Pierced Primers

[vossman]

So I shot a few reloads today out of my new S&W M&P 15. It worked very well BTW.
Had 2 pierced primers, I am thinking they are flukes but wanted someone else to look at them. Load is .223 55gr FMJ Hornady, 25, 25.5 and 26 gr of Varget, Lake City Brass trimmed to 1.75, Rem SRP.

Bottom row is 25 gr, middle is 25.5 and top is 26. Bottom primer was only slightly pierced, middle was pierced pretty well and I did not find any of the 26gr loads that had any damaged primers. I can see the primers flattening a bit with the higher loads. Too much pressure or maybe I need a different/harder primer? Pretty sure I could drop down to 24.5 and still get reliable function but IIRC 25 was the minimum.

[sabot_round]

Your minimum by the Hornady book is 22.8 gr of Varget. The max per the same book is 26.4 gr so your pretty close to max. Back it up a little bit and work your loads up. Are you looking for speed or accuracy?

[J]

What he said.

Most people load 5.56 light, to save money. Unless you are using it for 400m+ who cares? Save the powder and load more rounds. 23-24g Varget should do just fine. As long as it cycles the firearm, I like light these days for close range stuff.

[SA Friday]

Remington primer cups are fairly decent, but they have horrible standard deviations. Every time I've used them the velocities are all over place. The pressures had to be also. They have got to be burning powder without consistency. Try a different primer. I've had good luck with CCI and (believe it or not) Wolf.

You are loading pretty heavy on the powder. I haven't ever gone past 25.0 gr with Varget and a 55 gr bullet.

[vossman]

Both the Sierra and Speer book said 25 to start and 27 max. Good to know I can go lower, thx. Not really looking to do anything with these other than shoot. I have some 62 and 69gr that I want to use for 300+

[sabot_round]

If you're just plinkin, go with the lower loads and save some powder. If you need more data for Hornady bullets just shoot me a PM.

[vossman]

Thanks Sabot, I will start again at 23 and see what happens with the 55s. Appreciate everyones help too. V

[Zombie Steve]

Yeah, 25 grains of varget is not a hot load at all. Really accurate, though. I've shot that bullet with PMC and LC 73 brass, with and without mag primers... they always go over the chrono at 2,600 - 2,700 fps from a 16" barrel.

One thing that hasn't been mentioned is what OAL he was loading at. If the bullet is jammed into the lands (either because of seating depth, or if there's not enough neck tension they pull out when chambered), the bullet can't get a running start at the lands, and that ups pressure significantly.

If your OAL is somewhere around 2.210" - 2.220", load a dummy round, and chamber it. Let the bolt slam on it like normal. Take it out and measure again. It's usually a few thousandths longer (stops abruptly in the chamber, acts like a bullet puller). Growing .005" is pushing it. If it's more than that, I'd think your problem is neck tension. Are you crimping at all?

[vossman]

OAL measured 2.230, about the top third of the cannelure. .02 shorter than the two manuals had for OAL. I figured the Hornady bullet profile was a bit different so i used a Hornady ogive comparator and it matched a factory round to within .005.
I will try the slam test and see what I get, I did not crimp either. I am using the Forster Micrometer dies. If the bullet is pushing into the lands, I should see marks on it when I extract it right?

[Zombie Steve]

Well, you're doing what I would do... seat it to the cannelure. On the batch I was running, that meant 2.210". Not that uncommon to see one batch different than the next (mine were from 2009).

I don't crimp either, but if they really are getting yanked a bit, I suppose I would consider a light crimp, but that's kind of masking the problem. When you resize brass, what's the measurement inside the neck? Is this a bushing die (sorry, I'm a little ignorant of them, I just get by with regular old 2 die sets)? If so, I think neck tension is adjustable with different bushings, right?

One other question - did you fire anything else really hot lately? Have you looked at the end of the firing pin? If you pierced a primer before and didn't know it, the tip can get rough. They tend to pierce more and more regardless of pressures.