Tight Throat?

[Nvhunter92]

So I'm having a bit of an issue and hopefully you guys can provide some help. I have a new Christenson Arms in 7mm rem mag. I am using nosler brass and 162gr hornady ELD-X's. I had trouble finding my distance to lands using the hornady oal gauge as I was getting a number well below saami max (2.619" w/ comparator). So I used Jim Wheelers stripped bolt method and a fired case with light neck tension to "jam" the bullet into the lands and both methods were very close to each other and gave me a distance to lands of 2.737" using a comparator. During my fireforming process I had the bullets seated to a depth of 2.685" using a bullet comparator and everything worked well. I even stripped the bolt and ran the unfired rounds through the chamber and they fit with no resistance. After fireforming I neck sized my brass and seated the bullets to the same depth and went shooting. I also cleaned the gun very well. The problem is that when running the bolt forward I can feel resistance as the bullet enters the throat and the bolt is stiff to lock down. When I would try to unchamber the unfired round the bolt would lift with some resistance but I had to bang on it to get it to move rearward and there is scuffing on one side of my bullet near the case mouth (see picture). The rounds shot well and showed no pressure signs and the fired cases ejected like normal. I got home and took the firing pin and ejectors out of my bolt and ran one of the now twice fired cases into the chamber and the bolt closed with little to no resistance so I think my cases are sized properly. I saved one of the problem unfired rounds and started incrementally seating the bullet deeper but was still getting scuff marks even down to a length with comparator of 2.610". It didn't matter how the case was oriented, the scuff mark was always in the same place. I bumped the shoulder back using a Redding body die and same issue. I tried seating the bullet with a rcbs gold metal match die to a depth of 2.685"...same issue. I'm really scratching my head on this one. The rounds worked well on their first firing but not on the second but the cases chamber easily.

 

[Mikecr]

Tough problem & good information so far.
Can you measure the loaded runout off exposed bullet bearing, for reloaded(fire-formed) ammo?
Is this bushing/partial neck sizing? Do you expand necks after downsizing?
Just fishing here..

 

[Nvhunter92]

Tough problem & good information so far.
Can you measure the loaded runout off exposed bullet bearing, for reloaded(fire-formed) ammo?
Is this bushing/partial neck sizing? Do you expand necks after downsizing?
Just fishing here..

Thanks Mike,

I currently don't have a runout gauge. So the rounds that I was shooting that gave me problems were neck sized using a standard rcbs neck sizer with the expander in place. This gave me an outside neck diameter of .311 w/ out bullet and .313 with bullet. Since reloading those I bought a gold metal match bushing neck sizer and last night ran one of my previously sized cases through it with a .310 bushing which resulted in .310 w/out bullet and .312 with bullet...but the issue was still present.

 

[cjuve]

You may also want to check the run out on a fired case as well.

 

[Elk Hunter 338]

The CA rifles have a sammi chamber so really it should be on the looser side of things beings its a production rifle and made for factory ammo.

one thing is really in a hunting rifle only neck sizing will cause grief when unexpected and really you should be FL resizing and bumping shoulders about .002" for perfect hunting ammo!! this will alleviate a lot of variables!! this will size brass down to belt and do shoulder and neck all in one.
there is really one way to check for COAL to the lands and its the same every time and that's with a hornady comp case gauge, this way you can check burn in also.

what brass are you using ??? have they been trimmed since first firing?? how many rounds fired in this rifle?? have you checked for carbon ring?? this can happen very quickly!! have you tried any other bullet?? Ive actually seen quite a few hornady eldx over sized by a fraction

 

[Nvhunter92]

So just speculation; it seems to make sense to me that if my Throat was truly undersized or very tight I would have scuffing around the full diameter of the bullet; not just roughly 1/3? I was interested in reducing runout which is why I bought the gold metal match dies but they made no difference. But I was using a case that had already been sized in the standard neck sizer then running it through the match neck sizer and seating it with the match seater...could this be a problem and should I use a fired case and just run it through the match dies? My understanding is that the match dies should give less runout than standard dies.

 

[Nvhunter92]

The CA rifles have a sammi chamber so really it should be on the looser side of things beings its a production rifle and made for factory ammo.

one thing is really in a hunting rifle only neck sizing will cause grief when unexpected and really you should be FL resizing and bumping shoulders about .002" for perfect hunting ammo!! this will alleviate a lot of variables!! this will size brass down to belt and do shoulder and neck all in one.
there is really one way to check for COAL to the lands and its the same every time and that's with a hornady comp case gauge, this way you can check burn in also.

what brass are you using ??? have they been trimmed since first firing?? how many rounds fired in this rifle?? have you checked for carbon ring?? this can happen very quickly!! have you tried any other bullet?? Ive actually seen quite a few hornady eldx over sized by a fraction

So I did use a hornady oal gauge with comparator to get a max COAL but it produced a round that was under saami max by at least .03 which is why I used other methods to triple check. A factory rifle should be able to shoot a round at least up to saami max and all of my other rifles shoot a coal well over saami max. I understand that I will have to fl size after a few firings but these (nosler cases) only had one firing on them when they started giving me issues. I did use a Redding body and essential fl sized the case minus the neck (performed in separate operation) to double check it wasn't a headspace issue as well as stripping the bolt and chambering an empty case and they chambered with no resistance. They have not been trimmed as they are still .005 under max length even after the second firing. This gun had 50 rounds through it prior to the issues and I cleaned after every shot for the first 10 and after every 5 shots for the next 40 so I would be surprised if a carbon ring had already formed. I did check the hornady bullets and they measured right at .284. On a side note the gun shoots very well with many groups around the .6-.8 moa range even with the issues. But this is a hunting gun and I don't want to have to hammer my bolt back to eject an unfired round. The bullets aren't being pulled out of the case at all when I eject them though.

 

[cjuve]

I had a similar issue 1 time with a 338 Edge it was easily seen with a run out gauge. I thoroughly cleaned my dies and shell holder and have never had the issue again.

 

[Pdvdh]

Cooked chamber or crooked cartridge necks if you're bullet is only scuffing on one side.
Just roll some cartridges you reloaded across a smooth surface and look for bullet wobble / run out. Should be visible to cause that exaggerated contact on 1/3 of the bullet.
If no wobble visible, I'd run a fired cartridge neck on a concentricity gauge/tool, and see if your fired case necks are crooked. That would indicate a bad chamber.

 

[Nvhunter92]

I

I had a similar issue 1 time with a 338 Edge it was easily seen with a run out gauge. I thoroughly cleaned my dies and shell holder and have never had the issue again.

Interesting that it was such an easy fix for you, would it be a good idea to through my disassembled dies and shell holder in my ultrasonic cleaner?

 

[Nvhunter92]

Cooked chamber or crooked cartridge necks if you're bullet is only scuffing on one side.

I highly doubt the chamber is cooked as I had only 50 rounds through it when this started and I took my time shooting my groups...especially since I was breaking in the barrel and cleaning often in between shots. Crooked cartridge necks could be possible...

 

[ShtrRdy]

Also, could you check the diameter of the bullets your using? The chamber freebore might be right at the nominal bullet diameter.

 

[Pdvdh]

I highly doubt the chamber is cooked as I had only 50 rounds through it when this started and I took my time shooting my groups...especially since I was breaking in the barrel and cleaning often in between shots. Crooked cartridge necks could be possible...

One or the other... The bullet is only contacting on one edge. You'll need to figure out the why, and you will.

 

[Nvhunter92]

Also, could you check the diameter of the bullets your using? The chamber freebore might be right at the nominal bullet diameter.

I measured a sample of 16 bullets 15 of which were at .284 and one was at .2845