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7mm RUM case life

 
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  #1  
Old 11-04-2005, 12:56 PM
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7mm RUM case life

Just started neck size only on 7mm RUM, FL size with RCBS had case separations starting with third reload. Min. side load of 84 grains of RL-25 with Hornady 154 GR. SST and Fed 215 primer, getting 3100 fps. This is in a Savage 116 that has had the headspace checked. I'm starting to wonder about the finish in the chamber effecting case stretch, even with neck size only, I see just the slightest flattening of the primer into the primer pocket radius. Bullet is not touching the rifling by a long way 1/8" or better as they are loaded to fit magazine. Remington Factory ammo (160 gr. Nosler), shows more pronounced "hat" on fired primer and 3220 fps. First firing of unprimed Rem brass doesn't seem to fire form shoulder as far forward as factory round by .002. as measured with RCBS Precision case mic.?? Just started neck size only, and interested to see how cases perform after two-three firings.
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  #2  
Old 11-04-2005, 11:24 PM
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Re: 7mm RUM case life

I'm on my 3rd reload with some of my cases. So far a-ok. I've notice with the Rum's that when you are getting too hot a load that the model 700 gives that signature ejector plunger mark on the brass head. This is also usually an indication that you have just ruined that piece of brass as the primer pocket has usually expanded more than I'm comfortable with. not so much that you can prime the case with your finger but you notice that it doesn't offer much resistance to the rcbs hand primer. I don't know how people feel about Rick Jamison but he had an article on reloading the 7 Rum a few years back. Seems he had some problems with the case neck area work hardening after 3-4 reloads and needing to anneal them to lengthen their servicable life further. PS- I size my brass just enough that it chambers well. I use rcbs fl sizing dies.
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  #3  
Old 11-05-2005, 11:10 AM
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Re: 7mm RUM case life

Are you getting the velocities you want before getting the overpressure signs? I'm starting to think even the factory loads show overpressure in my gun.

I wanted to try Barnes new 150 gr. TSX BT bullets a while ago, but there was no loading info. I tried what was the minimum load of 83 grains of RL-25 with the Hornady 154 SST I had been shooting at 3100. With the TSX, the first load blew the primer and extruded brass into the ejector slot jamming the bolt opening rotation. I worked it up and down a few times, and it ejected the round and primer fell on floor. The chrono showed 3358 fps., the primer pocket was expanded to .222 from .208. No more solids for me, until there's some solid info in this cartridge. Savage has stopped chambering any rifles for the RUMS...but only tell me they were not selling well. I'm getting good accuracy with the SST's an inch at 100 yds. is easy at 3100 fps.

primers when FL sizing with RCBS-X dies:



Fed 215 on left handload, Rem factory round on right,
notice Fed has more flattening, Rem has a crater and less flattening????? So far neck sized cases show very little flattening.

One case that started to separate on third firing note strange dent at shoulder, gases going forward?????

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  #4  
Old 11-05-2005, 01:43 PM
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Re: 7mm RUM case life

The strange dent is due to gas blowing by the neck before expanding enough to seal. You need to keep the bullet in the neck longer to allow the pressure to build. This can be done by seating the bullet deeper into the case, reducing the neck diameter another couple a thou. or adding more powder. I had the same problem with my 7 RUM Sendero when I first started to reload for it.

The case seperation problem could be due to excessive headspace. May be a good idea to have it checked.

db
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  #5  
Old 11-05-2005, 02:50 PM
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Re: 7mm RUM case life

As I said in first post of this thread,..the headspace has been checked, I have a full set of Manson headspace guages. I have checked the fired brass with RCBS precision mic and cases are stretching .005 (which is in the middle .010 SAMMI allows, 2.4742/2.4842), from FL sized, and factory loads. In this case, I think the gases escaping the crack in the case reduced the pressure needed to seal the neck. It has never happened before except with the case breech. Funny, there was no blackening or residue at the dent? Bullets are seated to fit magazine, same as factory length. Some bullets were pulled and reloaded without re-neck sizing, could reduce bullet grip somewhat. I'm neck sizing only from here out. And since I'ts a Savage, I can reset the headspace of barrel if needed also, to reduce stretch of new brass too.
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  #6  
Old 11-06-2005, 01:30 PM
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Re: 7mm RUM case life

180, according to a ballistic tech at sierra, flattening of fed 215's is nothing to be alarmed about unless it is present with case head expansion. Seems the fed primers have a very soft cup. as for your fl resizing try setting the die to match your chamber. Here's how I do it on my dies
run a 7 rum case into a 30 cal die or use a 30 cal expander ball on your 7 rum die.
once you have a case that is 30 cal, start with your die screwed way up, run the case in the die and try it in your rifle each time, screwing the die down a bit after each time, when the case fits the chamber and you feel lightest resistamce lowering the bolt then screw the die down 1/4 turn and set the lock ring and tighten the set screw. your cases should exactly fit your chamber. hope this helps
JS
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  #7  
Old 11-06-2005, 03:04 PM
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Re: 7mm RUM case life

180 pilot, I'm getting 3450 fps with a load of 95 gr RL25, 150 partition, Fed 215, Oal 3.670. Have experienced no problems whatsoever. The dented case is usually caused from underpressure or brass that has hardened to the point that it won't expand reliably in the neck area for a good gas seal. Is that something else going on down by the case head area in that photo? I think that I would get that gun a thorough looking at by a very competent gun shop. I think something is not right. Look at/measure/concentricity,etc. of chamber and bore. Have you played with different powders like retumbo to see how it stacks up against what hodgdon says you get with their data? Have you tried a different lot# of RL25? When the powder charges and performance don't jive it gets a little spooky. I understand when it says a recipe will give you 3300 and your getting 3250 but when recipe says you should be getting 3000 and your getting 3300 that's what would scare me. and...if that gun can't even stomach the wimpy factory 7 rum loading I would start talking to Savage about standing behind their product and replacing your rifle.
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