New build. Same recipe... Now with pressure signs! 308cal

Cpt.Flan

Cpt.Flan

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Hi folks.

I need a little help from you guys!

Long story short... I had a rem 700 ( 20" 1-12 twist ). I had a load for it that was awesome.
43.5gr Varget / Lapua casing / SMK 175gr / FGMM primers. Loaded to 2.80"

I had no pressure issues. All good. Accurate and all.
Since I am getting more into precision bolt action shooting I realized fats enough that every little detail is important.

Now for this new match chamber on a Bartlein barrel. (24" 1-11.25 twist)
First of my old reloads did not chamber properly. Bolt was not closing.

I corrected this by a very small shoulder bump. I was told 0.002.
Perhaps too much? Casing gauge is on the way.
After doing this the ammo chamber perfectly. Bolt is closing smoothly.
Loaded to the same safe 2.80" Tool on the way also... hehe
Same load and same bullet.

But now I am getting PRESSURE SIGNS!!!
I chrony my rounds. 50X2660fps ( +/- 16fps )

Bolt is not hard at all and the round come out easy. No "sticky" bolt.

I get cratering around the fire pin hole and the primer gets a little flat.

I was surprised since the velocity is nothing crazy. Hodgon load data say 46gr is max load if I remember correctly but Sierra tell different. 43.5gr!!
Makes me basically at the max load already.

Not sure why I get pressure signs now.

Any ideas guys?



Thank you very much!
 
Last edited:
it's a different rifle/chamber, that's why. if you bought 2 of the exact same rifle, you will have different results with the same ammo.


you need to work up a new load plain and simple.
 
federal primers are rather soft, personally i wouldnt worry about it. in my match chamber i get flat primers starting at 42gns and up.. but no other pressure signs. swap in a CCI primer (knowen to have harder cups) and the primers dont flatten at all
 
Hodgdon's max published load is 45.0 compressed. You could try a harder primer like CCI, or try the same charge but load the bullet out closer to the lands. Either way I don't think you have an unsafe load. Mine was 44gr or 44.2? Varget for 2655fps under a 175 Hornady.

Obviously pressure is going to vary from one rifle to the next.
 
Very common for cut rifle barrels to be on the tighter side of the norm. That and likely a shorter chamber all lead to increased pressures.

We always work up our loads with any major new compenent and a new barrel is certainly a biggie. Never ever assume that a load for 1 rifle transfers over to another

Start 2 grs less, work up and I bet you will see very good accuracy, no pressures signs and velocity similar to where you are now.

It is very common for velocity to stay pretty much the same but pressure cues to become more obvious with small increase in powder charge when you are near the max for that rifle. So by working up, you can "see" the pressure plateau by watching the velocity and fired case cues.

Simple issue... back off your loads, work up again and enjoy a fine rifle.

last thing to keep an eye on is that neck thickness. Be prepared to start outside neck turning....

Jerry
 
I just can't understand this thread!
The OP is using a well known, often used powder for his combination of calibre and bullet weight.
There is no sticking of the bolt or of empties coming out of the chamber.
He has chronographed fifty rounds which are extremely consistent.
The velocity being 2660 for 175 grains appears to be abut ideal.
What more could he want????
 
I've got a few rifles that exceed book speeds, do it with the starting loads and cant get near book max charges. The trend is good barrels and tight chambers and usually short throats. If the speed is there, what's the problem?

What pisses me off is when the speed isn't there but the pressure is. Get that sometimes too, more often than I'd prefer.
 
Max loads are a rough guide to show you where the test rifle showed max pressure. What you need from load data is the start load. Max load is an idea where you might see pressure signs but not a set-in-stone maximum. As already answered, you went from a sporting chamber to a match chamber. You also have a brand new bore that may have tighter tolerances than your 700. This will raise pressure over the sporter rifle. Reduce, work back up. You're saving powder that will pay for that rifle in no time! (If current powder trends keep up)
 
H4831 said:
I just can't understand this thread!
The OP is using a well known, often used powder for his combination of calibre and bullet weight.
There is no sticking of the bolt or of empties coming out of the chamber.
He has chronographed fifty rounds which are extremely consistent.
The velocity being 2660 for 175 grains appears to be abut ideal.
What more could he want????
Click to expand...

Apparently , harder primers. - dan
 
A new barrel or chamber needs new work up.

However, if the only sign is the Federal primer, keep shooting. Suggest you switch to the CCI benchrest.

You can them load hotter for more velocity, watch for new pressure signs. A sticky bolt means you are in proof round range.
 
Cpt.Flan said:
Hi folks.

I need a little help from you guys!

Long story short... I had a rem 700 ( 20" 1-12 twist ). I had a load for it that was awesome.
43.5gr Varget / Lapua casing / SMK 175gr / FGMM primers. Loaded to 2.80"

I had no pressure issues. All good. Accurate and all.
Since I am getting more into precision bolt action shooting I realized fats enough that every little detail is important.

Now for this new match chamber on a Bartlein barrel. (24" 1-11.25 twist)
First of my old reloads did not chamber properly. Bolt was not closing.

I corrected this by a very small shoulder bump. I was told 0.002.
Perhaps too much? Casing gauge is on the way.
After doing this the ammo chamber perfectly. Bolt is closing smoothly.
Loaded to the same safe 2.80" Tool on the way also... hehe
Same load and same bullet.

But now I am getting PRESSURE SIGNS!!!
I chrony my rounds. 50X2660fps ( +/- 16fps )

Bolt is not hard at all and the round come out easy. No "sticky" bolt.

I get cratering around the fire pin hole and the primer gets a little flat.

I was surprised since the velocity is nothing crazy. Hodgon load data say 46gr is max load if I remember correctly but Sierra tell different. 43.5gr!!
Makes me basically at the max load already.

Not sure why I get pressure signs now.

Any ideas guys?



Thank you very much!
Click to expand...

The one thing you didn't mention is how the load shoots?
 
Cpt.Flan said:
And your point is? Anything helpful?
Click to expand...

My point is that you should know better. When you change a component in a load you work back up. When you change the whole chamber you'd have to be inordinately thick to assume that the handloads you tailored for a factory chambered rifle would run properly. I've never met a knowledgeable handloader that would use loads built for one rifle in another, let alone one with a chamber cut with a good sharp reamer.

Consider it a new rifle and start from scratch.
 
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