sticky bolt lift

A

AMMASHOOTA

Gary Gruber
I was out breaking in the new 300 WSM I just built. I was shooting what I thought was a mild load: 58.5 grains of IMR 4064 with a 150g SMK, new Norma brass, CCI BR-2 primers. OAL is 2.800 -- this is a hunting rifle. My book shows 60.5 grains as a max load. I had mildly sticky bolt lift, with no other pressure signs. Primers looked fine. Lots of powder fouling in the new barrel, no copper, which to me was an indication of too light a load, although my other Krieger barrel started out life pretty much the same way (fouling wise, not bolt lift).

I FL resized the now once fired brass, knocking the shoulder back 0.002. They chamber fine with no perceptible additional pressure required to close the bolt. Temperature was 75-80 degrees.

My gut tells me to back off on the load a bit -- but it just doesn't feel like it should be that hot with that much powder.

Any ideas?
 
Brass maybe?

Did you weigh the brass and compare it with other makes, or check the water capacity relative to others? Also, what did your chrono tell you? If you didn't measure velocity, you might want to load up another 3 or 4 and check it as it doesn't sound like there's any impending failure.

Something to do with the action maybe? Check the bearing surface for the lugs?
 
vtmarmot said:
Did you weigh the brass and compare it with other makes, or check the water capacity relative to others? Also, what did your chrono tell you? If you didn't measure velocity, you might want to load up another 3 or 4 and check it as it doesn't sound like there's any impending failure.

Something to do with the action maybe? Check the bearing surface for the lugs?
Click to expand...

It's funny that you mention case weight. I didn't bother weighing the cases from the first box of 20 -- I figured I was just breaking in the barrel, why bother. Last week I weighed 40 other cases and was concerned that there was no real evidence of distribution among them. There was a nearly 5 grain difference between lightest and heaviest, and half the cases fell in one pile, half in the other.

Never had this much variance with Lapua brass.
 
Lift

AMMASHOOTA said:
It's funny that you mention case weight. I didn't bother weighing the cases from the first box of 20 -- I figured I was just breaking in the barrel, why bother. Last week I weighed 40 other cases and was concerned that there was no real evidence of distribution among them. There was a nearly 5 grain difference between lightest and heaviest, and half the cases fell in one pile, half in the other.

Never had this much variance with Lapua brass.
Click to expand...

I had this problem with 6PPC. After measuring I found the problem was the base of brass near web. Talk to a gunsmith at a match and was told this is a common problem. Luckily he had a FL die that he made from a reamer he had made that addresses this. It fixed the bolt lift and click problem. So maybe a custom FL die is what you need.
Bill
 
AMMASHOOTA said:
It's funny that you mention case weight. I didn't bother weighing the cases from the first box of 20 -- I figured I was just breaking in the barrel, why bother. Last week I weighed 40 other cases and was concerned that there was no real evidence of distribution among them. There was a nearly 5 grain difference between lightest and heaviest, and half the cases fell in one pile, half in the other.

Never had this much variance with Lapua brass.
Click to expand...

The cases are very heavy around 250 grains so this is not that much variation. I believe your chamber was cut with a small at back end reamer. The click is usually taken care of with a new die that will size the back end of the case.
 
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