a JP bolt and firing pin. Cratering has stopped in my rifle. Definitely lower the charge weight, exceeding max charge in a semi auto is asking for trouble.
NorCalMikie
Gold $$ Contributor
Stiff load (hotter than needed) and maybe a headspace issue? Cases too short for the chamber, when fired, primer tries to back and gets stuffed back into the pocket by the firing pin and gets pierced (blown).
AR Fireformed . No pierced primers . Seated bullets magazine depth . 2.25 was COAL
Blowing primers and not piercing?
Cut down the gas.
Up buffer weight.
How do you determine/set headspace on your reloads?
Didn't blow primers with the virgin Starline brass you used but does with fireformed reloads?
Cut down the gas.
Up buffer weight.
How do you determine/set headspace on your reloads?
Didn't blow primers with the virgin Starline brass you used but does with fireformed reloads?
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I'll drop the charge by 1 grain. Dang it, the load was producing 3/4 MOA out of an AR.
Fine a lower node. Might find better groups.
Check your brass headspace after sizing. Sounds like excessive bump. Check fired headspace of virgin fireformed brass and then full length size to .003-.004" bump. Check to see that primers are properly seated below the face of the cartridge.
Ned Ludd
Silver $$ Contributor
Were the blown primers in virgin brass? If so, even loads well under MAX pressure can cause blown primers in virgin brass if the headspace/clearance is sufficient, as other noted. If this is what's happening, drop the charge weight until you find the next lower accuracy node. Then use that reduced charge weight as a "fire-forming" load until the brass has all been fire-formed. Then you can re-size the brass, bumping the shoulders back only a couple thousandths or so, and work the load back up. If the blown primers were happening in virgin brass at pressures/charge weights below MAX, you may find that once it has been fire-formed the issue will disappear.
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