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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... |
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..... . |
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 I'm going to load up some right now with 1.5 grs less and then work them up again... |
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 |
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. Pete |
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 |
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...
Will you run them over a chrony? And what bullet/weight ya shooting? |
Yep, shooting them over a chrony. 105gr Berger VLD. Leaving in about an hour to shoot them...
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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...?? |
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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Went out and checked the rest of the primed brass...picked one up and the primer fell out...thinking that's my problem... |
Originally Posted by stubblejumper
(Post 3409634)
If the primer pockets are oversized,your previous loads were likely too hot.
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I'll back them off the lands even more and try some more. I believe your Gibbs and my Ackley but don't really show pressure signs until too late, right? Isn't that a trait of the AI rounds?
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I believe your Gibbs and my Ackley but don't really show pressure signs until too late, right? Isn't that a trait of the AI rounds? |
Originally Posted by Ridge Runner
(Post 3409687)
jeep,
went through the exact same thing with my 6.5, ruined cases by the hundreds trying to get the velocity where the smith and several other guys said it should be. Keep'em at least .010 off the lands, (.020 is better) and then rework the loads, you'll get higher velocity with way less pressure signs. I went from ruining cases at 3000 fps with 60 gr of RE22 behind a 140, jammed .006, to 3280 w/ 61 gr re22 and get 5 loadings to the brass, cut the throat out .075" and now get 3340 with the same load. RR unless your boltface is cut up, it'll be ok, but lube the bolt lugs with grease if your gonna run it hard with high pressure loads. |
Ridge:
f you give the bullet a lil jump, seated deeper on the same load, as soon as pressure starts, the bullet starts to move if pressure in a sharp upward curve the bullet doesn't stop against the lands but has a smooth transition and gets faster quicker while pressure is still building instead of the pressure peaking trying to get the bullet moving and ruining cases. JeepKid: Looking forward to your report. Pete |
I'm also thinking that by seating the bullets so far into the case that it might also be causing a pressure spike. I think I might make them a little longer then try to work them up again...
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Right now I'm jumping .097, and the bullet is really deep in the case. Could that be a problem by itself?
Also wondering if the magnum primers could be causing something weird? |
RE-22...47-48.5grs.
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Originally Posted by Ridge Runner
(Post 3411051)
OK, have read alot of reports about heat sensativity of RE22, if you've shot the load before with no problems, then in August you start having pressure problems I'd look into that.
In the gibbs when I was blowing primers by the handful, it was summertime and it was RE22. have you checked MV's lately? here's a link of some AI/105 gr loads, but they don't list RE22 http://www.reloadersnest.com/query_b...lletWeight=105 maybe you can find something here that you can use. RR MV started at 3400, now it will be down around 3250... |
Originally Posted by Ridge Runner
(Post 3411594)
3250 is about the max MV for a 105 in a 243 AI
RR Loading some tonight, hopefully I'll have some time this week to shoot them. |
Thats what I thought too, I was just hoping with the Broughton that the 3400 would be about right. |
Originally Posted by stubblejumper
(Post 3411829)
Using a premium barrel will not normally add 150fps at the same chamber pressure.
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Originally Posted by Ridge Runner
(Post 3411911)
my 26" lilja barreled STW runs faster than most, by over 100 fps, with no pressure signs
140's/3550 160's/3340 RR |
my 26" lilja barreled STW runs faster than most, by over 100 fps, with no pressure signs 140's/3550 160's/3340 |
Not usually, but the 5c is known to be faster (100-200fps) then other barrels... |
Originally Posted by stubblejumper
(Post 3413325)
So how come yours isn't?Your own barrel goes against your theory.
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Well my first two loadings on the brass were...but now I would like to get more firings out of the expensive brass so I'll load it down and still get the same velocity as guys running more powder then me... |
Originally Posted by stubblejumper
(Post 3413449)
If you can only get two or three loadings out of your brass,you are developing way too much chamber pressure.The extra velocity is due to the extra chamber pressure,not some special barrel.
Read up on the Broughton 5c a little... |
Could be but I'm running the same load as other guys and they are only getting 3200-3250 when I was getting 3400... |
Also, the bullets were moly but I tumbled them to get the moly off...not sure if that would make any difference...I don't think it would...
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A too-light charge of slow-burning powder can cause the symptoms you report as well as too much powder. It takes over 65,000 PSI to blow primers. I can't recommend shooting any more of the loads that gave you this result! Best to start over!
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Well my Dad shot some .270 WSM today (2.5gr below max load, new brass) and he also blew half a dozen or so primers...I'm kinda thinking we got a bad lot of primers...??
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