I haven't noticed this in reloading other caliber rounds. My 6.5 Grendel hornady cases vary in length from 1.512 to 1.532. Book says 1.515 to 1.525. Strange? none were loaded hot. All reasonable research. 3 diff powders, CFE, 8208, & 4895. Sadly, I didn't separate.
Brass growth Question
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Trim it all once and don't worry about them again until you reach 1.530 length... even then all chambers are different.
I find the Grendel to be very forgiving on brass. I get 5-6 firings with a max charge of 8208 before I have to even think of trimming again.
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There may be wisdom in measuring the distance from bolt face to start of throat. The 1.530" dimension sounds awfully close to the SAAMI minimum chamber length.
Two things happen when the stuff stretches enough to engage the start of the tnroat. Neither are good.
The first is that one may start seeing more frequent failures to go into battery, or difficulty in closing the bolt.
The second is that if those warning signs are ignored the brass has nowhere to go when it should expand to allow the bullet to slide out on firing. That added clamp force can increase pressures by more than 5,000 psi.
If memory serves, the 1.525" recommended case length gives .005 to .007" clearance to assure no contact with the SAAMI minimum throat start.
PS I disvovered this after 10-15 firings with full length size each time.
PPS. I'll check these numbers when I get back to my desk or someone who has the SAAMI dimensions handy jumps on the numbers first. I will edit as needed.
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My copy of the SAAMI drawing shows the chamber neck dropping from 0.3000" to 0.2644" at 1.530" from the breech. These are the minimum dimensions. The max length is 0.015" longer.
The maximum cartridge length per SAAMI is 1.520" with the minimum being 0.020" shorter.shootersnotes.com
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Originally posted by JASmith View Post
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My copy of the SAAMI drawing shows the chamber neck dropping from 0.3000" to 0.2644" at 1.530" from the breech. These are the minimum dimensions. The max length is 0.015" longer.
The maximum cartridge length per SAAMI is 1.520" with the minimum being 0.020" shorter.
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The way I approach this, is to determine the exact chamber length in my barrels, and make sure that the case is .005 shorter than my shortest chamber.
Personally, I don't want to give up any more neck length than I have to. It has been my experience (admittedly limited) so far, that my Grendel chambers have quite a bit of room to let cases grow and it might take a number of firings before there is any problem. I like to have all my cases the same length (after sizing) but some of them need to "catch up" before trimming to as long as I can.
All chambers are a little different and kits consisting of a plug that you seat overlength in a shortened case and then chambering and measuring with calipers, are available.Last edited by Mad Charlie; 10-15-2017, 05:18 PM.
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Originally posted by Mad Charlie View PostThe way I approach this, is to determine the exact chamber length in my barrels, and make sure that the case is .005 shorter than my shortest chamber.
Personally, I don't want to give up any more neck length than I have to. It has been my experience (admittedly limited) so far, that my Grendel chambers have quite a bit of room to let cases grow and it might take a number of firings before there is any problem. I like to have all my cases the same length (after sizing) but some of them need to "catch up" before trimming to as long as I can.
All chambers are a little different and kits consisting of a plug that you seat overlength in a shortened case and then chambering and measuring with calipers, are available.
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