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Discussion Starter #1
I have developed a good load for accuracy (Sub 1")
75 grns RL 22 for Nosler Partition. Using Winchester Brass.

When I use the brass for the second time Gun is inaccurate
(3" group), [I reload in other guns, no such problem]. Any ideas or explanations.

The gun seems snappier and maybe more recoil, does this make sense. The gun is awesome with new brass.

Gun is a 300 win Mag from Sako in Stainless synthetic.

Could one round case the case to stretch enough to cause this problem?
 

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The Troll Whisperer (Moderator)
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Yes, two firings of a belted case can cause enough stretch to cause the case to be past maximum OAL.

See my answer to this same question on The Firearms Forum,
 

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Beartooth Regular
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kdub is quite right! I had a 7mm Mag that would move the shoulder forward a good .035-.040" on the first firing with new brass. It seems that manufacturers feel comfortable supplying a long chamber since the round headspaces on the belt.
The only way I found to make brass last and remain accurate was to buy brass new, then seat a bullet HARD against the rifling with a starting load of powder to fire-form the brass. This will form the brass without stretching it any in the web area. Then, set up your resizing die so that it does not push the shoulder back at all. The bottom of the die will be off the top of the shellholder several hundredths of an inch, more than likely.
Once formed this way, the brass should last through five or more reloadings and provide good accuracy. After the initial fireforming you should seat your bullets normally.
Try this and see if it helps! Let us know. IDShooter
 

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Discussion Starter #4
Thanks kdub and IDSHOOTER

I Have Shortened all of my cases to 2.165 (.005 short of speck) plus or minus .oo5 and Lets assume thatcase
stretching is the culprit ... I am in Canada and its 12 below
celius today so we will take a few weeks getting back with anb update

Thanks for the help.
 

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Dry Powder, You may want to try another sizing die. My .300 Win was never more than acceptably accurate and I chalked that up to the factory barrel. Then a buddy gave me half a box of factory ammo and it got a lot better in the accuracy department (hadn't fired anything but reloads in years). I bought a set of Lee dies at $12 and now have a rifle that's gone from almost 2MOA to 1.25" groups at 100 yds.
 

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Discussion Starter #6
Big Ed

My original post
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I have developed a good load for accuracy (Sub 1")
75 grns RL 22 for Nosler Partition, Using Winchester Brass.

When I use the brass for the second time Gun is inaccurate
ie 3" groups.
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also feels like it is too "snappy", I have found that the cases
did stretch more than 1/100's in some cases actually
2/100's after initial firing in other cases.

Since I use the same dies (Redding competition Full Body)
on new brass I have guessed that dies are not an early
favorite as something to look at. Although case stretching
is not extreme (new brass is 2.6150 and I have trimmed to that, I think I'am going to try the effect of trimming then try reducing the loads if that fails, I will be looking for new idea.

This gun was very fussy in about factory Ammo returning
2" to 2 ½” inch Mao's. But with new brass and either
180 grain or 200 grain Nosler partition it performs very well
at under 1" Mao, which is the best among my friends on a 300. We used the gun last year in a factory class event at a large club event and placed 4th. This was the only non heavy barrel gun in the contest.

Now that you got me talkin' the gun performed very badly (with new brass) on 200 gr Swift bullets, could check my notes but did not make a lot of sense when it shot 200 gr Nosler so well. I was using 72 gr RL 22. Who knows till the weather
breaks.
 
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