Home Forums Hunting & Shooting Hunting Rifles Shooting HOT Barrels DOES Erode the Throat

Guys,
<br>
<br>A while back we were all talking about if shooting a hot barrel really would damage the bore. It was based on an article by the late Frank Murphy in Precision Shooting. Mr Murphy said shootinmg when the barrel was hot didn't matter.
<br>
<br>I wasn't so sure, and posted (in my trademark detailed and wordy fashion) how I had eroded the throat in my 7mm Rem mag SS Sendero.040" in 400 rounds by shooting it hot. I also pointed out how my 300 SS Sendero barrel went 825 rounds with .010" of erosion, and that I didn't shoot it hot.
<br>
<br>Well, today I measured the throat of my 338-06. It is a Pac-Nor barrel. I shot it hot. In 88 rounds, the throat eroded over .060"!!! That is with a barrel made with high quality stainless steel, in a chambering that isn't overbore at all. The only explanation for the throat erosion is shooting it hot.
<br>
<br>No more shooting hot barrels for me!
<br>
<br>Blaine

AFP
<br>How do you measure it? I am curious. I'd like to measure mine.
<br>David

With the Stoney point system. I always measure when I start working with a new bullet, the periodically check aftre that.
<br>
<br>Blaine

How many shots did you fire hot in that .338/06?
<br>
<br>There is a lot of evidence on machine gun barrels. I have read some of it over the years and Hatchers Notebook has data on it.
<br>
<br>As I recall barrel "life" was up to 10,000 rounds! Now their standards and ours are not the same but another point was made that such barrels were restored to useful life by lapping them.
<br>
<br>It seems logical that the erosion comes primarily from the heat of the burning powder. Rapid fire must really heat that steel up.
<br>
<br>I have a old .243 Win that is erroded 4" up the bbl. Up to a few years ago I could get acceptable varmint accuracy by lapping the bbl and keeping it clean. It's a M-70 SS that I got new in 1957 so you can see that I don't give up easily on a bbl. I don't know how many shots are thru it but most were slow fire. Some were in matches that had a one minute per shot maximum. This barrel will still shoot the 100 gr Sierra very well but that's all and that is not a varmint bullet. This is varmint bbl.

You can shoot a .220 Swift for years if you don't get the barrel too hot, but you can fry one in a day on a prairie dog town if you just keep shooting. I guess it all depends on what your defintion of "hot" is.

Do,
<br>
<br>The barrel has around 400 total, and the .060" erosion occured in 88 rounds. This isn't actually so bad in this rifle, as it was throated to short anyway.
<br>
<br>Blaine

I don't have a Stoney Point tool so I have no easy way to measure. In my case ignorance was bliss. Now you have us all concerned.
<br>
<br>How does one shoot a .338 fast?

When I want to do alot of shooting with only 1 or 2 rifles and dont want to wait for the barrels to cool naturally, I will cool them down by running CO2 in the barrel. It only takes a minute to do this. Of course having and endless supply of CO2 helps!
<br>
<br> Stay cool man .......AA

AFP,
<br>
<br>Have you seen the article on TP and neck length? The theory is if lines drawn from the shoulder to an intersection point are far enough inside the case neck erosion would be lessened somewhat. I'll have to go back and look for the article(s). I believe the basic premise of the article was that of the shoulders directed the hot gases/powders to impact initially on the inside of the case neck instead of the throat of the chamber erosion would be mitigated. The cartridge you posted, 338/06, made me wonder if the powder/gases were being directed to your bore lead rather than the inside of the case neck.

Mag,
<br>
<br>Yes I have read those articles in Precision Shooting. It makes sense to me, and helps explain why a 6mm Rem's throat lasts longer than a 243's throat.
<br>
<br>The 338-06 has a long neck but shallow shoulder. However, it really has small case capacity for it's bre size, so it shouldn't be prone to this at all.
<br>
<br>Don,
<br>
<br>Increase case capacity. The 338 Win is much faster than a 338-06. My 338 Ultra is near the ideal case capacity for max velocity in 26" barrels. Of course, you have to let them cool between shots.
<br>
<br>Blaine

AFP (Blaine),
<br>
<br>I guess the shallow shoulder was my point...I thought it would be shallow since it was based on the 30/06 case, and opening it up to .33 caliber allows a larger portion of the powder out of the neck area to impact on the bore throat during ignition. Even though increasing the bore size to .33 improves the bore/powder ratio (Less tendency to be overbore) I think the larger bore diameter increases the TP erosion effect on the throat by essentially moving the TP further into the bore, and out of the neck by increasing the diameter of the neck. In the case of TP and bore erosion I believe you have to draw the shoulder lines past the TP and observe where that line hits the opposite side; on the case neck, or out into the throat? Opening up any bore size and leaving the shoulder angle the same will essentaily move that point where the projected line from the shoulder impacts the opposite side further forward.
<br>
<br>Also, shooting any while a barrel is hot can increase erosion. According to articles I have read in Precision Shooting all barrels develop stress cracks after firing. As the barrel heats up and expands the cracks in the barrel/bore surface also expand, allowing more superheated gas and powder particles into and under the exisitng surface, speeding up the surface erosion. If you let the barrel cool, the existing surface bears the majority of the impact of the gases and unburned powder impact. The surface inevitably develops stress cracks and erodes, but when the barrel is allowed to cool the cracks are not as wide and don't allow as much of the gas and powder into the cracks and under the existing bore surface. Makes sense to me.
<br>
<br>Just my 0.02$ worth.
<br>
<br>Ralph

I still think you are doing something weird Blaine. I have never heard of such throat erosion happening in so few of rounds. Perhaps the leade in your barrel had some burrs on it or one land was longer than the other. Now that things are smoothed out, the leade is longer. Check the leade again in 400 rounds and see if things have changed. Their can be many reasons for your measurements growing. I have personally never had this experience and I shoot my rifles hot. Of course, I don't sit and fret over meaningless measurements after each shooting session. I shoot until the barrel pukes, then I will set it back a thread or two, but I haven't had to do this yet, and I shoot a LOT of 7mm mag. My .22-250 went for 4,500 rounds and still shot around 3/4" groups at 100 yards with no riflings in the first inch of throat. Not great accuracy, but pretty good for being so abused. So, throat length is meaningless to me. I just seated the bullets out to get "closer" to the lands. I didn't experience any velocity loss with the badly worn lands or growing throat. It did start to throw fliers and I rebarreled it to .25-284, which now has 1000 rounds through it in less than a year. It still shoots wonderful and has been abused. Oh well, I will replace it when it pukes too (grin). If my barrel is too hot to touch quickly, or I smell wood burning, I know it is too hot and is due for some cooling. Shoot and enjoy. Throw that stoney point thingy away (grin). Flinch

Blaine,
<br>
<br>You wrote on measuring throat erosion --
<br>
<br><blockquote><font class="small">In reply to:</font><hr><p>With the Stoney point system. I always measure when I start working with a new bullet, the periodically check aftre that. <p><hr></blockquote>
<br>
<br>Stupid question -- was the erosion in 88 rounds based on using the same bullets, i.e., same lot? I know I've seen easily that much variation or more just from different lots and could have concluded from that that I had eroded the throat.
<br>
<br>If it was the same, I have to ask, how hot is hot? I use the rule of thumb (literally) of not starting to fire a group when the barrel's too hot to hold comfortably. I rotate 2 or 3 rifles per session or in summer, go into the clubhouse and catch up on the gun rags & catalogs.
<br>
<br>John
<br>

John,
<br>
<br>Not a stupisd question al all. I used the same bullet, measured the same way.
<br>
<br>Different bullets do give different ogive readings. One of the most dramatic--250 Hornadys would originally seat at the cannelure. Now the cannelure is quite a bit in front of the case neck. This is actually not so bad, since this chamber was short throated anyway. it's just that powder blasting and heat aren't really the best ways to lengthen the throat.
<br>
<br>In my opinion, the barrel needs to be "lukewarm" or less. I shot this barrel when it was almost too hot to touch. I'll not let someone talk me out of my position again that shooting barrels hot accelerates throat erosion.
<br>
<br>
<br>Blaine

I was once shooting at our local range next to a couple of guys who were shooting some kind of old surplus military rifle. They just kept shooting and shooting without giving the rifle any time at all to cool (except for the 4 or 5 minutes when we go check or change our targets). I looked over at one point and cosmoline was just boiling out of the barrel channel. I don't guess it mattered much since it was an old beater surplus rifle, but I hated to see a gun treated that way.
<br>
<br>I only shoot 3 shots per shooting session (about 10 minutes) per rifle. After 3 shots I'll put a damp rag over the barrel. This will cool the barrel completely down to the ambient temperature prior to the next session. If I'm shooting during winter, however, this is usually not necessary.

Blaine,
<br>
<br>I wonder if Hornadys are unusually prone to this ... the experience I was thinking of was with 150-gr. Spire Points in my .270.
<br>
<br>John
<br>
<br>

What is the alloy used by Hornady and say by Sierra? To me the Hornady's always looked a little redder if you would indicating more copper? This could be the alloy, dezincification or my imagination.
<br>
<br>I recall a match when a competitor was using Hornady's out of a 22-250 at 200 yards and he was hot. Then as the string when on his bullets started keyholeing and they were all over the paper. Everyone used either free military ammo or Sierra's.

Actually, the majority of the shooting was done with 185 Barnes XLCs.
<br>
<br>Blaine

This is going in the wrong direction. It has to be errosion from the heat. I don't think we can blame one bullet or the other.
<br>
<br>Some military bullets are made from steel! Someone should dig out the military data. There is a lot of history there.

Don,
<br>
<br>That was my thought exactly--the heat is the culprit. The 338-06 is not overbore, nor is known as a barrel burner. The barrel is a Pac-Nor, so we can't blame it on a bad batch of steel. The bullets were XLCs (most of them) which have the coating.
<br>
<br>Blaine