Jamming vs. barrel life

[Ccrider]

I like jammin mon, hope ya like jammin too.

B Marley..

Classic!

 

[JLT]

Elevated chamber pressure is BS. Equal powder charges yes jammed will make a little more pressure. If you work up a load to right you are going to find pressure and back down appropriately, so the jammed bullet is going to be a safe pressure just as a jumped bullet, but you are just going to be using less powder to get the right load touching, and more jumping.

It is not BS. It has been measured, documented and peer-reviewed. All other things being equal, seating the bullet to contact the lands will increase chamber pressure over a configuration that does not. That is a fact. Some folks will take that fact and run with it, claiming that it will wear a barrel faster.

Note that pressure and temperature are closely related - a corollary of the first law of thermodynamics. In this case, we are examining the difference in pressure/temperature at the front end of the pressure curve. A bullet seated to contact the lands will result in higher pressure immediately subsequent to ignition. That will (must) result in higher temperatures - the question with respect to barrel erosion is one of 'how much and for how long'? What has been measured, to state it simply, says 'not much' and 'not for long'. The deviation from pressure baseline is not dramatic (you may break wind while opening your bolt if you're otherwise loading at max for your rifle, all other things being equal) and measurements have shown the deviation is brief (we're talking milliseconds, here).

Bottom line - an increase in chamber pressure is NOT BS for jammed vs. jumped. It is real, measured and documented. Is it the Seventh Sign of the Apocalypse? No, not necessarily. Will it accelerate barrel wear by 50%? As I said earlier, 'No way'.

 

[urbanrifleman]

It is not BS. It has been measured, documented and peer-reviewed. All other things being equal, seating the bullet to contact the lands will increase chamber pressure over a configuration that does not. That is a fact. Some folks will take that fact and run with it, claiming that it will wear a barrel faster.

Note that pressure and temperature are closely related - a corollary of the first law of thermodynamics. In this case, we are examining the difference in pressure/temperature at the front end of the pressure curve. A bullet seated to contact the lands will result in higher pressure immediately subsequent to ignition. That will (must) result in higher temperatures - the question with respect to barrel erosion is one of 'how much and for how long'? What has been measured, to state it simply, says 'not much' and 'not for long'. The deviation from pressure baseline is not dramatic (you may break wind while opening your bolt if you're otherwise loading at max for your rifle, all other things being equal) and measurements have shown the deviation is brief (we're talking milliseconds, here).

Bottom line - an increase in chamber pressure is NOT BS for jammed vs. jumped. It is real, measured and documented. Is it the Seventh Sign of the Apocalypse? No, not necessarily. Will it accelerate barrel wear by 50%? As I said earlier, 'No way'.

Start jammed. Keep pushing the bullet into the case. Pressures and velocities will go UP the more the bullet is pushed into the case. More than even the slight raise from being jammed.

That is documented by me.

 

[ebb]

You are exactly right "all things being equal" but load with some sense and take pressure in to account as with all reloading and make more accurate round with less gun powder. Its real its just a non issue if you reload properly to begin with. If you take the book as gospel and believe that there is a true maximum, I guess this could get you in trouble, all guns are different, changing any component Could make a difference in pressure.

 

[dgeesaman]

I wonder if your backyard expert friends falsely equate jammed bullet seating with shorter barrel life because they know a short range br shooter who only jams and only gets 1200 rounds out of a barrel. Sounds like gun shop customer-at-the-counter wisdom.

(Meanwhile they take out their 22-250 amd 204 Ruger for prairie dogging without realizing...)

 

[BoydAllen]

A friend who shoots a lot, competes, and chambers his own barrels believes that jumping bullets causes faster throat wear than seating into the lands. I have no personal experience with this since I have always seated into the lanes for accuracy applications. One possible theory is that for the instant that it takes for the bullet to seal the bore, there is more blowby

It is not BS. It has been measured, documented and peer-reviewed. All other things being equal, seating the bullet to contact the lands will increase chamber pressure over a configuration that does not. That is a fact. Some folks will take that fact and run with it, claiming that it will wear a barrel faster.

Note that pressure and temperature are closely related - a corollary of the first law of thermodynamics. In this case, we are examining the difference in pressure/temperature at the front end of the pressure curve. A bullet seated to contact the lands will result in higher pressure immediately subsequent to ignition. That will (must) result in higher temperatures - the question with respect to barrel erosion is one of 'how much and for how long'? What has been measured, to state it simply, says 'not much' and 'not for long'. The deviation from pressure baseline is not dramatic (you may break wind while opening your bolt if you're otherwise loading at max for your rifle, all other things being equal) and measurements have shown the deviation is brief (we're talking milliseconds, here).

Bottom line - an increase in chamber pressure is NOT BS for jammed vs. jumped. It is real, measured and documented. Is it the Seventh Sign of the Apocalypse? No, not necessarily. Will it accelerate barrel wear by 50%? As I said earlier, 'No way'.

Just to be clear, most of us who seat bullets into the lands work up our loads with bullets seated that way, starting low and going up. Doing it that way, loading for best accuracy, our loads may have no higher pressure than if we were working up loads jumping bullets. I get really tired of fellows not mentioning that the only real danger from seating into the lands is if you make that sort of change in an idiotic fashion, without reducing the load and working back up.

 

[Idaho-Lefty]

The fella's logic is probably rooted in elevated chamber pressure. Jamming into the lands will alter the pressure curve (steeper, immediately subsequent to ignition) but it seems a bit of a stretch to expect this to have material effects on throat erosion. 50% increase in rate of erosion? No way.

AGREE with, JLT and Boyd Allen,..
I'll Address the "Elevated Chamber Pressure, issue" for, the NewBie's,..
When I went looking for, Accuracy Loads, BEST "Nodes" and, jumps for, the 6 MM, 107 SMK's,.. EVERYONE Said to, "REDUCE the Powder Charge" by 1/2 to a Full Grain, AFTER Finding, YOUR Rifles, "Pressure Max" at, .020 to .030 ,.."Off,.. the Lands", First ! THIS Method, worked Beautifully, in My, 6 XC !
It's NOT,.. Rocket Science !

 

[swd]

If you watch Eric Cortina’s interview with Lou Murdica, Lou, who has done lots of work for Berger and other companies, said a bullet seated off the lands has two pressure spikes versus a bullet seated in only has one pressure spike. So does a bullet seated off with two pressure spikes have more throat wear than a bullet in with only one? Who knows, who cares. I have some rifles I shoot off and some I shoot in. Work your load safely and it’s no big deal either way. Just go shoot and don’t worry about it..

 

[urbanrifleman]

Honestly, this obsession with barrel life on the internet. It seems to be one of the most popular subjects. I shot 22-250 for 10 years on groundhogs and I never thought one time about whether or not I was burning up the barrel shooting it. We shot them on prairie dogs too and never thought once about whether or not the barrel was being burned up while we were laughing our butts off having a great time. Now it seems people are obsessed with whether they're going to get 2,000 rounds or 1500 rounds and honestly I'm not sure most people shoot 2,000 rounds in a decade. Just my observation.

I know when I was shooting groundhogs I probably shot a hundred rounds a year on groundhogs. I had other rifles for target shooting. It would take a lot of years to burn up a 22 to 50 shooting hot loads just shooting groundhogs.

I mean if a guy shooting a hundred rounds a week I can see it being a concern. But most people just starting out might be lucky to shoot a hundred rounds a month if that.

 

[JFrank]

After reviewing my notes, Kr-3 had .005 throat erosion in 538 rounds while jumping 108 gr .026
Kr-2 had about the same .001 per 100 rounds while jamming 103 gr .025

Currently Nr-3 i’m seeing .002 per 200 rounds while jamming 103 gr VT .008

Jim

 

[AlNyhus]

Start jammed. Keep pushing the bullet into the case. Pressures and velocities will go UP the more the bullet is pushed into the case. More than even the slight raise from being jammed.

That is documented by me.

I can give multiple examples where the opposite is true.

People like to apply blanket statements to things but like a lot of stuff...it depends. Many of the things that contribute to this are not things we can control.

Good shootin' -Al

 

[LCazador]

I didn't read the previous posts; but the last few years I jam my bullets into the lands; with the 6ppc short range stuff and I usually end up jamming in my man cave after 4 o'clock listing to music as I stream music while sipping a little tequila; winding down till dinner.

Like Gary says there's other more important things like personal satisfaction. Don't worry be happy!

 

[jelenko]

if a guy shooting a hundred rounds a week I can see it being a concern.

Actually, I think when you're shooting a lot the barrel tends to become a consumable - it just gets replaced when it's time.

I compete in 'cross the course' and go through ~ 250-300 rounds a week. I replace my match, button rifled barrel at 3000 rounds.
I don't keep shooting until the barrel looses the accuracy I need. I've found the 50-100 shots that it takes for me to conclude it's the barrel is detrimental to my confidence and screws with my shot execution.

 

[RabbitSlayer]

What im wondering is how hot you running that seating depth is gonna blow your face off? Back it down a notch, turbo. That will increase your barrel life.

 

[JFrank]

What im wondering is how hot you running that seating depth is gonna blow your face off? Back it down a notch, turbo. That will increase your barrel life.

High node or low node doesn’t seem to matter, jump or jam the throat wear is about the same. What does more damage to my barrels is long strings of continuous fire.

 

[RabbitSlayer]

High node or low node doesn’t seem to matter, jump or jam the throat wear is about the same. What does more damage to my barrels is long strings of continuous fire.

I never let it get hot. 10 shots in the 6 creed max and let it cool 15 min at least.

 

[JFrank]

I never let it get hot. 10 shots in the 6 creed max and let it cool 15 min at least.

Sound wisdom..

 

[Evan]

High node or low node doesn’t seem to matter, jump or jam the throat wear is about the same. What does more damage to my barrels is long strings of continuous fire.

Nothing like shooting a heavy gun target as fast as you can cause the wind is whipping and you just hope they all go the same place. 10 shots in 15 seconds is pretty hard on it!

I agree with @jelenko - get to where you’re burning a barrel or more a year and it’s just a consumable and part of the cost you factor in to being competitive.

 

[Longrange57]

jamming bullets seems provides best results in 6br and 6.5cm in my experience. Usually I get 0.3-0.4 moa 5-shot group shooting 140gr or 105gr hybrids without any load development at 100m. Just quick obt modelling re powder charge and off we go.

The only question I am askin myself is how much this strategy affects barrel life. Does barrel life expectancy decrease by e.g. 30% or more? My load is usually 30gr N140 for BR and 42gr N555 for NeedMore.

Marchx, to answer your question, jump/jam has virtually nothing to do with barrel life. The heat and pressure is only there for a nano second regardless! I've had 10 BR's and 5 6.5 x 47's and like cartridges, various powders, jump/jam, etc. and barrel life has everything to do with powder burn rate, barrel temp (long or short strings), and basically nothing to do with jump/jam in the scheme of what is going on.
You can check my math, if I did this right, at 3,000 fps on 24 inch barrel, the bullet is only in the barrel for 1 fifteen thousands of a second. If you fire 3,000 rounds down the barrel, thats only 2 seconds of shooting that it took to burn up your barrel. In all reality, it was probably gone in 1 second. You can find this info in several places on internet or do the math yourself. Consider the fact that during the course of 1 second, the pressure at the lands is gone in about a tenth of a second as the bullet heads toward the muzzle. By the time you fire a round and grab the brass, its already cold. You see many good posts that have been made already, so don't get caught up in jump/jam having anything to do with barrel life. Summer days (95-110F) and long 10-20 shot strings, and to some effect, type of powder is what you need to consider.
I have attached some info I provided for some folks several years ago. It may be helpful and may not! However, my research came from scientist at powder manufacturing companies. They are making strides every day to have more consistent and more forgiving powders. As someone already said, barrels are replaceable and in competition or playing at the range, it all comes down to accuracy for whatever discipline you are playing in regardless of barrel life.

 

[wright brothers]

Long before the web we learned COAL made group sizes change more so than tiny powder changes.
Without even caring or thinking of barrel life we adjusted right away to the golden spot.

Fast forward to now,
LR57 said, "and to some effect, type of powder"

This is something I have been studying, and not just about barrel life.