Is this pressure or something else? LC Brass .308

[Adam0321/0306]

Good evening everyone. So I have been doing some load dev for a 308 of mine. The rifle is a custom Remington 700 with a 1:14 Hart barrel. The load is LC brass with 44.5 grains of IMR 4064, CCI 200, Sierra 2156 155 grain SMK. I am getting velocities averaging 2751. But I am having a hard bolt lift. The first 3/4 of bolt travel is fine, then it nearly feels like it has to cam over to fully open.

The picture showing the LC LR brass is having the bolt issue. The other brass, factory FC 308 is not causing any problems. I am well below the max charge. Even given the thicker case walls of the LC brass, I wouldn’t expect this to be a pressure issue.

Any input? Thanks.

 

[Shooter13]

Sounds like bolt "click" to me. How old (how many rounds) are on the brass? Has it been shot hot?

 

[DShortt]

Based solely on the images and your load data, I'd be inclined to believe it's something to do with the LC brass.
As mentioned above, what do you know about this brass?

 

[Adam0321/0306]

Thank you for the replies. I would say the brass has 3-4 reloads on it. Possibly 5. I try not to shoot it too hot.

 

[Straightshooter1]

Good evening everyone. So I have been doing some load dev for a 308 of mine. The rifle is a custom Remington 700 with a 1:14 Hart barrel. The load is LC brass with 44.5 grains of IMR 4064, CCI 200, Sierra 2156 155 grain SMK. I am getting velocities averaging 2751. But I am having a hard bolt lift. The first 3/4 of bolt travel is fine, then it nearly feels like it has to cam over to fully open.

The picture showing the LC LR brass is having the bolt issue. The other brass, factory FC 308 is not causing any problems. I am well below the max charge. Even given the thicker case walls of the LC brass, I wouldn’t expect this to be a pressure issue.

Any input? Thanks.

Hmmm??? With hard bolt lift, I'm surprised there's no ejector marks as a sign of pressure issue. The primers simply look like the firing pin hole is a little too big, which is common, so wouldn't equate that to pressure as the primers don't look particularly flat.

LC brass has less case volume than Federal or the like of Lapua, like. . . . it's at ~ 54.8 grs H2O vs Lapua that might be at ~55.6 grs H20. With case a volume 54.8 grs H20 and and loading 155 gr SMK's to a COAL of 2.800, your at ~ 107% case fill with 44.5 grs of IMR 4064. Running these numbers through my QuickLoad app shows the velocity to be right at what you're getting and the estimated pressure is right at SAAMI max.

That the FC cases are not a problem suggest to me there might be an issue with the case itself in your particular chamber and nothing to do with the load. I'd check the case's head space for the ones before firing and after firing and likewise measure the area at .200 above the base and just at the shoulder to see what the differences are.

 

[SKWERLZ]

is the speed the same for both cases?

 

[Adam0321/0306]

Here is a video of what is going on.

 

[Coyotefurharvester]

Has the brass required length trimming? How much neck expansion after firing?

 

[Adam0321/0306]

is the speed the same for both cases?

Sorry, I should have clarified. The FC cases are factory mil surplus M118LR. So they are factory loaded with 175SMKS

 

[Adam0321/0306]

Has the brass required length trimming?

It has. Some are even a bit past 2.005.

 

[Adam0321/0306]

Has the brass required length trimming? How much neck expansion after firing?

I have not measured neck expansion. But the brass does require about 5000 to be trimmed.

 

[SKWERLZ]

Looks like a clicker, case sizing issues.
Might want to investigate your virgin vs fired case dimensions at the .200 line.

 

[J_idaho]

Have you tried a case after sizing before shooting it?

 

[Adam0321/0306]

Have you tried a case after sizing before shooting it?

You mean to chamber a case after sizing and see how it ejects?

 

[C.E.Smith043]

 

[Coyotefurharvester]

You mean to chamber a case after sizing and see how it ejects?

Yes

 

[Jason D Hostetter]

It's probably the soft ass LC brass, over expanding and not shrinking back enough to get a smooth opening of the bolt. If you were using Peterson, Alpha, Lapua, or even Starline, you can't put enough Imr4064 under a 155, to destroy a piece of good brass. Imr4064 is really too slow for 155s when using good cases. That's why most people shoot H4895 or 8208xbr under 155s.

 

[J_idaho]

You mean to chamber a case after sizing and see how it ejects?

Yes

 

[Adam0321/0306]

Well, that does it. Sure seems to be the issue.

 

[Adam0321/0306]

Looks like a clicker, case sizing issues.
Might want to investigate your virgin vs fired case dimensions at the .200 line.

Fired measures at .466. Sized in an RCBS FL die measures .460