I have developed a load for my .308 that was yielding 1" groups at 200 yards. Today I had horrible results at 100 yards. I shot my .243 today also and had excellent results so I know the shooting conditions were very good. I'm scratching my head trying to figure out WTH is wrong! Today was the 6th firing of the Winchester brass and the only conclusion I can come up with is the case neck isn't putting a reliable squeeze on the bullet any longer due to changed metal properties. I use a crimp die and have not changed its setting since day one.

Several things come to mind-

If you haven't changed settings on the dies-

Any change in lot of components? (bullet, powder or primer)

Have you trimmed the brass so that it is the same length?

Have you annealed the cases so that neck tension has stayed the same?

Did you check the settings on your dies and measured the ammo to make sure it has not drifted somehow?

Any of the above have been culprits to me before.

I haven't changed anything (bullet, powder, primer, OAL). I am not familiar with annealing. Is it something the average reloader can do?

Yes you can do it but it takes a little bit of education to do it right.

You will need to practice on 40 or 50 cases that you can afford to throw away.

Maybe the barrel needs cleaned. How many firings do you have through it?

quote:

Have you trimmed the brass so that it is the same length?

I didn't see a response to this question. If your brass has grown long enough (easily done in far fewer than six firings with conventional resizing) it can pinch at the juncture of the chamber and leade which will result in erratic accuracy and possibly escalated pressures.

Sorry but the answer is I don't know . Stonecreek has given one likely possibility and I'm sure that if enough thought were given likely causes could be conjured up by many others.
Back in the early 60s I had perhaps 40ea. 22 Varminter cases that were made from 250-3000 cases. These same cases were used for more than 5 years and that rifle kept producing very small groups the whole time. The necks were never turned or annealed. Fluke??? roger

quote:

does multi-fired brass lead to decreased accuracy

Yes, under certain conditions. Standard FL dies may thin the neck, resulting in more slop when the round is chambered. New brass in 243 win, when loaded, gave a neck diameter of .276" the maximum allowed, a rarity. Accuracy was much better than normal in Rem 40x. Using standard RCBS FL die set, i kept records of the loaded rounds neck diameter & accuracy. As the necks diameter got smaller, the groups got bigger. The fix is Redding FL Type S Bushing die, no expander used.

One way to find out if the brass is at fault for loss of accuracy is to buy some new or once fired brass and load/shoot them and see what they will do.

You didnt say how bad the horrible groups were. If it went to 2 or 3 ins. at 100 Id say check your action screws or your barrel might be copper fouled.

quote:

Originally posted by Accuracy is all that matters:
I have developed a load for my .308 that was yielding 1" groups at 200 yards. Today I had horrible results at 100 yards. I shot my .243 today also and had excellent results so I know the shooting conditions were very good. I'm scratching my head trying to figure out WTH is wrong! Today was the 6th firing of the Winchester brass and the only conclusion I can come up with is the case neck isn't putting a reliable squeeze on the bullet any longer due to changed metal properties. I use a crimp die and have not changed its setting since day one.

How long since day one?
How long have you been loading?
About how many rounds do you think you have loaded and fired in rifles?

quote:

Originally posted by SmokinJ:
Maybe the barrel needs cleaned. How many firings do you have through it?

I have one 243 that shoots like a laser I have shot sub 2 inch 5 shot groups with it at 400 yards.

At right arounds 39 rounds it goes wild on me. A brass brush, a little hoppes a couple of patches it goes right back to shooting tight little groups.

It was driving me nuts until I figured that out.

I think the others are right about trimming brass. It is more likely that your brass has grown in length and less likely to be something mechanical. Brass stretches when fired and it gets stretched in the resizing process too. Do not be surprised to find loose primer pockets on those reloads.

There is more to trimming cases than just trimming to length; one should also be looking to create uniformity. Consistent length makes for consistent neck tension, bullet release, harmonics, and accuracy.

Bought a Ruger .257 Roberts Varmint , Tang safety in 1972. Used the same cases, never annealed, till 2000 when the necks started to split. Collected the cases and later cut , sized , neck turned and annealed them for my 7x41 wild cat. Still using them.
That .257 was a tack driver with that brass the whole time . Still is. roger

That's a lot of feedback in 12 hours - thanks to all of you.

Experience with reloading: I've been reloading rifle loads for 2-3 years. 200 rounds of .30-06, 300 rounds of .308, and 100 rounds of .243. The .243 yielded 5 shots touching each other yesterday at 100 yards. The .30-06 is a semi-auto Winchester that yields 1" groups at 100 yards so I've had success in developing loads that are satisfactory to me. I'm learning more all the time (just discovered this forum in November) and have aspirations to improve even more in the future.

Cleaning: This was the first 5 to be fired after cleaning the bore. I've never had a clean bore throw me off that bad before but perhaps I need to shoot another 5 to see what happens.

Trimming: Hornady's manual shows the cartridge length at 2.015" and the trim length is 2.005". I read the trimming information towards the front of the manual and they don't tell you if the 2.015" is the max length you should have. I have 50 pieces of brass that have been fired 5x, 20 of them have been fired 6x. I measured the 20 pieces and they range from 2.005" to 2.016". I don't full-length-resize, only neck-size.

I checked the rifle, the bore is clean, scope is tight and the trigger housing screws are tight.

Based on the feedback I've gotten here and thinking it through, I'm thinking the clean bore was the culprit.

Could be the first rounds after cleaning. How may times have you reloaded the brass in question? I know some folks toss .308 brass after 5 firings and some who anneal for more.

The five that led to the 2" group at 100 yards was the 6th firing. I was hoping to not have to buy new brass since it isn't showing any signs of stress. I will investigate annealing before scrapping it.

quote:

I don't full-length-resize, only neck-size.

Compare neck size to FL sized for accuracy. Control shoulder bump with the FL die.

I went out and fired two 5-shot groups at 100. Both had fliers. Excluding fliers, I had about a 1.25" group. Also had a 2.75" group at 200. That's not satisfactory to me.

After investigating the cost and required effort to anneal, the correct decision for me is to buy new brass.

Consistent case length is important too. So is a square case mouth.

By the way, a five shot group is not an indication of the load accuracy. It takes ten shots. Less than that you will likely find POI drift. It's not POI drift but too small a sample.

Flyers would be an indication of something going on. Do those groups all have the same POI? Neck tension would be my first suspect followed by non-square case mouths.

If accuracy is as important to you as it sounds pick up some Lapua brass. Best brass I have found for most rifles if they make it in your caliber. I shoot it in my 308 and have north of a dozen loading a through one batch.

Oh ya I recommend the annealing process after a half dozen or so firings in non magnum cases...

I have a 2009 Handloader magazine that tested numerous variables for the .308 load. Lapua did very well for virgin brass but fell way down the list after being fired one time without full-length resizing. I don't want to diminish your recommendation; it is quite possible Lapua would do better in a different caliber. The most interesting thing about their results was Winchester was in last place out of ten brands for virgin brass but moved up to third place for once-fired brass. Given the cost difference and my moderate success with Winchester brass, I am inclined to stay with it. In the current environment, finding any brass has proven to be a challenge. I lucked into a bag of 25 Remington today with a local retailer which finishes in fourth place just behind Winchester in the once-fired ranking.

I was waiting a full minute between shots in 15 degree weather for both 5-shot groups at 100 yards so I don't expect there would be POI drift.

Before troubleshooting the loads themselves consider a couple things.
Cleaning can ruin a barrel. I'm not saying it happened but how you clean is probably more important than neck tension. I trim brass but don't anneal. Check your crown. Re clean with brass or nylon brush. Rod choice is important. I have one rifle that shoot's well clean and gets screwy fast, but have another one that takes 7-10 shots to settle in. Once it's shooting I don't scrub it until it won't shoot. It takes a lot of shooting for it to fall off. In plain terms it is better with copper fouling than without.

I'd check brass length and get a Redding bushing type die.

Most sudden fall offs in accuracy have nothing to do with the rifle or ammo. The culprit is usually the scope and/or mounting system.

Check your action screws for proper torque (a rare problem unless you go from FL to WY).

Take off the scope and rings, check that ALL base screws are really tight. (loosen all, tighten one , check, repeat). Check ring fit in bases (turn in styles can loosen up if put on more than once), get another scope you know is good, mount it with properly torqued screws. Try shooting.
If your handloads still suck, buy a box of Federal Gold Medal match. If they work you have an ammo problem, if not it's the rifle or the shooter.

Scopes, especially mid priced variables, go bad far more often than rifles or ammo. My rule is to spend at least as much on a scope as the rifle.
Twice as much is even better.

$2800 scope/rings/base, $1500 rifle, 1/2 moa out to 1000 at least.