Load development in 80 + degrees

[jmason]

I was using a load I worked up over the winter until about a week ago when it started getting 80+ around here. I was getting pressure signs so I started putting my ammo in a cooler and that worked ok. I wanted to work up a new load in this heat so I did, but what I found was my gun will not tolerate any loads within about a grain of book listed or QL max. Shooting some 130 grain BTs over H4831SC and maxing out around 2950 with my 26" factory tube.

Would this be normal or should I be looking for something else causing pressure?

[J E Custom]

Originally Posted by jmason

I was using a load I worked up over the winter until about a week ago when it started getting 80+ around here. I was getting pressure signs so I started putting my ammo in a cooler and that worked ok. I wanted to work up a new load in this heat so I did, but what I found was my gun will not tolerate any loads within about a grain of book listed or QL max. Shooting some 130 grain BTs over H4831SC and maxing out around 2950 with my 26" factory tube.

Would this be normal or should I be looking for something else causing pressure?

What calibre ?

How close to the lands are you ?

And one other thing, check the trim length and look at the case mouth of a fired case
to see if it looks crimped.(You can take a loaded round and see if the bullet will go in
the fired case easy), Some times a rifle can be chambered with a short neck and it doesn't
want to release the bullet.

H 4831 sc is an extreme powder and is not known to be sensitive to temperature changes

Just a few thoughts on your problem.

J E CUSTOM

[jmason]

Shooting a 270 win., I'm at least .030 off the lands, trim and case length are good. The load I made up when it was cooler was a 140 BT w/ 57.7 of H4831SC. It defiantly cares how warm it is out side. So I figured I'd work something up in the summer heat to shoot in the summer heat.

This is happening w/ virgin rem brass too(forgot to add that earlier).

I really don't care if my lot of powder is sensitive or not. I'm just looking for a sanity check. By the sounds of your response you don't see this as something that could normally happen?

[old_heli_logger]

That virgin brass may very well have less case capacity...that will raise your pressure. I'm assuming you developed your load on fire-formed brass...

Good luck!

[jmason]

Originally Posted by old_heli_logger

That virgin brass may very well have less case capacity...that will raise your pressure. I'm assuming you developed your load on fire-formed brass...

Good luck!

I think I might be confusing you. I had a load made up from the winter 57.7gr of H4831sc and 140 BTs. When it got warmer out it was causing a heavy bolt lift and smearing the base of the brass as well as leaving a ring from the plunger in the bolt face. If I put my ammo in a cooler and shoot it I have no issues. This load is using the same brass I developed it with which is on it's 8th firing and has been annealed every time since the 4th firing.

So I decided to work up a load in the warm weather with some 130 gr BT's and H4831sc which started to show pressure signs around 58 gr. which is a full grain under listed max in the book and QL. This is with brand new brass. It is a lighter bullet, but at about the same charge as the 140 gr bullets I begin to see pressure. Now the book load was tested with a 24" shelien barrel and I have a 26" factory. I am getting a heavy lift but no markings on the brass.

Where the need for a sanity check comes in is I'm thinking the lighter bullet should be able to go faster than the heavy one without showing pressure at the same charge weight. The new load work up is using virgin brass but I can't see after fire forming being able to step up another grain of powder.

Is it somewhat normal to see pressure signs this soon (low powder charge) in 80+ degree weather?

[KY Gun Geek]

Don't shoot a 270, so no direct experience. However, I have been working on a 338 since March and had a similar situation - sticky bolt on a warm day (though I haven't tried the cooler yet).

I know I'm on the ragged edge - I bumped the charge until I got a sticky bolt (and loose primers) then backed off a grain. Weather got hot and I got some bolt issues again.

Backed off another 1/2 and have no problems.

No, I won't post the load, there's a good chance your rifle won't handle it. I will tell you I'm pushing a 225 gn Accubond about 2990. Powder is H4350 (an Extreme). But hey, I'm playing on the edge...

[JeffVN]

I go not believe your experience is unusual.

From living in Houston and doing reloading and load development (40 degrees in the winter and 90+ in the summer) and the same in Las vegas (40 degrees in the winter and 110+ in the summer), the key is muzzle velocity at the time you developed the load. You can down load during the summer to find the same velocity node.

My brother and I have done so with some level of sucess with his .308 (it took only 0.3 of a grain of RL-15 to put him back in the node), and my 7wsm (0.5 of a grain with H1000).

Jeffvn