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05-01-2008 | 09:47 PM

#7

Underclocked

Nontypical Buck

Joined: Feb 2003

Posts: 3,092

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RE: Length of 209 primers

Cheddite - .284 to .288
Remington .... .291 to .292
Winchester..... .297-.302
Federal.. .298

those are the numbers I've collected so far. It would seem that Winchesters of any variety are the longest.

Take notes, this could be important.

OK, the reason I'm asking is the lock up of certain guns will result in more or less gap between the action/bolt face and the primer depending upon the brand of primer chosen. My KP1 is such a rifle and it seems to me the breech plug needed a bit more length to achieve a good fit of primer to action. Because the plug is magnetic, the primer is fully drawn into the hole so a gap remains. This would result in ignition causing the 209 to be moved rearward enough to prevent any sealing action inside the pocket of the plug. Even the Win209s are not long enough to make contact.

My guess is this variance in primer dimensions (both length and width, but primarily

length) is the root cause of a lot of needless blowback in many guns. The manufacturers cannot design the plug clearance properly as a result. So they allow too much rather than too little in many cases. Several Pro Hunters I've read about are very sensitive to the primer length issue - and I think that is probably a good thing once the owner realizes it. If the action won't close using Winchester primers, try another brand (ideally in order of decreasing length) until you find one that fits just right. In the case of my KP1, there isn't a primer on the market long enough.

I'm wondering what would happen if I put one layer of clear tape over the primer...

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