Cold bore high pressure

Tiny Tim

Well-Known Member
Joined
Jan 26, 2015
Messages
444
Have you inspected your bore? Is it possible that something is growing (like rust) between range trips? It might cause higher pressure, especially if your near max and at higher temps, and get "knocked down/smoothed out after the first shot? Maybe a burr that's holding copper that you don't get cleaned out that corrodes with high humidity? Grasping at straws here, baffled.
 

fmuguira

Well-Known Member
Joined
Nov 6, 2010
Messages
320
+1 to Jebels comment; oil. Even a light coat can cause it. We were working with a new wildcat cartridge and measuring case expansion and noticed this. Shots afterwards were fine with exact same load. Even left a small extractor mark on brass.

Try drying your chamber wall and running no oil in bore. Or, at least less oil in bore.
 

Radman

Well-Known Member
Joined
Nov 23, 2019
Messages
107
Location
TN
Sounds corny but I wonder if you've an undersize bore, (then the heat from the first shot heats it up enough to expand it near the low-mean dimension)? Just a thought.
 

HVGBDT

Member
Joined
May 13, 2020
Messages
10
Location
Idaho
Have you tried HBN? Supposed to help with differences between cold shot & remaining shots. I also use it for final pass after cleaning the barrel.
 

Aled24

Member
Joined
Sep 20, 2019
Messages
13
Location
North Wales
Hi I have never had this problem but I try to limit the amount of solvent coming back into the chamber by using a bore guide that I have attached a cut down a empty fire formed case, granted you can only use it for that gun but it does save overspill into the chamber.
 
  • Like
Reactions: BKM

Tiny Tim

Well-Known Member
Joined
Jan 26, 2015
Messages
444
For the most part yes. However this morning I decided chronograph 5 rounds on a dirty barrel. The first load had the bolt stick and light ejector mark. I waited 10 min between shots and the didn't have an issue with the following 4.
He has the same problem without cleaning.
 

david g ranes

Well-Known Member
Joined
Sep 9, 2009
Messages
281
The first thing I would do is chronograph your first shot and then the next 3 or 4 to see if you are getting any velocity spikes then go from there. David
 

2rjshort

Well-Known Member
Joined
May 5, 2020
Messages
46
Location
Virginia
Velocity is fairly consistent with ES around 20 (currently doing load development) and the barrel is new so i doubt that there is rust growing in there. Its only happened once on a dirty barrel. I probably won't get to shoot again until early next week. I plan to shoot on a dirty barrel again then cool and clean and see if it resurfaces. I'll keep posted on what I find.
 

2rjshort

Well-Known Member
Joined
May 5, 2020
Messages
46
Location
Virginia
So yesterday evening I took a couple cold bore shots on a dirty barrel with near max loads. No sticking or ejector marks. I'm thinking maybe the one time it happened on a dirty barrel was an anomaly and I've had run back on solvent during my cleaning process. I'm actually cleaning now making sure to do everything to minimize or eliminate solvent in the chamber. I'm really thing that was my problem.
 

Trending threads

Top