Do to difficulty in obtaining 6 ARC brass I managed to get some Lupua 6.5 new Grendel brass. Formed in 6 ARC Small base dies and trimmed to spec. no issues. Fired the rounds with 28 gr CFE 223 over a cci match primer and Hornady 108 ELD match. Same load I have been using with the Hornady cases I have. Groups run 3/4 inch to 1 1/4 for 5 shot groups. This fired with an AR and a 22 inch barrel.
Now the issue on a few of the Lupua brass cases. After 1 or 2 firings I find the case will not go in my case checker. Close inspection reveals a ridge has formed at the base of the cartridge case . Never seen this before and am unsure why. It only occurs with the lupua brass. It has only happened to 3 out of the 100 Lupua cases I am using. Any suggestions?
If you look at cross section cut brass of Starkine, Lapua, and Hornady... You will see that Lapua brass is the thinnest of those examples in the area you are having problems with. Hornady has the thickest area above the case head by a considerable amount. For the 6 ARC and Grendel Lapua would be my last choice for brass. I couldn't find it but their is a thread showing the cross cut brass on this site some place.
Another thing you might check... When was the last time you checked your scale with certified check weights? Many a reloading problem has been traced to a scale that is not weighing charges properly.
This is a set of weights that only lacks the certification paper work but is a very good set for the money. I have this set and check my scale every time I fire up my Frankford Arsenal powder measure, which by the way is spot on every time. I check the actual weight that I am loading not just the zero setting.
If you can not see the tyranny of having a gun ban enforced by men with guns... Then you fail to understand why the second amendment was written in the first place.
May I guess this is fired in an AR? Think you need to get rid of the Lapua brass. PM me for an address to ship this Lapua brass to, so I may safely dispose of these for you
Seriously, I do expect the loads are either hot or you are experiencing timing issues.
Relatively common issue being experienced with many brass brand names. Jhonny's reloading bench had done a bit of a high light on same or similar issues.
Dino
Powder is weighed on electronic dispense and checked with beam scale
CZ527
Load is well below max and velocity and primer do not show pressure. The fired cases are good no visible signs of any problem. The damage occurs during the sizing operation,but not with hornady brass or new unfired lupua reformed. The rifle is an AR and the dies are RCBS small base. The shoulder is pushed back .003
(09-18-2022, 10:55 PM)Ordsgt Wrote: Dino
Powder is weighed on electronic dispense and checked with beam scale
CZ527
Load is well below max and velocity and primer do not show pressure. The fired cases are good no visible signs of any problem. The damage occurs during the sizing operation,but not with hornady brass or new unfired lupua reformed. The rifle is an AR and the dies are RCBS small base. The shoulder is pushed back .003
Anneal your brass before you size, it is taking to much pressure to size it and it is buckeling at the weak point at the bottom of the brass. Lapua brass in this load is pure crap. or you are over pressure.
If you can not see the tyranny of having a gun ban enforced by men with guns... Then you fail to understand why the second amendment was written in the first place.
I was using the RCBS Small Base die and found that it took way too much effort. It almost looks as though the die is flowing brass down towards the base as you size. What is the diameter of your fired brass before and after sizing and who made the barrel?
If you can not see the tyranny of having a gun ban enforced by men with guns... Then you fail to understand why the second amendment was written in the first place.
Great, yet unfortunate conversation on a matter that likely pertains to the op & many others who have had similar experience.
Can't help but think of the conversation that often comes up with Early 6.5 Grendel. Two diffrent bolts had been common, a.125 deep & a .135 deep bolt face. This conversation highlights the preference of the shallower bolt face & a barrel that is properly headspace for the shallower .125 bolt face. type I should be preferred for reasons experienced like the op's.
Possible too deep of a chamfer / or lead in to the chamber should be investigated IMHO.
Dino may be right about annealing to help fix it but this is not the first or even second post I have seen concerning Lapua brass and the 6 ARC. Johnnys reloading did a spot on YouTube on the same issue with Starline and later Lapua I believe.I have only ever used Hornady brass. Once fired arc and Grendel brass and haven’t experienced this issue. Once fired Grendel brass I size the neck and push the shoulders about .003-.005”. Then size a second time to push the shoulder the rest of the way. Trimming to length in between sizing. Some may disagree with that method but I’ve have zero case lose due to sizing and no issues like the OP reports but that’s the way I’ve done mine since day one. If ain’t broke. Annealing could fix your issue but you won’t know til you try it. I would like to know myself what’s causes it.
I had ridges forming once and even hairline cracks from early extraction. Once I got my timing in order they went away as far as happening on new cases. Once I got ridges, even a small base die couldn't take them out on my 550c press. Ended up tossing the affected brass since I run mine pretty hard and not worth chancing a separation.
6.5 Grendel forum has a lengthy, and I mean Lengthy, thread that might have some insights for you, although in your case what I would say is it is a combination of 2 things: small base die sizing + 2) Lapua construction at the head-rim/case wall interface. After 1 or 2 firings and resizes the case wall has been stretched some "non-zero" amount, especially with the small base dies. This 1-2 firings/resizing appears to be enough for the brass to relieve its sizing stress by crumpling at that Lapua interface. Now I'm sot saying Lapus is a bad brass or anything, it is great but its design apparently gets into trouble in this type of scenario.
I would recommend 2 things: 1. get whatever regular sizing dies you want, but not small-base dies. For an AR it's too much stress on any cartridge. 2. Get a few boxes of whatever 6Arc is selling, currently 108's and 105's, for 80-100 pieces of brass "not-Lapua"... after firing the factory round you can run some side by side comparisons of the 2 brasses in your new die and see what you find.
I have taken a few new Hornady 6.5 grendel cases I have on-hand, and trimmed/resized them down to 6Arc, they have worked for the 1 firing I did but I don't have any multiple firing-histories on them yet. I don't use any small base dies.
I can't say it is somewhat "common" -- hope I didn't say that earlier... and the thread link is above, mostly as it discusses Lapua and other brass's construction down at the case head/wall interface.
Case stretching is a common occurrence for resized brass, although it should not be much if resizing is done correctly, nonetheless some stretching will occur. Usually that occurs at the weakest spot, which seems to be a juncture more or less between the base/web area and the walls. Many brass style have a thickened material down there but Lapua's is more of a non-thickened, more or less straight transition at same or similar thicknesses to the wall. With a small base die, that die constricts the brass and casing all the way down to that area, but a regular die eases up down at that area... hence the name "small base die".
In OP's case the 2 things IMO, add together for his trouble. Other brasses may exhibit the same thing w/ small base die but after more firings, vice 1 or 2.
My thinking, anyway.
10-02-2022, 07:55 PM (This post was last modified: 10-02-2022, 08:15 PM by Dino11.)
I to am not saying Lapua brass is bad, just that their are documented cases of the problem.
That thread may be the one that shows the sectioned cases. But this issue has been known for a little while in the Grendel crowd and the ARC is a cousin to it so they exhibit similar problems, and you can math down the Grendel load data from it to get a starting load point. I have done this because in the beginning there was only the load data supplied by Hornady..
The only other thing that I can think of you are experiencing early extraction.
Yours is not an isolated occurrence.
I found a couple of pictures for you. The first one is Lapua Grendel brass, the second is just to show you how much difference different brands of brass exhibit. And these are Grendel as well.
If you can not see the tyranny of having a gun ban enforced by men with guns... Then you fail to understand why the second amendment was written in the first place.
Dino, roger on all that for Lapua brass. I'm not a fan b/c of cost mostly (that's just me), but my thinking stems from his comment that the ridge formation occurs during sizing operation, post #6 above. The formation-stress is happening when the SB die is bearing down on the case. My take on the pics he posts is the brass kind of looks to me to have been squeezed down the case, like a SB die might do to it. Right at that case/web/wall interface or close to it.
Also I would think (not an expert on this) that early extraction or early unlock would be accompanied with extractor chew-marks/stresses on the rim. And maybe not so much with a 22" barrel, but I'm not expert on that either.
Certainly am open to other theories however.
10-03-2022, 12:38 AM (This post was last modified: 10-13-2022, 08:44 AM by Dino11.)
Wish I could find that picture of the sectioned brass. It had three cases, and I even remember the order they were in, and that saying something because I don't remember what I had for dinner. It had a Lapua then a Starline then the Hornady. The Lapua was the thinnest by a pretty good margin, and the Hornady was the thickest by a lot. So much so I was wondering how I got 34gn of water in both the Hornady and Starline I measured.
Found the picture
Notice the line at the area above the case head in the second photo, this is once fired un sized brass
If you can not see the tyranny of having a gun ban enforced by men with guns... Then you fail to understand why the second amendment was written in the first place.
I agree with most that the Lapua brass may be expanding a bit at the head and your die is undersizing the body to much and bunching/deforming the case head. I use a bit lighter charge when loading Lapua brass and I use a Mighty Armory sizing die that doesn't squeeze the body down as much. It also has a much better finish inside the die. With Hornady brass I use 28.7gr of Lever and with Lapua brass I bring it down to 28.3. Haven't had a problem.
