6BRA Heavy bolt lift

[Slider333]

I'm confident your chamber needs polished. I had the same thing happen to my custom 6.5x.284. Once I figured it out and got my chamber polished the heavy bolt lift was gone. I would also make sure there is a good chamfer on it if you're going to have it polished.

 

[Rehner23]

Hey, thanks to everybody for your input. I haven’t been able to get to the range to test anything out, but I have checked what I can I the bench. To start, a loaded round cycles fine, no heavy bolt lift and not hard to close the bolt. A sized and primed piece of brass chambers fine as well..
Chambering a fired piece of brass is hard to close the bolt, and gives the same heavy lift as when it was freshly fired.
This didn’t change after cleaning the barrel and cleaning the chamber really well. I wrapped some patches around a .45 cal cleaning brush and realty focused on cleaning the chamber.
Using a Borescope with a fired case loaded and the bolt closed a could see I have plenty of room between the neck and the lands.
Next I will try different powder/ lighter charges and see if I can make a difference, until then I’m still not sure!

 

[Rehner23]

Ok, put up with a couple stupid questions...does resized, unloaded brass cycle fine? Does a loaded round cycle fine? Is there a light load that you can try to make sure it's a pressure problem? Have you closely inspected the chamber/neck of your barrel (with borescope)to look for a rough chamber/ wall? I clean my chamber with a bore mop and 99% isopropyl everytime I clean, might try that....and, as stated above, make sure to grease your lugs....rsbhunter

Loaded rounds cycle fine, as do sized, unloaded rounds.. I cleaned the chamber very well this time and haven’t fired a round since.
I will try a few light loads next time out

 

[rsbhunter]

Hope that fixes the problem ....never fun hunting down problems. rsbhunter

 

[Mark W]

Take one of those fired cases and color it with a black sharpie and run it in the chamber. This will show where it’s dragging. Maybe I missed it, but I never saw if a bullet is fitting in the neck of a fired case.

 

[Ruger15151]

My issue with heavy bolt lift wasn't at the .200 line but was a shoulder diameter sizing issue.

I had the same issue heavy bolt lift with my 6BRA using Lapua brass in a barrel chambered by Alex W. I was sizing with a Short Action Customs die and it was sizing the .200 line .001 but wasn't sizing the shoulder/body diameter enough (not shoulder bump). I changed to a Bullet Central Micro die which sizes the shoulder/body .0015 heavy bolt lift went away.

Micron Dies are great but pricey. You can order a Harrells Precision 6BRA #3 for about $125 and your issues should go away

 

[Rehner23]

My issue with heavy bolt lift wasn't at teh .200 line but was a shoulder diameter sizing issue.

I had the same issue heavy bolt lift with my 6BRA using Lapua brass in a barrel chambered by Alex W. I was sizing with a Short Action Customs die and it was sizing the .200 line .001 but wasn't sizing the shoulder/body diameter enough (not shoulder bump). I changed to a Bullet Central Micro die which sizes the shoulder/body .0015 heavy bolt lift went away.

Micron Dies are great but pricey. You can order a Harrells Precision 6BRA #3 for about $125 and your issues should go away

If it was a sizing problem, wouldn’t you have the same issue chambering a sized unforced case or a loaded round?.. both of those cycle fine until it is fired.

 

[Ruger15151]

If it was a sizing problem, wouldn’t you have the same issue chambering a sized unforced case or a loaded round?.. both of those cycle fine until it is fired.

No, because your die may be sizing the case just enough to get it to chamber smoothly. It only takes .0005 of sizing to chamber smoothly. However, the brass springback after firing isn't enough to extract the round smoothly. This is why the rule of thumb at the .200 line is .001 minimum. Sizing .0005 will allow the brass to chamber smoothly but will be very tight ( called "Clickers" ) on the extraction after the round is fired.

Not all dies size your brass to the same dimensions. It you have a factory chamber they all work. If you have a tight custom chamber like yours then you have to find a die that will work with your chamber or do what many do and have a custom die made.

Compare the diameter of a fired piece or brass with a sized piece of brass @shoulder/body junction. If you are not sizing that area a minimum of .0015 or more, you will have a tight extraction. If you are not sizing the case at the .200 line a minimum of .001, you are going to have a tight extraction.

 

[Ruger15151]

If it was a sizing problem, wouldn’t you have the same issue chambering a sized unforced case or a loaded round?.. both of those cycle fine until it is fired.

BTW.. I went back to your original post and you said you were loading up to 2880 fps. The lower node that we shoot in long range is 2920-2930 fps and the high node is around 3010 fps. You not likely to get to the high node with a 105 HB but you should be able to get to 2920 without any pressure issues like a traditional heavy bolt life.

Lapua brass doesn't have the same issues that guys are seeing with Alpha 6BRA brass.

You have a sizing issue, simple as that.

 

[MDT6BRA]

Chamber needs polishing, I would bet on machining marks

 

[Ruger15151]

Chamber needs polishing, I would bet on machining marks

Chambers don't need to be polished if the brass has enough springback.

 

[MDT6BRA]

I had a 300 win mag that did not exactly what he is describing and a smith polished, been flawless since.

 

[Ruger15151]

I had a 300 win mag that did not exactly what he is describing and a smith polished, been flawless since.

Did he polish or open it up and in doing so, leave a smoother finish?

If the brass is sized back enough, there will be enough springback after firing and the case doesn't even touch the chamber.

 

[Kracken McGraw]

You can order a Harrells Precision 6BRA #3 for about $125 and your issues should go away

That sounds like a cheap solution to me.

 

[MDT6BRA]

Did he polish or open it up and in doing so, leave a smoother finish?

If the brass is sized back enough, there will be enough springback after firing and the case doesn't even touch the chamber.

He polished the chamber taking the microscopic machining marks out of it just enough to keep the brass from “flowing” into them and getting stuck. I do agree you could polish too much and create a suction type senario. I don’t really see opening a chamber to the point that the brass would not touch it like you’re talking about. Really I don’t see how that is enough possible, I would think when the round is fired it’s going to mold to whatever it’s surroundings are.

 

[JBT47]

Haven’t read all posts but did you have heavy bolt lift when rifle was brand new? Could have hard carbon build up in the first 4-6” of barrel causing excess pressure and heavy bolt lift. Need to bore scope it to confirm. If carbon build up is culprit then Iosso used per Iosso’s instructions will clean it to bare metal.

 

[Rehner23]

Take one of those fired cases and color it with a black sharpie and run it in the chamber. This will show where it’s dragging. Maybe I missed it, but I never saw if a bullet is fitting in the neck of a fired case.

The bullet doesn’t fit a fired case, it slides in the neck with no resistance what so ever.
I don’t believe that is the problem.
Thanks though!!!

 

[Rehner23]

Well I believe I found the issue causing my heavy bolt lift. It would appear that it was case lube causing the problem. I use Hornady one shot case lube and I’ve never had an issue before with any of my rifles, but I guess this one’s different! I tried some different loads, tried to bump the shoulder a few more thou, made sure my sizing die was correctly sizing in a number of spots on the case… but cleaning the loaded rounds off with some brake cleaner and a rag has made all the difference.
I appreciate everyone that chimed in and gave your input, I’ve actually learned a lot about what can cause an over pressure situation.
Thanks !

 

[DHuffman]

27” Krieger, 4 groove.
CCI 450, Lapua brass. 105 Hybrid

I'd try a milder primer and all of the previously mentioned things.
Glad you resolved it.

 

[Lone Hunter]

Well I believe I found the issue causing my heavy bolt lift. It would appear that it was case lube causing the problem. I use Hornady one shot case lube and I’ve never had an issue before with any of my rifles, but I guess this one’s different! I tried some different loads, tried to bump the shoulder a few more thou, made sure my sizing die was correctly sizing in a number of spots on the case… but cleaning the loaded rounds off with some brake cleaner and a rag has made all the difference.
I appreciate everyone that chimed in and gave your input, I’ve actually learned a lot about what can cause an over pressure situation.
Thanks !

I did the same on a 6BR. Thought my powder charge was too hot but I didn’t get all the lube off the cases. Was using Imperial Sizing Wax. Cleaned the cases good and my heavy bolt lift went away. You have to pay attention to the little things also. Glad you got it figured out.