old ammo vs new ammo

[jhalcott]

A friend and I have talked about this. What could cause a difference in accuracy/velocity with ammo loaded several years ago and that loaded today? Same 8 pound can of powder and other components,also same. He thinks it's the powder deteriorating in the case. I think it's the stick powder breaking up from rough handling. Like bouncing around on the floor of the truck while hunting.Todays powders are built to last and do. I noticed that when I used 4831 in my 6mm and hunted groundhog's every weekend, I would get some pressure signs and misses in Sept/Oct. I'd load all my ammo by the first of May.Some ammo would be left over naturally. Groups with it did NOT always go into the 1" or less I expected.

[zasxcd]

I can't completely rule out powder deterioration, but would also suspect bullet alignment. Another possible suspect would be seating depth.

[stimpylu32]

Boy it could be a ton of diffrent things , could be the powder but not likely .

Some things that come to mind are case OL , were they all trimed to the same leingth ?

Was the same box / lot / brand of brass used ?

Were the powder charges all weighted or just despenced from a powder thrower ?

Were the loads all made at the same time ? could be bullet seating depth was changed from loading to loading .

Was the same box / lot of bullets used for all loads ?

Were the loads exposed to drastic temp. or moisture changes ?

See what i mean .

stimpy

[beemanbeme]

Depends on how much change in the accuracy.  I think the pressure signs tell the tale however. It's caused by a change in temperature.  A while back I shot some 7mag ammo that I had loaded up 16 years ago that had made two trips to WY and had been sitting in a ammo locker in an unheated shed the rest of the time.  It shot just like it did when I loaded it. 

[jhalcott]

  While I do not get as nit picky as my friend,(HE thinks every bullet should go thru the SAME hole) I do load target/varmint ammo to sub inch accuracy and a consistent velocity =/- 25 fps. My deer ammo falls into the 1 or 2 inch group category. When I changed to ball powders ,those fliers and pressure signs went away. He shoots a custom 300 Mag with handloads. I have seen his groups,and they are always sub inch at 100 yards. Sand bags ,rest and a 12x scope with a VERY sturdy table. I am not sure what powder he uses.
   What gets me is those pressure signs are not always accompanied by higher velocity. I fired 40 rounds over the chrono and got very consistent results from about 35 rounds . 2 were 50-75 fps slower and 1 was right at 3050(as were the 35 "good" ones) and 2 were above 3100fps. The brass was from a lot of 500 that I bought shortly after buying the rifle. I loaded 10 rounds and tested it the next weekend. the velocity was 3025 to 3075. Accuracy was sub inch as usual!

[Graybeard]

Unless the loaded ammo has been subjected to some really nasty storage conditions it's unlikely the age of it is at fault. Anyone of dozens of things could be different in the ammo.

I went out shooting today with my new FA 97 .45 Colt revolver and the very best group I got was with some old ammo I've had laying around for several years. Now my only problem is to figure out what the heck I loaded them with so I can duplicate the load. I think I've figured it out from my loading logbook but do need to pull a bullet to see if I can verify it.

[papajohn428]

I've heard for years that you should rotate ammo yearly, especially in police use, when a lot of it is riding around in the squad car, bouncing around and being subjected to all kinds of extreme temperatures in summer and winter.  I've left 100 rounds in a box under the seat for years, and when I fired it, it was fine.

Maybe rifle powders are different.............

PJ