DPMS LR260 Chamber Specs

ctimgo

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Aug 21, 2012
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I just got a new DPMS LR260 and can't find the chamber dimensions anywhere. Would they be SAAMI standard? The rounds I am loading will have a neck diameter of .294 when loaded (243Winchester brass necked up). I know that the SAAMI chamber minimum for a 260REM is .298 so as long as the camber is SAAMI I will be good. I would assume that DPMS would use SAAMI but when it comes to playing with things that do doom I like to be sure.
 
This will be no help to you, but, My GII hunter in 308 has a tight chamber.
If I don't use small base dies, the rounds will not chamber. Maybe you could cast your chamber.
 
Fire a factory round in the rifle and measure. Easiest method and it will get you withing a few tenths to a few thou.

If you need more precise measurements, do as the previous poster suggested and use cerrosafe to cast the chamber.

Most factory rifles are well within saami spec.
 
You are always much better off necking down, than necking up. Necking up thins the neck walls and after seating a bullet may leave you with more than generous neck clearances. Cast the chamber. Mic your loaded rds.
 
Ok I got some factory ammo and the neck measures .291. I know that the brass will be pinned to the walls of the chamber during firing but how much will the brass snap back after expanding during firing? If I know this then I can make a educated guess as to the chamber neck measurement when I measure the fired round.
 
Ok I got some factory ammo and the neck measures .291. I know that the brass will be pinned to the walls of the chamber during firing but how much will the brass snap back after expanding during firing? If I know this then I can make a educated guess as to the chamber neck measurement when I measure the fired round.

It depends on the hardness, thickness, and distance the brass has to expand to meet the chamber. Usually it springs back .0005-.003" on the diameter.

.001-.002 is a practical assumption.
 
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