New Chamber ?'s

[DaveMarine1]

Hello and I hope this does'nt come off as dumb but I have been around reloding for quite a while and have always had a good understanding of what pressure signs to look for. One of these is "bolt lift". I recently had a new chamber cut on my existing barrel. It is the same as I had before. Doing some loading though and shooting, I found that the bolt lift is fine, its just that the "pullilng back of the bolt to eject the round" is "sticky" at times. I believe that this is caused by the brass flowing forward in the chamber. The head stamp of the case has ever so slightly of an ejector mark. I am using new Lapua brass. LR primer .308 Lapua. The Wolf primers are flat like they always are and no signs of crater. I am shooting the 185 Jug's at 2714fps out of a 29" Brux 1:11.

My queston is, is this a result of fire forming the new brass and after it is fire formed and bumped back .001-.002 in the sizing die, will the "pulling back of the bolt" get smooth again? It isnt "get the hammer out and pound the bolt back" bad it is just a little sticky where you will need one hand on the stock and the other firmly sliding the bolt back. Or am I mistaken and this is what they call "heavy bolt lift"?
Just seeing if anyone has experienced this and if there is a slight correction that can be made. No need to over think this one. Thank you.

 

[wapiti25]

I think you are experiencing hard extraction not hard bolt lift but they can happen together. it may be the base of your brass and the chamber are too tight. How does unfired brass feel? Custom chambering reamers can be too small in the base for some brass such as Lapua which can cause more force required to extract. Some have a "click" when the extraction reaches the top of the bolt rotation. Polishing the chamber may be required in your case. I hope this gives you some things to look at.

 

[searcher]

The hard extraction could be related to high pressure (warm load). Given properly sized brass and a good gun, you don't always see primer cratering as your first sign of high pressure. If you have any unfired cases from the same batch you are using, check the measurement just ahead of the web on the case. If it is .001" or more smaller than an unsized and fired case - high pressure is likely. Given your "subtle" indication - backing off a grain or two will likely give you your answer. In rare cases, using charges BELOW the minimum with a very slow burning powder - usually with lighter bullets - can cause excessive pressure also - so don't automatically back off unless you are well above the minimum recommended charge weight. If you know someone with a borescope - look at the chamber for signs of roughness as another mentioned. Your fired cases can show this roughness in really bad cases. Heavy handed extraction is not a normal element of fireforming cases. I once had the same situation with a new barrel and reducing the charge would not eliminate the problem until I was to a point of getting very poor velocity. Turned out the chamber was not cut to SAMMI specs in that it was a bit short and I had to trim my brass back about .004" shorter than "trim length" just to get it to not pinch the bullet when chambering. The pinch was ever so slight and almost imperceptable when chambering - but it caused pressure spikes which gave me the same symptoms. While this is not likely - this is what I would look at if your problem persists after reducing the load and/or checking the chamber smoothness. All assuming your powder is relatively fresh, etc.