Max Load Gone Wrong - Blown Out Primer

[azsixshooter]

I tried to work up to a maximum load today from the Nosler book. A couple of days ago I reloaded these 20 once-fired factory Federal cases all with the starting load of 46.5 grains of AA3100 behind Nosler 120 grain ballistic tips in my CZ 550 American in 6.5x55 Swedish. All went well so I started working up by loading 3 rounds of 47 grains, 3 rounds of 47.5 grains, etc .5 grains at a time up to 49.5 grains. Then I loaded one round of 50 grains and 1 round of 50.5 grains, which was the maximum published.

The first set of three all left very faint impressions of the ejector slot on the case head. I knew that wasn't a good sign, but I carefully examined each case and primer and didn't see any other signs of excessive pressure and the bolt had opened smoothly. I could just barely see it, it didn't look nearly as bad as any of the examples I had seen in the reloading books I have. I decided to try one of the 47.5 grain rounds and told myself if I noticed that impression more pronounced or any other signs showing up I'd stop and go home and pull all the bullets.

I fired the next three and the little impression didn't show up at all. So I continued on inspecting each round as I went along for any problems. They were all great and I shot a couple of really good sub-MOA groups so I was pretty happy. I got up to the 50 grain hot load and fired that at a water bottle I had set out at around 330 yards or so.

The next one I decided to fire into a bunch of water bottles to try and recover the slug to check weight retention and expansion and what not. That one kicked like a mule (for the 6.5x55SE) and when I opened the bolt (it opened smoothly) I noticed there was gas leak all over the case head and no primer. I looked inside the action and there was the primer sitting in there. I checked out the rest of the case and didn't see anything that looked bad, no cracks or splits or anything. Then I noticed that the case head stamp was imprinted on the powder build up on the bolt face. I didn't think that was good, it reminded me of the Monroe Effect in the development of shaped high explosives. I went back and looked at the last round and didn't notice anything really unusual that would indicate I was approaching such an overpowered round. Until I got home and looked at it again. I set the second from last one on the table and noticed a little wobble. Then I realized that the primer was just barely starting to flow into the firing pin hole and I guess I should have noticed that and not gone on to fire the little barn burner round.

So basically, I'm just wondering where I stand now? Is something like this common enough and not anything to really worry about? Or should I have my rifle looked at by a gunsmith, maybe have the headspace checked or something? I've pretty much got all of the imprint cleaned off of the bolt face so it isn't really in the steel, it just kind of looked that way at first. I am planning on just shooting again with some of the less-powerful rounds that showed the best accuracy today and taking it in if I notice any major degradation in accuracy or anything. I'm cleaning it really good tonight, it's got a ton of copper fouling all the way to the crown and it's a real pain to get it all out. I picked up some copper-klenz and a fat ny-tough brush to really scrub it good.

I was just wondering if there's anything else I need to do or if this is a more serious incident than what it seems to me right now. I am wondering also about ever trying that max load again? In the Nosler book they used Norma cases which I would assume to be new (maybe incorrectly) and I used twice fired Federal cases. I was thinking that if I tried it again with stronger, fresh cases (like Norma or Lapua) maybe the primer would stay in the pocket and the load might actually be safe in my rifle. I'm not all that gung-ho to go shooting this max load again for any reason, but I'm more interested in the process and how those of you who have been doing this for a while would handle something like this. When I loaded the max I was very careful to zero my scale, check and double check the charge when I weighed it and then I re-checked the zero twice after I poured the charge into the case. So I think it's pretty safe to say that I didn't overcharge it. Oh, also it is a compressed load and I checked the COL right after seating the bullet and a few hours later at the range and it hadn't expanded at all.

Thanks for your help and advice and here is a pic of the failed case, loose primer, recovered slug and intact slug for comparison. BTW, I weighed the recovered portion at 56 grains. I did fire it into 5 1-gallon jugs about 15 feet from the muzzle though! Not as impressive as a 12 gauge slug, but it did a pretty fair job of shredding/detonating the first two jugs and coming to rest in the 4th one.

 

[JohnKSa]

I did fire it into 5 1-gallon jugs about 15 feet from the muzzle though!

So you're not even testing accuracy?

How can you tell when you have a good load-surely maximum velocity isn't your only criterion?

 

[azsixshooter]

I fired a 3 round group of each of the first 6 loadings at 100 yards. I only loaded up a round each of the 2 highest loads to see if they'd show any signs of excess pressure. Which they did.

I was shooting off the tailgate of my truck with a rolled up towel for a front rest, but I got a couple of .625" groups that made me happy. One was with the 47.5 grain loads and the other was with the 48.5 grain loads. And I had some good groups the other day with the 46.5 grain loadings too. So those are the three I think I'll load up a bunch for and head to the actual range where I can shoot off of a solid concrete bench at an officially measured distance. I expect to see some good things from those loads.

 

[Wildalaska]

If you are working up to maximum without a chrony, you are looking for trouble, plus the Swede likes moderate velocities anyway.

You now know that max doesnt work, I wouldnt revisit it with CORRECT cases. I would also check your data, max 3100 load in my book is 47 grains!

What was your OAL? Seating probs can cause a normal load to have pressure signs.

WildbecarefulAlaska TM

 

[azsixshooter]

OAL was 3.045" for all rounds I loaded today. I didn't see anywhere in the data book where they said what theirs was. I tried to get it .003" - .005" back from the lands as I've read. So basically I seat a dummy, color it black and chamber it. It showed a couple of little marks where it hit the lands so I turned in the bullet seater a full turn and tried again. This time no marks and it measured 3.045" so I seated them all to that depth. You think I should have only gone a half-turn? I had read that seating hard into the lands increases pressure, so I thought a little further away might be better than being right up in them.

I'm going on the data in the Nosler 6 book. I also have "The Complete Reloading Manual for the 6.5x55mm Swedish" and the Nosler section in there gives the max as 47 grains, as you said. However, I thought that maybe the powder might have been changed or something so I was just going with the most current data I had available.

 

[azsixshooter]

Do you guys think I screwed up my chamber or bolt?

 

[HiBC]

Well,sounds like an adventure.I don't want to be disrespectful,but I suggest you re-read your loading manuals about pressures and max loads.They say it very well and I don't think I can do better.I hope you wear shooting glasses.
My Nosler book gives a max load of 47 gr of 3100 with a 120 BT.It also says 87% load density.You were compressed?
Is this a pretty new rifle? Most new factory rifles,the bore gets blued.That does matter some.Its a bit toothy.6.5's have a very quick twist.You mentioned metal fouling.That can add to pressures.So take a deep breath,and please rethink your reloading process.It would be prudent to have the headspace checked.It is very likely OK.
Now,I think I should give your dignity a rest,but you were very close,my friend!! Be safe.
Just a suggestion,look at H-4350 and Re-19,and IMR 4350..
Please note if you try a partition you must reduce your charge,and substituting cases is not good.I would also toss any case you loaded over 47 gr.If you aren't sure,toss it.

 

[HiBC]

A couple more things,that faint little mark with the ejector?that is the brass flowing back into the narrow ejector slot.The thickest part of the brass.It gets shiny when you wipe it off opening the bolt.It might look faintbut it talks loud!! Too far!!
There is no guarantee your rifle will accept max loads.That is why we approach them.
I'm loyal to Nosler,use their bullets and like them.Be careful with your expectations of a 120 gr Ballistic tip.It is a lightly constructed bullet.

 

[azsixshooter]

Thanks, I appreciate the input. I thought it was curious, though, that that mark showed up on the first three rounds loaded with .5 above what the book listed as a starting load, yet disappeared in all heavier loads. I thought that maybe the pressure was higher because the space inside the case at that load level allowed the powder to burn up faster or something.

I don't mind if I can't use the max load, the ones that looked to group well are plenty hot enough for me. I just wanted to work on a good 120 grain load for antelope hunting. Now that I have a few loads here that look to group well I can start doing further testing with them. And now I kind of know the limits of what I can do with this powder and these bullets at least. Since the primer flowed back into the firing pin hole at 50 grains I am thinking the maximum safe load in this rifle is about .5 grains behind that at 49.5 (although the one group I shot of that load measured an embarrassing 2.125")

I learned a good lesson and didn't get hurt. Hopefully I didn't damage my rifle. I guess I'll find out next time I go shooting.

 

[darkgael]

pressure

"The first set of three all left very faint impressions of the ejector slot on the case head. I knew that wasn't a good sign, but I carefully examined each case and primer and didn't see any other signs of excessive pressure"

Ditto on what has been said. Those faint impressions WERE the warning. The error, no offense meant, was in firing the next shots. For whatever reason, those next shots did not imprint and so you went on. You were already over the egde. Lucky you. Lucky me...I've done it too.
A chrono is a great tool. Also, a caliper at the range. Measure the diameter of the casehead before you fire the cartridge and then after. Expansion of the head diameter should be less than 0.0050". It's another thing to look at, way better than primer flow.
Pete

 

[Loader9]

According to the data at Accurate Powders, a max load for the 6.5 Swed using a 129 gr Horn. bullet is 49.0 grs with pressure at 47,500. I wouldn't expect any major issues like what you have experienced using a 49.0 load. A 50.0 gr load is obviously right at max and maybe over max and I can see issues there but from what I see, you need to have the rifle inspected at a smitty. I'd bet on a mechanical issue providing the loads were correct as stated and no mistakes made. But I have to ask, looking at the data, it's apparent that 49.0 grs is a full case. How did you get 50.0 grs in it? Are you sure you had the right powder?
http://www.accuratepowder.com/data/...6 5 x 55 Swedish Mauser pages 229 and 230.pdf

 

[wncchester]

""The first set of three all left very faint impressions of the ejector slot on the case head. I knew that wasn't a good sign, but I carefully examined each case and primer and didn't see any other signs of excessive pressure"

Goodness. I remember an old hand being asked once "how do you learn what's a max load?" He responed that you simply "add a half grain at a time until something blows up, then back off a half grain." He made his point but ... that advice ain't quite worth following!

What you are experiencing is what is meant by starting low and ONLY MOVE UP IF CONDITIONS ALLOW. If conditions don't "allow", don't keep moving up!

We should take any one sign of overpressure as sufficent, not to try for three out of four. Ejector marks, however faint, mean a LOT of pressure. BACK OFF, at least a full grain. I'd go down two full grains myself.

 

[Wildalaska]

Since the primer flowed back into the firing pin hole at 50 grains I am thinking the maximum safe load in this rifle is about .5 grains behind that at 49.5 (although the one group I shot of that load measured an embarrassing 2.125")

NO!!!!!!!!

You just dont back down. You start your rework again with careful consideration to all data.

Go get a Chrony. Start all over.

WildanduseeurostuffAlaska TM

 

[HiBC]

I can see from your comments that you still intend to work above the published maximum.And The comment about backing off 1/2 gr from primer extrusion speaks to me.

If you follow WildAlaska's advice and get a chronograph(mine's a pro Chromy,Pacts are on sale at Midway $120 or so) you can learn some things.

Given the same barrel length as the test barrel,pressure and velocity are related.If you get the published velocity,you are at probably near the published pressure,but other factors can run the pressure up.

I have done a fair amount of wildcatting where current published data was unavailable.In a Sierra newsletter,I learned a technique that has been useful.
In modern ,high pressure firearms,begin with a starting load,add an increment of powder(say 1 gr).Record the chronographed velocities.Lets say one grain of powder yields 62 fps.(of course,samples of three). Still make all the other observations for pressure.As you add another grain,you will notice the chronograph tells you you got 63 fps. OK.Then,next time you up a grain,the chronograph tells you you only got 45 fps.That is the wall.More powder is NOT giving you significantly more velocity,but pressure will spike in a hurry.
Back down,at least to the last charge thet gave a uniform velocity increase.

Now,as I said,I use that for non-factory cartridges where I do not have published data to work with.Published data is BETTER.Their labs are better than I am.The point was,AT THE MAX LOAD<MORE POWDER GIVES A DIMINISHING RETURN ON VELOCITY.(It makes PRESSURE instead of velocity)

Realize,you need a margin of safety. If you make those 1 gr under primer extrusion loads on a 78 degree day,and go shooting next July,grab a few rounds out of a hot pickup,you might blow a case.
By the way,that case did not fail!!If it had,its a bit like a balloon popping.
Your stock would splinter,The extractor would blow off.The flow of hot ,high pressure gas would use the case metal to braze the bolt shut.That pressure would then go through the firing pin and bolt raceways to your eye.That is why I recomended shooting glasses.
You might try wearing an eyepatch over your shooting eye for a few days,and see if you think that will give you a better hunt.

I have shot a lot of antelope.It is my favorite hunt.They really don't care much about 100 fps.The fun part is getting closer.Belly crawling sage to sage,using a little low ground to be invisible.That is where the juices are.
They run forever with a forleg blown off,and they won't let you get close again.(Yeah,I was 16 with a borrowed 7 mag.scope on 9X,can hit anything,right?)
You get within 300 yds with your 6.5 and it won't matter what load you have.It will help if your rifle and eye still work.
You keep dancing with pressure signs,you will get hurt or wreck a rifle.
Do everyone a favor,don't offer your ammo to a buddy with a 6.5

 

[Jim Watson]

The first set of three all left very faint impressions of the ejector slot on the case head. I knew that wasn't a good sign, but I carefully examined each case and primer and didn't see any other signs of excessive pressure and the bolt had opened smoothly.

The old rule of thumb, used by Speer before bullet companies could afford pressure guns, was that at the FIRST sign of excess pressure, stop and reduce the load by 6%. Don't use the load that gave ONE sign of excess pressure, definitely don't increase it, REDUCE it. Your individual gun-component system's maximum load under that technique would be 44.2 grains.

Y'all be careful, now, you hear?

 

[Shoney]

azsixshooter:
Although the discussion above is excellent, more info is needed:
Were the cases once fired in your weapon or another?
How did you size them?

When I am working up rifle accuracy loads, I use once fired brass from my weapon, or once fired brass from elsewhere that has been full length resized, then fired in my chamber with a mild load.

The cases that I use for accuracy and accuracy testing are sized so the case is headspacing on the shoulder. It can be done with neck-sizing die or by “almost bumping the shoulder” with a FL die. This prevents excessive stretching of the case at the web. Which eventually results in rupture of the case or head separation.

If there is a headspace problem, the case being shorter than the chamber and resting forward of the bolt face, then when a max/near-max load is fired, the case expansion grips the chamber wall. If the case is somewhere in the middle of the chamber, gas can leak around the neck and pressure blows the primer back and gas escapes there as well. Sound familiar?

 

[azredhawk44]

AZSixShooter:

One thing I should have told you when discussing brass selection is the reputation Federal brass has for loose primer pockets.

WA recommends Lapua brass and has done so many times with regards to the 6.5x55 cartridge.

I'm a cheapskate and also shoot a 'Mercan cartridge with .308 winchester, so I use Winchester/Remington/Federal/Magtech/LakeCity/WhateverICanFindCheap. But, I always keep in mind the tendency of Federal brass to be softer than most other brass. Seems to last fewer reloads, and the primer pocket in particular gets really loose.

With an M1A, I get 3 reliable loads from Federal brass, sometimes I can stretch to 4 or 5 if I'm a skinflint cheapskate but they don't shoot much better than milsurp stuff at that point. I'll get 4-5 reliable loads from Remington, 4-5 from Winchester (with Remington edging it out slightly), and 5-6 from anything with a 7.62x51 NATO designation to it due to the thicker walls and originally crimped and tight primer pocket.

I doubt you did any damage to your rifle. If you want to have a smith check it, certainly do so.

Accurate's data for a 129gr Hornady SP and 3100 powder maxes at 49.0gr on their website. COAL is 3.025 for a compressed load. You said your COAL was 3.045 and your bullet was 120gr, being lighter.

All in all, I think what you saw was Federal brass misbehaving on a 3rd reload due to just-a-hair-over-max pressures.

Sleep easy, buddy. Ingrid's probably just fine. I was looking through my old emails from you regarding reloading though and you had mentioned that you were going to work with a load from AA for a 120gr Nosler that was published with 3100 powder and 43.0 to 47.0gr.

Sounds like you got your data crossed somehow. Maybe time to clean up the bench a bit?

 

[azsixshooter]

and you had mentioned that you were going to work with a load from AA for a 120gr Nosler that was published with 3100 powder and 43.0 to 47.0gr.

That is old load data from 2004 that I got out of "The Complete Reloading Manual for the 6.5x55 Swedish", though it is still the most current of its' kind on the store shelf, the copyright of the book is 2004. The actual Nosler data could be even older than that.

The data I used is from the actual Nosler Reloading Manual 6 which is the most current available. I thought it best to use the most current data directly from the manufacturer of the bullet I was loading.

They now list starting load for AA3100 as 46.5 grains, middle load as 48.5 grains and max (compressed) load as 50.5 grains. So that is why I was going by that data.

You guys are all giving me some truly valuable input that I have not seen in any of the manuals, so I appreciate it very much. I'll keep reading and following the advice of those of you who know a great deal more than most!

 

[LHB1]

AZsixshooter,
I didn't see any mention of HOW you measured/weighed your powder charges. Can you elaborate on that? Are you sure the powder charges were actually what you intended? Also, did you buy the powder or was it given to you? How old is it? Do you have two or more cans of similar powder so that you might have loaded the wrong powder by mistake? Just trying to eliminate some unknowns in the discussion.

 

[azsixshooter]

I used an RCBS 505 to weigh every charge. I checked the zero between every load to be sure it was still right on.

I bought the can of Powder last week from Sportsman's Warehouse and it is the only can of powder I have.