Hard bolt lift question

[Eris]

I've got a bighorn origin action. It's a two lug floating bolt head action. The issue I'm having is coming up during load development. I'm running charges from the bottom of the scale to about 10% below max ( don't need a lot of velocity). When I fire a round and go to cycle the bolt, the bolt lifts smoothly for about 80 degrees, but then comes to an abrupt stop. I have to force it to get over the stop and continue the remaining 10 degrees to extract and eject the spent brass. My rounds are loaded with .003" shoulder bump. When I cycle the bolt on a piece of sized brass, the stop doesn't happen. When I cycle it on a fired piece of brass it happens every time, regardless how hot or mild the load was. What could be causing this hang up? Brass is Lapua on its second firing

 

[338 dude]

I've got a bighorn origin action. It's a two lug floating bolt head action. The issue I'm having is coming up during load development. I'm running charges from the bottom of the scale to about 10% below max ( don't need a lot of velocity). When I fire a round, the bolt lifts smoothly for about 80 degrees, but then comes to an abrupt stop. I have to force it to get over the stop and continue the remaining 10 degrees to extract and eject the spent brass. My rounds are loaded with .003" shoulder bump. When I cycle the bolt on a piece of sized brass, the stop doesn't happen. When I cycle it on a fired piece of brass it happens every time, regardless how hot or mild the load was. What could be causing this hang up? Brass is Lapua on its second firing

Check your brass to make sure your chamber is clean if the brass does not look like it has some kind of grit in bedded in it and it is not a hot load it may be a timing issue for extraction that would be your bolt but with a custom action I find that hard to believe

 

[Eris]

Thank you, chamber is pretty clean , but I'll give it a thorough cleaning just to hopefully avoid having to send it in.

Thank you

 

[Shawnba67]

Is there any chance this is a new barrel?
If so check your fired brass to see if its straight, a crooked chamber can cause a bind up.
This is all very unlikely fortunately.

 

[Dusty Stevens]

You need a small base die or at least some dies better fitted to this chamber which seems oversized

 

[Fast14riot]

Sounds like "bolt click" from improperly sized brass. Try a .001"-.002" feeler gauge under the case head in the shell holder while sizing, see if this changes the outcome, especially if you are bottoming your die out on the shell holder. Could be an indicator that your die is too long. Lapping a shell holder down a few thousandths can alleviate the issue most times. I had to take .010 off a shell holder for one of my Redding type S dies for this very reason. Shoulders measured -0.001"-0.002" however I occasionally had hard chambering and bolt click on extraction. Lapping shell holder and no longer bottoming out fixed it.

 

[DaveTooley]

Sounds like a clearance issue.
Questions

Has this brass been fired in a different barrel?
Caliber?
Anything special about the reamer as in non SAAMI spec?

 

[Eris]

Saami spec 6.5 creedmoor reamer. Brand new brass only fired in this rifle.

Interesting range trip today. I cleaned the chamber out really well last night. Lubed it then swabbed all the lube out. Shot two 10rd groups, one at 2650fps, one at 2730ish. The first five rounds, a mix or both groups, extracted just fine, zero issue. The remaining 15 rds repeated the issue on primary extraction. I think the little bit of lube in the chamber helped until it wore off. I'm thinking that little nick in the chamber might be the issue. I'm going to fire a box of factory ammo through it to verify. Head space was checked and is within tolerance

 

[Dusty Stevens]

Did it get tighter as the barrel heats up?

 

[DaveTooley]

Saami spec 6.5 creedmoor reamer. Brand new brass only fired in this rifle.

Interesting range trip today. I cleaned the chamber out really well last night. Lubed it then swabbed all the lube out. Shot two 10rd groups, one at 2650fps, one at 2730ish. The first five rounds, a mix or both groups, extracted just fine, zero issue. The remaining 15 rds repeated the issue on primary extraction. I think the little bit of lube in the chamber helped until it wore off. I'm thinking that little nick in the chamber might be the issue. I'm going to fire a box of factory ammo through it to verify. Head space was checked and is within tolerance

Firing factory ammo will tell whether there is something happening in your reloading process. I don't believe you mentioned if this was a problem with new brass.

 

[Eris]

Did it get tighter as the barrel heats up?

Yes it did.

The problem was there with new brass as well.

 

[Raythemanroe]

.003 bump down to ..0015-.002 and make sure you are not getting any kind of oil or similar on brass or chamber and try again..

Ray

 

[Dusty Stevens]

Yes it did.

The problem was there with new brass as well.

Youre shooting too hot of a load. Its so close to that edge its going over when the barrel heats up

 

[Eris]

I don't think that's the case since even the light loads I ran yesterday were doing it. I also never let the barrel heat up excessivel . I shoot a 5 shot string over about 2 minutes. Let the barrel cool for 10 minutes while I shoot the 22lr. Also, if the barrel got too hot, I world think I'd see some increased velocity but it never climbed. I took the barrel off and polished out the burr that was in there. One less thing to worry about tomorrow. I've got 20 reloads, same as today, and a box of factory ammo. Hopefully the problem is gone. Also verified my shoulder bump against fired cases. It's consistently .003" but I loaded a few up at .0015"-002" just out of curiosity.

 

[Dusty Stevens]

I don't think that's the case since even the light loads I ran yesterday were doing it. I also never let the barrel heat up excessivel . I shoot a 5 shot string over about 2 minutes. Let the barrel cool for 10 minutes while I shoot the 22lr. Also, if the barrel got too hot, I world think I'd see some increased velocity but it never climbed. I took the barrel off and polished out the burr that was in there. One less thing to worry about tomorrow. I've got 20 reloads, same as today, and a box of factory ammo. Hopefully the problem is gone. Also verified my shoulder bump against fired cases. It's consistently .003" but I loaded a few up at .0015"-002" just out of curiosity.

Keep us posted on it if its fixed for sure

 

[Eris]

Looks like the problem is fixed / found a couple problems. First problem is my resizing die isn't fully resizing the base of the case. I measured the redding die I have been using and measured a friend's Forster die. The redding die is .0015 larger. Loaded a couple hot rounds with his die and the sticky case went away, but I was getting flattened and cratered primers as expected. I also polished out the chamber lightly with 600 grit sandpaper to get rid of the gouges that were in it. No more scratched up brass now. The redding die sized the bases about .001 under chamber size. Using the redding sized brass, there was a little bit of sticky bolt, nothing near as bad as before. Using Forster sized brass, no sticky bolt with the same load. Also no sticky bolt with factory ammo.
Thanks for all the suggestions from everyone. Looks like I need a new sizing die now. For what it's worth, the factory ammo and Forster sized brass bases were both .003 under chamber dimensions.

 

[Dusty Stevens]

See post #5. You can keep your current die

 

[Eris]

Why keep the current die when it's not sizing the base enough? The Forster die sized perfectly and the die dimensions in both are different. Screwing the redding die in deeper wont help. It's dimensionally different than the Forster. Also, I bought the redding die used. Inside does not look mirror polished like any other die I've owned. There are swirl marks like the previous owner tried to polish it. Maybe he overdid it.

 

[Fast14riot]

Taking .005-.010 off a shell holder is the cheapest way to test it before dropping on another die.

 

[Eris]

Taking .005-.010 off a shell holder is the cheapest way to test it before dropping on another die.

It's a Forster Co ax.