Primer Blow Out with NO Over Pressure Signs?

[XC700116]

When brass flows into the ejector you are already pushing it. Primer cratering is not a very reliable indication of pressure.

Yes, my LR rig will crater primers with very light loads and soft primer cups.


Also from what you said about tying to measure the OAL to the lands, I'd try loading a bunch, or just further seating the loads you have to 2.780 to make sure you're not jamming at all. If the pressure signs go away, you have your answer, but continue with caution.

[BuffCyclist]

Yes, my LR rig will crater primers with very light loads and soft primer cups.


Also from what you said about tying to measure the OAL to the lands, I'd try loading a bunch, or just further seating the loads you have to 2.780 to make sure you're not jamming at all. If the pressure signs go away, you have your answer, but continue with caution.

But wouldn't seating the bullet 0.02" deeper cause other pressure signs?

[Hoser]

But wouldn't seating the bullet 0.02" deeper cause other pressure signs?

Seating rifle bullets deeper causes the pressure to go down.

[BuffCyclist]

Seating rifle ammo deeper causes the pressure to do down, in rifles.

That is completely counter-intuitive (as long as the bullet isn't jammed against the lands). Seating it deeper means less case capacity, so when the primer ignites there is a smaller volume being expanded before pushing the bullet forward and before the powder ignites.

I've read a lot from you Hoser and know you are extremely knowledgeable on the subject, so I'll believe you, it just doesn't make sense.

I just googled it too and found an article by Barnes Bullets that corroborates this, but it also shows pressure spikes if the bullet is too far from the lands.

I have lots of time to figure this out, just found out my rifle is subject to the X-Mark Pro trigger recall, and sadly I don't have the funds for a brand new trigger right now so I think I'm going to have to ship the rifle back. :-(

[BuffCyclist]

Okay, so I decided to try the wood dowel method of measuring the bolt face to the lands again.

I seated a bullet in an empty case (FGMM once-fired in my rifle, BARELY sized the neck so it was a little tight but that I could easily push the bullet deeper by hand). Carefully put the round in the chamber, slowly slid the bolt forward until it stopped, then used a small bungee cord to hold it forward and up. Slid a wood dowel down the barrel until I touched the bullet and marked the dowel. Ejected the round carefully, then slid the bolt face forward again, bolt up, bungee and measured with the dowel again. Here are my measurements:

1 - COAL Before - 2.968"
1 - COAL After - 2.952"

Decided to fully close the bolt this time, and got nearly the same after measurement:
2 - COAL Before - 3.041"
2 - COAL After - 2.950"

Left the bolt in the up position again:
3 - COAL Before - 2.983"
3 - COAL After - 2.955"

I can continue doing this all day, but I have a feeling the COAL base to lands will be 2.950" +/- 0.01", so I have a feeling I am not jammed against the lands. And yes, while I don't have a way to measure the o-give yet by marking the bullet tip with sharpie and looking for the scratch mark from the rifling, it is at least 0.55".

The markings on the dowels are as follows:

1 - 3.015"
2 - 2.955" (closed bolt, not sure if this is accurate though)
3 - 3.016"
4 - 3.022"
5 - 3.010"

[TheBelly]

Okay, so I decided to try the wood dowel method of measuring the bolt face to the lands again.

I seated a bullet in an empty case (FGMM once-fired in my rifle, BARELY sized the neck so it was a little tight but that I could easily push the bullet deeper by hand). Carefully put the round in the chamber, slowly slid the bolt forward until it stopped, then used a small bungee cord to hold it forward and up. Slid a wood dowel down the barrel until I touched the bullet and marked the dowel. Ejected the round carefully, then slid the bolt face forward again, bolt up, bungee and measured with the dowel again. Here are my measurements:

1 - COAL Before - 2.968"
1 - COAL After - 2.952"

Decided to fully close the bolt this time, and got nearly the same after measurement:
2 - COAL Before - 3.041"
2 - COAL After - 2.950"

Left the bolt in the up position again:
3 - COAL Before - 2.983"
3 - COAL After - 2.955"

I can continue doing this all day, but I have a feeling the COAL base to lands will be 2.950" +/- 0.01", so I have a feeling I am not jammed against the lands. And yes, while I don't have a way to measure the o-give yet by marking the bullet tip with sharpie and looking for the scratch mark from the rifling, it is at least 0.55".

The markings on the dowels are as follows:

1 - 3.015"
2 - 2.955" (closed bolt, not sure if this is accurate though)
3 - 3.016"
4 - 3.022"
5 - 3.010"

What is your magazine OAL?

[J]

What is your magazine OAL?

In the B&C that comes on that, WAY too long. I bet he could get over 3.00 in there.

[TheBelly]

In the B&C that comes on that, WAY too long. I bet he could get over 3.00 in there.

Long enough to measure it and get it off the lands .002"?