Winchester White Box 62gr Cases too long??


I have 940 rnds of this stuff Factory sealed 20 rnd boxes. I have shot 6rnds in my AR and the primers come out flat; hot due to long case 'pinning' the bullet in chamber.

Anyone heard of this for factory Winch. White box?
It's non-magnetic labeled 223 Rem 62gr FMJ USA223R3...

Edit: Standard case length 1.760
This White box 1.768 .008" longer than max case OAL ????
Don't think it's "pinning".

.223 chamber reamer cuts the base to case mouth dimension to 1.7720" and 5.56 reamer cuts to 1.7750". This is more than enough room for the case dimension you posted. .004" if your barrel has a .223 chamber and over .030" of "spare room" if the barrel has the 5.56mm chamber.

The problem is more likely the Winchester primers that are softer than all the other manufacturers for some reason. I have had Winchester primers flattened out with loads that were "starting loads" in the spec's. Military loads usually use a different primer designed to be a little more durable and with controlled sensitivity (like the CCI #41's) to prevent Slam-Fires. These primers are most likely just run of the mill Winchester civilian Small Rifle Primers.

Take a micrometer to the base of the cartridge, just above the extractor groove. Record this measurement and then fire the round. If the base doesn't increase in size you don't have a pressure problem with the cartridge. Just make sure to measure as low as possible so you are measuring the solid part of the case.

Assuming your comment "non-magnetic" referred to the bullet as well so they shouldn't be SS-109's. If so they are definitely not NATO so again, it's probably just soft winchester primers that are making you think you have high pressures.


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