question about warm barrels and groups

[VLSS]

So Im an impatient person. When I go to shoot I usually take all my shots in a group right after each other with no to very little cool down. Im wondering how much does it affect accuracy? I was shooting a couple days ago working up a new load and found a decent one that put the first 3 shots in .5 or smaller at 200 but the last 2 opened the group to 1.5. So is it possible because I shot all my shots fast with no cool down that it opened my group up? I just started reloading and worring about great groups so I never paid attention to this until now. Thanks

[Wrangler John]

Competition benchrest shooters try to take five shots for group as fast as possible when conditions are just right. The idea being to get all the shots in before conditions change. That's why they made dual port actions, where cartridges are loaded on the left and eject on the right. Their barrels heat up - but they use heavy barrels that are stiff and act as a heat sink. Thin, featherweight barrels are known to change impact point as they heat from firing.

It's said that some button rifled and hammer forged barrels will change point of impact when heated due to unrelieved stress in the steel. Maybe, maybe not. Then there are cut rifled barrels which have little or no stress induced from the rifling process that are said to be unaffected. Conventional wisdom says that barrels shouldn't be overheated during break-in or they will develop new stress. There is no definitive answer, but we ritualize the break-in process as a paean to the gods of barrel superstition and ignorance.

There is a lot of evidence that rapid firing and heat have a detrimental effect on the chamber throat, causing accelerated erosion of the steel. So allowing a cool down between shots prolongs accuracy. My suggestion is to take a little time between shots, maybe a minute or two. This was especially true when I had to send a rifle out to be rebarreled, now that I own Savages and can rebarrel them myself, not so much. Still, a barrel costs $400+, so I'll wait a bit between shots.

Shooting is a good way to learn discipline, like any marshal art. Patience and tranquility of mind are the key to good shooting.

[Snoplop]

Good post!


Been pondering (read - scheming how to sell the idea to my wife) one of those fancy Carbon Composite barrels from ABS
and wonder what your thoughts are..or if any have used them with a degree of success.
Besides the fact it would cost an arm an leg. If they are as good as they say, would that alleviate some of the issues?

Thoughts are for a carry gun that doesn't weigh a hundred pounds but has the potential accuracy of one that does.
And next time I feel froggy can shoot the daylights out of it with no ill effect.

Hmmm..Just saying that sounds like I'm on a fruitless venture...

Thanks

[VLSS]

Thanks for the info John. So its most likely my ammo or me is at fault for the bigger than I want group.

[Jim White]

Hot barrels can have an effect on groups because of the heat waves distorting the view through the rifle scope.

Hot barrels also heat up rounds inside the chamber. So if you're using a powder charge that is sensitive to heat changes
don't chamber the round until you're ready to shoot. Get it out the tube as quickly as possible (but make a good shot). In the event you can't get a good round out, unload it and let it cool. When you're ready to try again, grab another round.

HTH,

[Wrangler John]

Good post!


Been pondering (read - scheming how to sell the idea to my wife) one of those fancy Carbon Composite barrels from ABS
and wonder what your thoughts are..or if any have used them with a degree of success.
Besides the fact it would cost an arm an leg. If they are as good as they say, would that alleviate some of the issues?

Thoughts are for a carry gun that doesn't weigh a hundred pounds but has the potential accuracy of one that does.
And next time I feel froggy can shoot the daylights out of it with no ill effect.

Hmmm..Just saying that sounds like I'm on a fruitless venture...

Thanks

Well, maybe not fruitless. If you try an ABS barrel and it works better than anything before, or even if it is an abject failure, you have learned something. Learning something new through experience is not a fruitless pursuit. These carbon wrapped barrels have been around for some time. Winchester cobbled up a shotgun back in the 1970's with a carbon fiber wrapped barrel. It didn't last long for whatever reason - most likely too avant-garde for the day, and probably didn't possess a real advantage. Shooters tend to be traditionalists that are slow to adopt new technology.

My thought experiment on carbon fiber wrapped barrels is this: While the carbon fiber, as ABS claims, may stiffen the barrel, and their process may conduct heat better than steel, it's the steel barrel that still takes the brunt of firing. Firing a cartridge produces a high pressure, high temperature gas that acts a a plasma. This high pressure plasma is in direct contact with the barrel steel, which reaches a corresponding temperature briefly. It is this change of state that erodes the chamber throat and introduces copper and carbon laden gas into the throat and bore. Copper and carbon produce fouling in the bore that increases pressure and strips even more copper from the bullet. While the carbon fiber wrap may conduct temperature away from the steel liner, it can do nothing to lower the pressure/temperature inside the bore during firing, or anything about the abrasive action of powder and bullet particulates. Next, is that while the exterior of the carbon fiber may remain cooler, rapid firing will still produce accelerated wear on the chamber throat and bore. Machine guns often used Stellite high cobalt tool steel chamber inserts or coatings to reduce wear. Stellite is the same hard facing alloy I used to protect dozer grouser pads and blades, it is high temperature and abrasion resistant. Reducing heat build up likely will extend barrel life a certain percentage, but the barrel will still be wearing faster when rapid fired, and wear out quicker. (they also chrome line barrels to reduce erosion).

Then carbon fiber composites are dependent on epoxies for their construction, they are only as stable as the epoxy. Most epoxies are heat sensitive, although a few years ago General Dynamics (or was it Pratt and Whitney Rocketdyne ?) developed one that could sustain 1,400 degrees for 24 hours (it was probably classified at the time). Given the difficulty of transporting heat across a boundary between dissimilar materials (which is why a thermal paste is used between computer CPU chips and heat sinks) I would be reluctant to believe everything claimed in advertisements. The greatest advantage in carbon fiber barrels seems to be weight reduction. Question remains: Is the extra cost worth any additional advantage over a steel barrel?

There just ain't no free lunch when it comes to shooting through a steel barrel. Now if somebody comes up with a ceramic barrel, then we may have something. Until then, save the money and take your wife out to dinner. Let her know you rather have dinner with her than buy a new toy.

[TXNinVA]

I use the OCW method for finding the handloads my gun likes. The barrel gets hot using that method, but I find a round that works well under any condition. It may be more accurate with a different load under specific conditions, but you don't get to pick when you hunt.

http://optimalchargeweight.embarqspace.com/

[Jim White]

I use the OCW method for finding the handloads my gun likes. The barrel gets hot using that method, but I find a round that works well under any condition. It may be more accurate with a different load under specific conditions, but you don't get to pick when you hunt.

http://optimalchargeweight.embarqspace.com/

I tend to try and find a load that works with how I'm using the rifle. For the big game rigs I use the cold barrel grouping because at best I figure I'm only getting one shot. At best maybe two.

Jim