Heavy bolt lift when theres no over pressure

[JRBullock1987]

I have a left handed zermatt origin action, proof s.s. pre-fit in 6.5cm, Triggertech special trigger, acc elite chassis. Oss 7.62 hx qd suppressor. Using hornady 140gr match, h4350 (39.8gr) so not a high velocity load (2720s), cci #200, alpha ocd LRP brass about .002" shoulder bump. I will randomly get heavy bolt lift and when I do the neck of the brass extracts dented in. Thats with slow extraction so the denting is happening during initial bolt lift or during chambering but I've sat there and cycled loaded rds a ton and they never have issues so im thinking it's happening during bolt lift or something. I can't figure out what's causing the bolt lift problems with no where near signs of pressure. Ive cleaned the chamber really good and it'll be fine for a bit then it'll start happening randomly again but it'll be like one round then no issues then another random rd with heavy bolt lift. Anyone have an idea what would cause this. I just purchased a borescope and it'll be here in a day but I dont think there's anything in the chamber bc its random rounds then it'll extract fine. Yesterday I took my rifle apart so I could see in the barrel and there's wasn't anything wrong with it. I cleaned it really well and rebuild my rufle and it happened again today with random flyers. It just started and wasn't doing this until yesterday. Itll do it even with a clean barrel and like 10 rds through it. Help would be greatly appreciated.
Thanks.

 

[oldrifleman]

That can’t happen during chambering as the bullet would have give in order for the brass to compress (dent the brass).

 

[JRBullock1987]

That can’t happen during chambering as the bullet would have give in order for the brass to compress (dent the brass).

Can you think of what would cause something like this to happen? I just f8nuahed building this rifle its only got about 300 rds through it and really don't want to have to start saving g for a new one. Lol

 

[oldrifleman]

are you letting the brass fly on extraction or picking it out of the action? Normally that would be from hitting the action during ejection. With slow extraction not really sure what it is hitting

 

[spife7980]

Can you think of what would cause something like this to happen? I just f8nuahed building this rifle its only got about 300 rds through it and really don't want to have to start saving g for a new one. Lol

It’s ejection, not extraction, that’s giving you the dent. Fault common when it smacks the action after getting flipped out

 

[JRBullock1987]

are you letting the brass fly on extraction or picking it out of the action? Normally that would be from hitting the action during ejection. With slow extraction not really sure what it is hitting

Very slow it's a mechanical extractor i think its called so i just go slow and either pull it out or let it fall into my hand with very little force. Its def not from that. It's coming from lift the bolt or something idk

 

[JerkyFreak]

You ssem to measure the muzzle velocity. What is the MV of the heavy-bolt-lift rounds compared the the normal extraction rounds?

Does the action have a spring-loaded plunger ejector?

Place some photos showing the case head of the cases that had heavy bolt-lift.

 

[ma smith]

heavy bolt lift has nothing to do with the neck as far as I am aware. The neck simply expands out and then forward (hence brass trimming). Unless your brass trim length is out of spec prior to firing (or your chamber has a defect) there should be room for the neck to grow slightly upon firing.

Denting is almost always caused by ejection/obstruction of some kind in experience. Its nothing to really freak out about if you have a madrel die. (Alot of people have them as part of their reloading process and it will usually clean right up.)

Although obviously its also a legitimate question / issue to track down to make sure there's nothing else going on.

 

[JRBullock1987]

You ssem to measure the muzzle velocity. What is the MV of the heavy-bolt-lift rounds compared the the normal extraction rounds?

Does the action have a spring-loaded plunger ejector?

Place some photos showing the case head of the cases that had heavy bolt-lift.

Heavy: 2750-60s / reg: 2730s-40s. Not much difference. All the rounds are the same charge weight. 39.8gr
No it's a mechanical ejector I think it's called where I can control the amount. First 3 pics are of heavy bolt lifts. Pic of 2 is reg. My brass headspace has been 1.482 but the heavy bolt lift are 1.484". I have been bumping g back to 1.479"

 

[whatsupdoc]

Origin has a mechanical ejector, no plunger. Next time at the range carefully extract the fired case and peek into the
ejection port and look if the case is coming out straight or is the extractor causing it to bang against the chamber.

What do your primers /case head look like?

 

[JerkyFreak]

Photos of he case head please. The base to see the primer and maybe ejector marks/swipes.

Also, do you have a headspace comparator? If so, what is the difference in base-shoulder measurement between normal and heavy bolt-lift cases.

 

[JRBullock1987]

Origin has a mechanical ejector, no plunger. Next time at the range carefully extract the fired case and peek into the
ejection port and look if the case is coming out straight or is the extractor causing it to bang against the chamber.

What do your primers /case head look like?

They look fine. Primers are still rounded. Case head doesn't have any marks or anything out of the normal. Same with the primers

 

[AznTactical]

Very heavy bolt lift with 6br. Enough that my head has to come off gun so I can grip it and rip it open. Small base die fixed it for me. Google up small base die and clickers.

 

[JRBullock1987]

Photos of he case head please. The base to see the primer and maybe ejector marks/swipes.

Also, do you have a headspace comparator? If so, what is the difference in base-shoulder measurement between normal and heavy bolt-lift

I'm cleaning the carbon off the brass right now to be able to see the shoulder/necks a bit better. The normal are 1.482"/ heavy are 1.484". 95 percent are between 1.481"-1.482"

 

[JRBullock1987]

Photos of he case head please. The base to see the primer and maybe ejector marks/swipes.

Also, do you have a headspace comparator? If so, what is the difference in base-shoulder measurement between normal and heavy bolt-lift cases.

Found one i haven't recapped yet.

 

[carbonbased]

I just f8nuahed building this

in for the creative misspellings!


(I get autocorrected into that crap too)

 

[JRBullock1987]

in for the creative misspellings!


(I get autocorrected into that crap too)

Hahaha