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Pressure signs at low powder charges.

CRhoades

I just got a new to me 6 Dasher, supposedly had 30-40 rounds through it.
40xbr
28 in Krieger 8 twist .2704 neck.
.050 firing pin protrusion.

First fire forming load with the false shoulder method was 30 grains of varget with a 105 Jlk. Primer cratered badly and ejector mark was clearly visible. Blow length is 1.53-1.534.

Since then I've tried down to 26 gr varget and 25 gr Re-15 and all have cratered primers and ejector marks. Sticky bolt lift occurs at 31.3 grains varget

Next I tried some formed brass with 30 gr varget, 105 Jlk and 3 different primers: cci 400, 450 and rem 7.5.

I tried turning the necks on a couple down to about 4 thou clearance( non turned is about 1.5 thou clearance)

Cast the chamber. Everything looked good there.

Swapped firing pins, which helped on the cratering.

Tried some 107 Smk.

Played with seating depth quite a bit.

Removed the ejector.

Scrubbed the throat with JB, thoroughly cleaned the rest of the barrel.

I think that's about all I've tried, every load whether fire forming or formed already is showing signs of pressure.
What are your opinions?
 
You have a Remington action and it probably needs to be bushed by Gre-Tan. The larger firing pin hole, as it sits now, needs the bush job so that it will not allow the cratering. AND the possibility exists that you are pushing the shoulder back too far, say 10K, causing the case to be pushed forward upon the firing pin strike, and tremendous rearward thrust, as the pressure goes forward, slamming the case head against the bolt-face causing: 1.) your primer cratering from the "un-bushed" bolt and 2.) MAYBE causing the case web to expand upon the slamming effect of the rearward thrust.... I am not a 'smith nor a ballistician, however, I can see these as culprits. Whether or not they are the cause, remains to be seen.. Just my 2 cents worth..
 
Too much head space on the brass I use faulse shoulder and jam . The brass you have fire forum remove the fireing pin don't size an put blue painter tape on on the head. If the bolt close with out any pressure you have excessive head space . Larry
 
Thank you gentlemen,
I have no doubt it could benefit from a bushing job, it's on my list of things to do.
I just went and measured the headspace with a .375 comparator, they were 1.236-1.238. One that had been fired multiple times was 1.240. With a piece of tape on the bolt nose and the firing pin and ejector removed the 1.240 case would not close, the 1.238 case required heavy pressure to close, and the 1.236 required moderate pressure to close the bolt on.
This kinda leads me to believe it's not a headspace issue??
 
CRhoades said:
Thank you gentlemen,
I have no doubt it could benefit from a bushing job, it's on my list of things to do.
I just went and measured the headspace with a .375 comparator, they were 1.236-1.238. One that had been fired multiple times was 1.240. With a piece of tape on the bolt nose and the firing pin and ejector removed the 1.240 case would not close, the 1.238 case required heavy pressure to close, and the 1.236 required moderate pressure to close the bolt on.
This kinda leads me to believe it's not a headspace issue??
Click to expand...
 
You answer your own question . I use tape when I head space my barrel . A little resistance with one piece and won't close with two . Larry
 
I've seen a .236 or tight bore barrel do this before. Only other thing I've seen that caused this was a screwed up chambering. Drove us Nuts!!! Rechambered, problems went away.
 
CRhoades said:
Near as I could tell, the pressure ring is 85 thousandths above the neck-shoulder junction.
Click to expand...
If that's true your throat sounds good to go. Maybe like they said, a too low of charge.. I would try a BR4 primer they are a little harder. The cratering is from the firing pin and hole. Maybe a bad lot of Varget. I had a lot that was hot. Matt
 
falconpilot said:
I've seen a .236 or tight bore barrel do this before.
Click to expand...

Be my first guess too if neck dia. fits with your case dimensions. Maybe try some Lapua bullets? They're a little smaller diameter than Sierra's. Or try Berger hunting bullets with their thinner jackets.
 
I remember reading a post similair to this. It turned out to be that the reamer throat dia and the bullet dia were to close and caused high pressure.
 
CRhoades said:
The loaded round diameter measures .269, looks like they need turned. I was hoping to not have to do that.
Click to expand...
Will a bullet slip into a fired case with no resistance? Remove a fired cartridge, turn it upside down and place it over a loaded round. Do the mouths touch without having to push down?
 
Yep .269 is too tight for a .270 neck chamber. I bet that is where the pressure is coming from. I like them to have enough room to let the bullet go. One thing is a slight skim will give you clearance and more concentric ammo. It should help you. I like .003 clearence. Matt
 
My brass the necks all come out after fireng at . .269 or. .269.5 with a.270.4 chamber depending on the spring back of the brass.
And if the neck is done with a vld tool I can twist a bullet in the neck . Tight but will go.
I Trim my brass to .012.3
With . .013 neck the loaded case will end up at .269 that is tight but still safe. Larry
 
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