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300 RUM saami min headspace to datum line?

 
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Old 04-10-2012, 04:31 PM
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Re: 300 RUM saami min headspace to datum line?

Yup, factory extractor for a couple more days, soon as the parts get in we're dealing with that issue.

As far as loading over pressure and to the lands, I think I've elimnated that as an issue. I ran initial load development .010 off the lands and found best accuracy on the light end of the load chart (89-90gr. .350 average groups) with no pressure signs. I then ran a seating depth test backing off in .030 increments with 90gr. charges and found exceptional accuracy at .070 off the lands and 90gr. It was during this stage that I had the first few cases stick. That's when I revisited the headspace issue. I took a long hard look at the extractor today and it doesn't look bad but it does appear to have a slight twist which agrees with what I was seeing on the rim of the stuck cases once I tapped them back out. Good excuse to change the extractor anyway, should have done it with the rebarrel but it just got overlooked.

Once I get the extractor done, I'm going to revisit my load development to make sure I'm not over pressure but I'm not seeing any pressure signs on the fired brass now so I don't expect that to be any different. It does look to be a tight chamber from what I'm measuring on fired brass so we'll see what happens. I've had a few tight chambered guns but never run into this issue before so it's kinda throwing me for a loop.

Thanks for all the input guys, I do appreciate it!
This thing has been driving me up a wall for the last few days over this. I'd be looking for something more substantial if it wasn't shooting but it's still staying at 1/2MOA avg. through all this crap. That's why I figured I would ask here and get some outside opinions.
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Old 05-01-2012, 02:06 PM
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Re: 300 RUM saami min headspace to datum line?

Well, after waiting for backordered parts and a trip out of town, the rifle has a brand shiny new sako extractor sized for the lazzeroni class cases. Lots of surface area to grab the rim on this one! However, no joy on the sticky case issue. It does extract them everytime but not without some effort. The bolt lift is fine until you get to the last bit of lift before it pulls the case from the chamber, then it wants a tap to get the brass moving. I'm into a new batch of retumbo so i downloaded to 88.0, 88.5 and 89.0 gr. charges and still have the issue. My brass is coming out with a bunch of fine scratches on it though. Looking at the chamber with the bolt out and some light you can see that it's kinda rough looking...not happy... I've gone through all the normal culprits, think maybe the chamber needs polished? Best way to go about it? as always, any and all input would be appreciated.
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Old 05-01-2012, 10:20 PM
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Re: 300 RUM saami min headspace to datum line?

Frustrating from here. It'd take a minute to diagnose in hand. Sometimes, a reamer flute will pack full of chips and stick to the side, tearing a gouge around the chamber. When you fire, brass could flow into this and make the brass sticky. You would see evidence on your brass.

I'm wondering how much extraction cam is active. The extraction cam is a shortcoming of the 700. If your smith had to take much to true the lug abutments and bolt lugs, this can minimize the amount of extraction cam left working.

I polish in the lathe, after chambering. You could use a drill and a dowel. 320 grit is as fine as you want to go. Tape one end of your paper to the dowel, wrap the dowel until it's near chamber size. A bit of toilet paper sandwiched could provide a little cushion. You don't want it tight. The end of the paper will flap out and polish. Use some WD-40 for lube. Wet the paper and the chamber.

Just spin it for a bit. You just want to polish, not open things up.
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  #11  
Old 05-01-2012, 10:57 PM
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Re: 300 RUM saami min headspace to datum line?

grit, thanks for the reply. I thought about polishing it up myself and giving it another go then it occured to me yet again that i didn't get what i paid for...it's going back to the smith tomorrow so they can figure it out. I just wanted to be sure it wasn't something i was doing that was causing the problem before i went that route and I've reached the end of my chain, $70 in parts and around $70 in components and it still sticks cases..time for them to make it right. I figure I've got abotu $2200 into a rifle that shoudl drive tacks ( it does) and pull the damn brass out of the chamber so i can drive the next one! I'll post up an update once I hear from them and get it back, if its right, a good review will be in order, if not, well, we'll see how that goes..
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  #12  
Old 05-01-2012, 11:13 PM
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Re: 300 RUM saami min headspace to datum line?

I know, it's hard to send one back, once you get it. My bet is, they'll fix it up and have it back, runnin' smooth in no time. Luck .
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  #13  
Old 05-02-2012, 12:19 AM
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Re: 300 RUM saami min headspace to datum line?

Quote:
The bolt lift is fine until you get to the last bit of lift before it pulls the case from the chamber, then it wants a tap to get the brass moving.
I'm with Grit, I suspect yuor extraction cam is not sufficient due to loss of metal from bolt lugs and lug abutments during the truing operation. Probably just needs the handle knocked off and put in the correct spot.
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  #14  
Old 05-16-2012, 01:41 AM
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Re: 300 RUM saami min headspace to datum line?

Rifle came back today..Had a talk with the smith and he tells me he shot it with 6 different powders at sierra max loads and had no issues until he put retumbo in it, then he got stuck cases. He also said he still had stuck cases with retumbo at 4gr. below max.. Tells me the scratches are from dirty brass but he polished the chamber again anyways. Not sure this sounds quite right to me but I'm going to give it another go. Got the Vortex remounted today, picked up some H1000 and loaded up 6 steps from starting load in 0.5gr. increments to take out tomorrow and see what happens. I'll drop a line back with some results..
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