Stuck case in chamber

[BearDog]

I recently had a proof barrel put on my .300WM Sendero. I'm working on developing a load, and have yielded good results from 70gr of IMR4831, with a Nosler AB 180gr. In fact that is the same recipe for the weapon prior to adding the new barrel.

Here is my "hmmmm" moment. I had no indication of over pressure from that build. No bulging, cracking, sticking, and primers looked good. HOWEVER...when I went up to 70.5 during my test, my case was stuck and I had to try quite a few times to get the bolt to latch on and extract. This was the same for all of the rounds loaded at 70.5. At 71 gr I had to use a rod to get it out. I tested it again with a factory load and had no issues with extraction. All my cases are full length sized and under max case length. Bullet is seated .005 off lans. The max load for that powder is 73.

Why this worries me is if I'm getting stuck with a .5 gr increase going 70 to 70.5, is 70gr too risky to use when hunting? I was lucky enough to draw a moose tag for my home state and can't have a stuck case screwing that up. I don't know if temp changes will impact the material enough to where even the expansion for my 70gr charge will cause the case to stick. Could it be something else??

 

[BoomFlop]

How did you determine you are .005 off lands? I would never run a hunting round any where close to .005 off lands. I would especially not do it on a load work up for a belted case either. My guess is you are actually in the lands.

I would back it off at least .020 and work up again.

Good luck
Steve

 

[jdyoung]

How many rounds fired total ? Have you checked for build up of copper/fouling in the throat ? You may have set it for .005" off the lands, but buildup can reduce that. Had that happen with a 7Wby and factory Wby ammo. Wby's have a longer throat and this buildup was quite a lump.
Still, like BoomFlop wrote above, I wouldn't load that close off the lands on a hunting round.

 

[BearDog]

How did you determine you are .005 off lands? I would never run a hunting round any where close to .005 off lands. I would especially not do it on a load work up for a belted case either. My guess is you are actually in the lands.

I would back it off at least .020 and work up again.

Good luck
Steve

I used an overall length gauge, and comparator to measure ogive and took an average over 10 measurements. I then made a dummy round and tested cycling and extraction to make sure there was no sticking. I did not have any pressure in closing or opening the bolt. I also measured my Ogive length before and after closing the bolt on my initial test on my dummy round to assure closing the bolt did not move the round and change my seating depth and give me a false measurement.

I've always understood that for hunting rounds you should load them to two thou off the lands. I figured having it at five thou was being safe and I had room to play with?

I'm not following how having the round touching the lans (if that's the case) would cause the case to stick after the round was fired?

 

[BearDog]

How many rounds fired total ? Have you checked for build up of copper/fouling in the throat ? You may have set it for .005" off the lands, but buildup can reduce that. Had that happen with a 7Wby and factory Wby ammo. Wby's have a longer throat and this buildup was quite a lump.
Still, like BoomFlop wrote above, I wouldn't load that close off the lands on a hunting round.

It's a brand new barrel. Less than 40. I also went through the break in and cleaning process they recommended.

 

[BoomFlop]

The general rule is .020" off lands, not .002" off lands.

You are shooting an upper end charge basically jammed in the lands, I'm more surprised that you could even get the bolt open than I am that you hit heavy pressure.

Steve

 

[jdyoung]

It's a brand new barrel. Less than 40. I also went through the break in and cleaning process they recommended.

If you have a borescope, I would give it a look to check for fouling. Especially in the throat.
With the problem I had on my 7 Wby, bolt was hard to open. I didn't have a bore scope. They where not prevalent back then except for high end gunsmiths.
I put some Sweets 7.62 copper solvent on a patch and started it in the throat , left it there for a number of minutes. When I pulled it out, it was all turquois color. The sign of copper load up. I worked all the copper out and problem was solved.
What was your initial starting load ????

 

[Buck Fever]

Maximum book load means almost nothing, they were not using your jug of powder or your chamber.

I agree on backing off the seating, getting in to the lands too quickly can cause high pressure.

Temperature can push ammo over the edge but you could always carry your ammo against your body to regulate its temperature before you load your gun.

 

[RT2506]

With custom chambers they sometimes tend to be a bit more tighter than "factory" chambers. I have a Shilen barreled 264 Win mag and am shooting Retumbo with 130 gr Accubonds. I ran into pressure 2 grs below book max with the bullet 20 thousands off the lands. This rifle has a tight chamber. The FL sizing die just barely does any sizing at the web. Even with the lower power charge I am getting the velocity that the highest charge would deliver.
I am surprised that someone would fire higher charged loads after they had stuck cases without finding out why. Fingers and faces don't grow back. Be careful. Back off the load and back the bullet off at least 20 thousands and work up to what YOUR RIFLE's load is. That is my advice.

 

[Doublezranch]

This is the way I find the lands. I used to do the dummy round and comparator however I was finding lots of discrepancies. I started using Alex's method and it is very consistent. Give it a try and see if it changes things for you.



Jayson

 

[BearDog]

With custom chambers they sometimes tend to be a bit more tighter than "factory" chambers. I have a Shilen barreled 264 Win mag and am shooting Retumbo with 130 gr Accubonds. I ran into pressure 2 grs below book max with the bullet 20 thousands off the lands. This rifle has a tight chamber. The FL sizing die just barely does any sizing at the web. Even with the lower power charge I am getting the velocity that the highest charge would deliver.
I am surprised that someone would fire higher charged loads after they had stuck cases without finding out why. Fingers and faces don't grow back. Be careful. Back off the load and back the bullet off at least 20 thousands and work up to what YOUR RIFLE's load is. That is my advice.

I've had extraction issues with this weapon before. I actually had to have the extractor replaced before I got into reloading. In hind site that was dumb of me to do, but I did not have any indication of over pressure in the case or primer and it didn't click with me that it was a pressure issue until I went up to 71gr and I had to use a cleaning rod to get the case out. I thought the extractor had busted again....especially with the max load for 4831 being at 73. I'll set it back to .020 instead of .005 and start my test over.

 

[BearDog]

Let me throw another one at the hive. I made a mistake referring to my measurements earlier. My average Chamber length was 2.890 (case length to ogive). I loaded all my rounds to 2.850 (ogive). That would give me .040 off lands...not the .005 like I had thought. Guess that's why you keep notes.
I've added a photo with the primers and charges. You can see there is some flattening, I just don't really believe that it is significant enough that I should be concerned with the pressure at 70grains. Again this yielded the best group at about .5moa. Could slight flattening be an indication of excessive head space? It's still closer to the lands than factory ammo, but with higher charge, I'm wondering if this could be a culprit to the stuck case at 70.5g, and if my 70g load, which shot great and had no extraction issues, should even be a concern at all?

 

[Buck Fever]

Have you measured the brass to see if your sizing is different than the box ammo?

 

[BearDog]

Have you measured the brass to see if your sizing is different than the box ammo?

Yeah, the only thing I don't have a measurement for is the diameter. Everything else matches the specs from my reloading manual.