Heavy bolt lift causes

[jpjulian]

I am looking for reasons, other than high pressure, that can cause a stiff, heavy bolt lift. GA Precision built on a Defiance action, Bartlein 6mm Creedmoor, Lapua SRP brass, #450 primers, Berger 108 at 2.160 B.T.O., 41.0 N555 powder and 20 round average of 2,960 fps. Lapua brass was fired several times in the last barrel but first load in this chamber. No flattened or cratered primers. No ejector marks. No other signs of pressure. Good groups about 1/2 moa to expected poi. I am not discounting high pressure but looking for other possible causes. Ideas?? TIA

 

[Chiquita]

I don't quite know the proper terminology, but I think it has to do with the relationship between the bolt and the reset of the trigger.

 

[memilanuk]

Is it just after firing a round, or does it persist when cycling / dry-firing the action?

 

[Jeff Porter]

Clean the lug/chamber may be some brass boogers in there. New barrel install - is this a coned breach set up dragging on the bolt nose?

If it runs fine dry cycling it is likely pressure. New barrel, new set if internal ballistics.

Check a piece of brass with bore scope and make sure your new chamber is not a touch shorter and your fired brass is up in the leade area

 

[old_heli_logger]

Try new brass

 

[Sandstorm]

Its your brass fired in another chamber..Try new brass like old_heli-logger says.

 

[DaveTooley]

Your old brass has developed a memory. That being the other chamber. FL sizing gets it back into the new barrel but upon firing it goes back to it's former size.
You need new brass.

 

[boltfluter]

Your old brass has developed a memory. That being the other chamber. FL sizing gets it back into the new barrel but upon firing it goes back to it's former size.
You need new brass.

As a few have mentioned. This is the first place that requires a little testing.
Paul

 

[Mulligan]

New brass is a great place to start.
However, sometimes it is a mis-match between resizing die and chamber. Bolt thrust can give you the feel of "pressure" without any of the other signs. The resizing die/chamber reamer relationship is critical. Additionally, brands of brass matter when selecting reamer specifications. This forum is full of threads about Alpha this and Lapua that........... with similar "pressures out to soon" or "clickers issues".
There has to be harmony between brass, chamber, and resizing die. Your smith (assuming that is who owns the reamer) will know what brass and dies have been used successfully with that reamer.

CW

 

[ELR LVR]

Have read about high humidity resulting in this.
humidity in the actual barrel causes more resistance to bullet travel, causing higher pressures than normal.

 

[seagate]

Cleaning fluid left in chamber can cause heavy bolt lift

 

[LCazador]

Your sizing die doesn't restore head dimension. You can answer your own question by measuring brass at the .200" line and headspace after resizing. An over expanded case head can only be caused by excessive pressure.

 

[Florida Wally]

I am looking for reasons, other than high pressure, that can cause a stiff, heavy bolt lift. GA Precision built on a Defiance action, Bartlein 6mm Creedmoor, Lapua SRP brass, #450 primers, Berger 108 at 2.160 B.T.O., 41.0 N555 powder and 20 round average of 2,960 fps. Lapua brass was fired several times in the last barrel but first load in this chamber. No flattened or cratered primers. No ejector marks. No other signs of pressure. Good groups about 1/2 moa to expected poi. I am not discounting high pressure but looking for other possible causes. Ideas?? TIA

I have had this happen when using brass fired in another chamber. After getting cases stuck in the new chamber, I realized the new chamber was smaller. The solution was to use a small base resizing die. The regular full length sizing die didn’t size the body shoulder junction enough and that was likely the cause of the cases getting stuck. Once I resized the brass with the small base die, I could see a bright shiny ring where the oxidation was scraped off of the brass right where the body ends and the shoulder begins which showed where the brass was being sized more than other areas. After using the small base die, I no longer had any issues with the older brass.

 

[Steve Donlon]

I had that situation and it was the brass. It needed to be neck turned. The brass was to thick at the shoulder junction. It could be the other way around with a tight chamber, but for me, it was the brass. Or maybe a donut. Measure the top of the neck and the bottom of the neck at the shoulder to make sure they are the same with a seated bullet in the neck. If all the bearing surface is in the neck. In my case it was and the bottom of the neck was .003" bigger, thus the heavy bolt lift.

 

[gravelyctry]

Galled bolt lugs?

 

[spike-55]

Your old brass has developed a memory. That being the other chamber. FL sizing gets it back into the new barrel but upon firing it goes back to it's former size.
You need new brass.

This^^^^^
You can try to anneal and see if it will help, but likely you need to replace the brass
stan

 

[jpjulian]

Galled bolt lugs?

nope

 

[jpjulian]

Your old brass has developed a memory. That being the other chamber. FL sizing gets it back into the new barrel but upon firing it goes back to it's former size.
You need new brass.

I have some new Peterson brass. Guess that would be a good place to start. Thanks for the tip.

 

[jpjulian]

This^^^^^
You can try to anneal and see if it will help, but likely you need to replace the brass
stan

I anneal each loading.

 

[jpjulian]

I have had this happen when using brass fired in another chamber. After getting cases stuck in the new chamber, I realized the new chamber was smaller. The solution was to use a small base resizing die. The regular full length sizing die didn’t size the body shoulder junction enough and that was likely the cause of the cases getting stuck. Once I resized the brass with the small base die, I could see a bright shiny ring where the oxidation was scraped off of the brass right where the body ends and the shoulder begins which showed where the brass was being sized more than other areas. After using the small base die, I no longer had any issues with the older brass.

I don't think a small base die is in my future but it is a consideration if one is available in 6mm Creedmoor. Thanks for the tip.