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-   -   Blown primers...overpressure (https://www.huntingnet.com/forum/reloading/300658-blown-primers-overpressure.html)

jeepkid 08-15-2009 07:57 PM

Blown primers...overpressure
 
I was shooting the .243 AI yesterday and had 4 rounds blow/smoke the primers. They blew holes between the primer and case. The other rounds had a slight tight bolt lift but not bad at all. All the other primers were fine, not flat at all.

What could it be? Just too much powder?

I went ahead and pulled all the bullets and I'm starting over anyway...

LaneNebraska 08-15-2009 08:28 PM

I would make sure the bullet was NOT touching the lands, and would back the load off by at least .5-1 grains.

Might be the difference between standard and magnum primers as well.

Sticky bolt, means you are already well over-pressure in my safety world.:s1:

You should also check your bolt's extractor and firing pin for any physical damage.....


.

jeepkid 08-16-2009 07:06 AM


Originally Posted by Ridge Runner (Post 3409229)
how many loadings ya got on those brass? what brand are they? and do you notice a different "feel" to seating the primers. Check casehead expansion on one of the blown primer cases.

Thats the thing with custom chambers, If a min. spec reamer is used, the first pressure sign you'll see is the primer pocket gets a bit loose. Now is when you look for a happy medieum of velocity and case life. I get 3 firings from my 6.5 Gibbs, 5 from the 7mm AM.
RR

Second loading with Lapua brass (first loading was fireform). Didn't notice a difference is primer seating, used CCI magnum primers.

I'm going to load up some right now with 1.5 grs less and then work them up again...

jeepkid 08-16-2009 08:35 AM


Originally Posted by Ridge Runner (Post 3409363)
are the bullets jammed? that will cause a pressure spike. same lot# of powder? why a mag primer? I've shot 110 gr of WC872 (real slow ball powder) down to 20° lit up by a 210.
RR

Not jammed, just touching. But I'm also going to back them up a little more also. Same powder. Don't really have a reason for mag primers, I just always seem to use them...

Pete D. 08-16-2009 10:16 AM

pressure
 

use the same load and just seat them deeper, velocity would probably go up a tad and pressure go down by just giving them a lil jump.
I don't follow the logic of that. If he uses the same load - showing at this point two classic signs of overpressure - and seats the bullet deeper, he is burning the same amount of powder in a smaller space. That would result in higher pressure, not lower. That little jump to the rifling may not be enough to lower pressure if the real cause of the pressure signs is another factor.
Pete

jeepkid 08-16-2009 10:25 AM


Originally Posted by Ridge Runner (Post 3409433)
grasping straws mostly here, if this is the first full power load on them its probably just overpressure, but you could probably use the same load and just seat them deeper, velocity would probably go up a tad and pressure go down by just giving them a lil jump.
RR

Old ones were 2.737 OAL, just loaded 9 at 2.730 and 47.0, 47.5, 48.0 grains instead of 48.5. Will test them out in a couple hours and see what happens. I have shot this load many times in another batch of Lapua brass and never had the primer thing happen...

LaneNebraska 08-16-2009 10:49 AM


Originally Posted by jeepkid (Post 3409496)
Old ones were 2.737 OAL, just loaded 9 at 2.730 and 47.0, 47.5, 48.0 grains instead of 48.5. Will test them out in a couple hours and see what happens. I have shot this load many times in another batch of Lapua brass and never had the primer thing happen...

That 2.730 and 47.0 sounds like a winner:s1:

Will you run them over a chrony? And what bullet/weight ya shooting?

jeepkid 08-16-2009 11:18 AM

Yep, shooting them over a chrony. 105gr Berger VLD. Leaving in about an hour to shoot them...

jeepkid 08-16-2009 02:25 PM

Just shot them and the 47.0's were fine, then one out of three of the 47.5's blew a hole next to the primer and then I shot one 48.0 and it also did so I didn't shoot any more.

Could it be a bad batch of primers? Its the same load that I've shot over 50 times with no trouble before...??

jeepkid 08-16-2009 02:47 PM

Went out and checked the rest of the primed brass...picked one up and the primer fell out...thinking that's my problem...


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