Blowing Primers and other signs of high pressure in a mild load

[the long shot]

I have switched from my old standby load with Varget to IMR4350. The IMR4350 patterned well on the low end of the powder range and I went with that charge.

I went to a club match and I blew two primers. I did some practice the other day and I blew two primers and was getting ejector marks on the brass.

I clean my rifle regularly and double checked the charge on Hodgdon load data and the range for the load with a 168 grain bthp is 54 grains to 58 grains in a 30-06.

What could be the other cause of these high pressure signs? I don't want to, but may have to pull 100 rounds of preloaded ammo and lower the charge.

Savage 110, CCI LR primers, Black Hills Brass, 54.3 IMR4350 powder. The previous load was 48.6 grains of Varget with all the same components.

I pulled the bullets and weighed the charges. Charges were consistently within .1 of 54.3 grains. Brass length varied from 2 thou under to 6 thou over max trim.

 

[dmoran]

Possibilities:

Carbon layer buildup in the barrel can cause pressure.
Media or obstruction trapped in the brass.
Miss-weight of the charges, and/or scale calibration.
Wrong powder.

Good Luck
Donovan

 

['Freak]

Which of the many differently constructed .308 caliber 168 grain HPBT projectiles available are you using?

 

[the long shot]

Which of the many differently constructed .308 caliber 168 grain HPBT projectiles available are you using?

Nosler

 

[bheadboy]

the brass may be the problem, water capacity is very different between mfgers, check yours and compare to charts and see if your brass is thicker (less volume)
If the only change is powder, then what were the varget loads that worked without pressure compared to the chart you are using? if they were on the low end also then I would settle on the brass being the problem --stay low.
Bob

 

[deadidarren]

what speed are they doing it way well be a hot load for that rifle

 

[savagedasher]

Possibilities:

Carbon layer buildup in the barrel can cause pressure.
Media or obstruction trapped in the brass.
Miss-weight of the charges, and/or scale calibration.
Wrong powder.

Good Luck
Donovan

Donovan is correct . One other thing when the brass was sized you could have excessive head space
Larry

 

[Joe Wade]

Your load is right in there. My 30-06 favorite load is:
56grs. IMR4350, Rem or Win brass, Hornady 165gr. BT Interlock. in Ruger M77 with 24" barrel.

I would pull your bullets, work up a new load with your current components.
The RCBS collet style bullet puller makes pulling bullets easier and saves your components.
Good luck on your testing.

 

[Scott Harris]

The fact that you are blowing primers is the only important piece of data you need to be concerned with......lower your charge. It does not matter what any books say, the particular set of components you are using are causing extreme high pressure signs..."lower the charge!" You should start by going a minimum of one full grain lower.

 

[243winxb]

Is the primer falling out or is there a hole is the edge of the cup? Nosler data http://www.nosler.com/nosler-load-data/30-06-springfield/ 57gr is max. Note that there brass holds 60.2 grs of water. What does yours hold, more or less?

 

[dmoran]

When you go from a load working fine, to it blowing primers, something had to change and/or interfere....

Carbon layer buildup in the barrel can do just that that causes pressure.
An obstruction trapped in the brass.
Miss-weight of the charges, and/or scale calibration.
Wrong powder.
A component change.
And as Larry wrote, excessive head space from over sizing

Good Luck.... and let us know what you find to cause it...
Donovan

 

[the long shot]

the brass may be the problem, water capacity is very different between mfgers, check yours and compare to charts and see if your brass is thicker (less volume)
If the only change is powder, then what were the varget loads that worked without pressure compared to the chart you are using? if they were on the low end also then I would settle on the brass being the problem --stay low.
Bob

water capacity is 62 grains for this brass.

 

[the long shot]

Is the primer falling out or is there a hole is the edge of the cup? Nosler data http://www.nosler.com/nosler-load-data/30-06-springfield/ 57gr is max. Note that there brass holds 60.2 grs of water. What does yours hold, more or less?

I measure capacity at 62 grains of water for this brass.

 

[the long shot]

When you go from a load working fine, to it blowing primers, something had to change and/or interfere....

Carbon layer buildup in the barrel can do just that that causes pressure.
An obstruction trapped in the brass.
Miss-weight of the charges, and/or scale calibration.
Wrong powder.
A component change.
And as Larry wrote, excessive head space from over sizing

Good Luck.... and let us know what you find to cause it...

I put it though a Montana Extreme treatment and was only able to extract a little more carbon from the barrel.
Donovan

 

[dmoran]

I put it though a Montana Extreme treatment and was only able to extract a little more carbon from the barrel.

Hard carbon layer have to be mechanically removed (brushing, elbow-grease, etc..). There is no cleaner that will do it by its self. I suggest to look down the barrel with a bore-scope (look for someone in your area that has one if you don't yourself).
It may not be carbon layer of the barrel, but often enough that is what can cause bad pressure increases and blown primers from an established load.

Donovan

 

[bheadboy]

if the varget was ok, and the change took place with the 4350, carbon layer would not have instantly occurred

it seems to me with the water capacity as you measured is ok, the question is did you change the size die setting when you changed the powder, if not then the headspace comment is not a factor. thus you get to the bottom,

if size and seat die are not readjusted with the powder change, and the primers brass are the same, then the only remaining solution to is powder load too high, pull a bullet and weigh the load in the case, is it the expected load?

check the 4350, is it IMR or H, they are not the same and speed/ pressure are different which were you using?

IMR is faster, takes less powder and has more pressure than H

Bob

 

[jlow]

Best way to check the carbon problem is to use a borescope but most people don’t have one or access to one. Another way to tell if it is the powder or the dreaded carbon ring is to load up some of your old standby with Varget and see if you have any problem. If it worked like before i.e. it is OK then it is the powder, if the old standby is now also blowing primers and showing significant ejector marks like in your photo, then it could be the carbon ring. You don’t need a lot of Varget, just enough to run the test.

 

[1shot]

BHEADBOY is on the right track I think. Is this a fresh can of 4350? If it is, you may have obtained a very fast lot. This happened to me at the Nationals but in the reverse. I ran out of 4831sc at a bad time and had been shooting the same lot # for 16 lbs. and had a real screamer of a load with low single digit ES/SD. I marked it in the tray so that I got to them, I was sure to use it as a sighter. Sure enough, 1.5 moa low. fired another to confirm before going for record. After the matches, I chronoed the "new" load and I was down 70-90 fps. If you can, try a different lot and see if you have any significant changes.
I hope this helps,
Lloyd

 

[Catfur]

Was it raining when you tested and had blown primers?

Much hotter than when you shot before?

 

[searcher]

Brass trimmed to specs after any sizing? Just covering the bases.