Can two different brass types yield different results with the same load? For instance I have winchester standard brass and winchester nickel plated brass, when I shot the same load from each type of brass I got different results. The standard brass loads had were all inside a nickel and the nickel brass was an 1.5" spread. I mostly have nickel brass this certain caliber otherwise I would stick with the regular. Any ideas/advice?

I saw the same differences with two different brands of brass. Same powder, load, bullet and primer. They shot six inches different.

Considering they were both win brass, I would not anticipate that issue. I reload win brass in both nickel plate and standard brass interchangeably. The difference you may run up against is loading different brands of brass. Different brands may have slightly different case capacities leading to slightly different pressures.

I always run mixed headstamp range brass. My AR shoots right at 1", and my 700 CDL in 30-06 does 3/4". It may cause your problem, but I have never experienced different cases causing accuracy issues.

I ran into this with Hornady brass (Match vs. non-Match headstamped), though not to that extent. With the outside dimensions identical the Match brass weighed consistently less than the non-match. That tells me the interior dimensions must be different. Higher weight brass, thicker case, less case capacity, higher pressures from identical loads. That's my theory, at least. I haven't done any testing, but I would guess it would be more pronounced with loads pushing the max in case capacity or velocity, or both. Again, that's only one man's theory.

edited to add: Without looking at my books, I think the non-Match brass weighed 78-79 grains and the Match headstamped weighed 72-73 grains. Not much, but when you consider the relatively small scale of case capacity, it could be significant.

edited again to add: This is .308Win brass, not .223 of course.

Could be anything. More info would help. My best guesses are.....
If pistol, this is common. You have cases made for wadcutters or not. Some of the other calibers will have different interior profiles depending on what weight bullet to prevent setback. So the cases for 125 and 147 grain ammo may be different on the inside.
With bottleneck rifle my first question would be if both lots have been fired the same # of times. Assuming that the cases are properly trimmed, you may still need to ream the necks. As the brass flows forward it lengthens and also thickens the necks. Annealing the cases may help, since nickel plated brass seems to work harden faster for me.
Details matter, so please be as specific as you can. Caliber, load data. Were these 3 or 10 shot groups? 25 yard pistol or 600 yard rifle? Shot on the same day/temp starting with a clean cold rifle each group or not?

I have some nickel and brass cases for my dads 280 I had loaded mixed together. They were all Winchester cases. The nickel cases were not as consistent as the brass. I didn't care for them and have quit using them.

It is for a model 70 in 25wssm. I finally found a load that worked well in the regular brass. I tested it and a two tenths variance each way in the nickel brass. I went from having 3 shots inside of a nickel to a 2 inch pattern. The only difference was brass. I shot the same day in the heat of the day. I had loaded all the rounds the night before and once I found the one that worked, I loaded 9 more and went back to shoot. Same weather conditions. The first time I shot was trying to fine tune some loads from the day before. The second time I shot was trying to fine tune that. My first were 5 round groups then 3 rounds groups on the other two sets. All at 100 yards. I think I have pictures I can post of all my groupings if that will help.

I wouldn't think that the nickel brass would have anything to do with that, however, your data seems to indicate that is does. If it were me, I would scrap the nickel plated brass.

That's the majority of the brass I have. I have very few of the standard brass. After 3 rounds of test loads I have about 20 pieces of standard brass left and 2-300 nickel. So I guess its back to square one.

square one sucks.

Definitely....different brass makes a difference on accuracy.

I still think you're getting pressure variances from standard to nickel plated causing the difference. It's more difficult having nickel plated brass because without doing a CC test you don't know which has the higher case capacity. Brass to brass is one thing, brass to nickel plated all bets are off. Maybe charge one of each to the rim and weigh the charges a few times, maybe you'll see a pattern.

edited to add: Do you have/have access to a Chrony? That might tell you which has the higher pressure if you can find a predictable/repeatable pattern.

I don't have a chrony but I am thinking about getting one.

That is a BIG variance. I would still check case length and neck thickness. I am interested in how this works out. Have you tried filling an empty nickel case, spent primer left in, with water and then dumping the water into a brass case? Or a fine powder like bullseye, H335.

OK, what recipe are you using? What powder, what charge, what bullet weight and type? That info will help immensely.

Excellent ideas! Baking soda would work, even. I think case capacity is the issue here.

Federal large rifle primer, IMR 4350 42.0 grains in standard brass, Speer 120 grain btsp bullet # 1410. When I used the nickel brass I loaded 41.8 grains, 42 grains and 42.2 grains IMR 4350.

I happened to have one each of the brass. I think the standard has more volume of space. I tried to use water but they were deprimed so there could be some error. If I'm correct, I should be able to back my load off until I have the same volume of open space and I should get close at least, correct?

Close, but even the experts cannot predict with accuracy and have to do trial and error.

Yes, even cases from the same manufacturer made from different alloys or in different lots can (not always, but can) affect accuracy.

This is doubly true with nickel plated cases because the nickel alloy bonds to the brass and makes it less flexible, and it can alter the outside dimension of the case as a result of coating inconsistencies. On most guns it won't make much, if any, difference, but if you have a tight chamber or a tight neck it can cant the projectile in the bore due to differences in neck thickness, shoulder thickness, etc.

Nickel cases aren't as flexible as brass, so it takes a higher pressure to seal the case against the chamber walls - if you are using the exact same load, you won't have as good a seal and as a result a differnt chamber pressure, which can affect accuracy as well.

Generally these differences are pretty subtle, but in your particular case whichever combo is making a very noticeable difference with the nickel plated cases. It happens on occasion, and your solution to not use them is the best action.

I quit using nickel cases a long time ago (outside of pistol, where I don't care) because they are just not as uniform across the board as normal brass cases are.

I wouldn't be so quick to toss all your nickel brass since that's the majority of what you have. I'd load three or four each of 39g, 39.5g, 40g, 40.5g,and 41g and try them before I shitcanned the whole batch of brass.

Yes, different brass can and will yield different results. Pick the one you have the most of, and work up your load with that brass.

I sort mine by mfg, make notes when reloading so I can reference

have you anneal the brass after a couple of reloads?

I Agree with ChadTRG42, separate the brass and develop the load for the more abundant cases.