Old primers ,just as good ,or ,maybe just to get by?for hard times?

[Shootrj2003]

I am shooting reloads right now at 100 yds,loads that have been more accurate before,out of my Marlin 336 30/30, 30.0 gr. 3031 150 gr. Sierra,4-5" groups at 100 yds,using old stock Staynless yellow box(50-60s?) Now,while this would definitely kill the deer,4-5"groups are not my idea of accurate in this rifle,1 1/2" is,the load is at the higher levels yes,but worked up to and used before.,also 170 gr.sierras do better in this rifle, but not that much,It could be the result of the cumulative deficiencies.or barrel wear over time? However the glaring one possibility,unknown primers bought at a yard sale ,60 years old,with unknown storage till I got them.do they work,yes,but not much of a difference could mean a lot for target grade accuracy ,even at 100 yds with a 30/30,for hard times,shtf,to fill the pot good enough not to throw away but I'm thinking not target best shooting grade.
Factory Federal 150 gr. These were more in line , unmeasured,but in the realm of ,2 seperate 3 shot groups,5 rds in ( one flyer)2"- 2.5"and impacted the target higher,still not a great group,but way more livable! I will buy fresh new primers and try the same loads.

[krunchnik]

I genuinely doubt old primers will make that large of a spread.

[Unclenick]

The way to tell if the primers are a problem is with a chronograph. If the velocity SD is not appreciably higher than the commercial loads gave, they are not to blame.

I don't know which of the 336 models you have, but, in general, you want to avoid resting the front stock on sandbags, as the barrel and magazine can be pushed against through it. Try having the bag under the action and, if necessary, the lever to keep it out of contact with the front stock.