Semi auto magnum reloading

[Benihaus]

Vague title but wanted to get attention because I had an event that I can't find an answer for and need your brains to figure out my fail. I was sighting in my 1981 BAR 7mm RM shooting my deer loads:
140grain
Nosler balistic tips
RP cases trimmed to 2.490 2nd reload Small base sized [because of BAR] on first reload but FL on second)
CCI 250 LRMP
64.1grain of IMR 4350

First mag (3 rounds) it was darts, ZERO signs of problems and spot on
waited 30 minutes while others shot and attempted second mag, I tried to run some of my first elk loads and had FTF on all attempts, after looking at the scrapes on the ogive (and later buying a gauge) I realized my OAL was too long for that bullet tip 175 seirra GK and the bullet would not reach its band and properly headspace... thus the failure to fire.
after trying to get the elk mag to run I put in another mag of the deer loads.
this is where the problem came in.
The first round fired great, but the second round sounded and felt off and did not hit the target at all. I dropped the mag and ejected the next round and didnt see any issues nor in cycling the action did I feel any problems. I reloaded the final round into the mag and loaded the weapon.. shot great on point but popped the primer out of the case.
I picked up the cases and on the first there was no issue, the second I actually pierced the primer cup (I know I should have looked immediately after noticing an abnormality) and the third the loose spent primer looked normal aside from being removed from its home.
I am VERY confident in my reloading consistency particularly with this batch as I got a new trimmer and measured every step meticulously, all of the cases looked fine with no other signs of over pressure.
what did I screw up?

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[deadeye]

Did you full length size before or after trimming?

I think you need to get one of these and adjust as necessary.

EDIT http://www.grafs.com/retail/catalog/product/productId/9765

 

[Benihaus]

Did you full length size before or after trimming?

I think you need to get one of these and adjust as necessary. Lyman Products Your Primary Source for Reloading Equipment

Trimmed after sizing. And I did take these bullets out of the middle of the box. I didn't see a gauge for the 7 rem mag.. is that because it headspaces off the band?

 

[Benihaus]

What would cause the puncture?

 

[deadeye]

Puncture and primer pop out is usually over pressure.
Speer book lists 145g bullet using IMR 4350 at 56-60g are you positive on the charge you are using.

IMR states 140gr using 4350 @59-62.8gr


Graff and sons has the gauge you need I think, I changed the link.

 

[deadshot2]

Just a dumb question but did you weigh each load? Or did you only weight the first few dumps through the powder measure and then just fill the cases.

Some powders just don't yield consistent loads when you don't weigh.

Were there any other pressure signs? Ejector marks, wipe marks on the face of the case head, abnormal "stretch marks" on the case wall?

 

[Benihaus]

Nosler shows 66 grain max of 4350 for the 140g btip in a remmington magnum. I use a RCBS charge master rig and trickle the last .2 on every load. There is in fact a wipe mark on the face of the head, but only on the 2 that had an issue. Im wondering if 64.1 is just over max for this rifle and the ones that shot great were just lucky.

 

[deadeye]

Nosler shows 66 grain max of 4350 for the 140g btip in a remmington magnum. I use a RCBS charge master rig and trickle the last .2 on every load. There is in fact a wipe mark on the face of the head, but only on the 2 that had an issue. Im wondering if 64.1 is just over max for this rifle and the ones that shot great were just lucky.

65 is max for the 140g

I found with 300mag using max can make primer pocket life short. Also have you worked up the load for best performance in your rifle rather than just starting with 64g? The results you will get versus the stated "best load" will differ based on twist rate, length of barrel and condition of rifling.

 

[P7M13]

Back off on your powder.
I tried running 66gr 4350 under 139gr pills in my Vanguard. 2/2 gave me heavy bolt lift so pulled the rest.
I first think loose primer pocket when I have an ejected primer. But if you have primer out and pierced also, I suspect high pressure.

All the rounds I have with ejected primers I set aside for close inspection later.

 

[Benihaus]

65 is max for the 140g

I found with 300mag using max can make primer pocket life short. Also have you worked up the load for best performance in your rifle rather than just starting with 64g? The results you will get versus the stated "best load" will differ based on twist rate, length of barrel and condition of rifling.

your right I was looking at the 120 grain pills when I said 66 is max. I worked up to the 64.1, and it ran quite well but I think I'll start back at 61 and work it up again paying extra attention to the primers. I looked at the rest of the spent cases from that day and the primers are all very slightly cratered.

 

[P7M13]

Post a close-up of a bunch of the spent cases.

I pay attention to my load when I see the cup shoulders squaring off and definitely when the firing pin strike looks like water splashing up.

 

[unklekippy]

All belted magnums headspace on the belt.

I recently had some problems with my .308 load of a 150gr.Nosler Ballistic Tip with 48.0 gr.'s of BL-C(2). I have used tis charge for years and with many different bullet weights(until recently, I only lowered the charge when using bullets heavier than 150.). Then, after opening a new bottle, the bolt on my brand new Savage stuck. I can't imagine this is the case, but it almost seems that the powder itself is a little hotter, since the new bottle is the ONLY thing different than the last 1,000 times I have used this load. I am going to start at 46.0 and work up.

I don't know if I have helped at all, but I wish you the best and hope you get it straightened out.