300WSM extraction problem at 1K match...

[Bc'z]

I too had no problems with chambering or extraction.
1st OCW test hit preasure immediately,
Backed off 2 full grains for second OCW still preasure...
That's when I started measuring.
Mark proofed my rifle, this was done with Remington brass neck wall thickness .012
Lapua neck wall thickness. 0165.
Guess who's going to learn how to turn necks?

 

[mikeeg02]

Feels more like tightness at the base of the case.

I'm planning to get to the range before the next match and do some experimenting. Shoot some rounds over the Chrono with the barrel relatively cool and then purposely get it hot like at a match, shoot some more rounds with the same load and see if velocities and pressure signs increase enough to duplicate the extraction problem I had Saturday. Then, when I get the barrel cooler I ordered, I'll do something similar and see if the cooler makes a difference. Leaving the load alone if the cooler resolves the problem would be the preferable solution for me.

The reason I asked about when the bolt lift is, is because typically if it's from the start of opening the bolt, the load is either too hot, or it could be a warmer load, and there isnt enough headspace.

Have you measured headspace fired and then sized ? What are you getting ?

I think you said it was later in the day, and in the 75* range when you started the hg relay and things went poorly. Even though h4350 is pretty stable, what temperatures did you do you load development in? You also said the morning string for lg it shot without issue, is it fair to assume it was cooler then too?

 

[chuckgreen]

That day we started the LG relay about 9am at 70 degrees...we shot the HG directly afterward finishing about 11am with the temperature having risen to about 75. Temperature did not increase much during the morning. The temperature was about the same as when I did my last testing of the load used a few days earlier.

The only thing that really changed during the match was the temperature of the barrel that stayed relatively cool during the LG strings but got very, very hot when I started dumping the 10 round HG strings as fast as I could. That's when the bolt lift started getting stiffer and stiffer.

I can't help but strongly suspect that the high temperature of the barrel and chamber towards the end of the match did something to increase pressure and expand the cases when fired to the point that extraction became difficult.

I'm hoping that perhaps the "Chamber Chiller" device that's on it's way to me will allow me to really cool down the barrel between LG and HG relays, usually about a 20-30 minute period, and then again between each HG string. Could be that's all I need to do to resolve the problem.

We'll see....

 

[mikeeg02]

Being that close, the temperature is negligible. I would be curious to see your results from measuring some cases fired and sized. Barrel heat could be to blame, but we should still cover all the bases.

 

[Bc'z]

Can a bullet drop freely into a fired case?

 

[greisdor]

Hi Chuck, I ran your load thru Quick Load - it is suggesting you’re at the upper level of the Pressure curve. 65,000 PSI. This must be why you see ejector marks.

Also, Norma brass usually requires shooting them two to three times before pushing them that hard. This hardens them up. U could try Beltram brass too.

 

[davidjoe]

In other threads a lot of guys have seen pressure increase in the round count area you described. I have. I could see brass head pressure signs increase steadily in the box across the lines and rows of about 30 shots affected by this issue. The barrel, 1 of 3 or so new barrels will do this, almost always settles in the expected normal loading zone after initially accepting higher charges without pressure signs. I don’t chase that anymore realizing it’s transitional.

 

[chuckgreen]

RE: Questions...

I measured some fired cases using a Whidden bump gauge and got 1.7285. Sized them with the same sizer and setting I used to load the rounds for the match and get 1.7265. I've been bumping the shoulder back .002 using a full length sizer.

And no, a bullet will definitely not drop into a fired case. Can't even push it in by hand.

Didn't realize I was that close to the top of the pressure range. Next firing will be the third on this brass and will probably back off to 60.5gr. Did some testing earlier with that charge and got some 5 round 100 yd groups in the low 2's at that level with slightly lower velocity of around 2,830fps from a fairly cool barrel. That might be good enough.

I really do appreciate all the comments. Helps me put things into perspective.

 

[mikeeg02]

RE: Questions...

I measured some fired cases using a Whidden bump gauge and got 1.7285. Sized them with the same sizer and setting I used to load the rounds for the match and get 1.7265. I've been bumping the shoulder back .002 using a full length sizer.

And no, a bullet will definitely not drop into a fired case. Can't even push it in by hand.

Get those necks turned down a little more consistent. Im 99% sure you just found your issue. Once you have done that, strip the bolt and see that it closes the same with or without a piece of sized brass in it. If you can feel more resistance in the bolt handle with a case in it, you may have to bump the shoulder back just a little bit more. .002" is a generalized statement, but not the absolute.

 

[46and2]

Get those necks turned down a little more consistent. Im 99% sure you just found your issue. Once you have done that, strip the bolt and see that it closes the same with or without a piece of sized brass in it. If you can feel more resistance in the bolt handle with a case in it, you may have to bump the shoulder back just a little bit more. .002" is a generalized statement, but not the absolute.

This^^^^

 

[dkhunt14]

I'd really like to hear Matt's input on this. I have experienced something close to this and believe it's a sizing issue. I'm pretty sure Matt uses a custom seater which eliminates this issue. Matt?

I believe his clearance should be more. Another .001 to .002 wouldn't hurt a thing. Usually when a bolt lift is hard at the top of lift, it needs more sizing at the base. The first firing or two on a case doesn't show this because the brass is small and takes a few firings to get to this point.

Mike is right and more clearance wouldn't hurt. But I also believe the case is not sized enough at the base and will need a tighter die. When the load is too hot it will lift hard all the way from the bottom and not just click at the top. I doubt given the round count that carbon is an issue as long as he cleans good after the match. It would be interesting to know the freebore and dimension of reamer at .200 line. Alot of times that will tell the story.
I wasn't on here for a few days because I had a heart attack Saturday night. I went to the hospital and they put a stent in for the blockage. I came home yesterday afternoon and seem to be doing fine. Matt

 

[FURMAN]

I believe his clearance should be more. Another .001 to .002 wouldn't hurt a thing. Usually when a bolt lift is hard at the top of lift, it needs more sizing at the base. The first firing or two on a case doesn't show this because the brass is small and takes a few firings to get to this point.

Mike is right and more clearance wouldn't hurt. But I also believe the case is not sized enough at the base and will need a tighter die. When the load is too hot it will lift hard all the way from the bottom and not just click at the top. I doubt given the round count that carbon is an issue as long as he cleans good after the match. It would be interesting to know the freebore and dimension of reamer at .200 line. Alot of times that will tell the story.
I wasn't on here for a few days because I had a heart attack Saturday night. I went to the hospital and they put a stent in for the blockage. I came home yesterday afternoon and seem to be doing fine. Matt

This is great information. I have been having this issue with a mild load in my 6.5PRC. I suspected this and plan on getting custom dies.