Friend of mine has a brand new 12 VLP in .223. Shooting two different types of ammo - cheap PMC and Hornady 75gr BTHP Match - he's getting all kinds of pressure signs. Almost all of the rounds have the primers cratered, a few were pierced, and one was a complete blow out. I shot some of the same PMC ammo in my AR and it showed no pressure signs. The barrel was thoroughly cleaned prior to shooting and he was cleaning after every few shots to help with barrel break-in. He's going to call Savage today, but I thought I'd post it on here and see what the group thinks...
Staring at the brass and primer for "signs of pressure" is about as accurate in terms of pressure measurement, as tossing a 2# rock up in the air to "see if the wind is blowing".
More likely is firing pin protrusion is off, OR that long bullet is stuffed into the lands.
What we really need to know is the velocity, and would be great to have his velocity AND your velocity.
I'm a firm believer in the theory that if it bleeds, I can kill it.
Other than being sure the camber is cleaned, I concur with darkker. Hard bolt lift?
One suggestion and I don't know if its valid as I don't venture there, is to have a shell holder with you, if it does not slide into the shell holder easily its been pressurized.
We did chrono the Hornady ammo with my megnetospeed and it was coming up a bit faster than the listing on the box. I don't recall the exact numbers but the box said 2790 and he was getting 50 - 60 fps more. We attributed that to the 26 inch barrel on his rifle. The bolt hasn't been tight and no problems extracting.
Last edited by Texan Til I Die; 07-18-2016 at 02:38 PM. Reason: additional info
Interesting; Here is the link on use of the shell holder for pressure as well as a lot of other good information.
http://bulletin.accurateshooter.com/...rtridge-brass/
Barrel length, with the "usual suspects" in terms of propellants, doesn't make much difference in that cases....case. Assuming that the magnetospeed is accurate.
That increase of speed is most likely from increased pressure.
Although with a Savage it would be a break from the "norm", I would still wonder if the throat is too short for that bullet.
Did you try and chamber a round, then eject it and see if the bullet has contacted the lands?
I'm a firm believer in the theory that if it bleeds, I can kill it.
Even more interesting is there are 5 articles on checking your cases for overpressure. (dig)
The Dunning-Kruger effect is alive and well.
Just got some new info. He reloaded some rounds using load data that was in the lower half of the range (not sure what powder he used, but he's not a newbie to reloading) and got the same symptoms. He also seated the bullets so they were just off of the lands.Originally Posted by darkker
Barrel length of the AR you were shooting?
What barrel length does Hornady use for their testing?
And are there the indicators (more than one) of the other pressure signs?
Firing pin clearance is good?
The Dunning-Kruger effect is alive and well.
Your velocity was probably higher due to the fact you are measuring right at the barrel. Factory numbers are more like 10-15 ft from the muzzle.
"An armed society is a polite society"
"...shall not be infringed" What's the confusion?
Sounds just like the problem I had with a new 12FV. It was loose firing pin fit. You might pull it and measure carefully with a micrometer if possible. Should measure .069 to .070.
If it's down in the .067 - .068 range, replace it. I tried sending mine back, but the repair guys shot it with ammo loaded with magnum primers and it showed no cratering so they just sent it back, ignoring the included shot Hornaday 75 gr. BTHP match ammo that had pierced primers.
If you order a firing pin, get two or three. You'll have to sign a waiver to be able to buy it. Be sure to ASK to sign the waiver if the CS person refuses to sell you a firing pin.
My AR is a Rock River Varmint with the 20 inch bull barrel
Hornady uses a 24 inch test barrel for their velocities
No other pressure signs besides the primer issues
I haven't talked to him to see what Savage said, but it's looking more and more like a firing pin issue. I found several references on this site and on others where people had almost identical problems that were resolved by replacing or repairing the firing pin.
Yep
The Dunning-Kruger effect is alive and well.
Agreed, 2 inches on the 12 is "likely" (not guaranteed) to give some velocity increase (50 FPS) rifle differences from test can add a bit as well (it can also subtract)
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