Gunsmithing Bighorn Origin (Still/Stuck Bolt) All of a Sudden

[xocyrusx]

Hello All,

Looking for some help... 2 weeks ago I went out to range and cycled 200 rounds (540 Total) on my bighorn origin, mdt acc chassis, 6GT Barrel with no issues and great accuracy. Was having mag feeding issues but I chalked that up to being polymer mags and was going to try a new metal mag next trip.

Last night in prep for my next trip (Saturday) I went to test out my new mag to my surprise testing some rounds just cycling them safely I couldn’t even get the bolt to close without a heavy hand using the old mags and new one. I tried my old mags and the same issue of Its super stiff running the bolt back and forth to the point once chambered the bolt even gets stuck at times.

I then thought it maybe it’s something got stuck or a cleaning was due as I was planning to do one anyway and went through my normal cleaning. To no avail there was nothing stuck and the rifle was surprisingly pretty clean. Today I went through and fully broke down the rifle piece by piece and cleaned everything and re assembled. Still the same issue. I thought it maybe a carbon build up so I soaked the and scrubbed the barrel with a carbon breakdown.

i checked the chamber and everything looks ok. I don't have a borescope to fully check though... I thought it may have been my reloads and they are the same dimensions and measurements as 2 weeks ago. Even checked with a go no go gauges.

I am out of ideas at this point and would appreciate some help before heading to a smith.

 

[Hobo Hilton]

Try some factory rounds and see what happens.... If it sticks then that eliminates an issue with your reloads.

Hobo

 

[xocyrusx]

Try some factory rounds and see what happens.... If it sticks then that eliminates an issue with your reloads.

Hobo

Thank you for the idea. Maybe tough to get 6GT factory cheap enough to test.

 

[John Glidewell]

I have only seen this once and it was the brass not being sized down enough near the case head. How much did you bump the shoulder?

 

[Steel head]

Thank you for the idea. Maybe tough to get 6GT factory cheap enough to test.

Check your headspace and base expansion on the problem rounds.

 

[backsideof45]

I dont know if you can adjust mag height on your chassis but I'd look into that.

 

[xocyrusx]

I have only seen this once and it was the brass not being sized down enough near the case head. How much did you bump the shoulder?

Fired cases were at 1.347/8 and sized back to 1.345. The weird part is the same brass I am having an issue with fired without any issues 2 weeks ago. Even done at the same time.

 

[Steel head]

Fired cases were at 1.347/8 and sized back to 1.345. The weird part is the same brass I am having an issue with fired without any issues 2 weeks ago. Even done at the same time.

Base growth could still be getting you.

 

[John Glidewell]

Try pulling your firing pin out and chambering a round with out a mag. This releases any tension and you will or should be able to feel if the case is binding. If it is tight to close, then it is most likely a brass issue.

 

[xocyrusx]

Check your headspace and base expansion on the problem rounds.

That’s what I was thinking it was a sizing issue butall ThE sizing between the rounds fired 2 weeks ago and what I tried today are all the same brass sized and prepped all at the same time. Everything measured top and bottom all are the same as they always have been.

 

[xocyrusx]

Base growth could still be getting you.

I did forget to mention that I am getting some scratches on the bullet and brass.

just lost as it’s the same ammo prepped 2 weeks ago and fired off half of it without issue and now issues.

 

[xocyrusx]

I will try

Try pulling your firing pin out and chambering a round with out a mag. This releases any tension and you will or should be able to feel if the case is binding. If it is tight to close, then it is most likely a brass issue.

I will try this with out the pin to see what happens.

 

[DAVETOOLEY]

Take two rounds that are causing the problem. Pull the bullet and dump the powder. Strip your bolt then start sizing the case and trying it in the rifle. I have never setup a FL die by using numbers. I take two cases, maybe three. Start with one and creep down with the sizing die until the bolt closes with the force, or lack there of, you like. Then take the second piece of brass and see if you get the same result with a single pass. Most of the time that will be close but may need to tweak the die slightly.

 

[Mordamer]

Just to be clear, does the bolt cycle perfectly normal with no rounds in the gun?

 

[xocyrusx]

Just to be clear, does the bolt cycle perfectly normal with no rounds in the gun?

yes it does. No issues. The same ammo I prepped 2 weeks ago now Half worked flawlessly 2 weeks ago and now issues.

 

[xocyrusx]

First off I want to thank everyone of you that has responded as I truly appreciate your time and assistance.

i guess there is progress to figuring this out. So I loaded 2 dummy rounds to my normal specs and the same as the rounds I loaded 2 weeks ago that ran flawlessly and before seating I ran the cases through the bolt and no issues. Everything cycled fine.

I then seated 2 bullets and and then the first was a struggle to chamber and on the second it got stuck. In the process of running the bolt back the bullet was in seated from the case.

i think I can deduct from this its not a brass issue or the action but maybe the barrel or the bullet...

fair?

 

[John Glidewell]

Carbon ring? You did mention there were marks on bullet. Clean throat really good and see if it improves. If you have access to a bore scope I would look in there first.

 

[xocyrusx]

Carbon ring? You did mention there were marks on bullet. Clean throat really good and see if it improves. If you have access to a bore scope I would look in there first.

Thats what I think to be honest.... I forgot to post the pic... this is the case and bullet that was pulled apart....

 

[xocyrusx]

@Gwain and @Steelhead you both were on to something!!! So after full dissemble I took several cartridges and slid them into the barrel directly. On some I could feel 2 points of contact... went the boretech / bore scope (thank god for Amazon same day) route and found it was carbon ring sticking to the bullet.

Once that was cleaned up I could feel 100% just sliding the cartridge into the barrel that the case bottom was not sized fully. The. It hit me after trying other rounds I loaded 2 weeks ago.... the ones giving me issues were ones I pulled bullets from and I must not have fully sized them. Broke them fully down reset my sizing due from scratch gave them a full press and tested just the brass in the barrel. Much better. Rebuilt the cartridge tested and good! Tested 4 problem cartridges that I knew still had issues and they did... broke them down and rebuilt worked great and no issues.

thank you to all that responded and really appreciate everyone’s assistance.