This is for those skeptical of Thunderbolts being "Thunderduds" (Believe me, I was one of them around 40,000 rounds ago several years ago and actually swore them off forever ... But many THR members asked me to reconsider when I started my 10,000 round comparison test ... And I was glad as it was 100% reliable during several thousand rounds of 10/22 and T/CR22 break-in period).
What I did to rule out any firearm related issues like firing pin/fouling/strike issue and accuracy trend verification was to use a known reliable reference ammunition which started out as CCI SV 40 gr LRN (that I use for chrono reference velocity baseline for powder work up) and later Aguila 40 gr CPRN.
I always started documented range sessions where I captured all 5/10 shot groups shot at 50 yards with known reference ammunition and if there was any accuracy/firearm concerns, I would shoot some reference ammunition groups to verify (If reference ammo produced tight groups with no duds, it wasn't the firearm).
So it would be good for the OP @tark to test "known reliable ammunition" so if Thunderbolt experiences duds but not "known reliable ammuition", then we can better blame Thunderbolt for duds.
As to the poll, I say 0 if Thunderbolt lot is fresh and box hasn't been damaged during shipping/transport to move the priming compound away from the rim. But realistically factoring truck suspension/road surface condition/rough handling of shipping companies along with rifle firing pin/spring/channel fouling factors, it may be 0-5. (Now,
if known reliable ammunition also experiences duds ... then it raises further questions about shooting variable )
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For my last round of comparison ammunition testing at 50 yards, scope was zeroed with "boxed" Aguila 40 gr CPRN and CCI SV was shot next to establish baseline accuracy POI vs POA before shooting new brands/lots of ammunition (Green circles were POA and slower velocity rounds showed lower POI from bullet drop). Top row shows my final two zero groups of scope with Aguila to POA and CCI SV groups shows drop in POI from bullet drop (And yeah, slight drifting of POI to left is shooter input on trigger/muzzle) -
https://www.thehighroad.org/index.p...t-shipped-pricing.902560/page-5#post-12304852
Last Aguila group on bottom right was shot to re-verify POI vs POA/accuracy and I say we were still zeroed. (Second Aguila 40 gr group from left on bottom row is new lot of "loose bulk" 250 round pack compared to 50 round "boxed" lot of same lot # I used for reference for all of my 10,000+ round testing ... Yes, I bought A LOT of it to use as reference ammo)
This is what I mean by using "known accurate/reliable ammunition (Of course, I didn't experience any duds during the testing) 
This target shows me "walking up" the "boxed" Aguila 40 gr CPRN groups to zero the scope before shooting the previous target. I later decided to shoot Aguila "Lead" RN groups on same target instead of using a new target (Call me cheap
).
Notice all CPRN groups on top row maintained 3/4" and 40 gr LRN groups on bottom row produced smaller groupings slightly below POA due to slower velocity (Which has been consistent during 10,000+ round testing) except for my input on trigger to push POI to left.
Every last one went "bang"
