warm barrel?

[bob4]

I'm working up a hunting load for a 300wm. Pretty sure I found my first node but here's what I got today.
The first round of three went fine. Velocity was on track with shooing same load the other day. So I thought if I can do this 3 times it's off to some distances. 1st pic is second go.

Note the FPS in the second pic. The barrel was warm for this round but not what I would call hot. Everything else was identical. Case,bullet,charge and ogive. Did I get higher FPS because of a warmer barrel? Therby spreading them out. FYI: These are @ 50yds at home. So I expect tight groups before I head off to 100yds+.

 

[MRH]

Good chance. What gun and barrel - standard, thin, heavy?

Some of my regular contour bbls act like that while only warm

 

[jmr40]

I'd be surprised if a warm barrel made 150 fps difference. You generally see .5-2 fps difference in speed for each 1 degree of temperature change depending on the powder. And this is the temp of the powder, not the barrel. You'd have to leave the loaded cartridge in a HOT chamber a long time to raise the temp more than 5-10 degrees.

I don't know why, but don't think this is the reason.

 

[GLOOB]

Did I get higher FPS because of a warmer barrel?

In most cases, yet. Warmer chamber = faster powder burn rate.

But if you cleaned the barrel recently, the velocity also might increase some through the first several fouling shots.

 

[jwalts27]

When I shoot my 308 Ruger American I start to get flyers after 7-10 shots.

 

[Sunray]

"...because of a warmer barrel..." Nope. Warm barrels don't resonant the same way a cold one does.
"...before I head off to 100yds..." You really should test loads at 100, not 50. Fifty yards doesn't tell you much. And a hunting load only matters for the first shot out of a cold barrel.

 

[bob4]

" You really should test loads at 100, not 50.

In the pics above I would much rather go to the range shooting like the first pic then the second. This I can do at home and make a new load immediately if I need to. Is the first time I'm doing this @ 50. Seems to me like it should help out. Maybe I'm wrong.

 

[gamestalker]

I have 3 Americans, 22-250, .243, and .270 win.. So basing it on the American alone, I have noticed my groups opening up as I approach the 4th shot, and after that there is a very noticeable spread.

Now I do load and shoot the 300 WM, Rem. 700 though, 26" SS barrel. Same story here though, the group opens up significantly as the barrel warms up, which is anything beyond the 3rd or 4th rounds. I've run 155's, 165's, and 180's and all show some group degradation as the barrel warms up.

I did however notice that the 155's with a near max charge of IMR-7828, don't open up as badly with a warm barrel, not sure why. It seems to some how be associated with the higher velocity, as I've noticed a trend at each velocity gain with bullets weights? In other words, the quicker the bullet gets out of the barrel, the less amount of group spread I'm seeing present.

GS

 

[bob4]

Interesting GS. Are you waiting any significant length of time between shots? I'm using a Rem 700/26", just not the stainless barrel. I'd be interested to see your results from working up 165's.

 

[spitballer]

Immediately I would suspect fouling, but my rate of fire at the range averages 1 shot a minute so barrel temp wouldn't be a factor for me. I ended up compromising on the fouling issue by using just enough pressure to keep my fouling shot at the same height as the shots that follow. Admittedly I tend to get some rolling left and right for the first couple of shots with this method, but then the groups tighten up very nicely. More importantly to me, I can get off many more rounds before having to perform barrel maintenance. This might not be a good method for a hunting round though, especially for dangerous game.

 

[gamestalker]

Bob, well no, I'm referring to what happens when shooting back to back without a cool down period. Taking only the time necessary to get off the next clean shot off of a shooting rest, so very little time between shots. I don't do a lot of this, but with each new hunting load development, and, or rifle, I like to shoot a couple of hot barrel groups, so I can know what to expect in the field if for some reason I find myself having to shoot multiple times at my quarry, which can tend to happen when varmint hunting.

Same with a cold bore shot, though this is obviously the most important aspect of a hunting load. So most of my sight in groups are obviously performed with adequate cool downs between shots. This to me seems very important when shooting a standard barrel production rig.

GS