Marlin 336 .44 mag ( micro groove )

[redneck1]

I've had this .44 336 marlin for a good long while now
And I've been using the same load for at least 15 years and its always shoot good .
I've been out of gas checks for awhile and recently acquired a few of the old brass checks.
And my rifle hates them .. Groups opened up to about 10 inches @100 yards .
Other then the checks being brass instead of copper I changed nothing .
Same cases , same batch of unique , same bullet , same batch of lead .
Same lube ...
Anyone had this happen ?

I know the microgrooves can be picky , but I've never had gas checks make a huge difference before .

[Outpost75]

IIRC the old brass Ideal gaschecks do not crimp onto the bullets like Hornadys do. Unless they are a perfect fit on the heel of your bullets, they may occasionally come off and cause fliers. With loads below 1400 fps rifle velocity, using 10 grains of Unique, you do not need a GC.

[Walks]

When I finally ran out of the old Lyman brass gas checks, I switched to the Hornady crimp-on type. Which are probably copper. The Saeco 180gr FN in .38cal shrunk it's groups from 3+" at 100yrds in My Marlin 1894CS to less then 2".
The load was a Max+ with 2400.
Now have some aluminum on hand, looking forward to trying them for accuracy.

[redneck1]

I use gas checks on bullets that have a shank for the check ... Might not always have to , but I've never had to de-lead a barrel either .

No signs of the check coming off either , I dug into the back stop and found 6-7 of the 25 I shot and all still had the check

[bigted]

The harder checks will sometimes seat a little off square. A less then square boolit base will give those erratic groups as the boolit base never exits the barrel in the same location and so if they are not completely square ... those boolits act just like a crooked or damaged crown on the barrel.

[redneck1]

Thats a possibility I guess , eh , whatever it is my rifle doesn't like it .
Guess I'll save a few bucks and go back with copper checks .

[dogmower]

barrel wear?