Bullet seating issue

YoteslayerWA

YoteslayerWA

Well-known member
I have been reloading for a .260 rem I had built and it has been shooting lights out with new lapua brass. I am now on my second firing with this brass and have noticed my groups have opened up a bit. Upon inspection of my loaded rounds, I am seeing very fine shavings of brass around the lip of the case. Am I right to assume that is likely the issue with my groups opening up and how does a guy go about fixing that?
 
Most likely the mouths need a chamfer. Could be the issue, if they shoot satisfactory for what your doing with them I'd shoot them up then size, trim and chamfer. If you can't live with the accuracy they're giving you'll have to break them down and start over. I'd also measure the shoulder on a new case if you still have one unfired, and see how it compares to what you've loaded. It could be you're resizing not quite enough or maybe too much, on a bolt gun I try for 3 thousandths of shoulder bump as compared to a fired case.
 
I always chamfer during my brass prepping and also thought maybe I was not doing it enough. I got a bit more aggressive on the next set of reloads and it didn't seem to help.

I am using standard rcbs dies and have thought about splurging and getting a set of competition dies from lee.
 
204 AR said:
Most likely the mouths need a chamfer. Could be the issue, if they shoot satisfactory for what your doing with them I'd shoot them up then size, trim and chamfer. If you can't live with the accuracy they're giving you'll have to break them down and start over. I'd also measure the shoulder on a new case if you still have one unfired, and see how it compares to what you've loaded. It could be you're resizing not quite enough or maybe too much, on a bolt gun I try for 3 thousandths of shoulder bump as compared to a fired case.
Click to expand...
Unless your die is canting the bullet due to punch not fitting the ogive, have no idea what could cause shaving of jackets w/adequate chamfer, but I doubt that the tiny scratches on your bullets would affect group sizes enough to matter to anyone other than benchrest competitors But that is just my opinion.

Years ago I bought a coffee can full of m2 ball 150 gr. FMJ bullets which had been pulled w/a pair of wire cutters. Planned to load a bunch of plinking ammo and they were cheap!
They shot as well as any m2 ball shot. I dug up a few in the backstop and the wire cutter marks were almost undetectable, having been ironed out by the rifling.

I think Russ' thoughts on sizing is more likely to affect your group sizes. How many times have your cases been reloaded? Have they been annealed? Brass work hardens a bit every time it is fired/resized. A case that has been fired only once is much softer than one which has been resized several times and the harder the case, the more "springback" you get after running through your sizing die. This would have an effect on neck tension variations as well as headspace differences. Just a thought.

To illustrate this theory, a good friend of mine, who had reloaded all his life experienced a slamfire which wrecked his M1 Garand at a match a few years back. He kept his brass in lots, based on number of times fired & had reloaded a lot of brass which was reaching the end of its life span so he would not have to pick up the MT's during the match. His dies were set up the same as always, but it was determined that all of his reloads that day were just enough oversized (compared to his loads from less fired lots) that they chambered hard in his rifle due to excessive case hardness caused by springback.
 
Good advice above. Not knowing what the actual difference in accuracy between the first and second loads, or possible difference in conditions between them, makes it just a guessing game from this side of the keyboard.

Could be what the guys have already suggested. Could be wind was worse the second firing. Or the bore was dirtier. Or lots and lots of things.

If you are talking about a difference of like 1/2 inch five shot groups opening up to 3/4 inch groups, and it is ammo related, a difference between new and reloaded brass is as the guys have already talked about. The brass has now been resized. A possible cause for reduced accuracy after resizing could also be the introduction of runout. Standard dies can be setup to where they'll pull a neck out of concentricity.

- DAA
 
Not knowing what the actual difference in accuracy between the first and second loads, or possible difference in conditions between them, makes it just a guessing game from this side of the keyboard...............

The brass has now been resized. A possible cause for reduced accuracy after resizing could also be the introduction of runout. Standard dies can be setup to where they'll pull a neck out of concentricity.
Click to expand...
I got some runout, even w/benchrest dies and neck turning, and did a lot of experimenting w/runout when shooting NRA XTC matches (Position shooting, standing, sitting, prone w/o artificial support and w/aperture iron sights) I even marked each individual case w/amount of runout and the high point of runout and experimented chambering high points around the clock to try to determine actual improvement, if any. For my purposes, I did not find sufficient measurable difference in grouping to justify continuing neck turning for the short range segments. I did continue to do so for the 600 yd ammo as I was convinced it did help @ the longer range. Might have been mental, but whatever, my scores did improve a bit.

Again, this was iron sights, but w/sling and jacket, prone can produce fairly precise results:
1701542529616.jpeg
 
YoteslayerWA said:
I have been reloading for a .260 rem I had built and it has been shooting lights out with new lapua brass. I am now on my second firing with this brass and have noticed my groups have opened up a bit. Upon inspection of my loaded rounds, I am seeing very fine shavings of brass around the lip of the case. Am I right to assume that is likely the issue with my groups opening up and how does a guy go about fixing that?
Click to expand...
Where are the shavings from? The bullets I assume, not the brass. You likely need a more aggressive chamfer, try a VLD type steep angle chamfer tool. Pull a loaded bullet, is it damaged from the case mouth?

Virgin Lapua brass shoots extremely well. It's possible something in your reloading process is changing your brass enough to cause a change in accuracy. Like shoulder bump? Or neck tension?
 
YoteslayerWA said:
I have been reloading for a .260 rem I had built and it has been shooting lights out with new lapua brass. I am now on my second firing with this brass and have noticed my groups have opened up a bit. Upon inspection of my loaded rounds, I am seeing very fine shavings of brass around the lip of the case. Am I right to assume that is likely the issue with my groups opening up and how does a guy go about fixing that?
Click to expand...
More info on your steps/case prep processes in order to diagnose. So you fire formed 100 Lapua cases, then what happened next?
 
If it where me i would pull the worse looking bullet. You will see the scrapes, Want to know how i know this?

I believe accuracy is affected with high velocity, out of balance bullets spinning at extreme RPM's

If your RCBS seating die was letting your rifle shoot such good groups in the beginning, i doubt it is that.

On standard seating dies, gently and slowly seat the bullet a bit, turn it 90° and seat it a bit more, then repeat on last time. Basically 3 little turns. It will make your bullets measurably more straight.

I have Lee, RCBS, Redding and Forster dies. I like them all.

If your de-cap/expander assembly is bent, or screwed in crooked, it won't matter how fancy your seating die is.

You have checked your action screws right?
 
Did you process your brass exactly the same on the first firing, as the second? For example did you just load the virgin brass as is, but FL sized the second time? Try to narrow down what changed.
 
Check the runout on the neck. Many years ago I was setting up for my 30-06 & bought a set of Lee dies. I went from groups under an inch at 100 yards to about 3 inches.

I tried all manner of things. Finally bought a tool from RCBS and checked the runout. the necks were canted & the runout was some insane amount. I bought a set of redding dies, runout was minimal & I got my accuracy back.

To be fair this could happen with any brand, in my case it just happened to be Lee. But it took the tool to nail it down.
 
One of the simplest and easy to do things that improve runout is to polish the expander ball w/crocus cloth in a drill (or replace with a carbide ball).

In addition to tumbling my brass, I take a bronze bore brush of appropriate size and make a couple of passes inside case necks to remove any remaining carbon and then lube inside necks w/graphite before sizing. I believe most of your runout occurs when pulling expander out of case after sizing. Case head is essentially unsupported and any tilt can cause a slightly crooked neck. One thing that helps eliminate any tilt is to set your die up so that the expander ball enters the neck of the case while the upper end of case neck is still inside the die. A straight entry goes a long way to keep necks straight.
 
hm1996 said:
One of the simplest and easy to do things that improve runout is to polish the expander ball w/crocus cloth in a drill (or replace with a carbide ball).

In addition to tumbling my brass, I take a bronze bore brush of appropriate size and make a couple of passes inside case necks to remove any remaining carbon and then lube inside necks w/graphite before sizing. I believe most of your runout occurs when pulling expander out of case after sizing. Case head is essentially unsupported and any tilt can cause a slightly crooked neck. One thing that helps eliminate any tilt is to set your die up so that the expander ball enters the neck of the case while the upper end of case neck is still inside the die. A straight entry goes a long way to keep necks straight.
Click to expand...
I prefer expanding in a separate op. Expander mandrel/die is more consistent imo.
 
shanedogg said:
I prefer expanding in a separate op. Expander mandrel/die is more consistent imo.
Click to expand...
That probably would be an improvement over the old method. Before they came out with bushing sizer dies, I contacted RCBS and asked them if I sent a worn out 30-06 sizing die back if they could open up the neck to provide proper neck tension on neck turned brass. Explained the die had loaded thousands of rounds so was not complaining and would be happy to send a check if they would advise cost. They said send it on w/3 fired cases and they would fix me up. Expected a bill or COD when die was complete but received the custom die w/note No Charge. Now that's customer service!! That eliminated my runout problems.
 
hm1996 said:
That probably would be an improvement over the old method. Before they came out with bushing sizer dies, I contacted RCBS and asked them if I sent a worn out 30-06 sizing die back if they could open up the neck to provide proper neck tension on neck turned brass. Explained the die had loaded thousands of rounds so was not complaining and would be happy to send a check if they would advise cost. They said send it on w/3 fired cases and they would fix me up. Expected a bill or COD when die was complete but received the custom die w/note No Charge. Now that's customer service!! That eliminated my runout problems.
Click to expand...
That's excellent! I wish I didn't despise turning necks! I presume they really paid attention to that die being reamed and hardened. I learned quick early on that RCBS tools for the most part( I still utilize a RC press) are decent, but their dies are, well a lot left to be desired. After changing to Forester, Redding, Wilson, Whidden, and the budget friendly Hornady match-the match only, you'll find that that concentricity gauge will not be needed for .003" and under runout requirement. Of course comboed with an expander mandrel 2nd op and good bullets....
 
So my original reloads were with virgin Lapua brass. Second go around were once fired brass. I FL resized them and then tumbled them to clean. After tumbling I clean out primer pockets and flash holes then seat new primers. Then I chamfer and debur before giving them a powder charge and seat a bullet.
 
I did not read every word of every post, but read most of it. It sounds like your original reloads were with virgin brass. So I am assuming then that you did not run them through your resizing die, and loaded them as is. Those rounds would have had the neck tension set by whatever it was when Lapua formed them. The second time around you ran them through your resizing dies. It sounds to me like your dies sized the necks down tighter, and now you have more neck tension than before. That increased neck tension may be shaving copper off of your bullets. Something to check.

Maybe I miss read some of what was posted, or miss under stood your answers. But that is what I would look at first.
 
Lapua brass usually has fairly tight necks from the factory. If you're using a standard FL die with expander ball, chances are your sized necks actually have less tension than new brass that has not been sized or had a mandrel run through the necks. Only way to know is to measure.
 
YoteslayerWA said:
So my original reloads were with virgin Lapua brass. Second go around were once fired brass. I FL resized them and then tumbled them to clean. After tumbling I clean out primer pockets and flash holes then seat new primers. Then I chamfer and debur before giving them a powder charge and seat a bullet.
Click to expand...

As stated in the two posts above, neck tension variations can definitely have an effect on accuracy. The fact that the first group(s) were shot w/unfired brass and 2nd w/once fired cases adds one more variable in that the 2nd round cases were fire formed to your chamber besides a very probable variation in neck tension.

I often use(d) unfired cases in which to develop a load, but have never compared groups between fired/unfired brass. Over the years, I have noted that MV with a given load is usually a bit lower w/new cases than with once fired cases, and a MV variation would also add to the variation.
 
I went to the reloading bench today and took some measurements on some resized brass compared to a couple reloads and neck tension was .002. Which seems like a good number to me. I am starting to wonder if my bullets are not 100% straight while being seated.
 


Write your reply...
Back
Top