7saum not chambering.

toddlouis

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Hey all. I can post pictures if needed.

I bought a 7saum off a member here, and it’s new unfired but the bolt will not close.

i did noticed when I closed a sized only brass that the necks would get pinched down a little bit about 1/4th of the neck down. So I got a neck turner and turned 1/1000th until it closed in the chamber without any resistance, then I trimmed to book length. Seated a bullet to book length and it still won’t close. I’ve tried multiple passes at different neck turning, and bullet seating depth (its built on a long action)

I don’t want to keep shaving my 7saum brass as it was expensive and hard to source.

is the issue a head spacing? Or could it not have been cut deep enough, as it was supposed to be a saami reamer. Or should I just send it to a gunsmith to get the issue figured.
 

Black Hat

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Feb 7, 2019
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Queensland
If the bolt will close after turning the neck, but not after seating the projectile, seems likely it could have a tight neck chamber would be best to confirm, as when you seat the projectile it will grow the case around .005 depending on your neck tension.

I would measure how much the cases expand once you seat the projectile in a turned case that fits and turn that amount off.

Around .003 to .004 is what I would run minimal neck clearance.
 

L.Sherm

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Jul 26, 2017
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Man that sucks having a problem on a brand new rifle, have you talked with the seller about it?
Sounds like its a tight neck problem.
Are your dies bushing? If they aren't and you have to keep turning them to get them to chamber theres a point the die isn't gonna size the neck far enough.
Brass with a wall thickness of .0115-.012 should still be fine if you have to turn down that far. A loaded round neck dia. of .305- .306 will be about that. Ive seen some 7mm reamers have neck dia. of .312.
I would see if you can find out who chambered it and what the specs of the reamer are or do a chamber cast with cerrasafe
 
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toddlouis

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alaska
If the bolt will close after turning the neck, but not after seating the projectile, seems likely it could have a tight neck chamber would be best to confirm, as when you seat the projectile it will grow the case around .005 depending on your neck tension.

I would measure how much the cases expand once you seat the projectile in a turned case that fits and turn that amount off.

Around .003 to .004 is what I would run minimal neck clearance.
Ok. I will do that. I just borrowed a vernier caliper from a friend. And did 2 thousandths at most. But Ill have to measure some more and cut some more. Thanks for the suggestion.
 

toddlouis

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Aug 29, 2019
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Man that sucks having a problem on a brand new rifle, have you talked with the seller about it?
Sounds like its a tight neck problem.
Are your dies bushing? If they aren't and you have to keep turning them to get them to chamber theres a point the die isn't gonna size the neck far enough.
Brass with a wall thickness of .0115-.012 should still be fine if you have to turn down that far. A loaded round neck dia. of .305- .306 will be about that. Ive seen some 7mm reamers have neck dia. of .312.
I would see if you can find out who chambered it and what the specs of the reamer are or do a chamber cast with cerrasafe
He did say it was a sammi reamer but I got a box of factory ammo that doesn’t close either. I just got RCBS because that’s all I could find for 7saum lol but I do have bushing dies for other calibers. Might have to invest in one. But .312 sounds like it would be right. Im in contact with seller and hopefully, contact the smith today. Thank you.
 

swampbug

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Dallas
The chamber neck size should be stamped on the barrel by the caliber size. You would need approx .003 under that for your measured loaded round.
 

ShtrRdy

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Try coating the entire outside of the case with a black permanent marker then try to chamber. Pull the case out and see if there is any masks in the marker - either scrapes of smear.

Is the case hard to extract after you've tried to chamber one?
 

ridgeline300

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Feb 19, 2020
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Southern Idaho
I recently had a 7 saum built and we had a similar issue... nosler brass would close fine but ADG was just enough thicker that it would not close. Ended up needing to send the reamer back for a new one and then it worked fine. I don't know if that is a common deal or if we just got a bad reamer.
 

toddlouis

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alaska
Try coating the entire outside of the case with a black permanent marker then try to chamber. Pull the case out and see if there is any masks in the marker - either scrapes of smear.

Is the case hard to extract after you've tried to chamber one?
I will do that. The ADG brass I have is to thick, didn’t want to neck turn that at all since I’m getting a 7max soon. But I got some norma that I’ll try that on. It has a little bit on the neck that is gets a mark on it. And, it is a little hard to extract just a case.
 

toddlouis

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Aug 29, 2019
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alaska
I recently had a 7 saum built and we had a similar issue... nosler brass would close fine but ADG was just enough thicker that it would not close. Ended up needing to send the reamer back for a new one and then it worked fine. I don't know if that is a common deal or if we just got a bad reamer.
Yea. I figured that nosler would work, but I have norma and the problem still happens. I wouldn’t mind just sending it out to get re-reamed
 

gophernator

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Feb 19, 2018
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Kansas prairie
Try coating the entire outside of the case with a black permanent marker then try to chamber. Pull the case out and see if there is any masks in the marker - either scrapes of smear.

Is the case hard to extract after you've tried to chamber one?
The other problem may be very slight difference in the case diameter at the primer/rim. A couple thousands difference can definitely cause the issues you are seeing. Compare the diameters just above the base with your calipers. Five thousands is enough to prevent bolt closure. Good luck!
 

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