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Posted: 11/28/2007 5:58:40 PM EDT
I am certainly no expert on anything but my findings on barrel throat erosion should prove interesting.

In the past week I done a little investigating on throat erosion on two identical barrels.

Both barrels are Wilson 1 in 8 twist 416R stainless steel from Rock River Arms.

Both have Wylde chambers and neither barrel was cleaned with abrasives such as J-B, Rem Clean, etc. I might add that both barrels were cleaned following each match or practice session.

Barrel "A" is on my reduced course rifle and I have fired 3679 rounds.
It reads just over a "1" on the throat erosion gage and still shoots very well. At our last league match, I fired a 196-11x on the 200 yard MR-42 target. The day was sunny and very bright. Bright light is very hard hard on my old baby blues. I shot the four nines, not the rifle!

Barrel "B" I removed from a club members rifle last week. He fired 3368 rounds out of that tube and the throat erosion gage reads almost a "6"!
His scores were down from last years and his x count was low too. He's an old Marine and like all of us old shooters, we tend to blame our old eyes. However, in his case, he was over due for a new barrel!

I don't have access to a bore scope but just looking at both barrels with the naked eye into good light, there is more wear in barrel "B".

Thinking that the two barrels are probably from different heat numbers, I had a metallurgist at the plant where I work check them out. His viewing of the make up in both barrels of the grain structure and mechanical properties under a 100x mico-scope showed them to be nearly identical.

Still uncertain of why there was a big difference in the throat erosion, I followed up on the loads we shot from our barrels.

The powder used in barrel "A" was 98% IMR-4895 surplus and some RE-15.

The powder used in barrel "B" was all WW-748 ball powder.

To my knowing, the ball powders like 748 burn at a lower flame temperature than the extruded types like 4895.

During the initial cleaning of my brass, I use a touch of liquid car polish in my walnut tumbling media. Before priming, loading of the powder and the bullets, I tumble them in untreated corn cob.

The other shooter used no polish or additives in his tumbling media.

So why is barrel "A" reading a "1" and still out shooting barrel "B" that has less rounds fired and reading nearly a "6".

The only possible difference that I could come up with was the bullets.

All flat base 60 gr. Sierra varmint bullets were fired from barrel "A" and all 69 gr. SMK boat-tail bullets were fired from "barrel "B".
Then could it be bullet jacket material? According to Sierra, the jackets are the same on these two bullets.

It is therefore in my opinion that boat tail bullets cause nearly three time more throat erosion than flat base bullets.

As I mentioned earlier, barrel "A" is on my reduced course 200 yard rifle.

Are the boat tail bullets more accurate at 200 yards? In my opinion, no! Not to toot my own horn but with this rifle and these bullets I have won our High Power League three consecutive years in a row averaging in the mid 480's and I will soon be a senior shooter.

Now I ask why would any high power shooter, shoot boat tail bullets at ranges under 300 yards? They cost more going into the brass case and much more when they leave the barrel, if you consider barrel life.

I know I have heard it said before by some that it's easier to just load/buy two different bullets than it is three. Could it be to some that it's psychological. Meaning it says "match" on the bullet box?

Okay, this should prove to be a interesting topic and I am not flaming anyone who shoots B-T bullets even at 100 yards. I just wanted to air my findings.

Dave McGrath
Link Posted: 11/28/2007 6:14:42 PM EDT
Dave,

1. Don't assume the barrel steel is identical. Chemistry plays a big part in barrel wear.

2. Flame temperatures are different between IMR4895 and WW748. 748 is a double based powder, and burns hotter.

3. 748 is also a "ball" powder, and gets ejected more readily from the case. This can cause a sandblasting effect on heat softened steel.

I wouldn't place too much faith on the boattail vs. flat based projectile issue. A true "apples-to-apples" comparaison would use identical barrels (same lot of steel, preferrably from the same bar), and identical powder charges. Changing only the bullet, I doubt you'd see a difference in wear.
Link Posted: 11/28/2007 8:37:25 PM EDT
[Last Edit: 11/28/2007 8:41:03 PM EDT by We-rBorg]
Dave, I don't know where you heard that ball powder has a lower temp,, but even in Hatcher's notebook, he states that ball has a higher temp than extruded does.
'Borg
ETA,, Win powder still uses calcium carbonate in their coating and is hard on a Bbl.
ETAA. method of cleaning also has a lot to do with it,, I have a Wilson that has 4500 through it and it still shoots 600 very well,, I've never used a brush on it and shoot all boattails, 77 and 80 gr
Link Posted: 11/29/2007 4:16:00 AM EDT

Originally Posted By wrangler:
Now I ask why would any high power shooter, shoot boat tail bullets at ranges under 300 yards? They cost more going into the brass case and much more when they leave the barrel, if you consider barrel life.

I know I have heard it said before by some that it's easier to just load/buy two different bullets than it is three. Could it be to some that it's psychological. Meaning it says "match" on the bullet box?


People copy what they see winners do even if they don't need to. When the switch over came to the AR most of the military teams shot 69 sierras loaded in Federal because they gave good performance at 200 & 300 and were comparable to the 168s that they shot with the M-14s and Federal had the capability to meet the quantity required by the teams. The military teams simply don't have the capability to load all the ammo for the short course and they already had a relationship with Federal supplying them with ammunition for the M-14s. They simply tested the offerings federal had, saw that it shot well and made the switch. I don't know if Federal loads flatbase match or varmint bullets in their premium line. People saw that they were shooting 69s and the rest is history. Same thing happened when the 77s came out.

60s shoot great and I wouldn't hesitate shooting them at the 200 yard line.

B
Link Posted: 11/29/2007 6:40:30 AM EDT
I had good experiences with 53 flat based bullets at 200 as well. Too bad they are almost the same price as 69s. I will have to try them at 300.
Link Posted: 11/29/2007 7:45:13 AM EDT

Originally Posted By Asa:
Flame temperatures are different between IMR4895 and WW748. 748 is a double based powder, and burns hotter.


Completely agree. Although WW advertises a "low flame temperature", it is a double base propellant and has to have a higher flame temperature than single based IMR.I have E-Mailed WW a few times to ask about this but have NEVER received a reply. When I worked for Hercules Inc, we did flame temperature calculations on our (RelOder) propellant and those of our competitors (IMR and WW). IMR was the coolest and WW the highest. That's why I use mostly single base propellant (VARGET, IMR, and VV N140). I also use a bit of RE15 just because it's so good.
Link Posted: 11/29/2007 9:08:44 AM EDT
Well I see the point on the hotter ball powder but just to be argumentative I wonder if there is a factor with the boat tailed bullet.

I'm considering the possibility of the boat tail acting like a reversed shape charge redirecting energy off of the boat tail and back toward the barrel wall.

We know for certain that a shaped charge can focus energy to the center. I wonder if the boat tail can do that to a much lesser extent but in an outward direction.

I have no training in the field I just watch and read and sometimes think.
Link Posted: 11/29/2007 12:54:51 PM EDT

Originally Posted By Asa:
Dave,

1. Don't assume the barrel steel is identical. Chemistry plays a big part in barrel wear.

2. Flame temperatures are different between IMR4895 and WW748. 748 is a double based powder, and burns hotter.

3. 748 is also a "ball" powder, and gets ejected more readily from the case. This can cause a sandblasting effect on heat softened steel.

I wouldn't place too much faith on the boat tail vs. flat based projectile issue. A true "apples-to-apples" comparaison would use identical barrels (same lot of steel, preferrably from the same bar), and identical powder charges. Changing only the bullet, I doubt you'd see a difference in wear.


Thanks Asa;
I was informed wrong about the flame temp on the ball powders.

On the barrel steel, that is why I took them to the Met Lab at work. However the barrel I own is still on an upper and he could only look at it from the sight tower on out. Both had equally good properties and 416 R is the standard of SS for barrels because sulfur has been added so it can be machined.
I knew 748 was a ball powder. I had never read where it was ejected causing a sand blast effect but I'll certainly take your word on it!
I don't use any ball powder but it certainly has a following especially with those that own the Dillon progressive loaders.
Perhaps the shooting fraternity should be educated on such things. Maybe that is why WW/Olin or Hodgdon don't make these adversive effects known.
Know of any web sites for those interested in the effects of flame temp and sand blasting effects for ball powders?

Dave McGrath
Link Posted: 11/29/2007 12:57:51 PM EDT

Originally Posted By ArmyOrdGuy:

Originally Posted By Asa:
Flame temperatures are different between IMR4895 and WW748. 748 is a double based powder, and burns hotter.


Completely agree. Although WW advertises a "low flame temperature", it is a double base propellant and has to have a higher flame temperature than single based IMR.I have E-Mailed WW a few times to ask about this but have NEVER received a reply. When I worked for Hercules Inc, we did flame temperature calculations on our (RelOder) propellant and those of our competitors (IMR and WW). IMR was the coolest and WW the highest. That's why I use mostly single base propellant (VARGET, IMR, and VV N140). I also use a bit of RE15 just because it's so good.


Thanks A.O.G. Very good to know this. I wonder why your still waiting on a reply!

Dave McGrath
Link Posted: 11/29/2007 1:10:19 PM EDT

Originally Posted By We-rBorg:
Dave, I don't know where you heard that ball powder has a lower temp,, but even in Hatcher's notebook, he states that ball has a higher temp than extruded does.
'Borg
ETA,, Win powder still uses calcium carbonate in their coating and is hard on a Bbl.
ETAA. method of cleaning also has a lot to do with it,, I have a Wilson that has 4500 through it and it still shoots 600 very well,, I've never used a brush on it and shoot all boattails, 77 and 80 gr


I'am not sure Ken but I think it was in an old WW reloading pamphlet or in an older Hodgdon re-loading manual.
I never throw anything away but I can never find where I put stuff!

I thought calcium carbonate was discontinued back in the 60's. I had wrote Hodgdon a letter as to it's use and I did get a reply from Bruce Hodgdon. That was a few years ago, and he said that none of the ball powders they package has any in it's make up. Isn't WW/Olin the manufacture of their line of ball powders?

Dave McGrath
Link Posted: 11/29/2007 3:49:13 PM EDT
Calcium carbonate isn't used as a coating. It is in the propellant formulation and is there for a "stabilizer". Both nitrocellulose and (if double based) nitroglycerine are degrading from the moment they are made. Fortunately, they don't degrade beyond use for several decades. As they degrade, the most troublesome product is acid which will increase the rate of decay. The CaCO3 absorbs the acid and retards the decay rate. Think of it as TUMS for gunpowder.
Link Posted: 11/29/2007 4:11:37 PM EDT
Did you think of measuring the throat before you shot it. I bet they weren't the same to start with.
Link Posted: 11/29/2007 7:45:27 PM EDT

Originally Posted By wrangler:
Know of any web sites for those interested in the effects of flame temp and sand blasting effects for ball powders?

Dave,

No I don't. But I can recommend a textbook. It's long out of print, but can be found in engineering libraries (University or large aerospace/military firms). Copies in the open market are very rare, and thus somewhat expensive.

Gun Propulsion Technology
Edited by Ludwig Steifel

Progress in Astronautics and Aeronautics; Volume 109
Copyright 1988 by the American Institute of Astronautics and Aeronautics

ISBN 0-930403-20-7

And there's this work out of Australia. It builds upon part of what Steifel edited:
dspace.dsto.defence.gov.au/dspace/bitstream/1947/4091/1/DSTO-TR-1757%20PR.pdf
Link Posted: 11/29/2007 8:06:28 PM EDT
Link Posted: 11/30/2007 3:45:11 AM EDT
Dave,
I have read the same thing about 748 being lower flame temperature; it is right on the jug. Also they never say lower than what! I knew that ball powders burn hot though.
Link Posted: 11/30/2007 1:04:48 PM EDT

Originally Posted By Asa:

Originally Posted By wrangler:
Know of any web sites for those interested in the effects of flame temp and sand blasting effects for ball powders?

Dave,

No I don't. But I can recommend a textbook. It's long out of print, but can be found in engineering libraries (University or large aerospace/military firms). Copies in the open market are very rare, and thus somewhat expensive.

Gun Propulsion Technology
Edited by Ludwig Steifel

Progress in Astronautics and Aeronautics; Volume 109
Copyright 1988 by the American Institute of Astronautics and Aeronautics

ISBN 0-930403-20-7

And there's this work out of Australia. It builds upon part of what Steifel edited:
dspace.dsto.defence.gov.au/dspace/bitstream/1947/4091/1/DSTO-TR-1757%20PR.pdf


Wow! Thanks a lot Asa! You and Army Ord. Guy have been a great help!

One other question. Is all ball powder double base?

Thanks again!

Dave McGrath
Link Posted: 11/30/2007 1:08:01 PM EDT

Originally Posted By BRONZ:
Did you think of measuring the throat before you shot it. I bet they weren't the same to start with.


I measured mine (barrel "A") and it read "0". The gage I have was set up for the Wylde chamber so I'm assuming that barrel "B" was also a zero.

Dave McGrath
Link Posted: 11/30/2007 1:14:16 PM EDT

Originally Posted By airgun1:
Dave,
I have read the same thing about 748 being lower flame temperature; it is right on the jug. Also they never say lower than what! I knew that ball powders burn hot though.


Thanks Airgun. I'm going to print a couple of the posts on this thread and give it to the owner of barrel B. Since he uses 748 all the time, I'll bet his jug is marked the same as yours. Misleading to say the least!

I'll not bet that he changes powders but I'll bet I change another barrel for him, soon!

Dave McGrath
Link Posted: 11/30/2007 6:54:47 PM EDT

Originally Posted By wrangler:
One other question. Is all ball powder double base?

Dave,

I think so - but am far from 100% sure. However, there are lots of other powders that are double based, including Bullseye, and some of the Reloder series (I think?)

IMR extruded powders are single based, as are most of the Hodgdon extruded powders.
Link Posted: 11/30/2007 8:34:23 PM EDT
height=8
Originally Posted By BRONZ:
Did you think of measuring the throat before you shot it. I bet they weren't the same to start with.


Yes, bronz is right on.

The throat erosion gauges, especially for the M16/AR15, are comparative gauges. The value you obtain from the gauge, is for the most part worthless without the original reading from the barrel "as new".

Even if you have two barrels cut by the same gunsmith with the same reamer, it's not going to guarantee that the gauge will read anywhere near the same value (same ring) between the two. This is because the barrel extensions may be slightly different in length, and the upper receiver may have some anamolies at the thread area which will cause the readings between the two upper and barrel combinations to differ.
Link Posted: 11/30/2007 8:52:56 PM EDT

Originally Posted By wrangler:
One other question. Is all ball powder double base?


WW ball powder is probably all double base. The only way to tell positively is to test for the presence of nitroglycerine. Obviously, most of us don't have a lab to do this testing. The next best way is to request a manufacturer's Safety Data Sheet which is required by federal law to be provided to customers of chemical products. The intent of the law is that the customer isn't exposed to harmful or dangerous chemicals without his knowledge. If the Safety Data Sheet says "nitroglycerine", it's double base. Double (or single) based propellant is strictly a function of the chemical composition, not its shape. "Stick" powder is squeezed through dies and cut off just like spaghetti (only shorter). I believe that"ball" powder is spattered or sprayed into a fluid medium (liquid or gas?) where the individual droplets harden. Then the particles would have to be sieved to sort out the different sizes. There is also "rolled" ball powder where the particles are slightly flattened to make them all no thicker than a preset thickness.I have formulated and made extruded propellants (stick powder); however, my knowledge of ball powder is what I have heard from others in the business.
Link Posted: 12/1/2007 3:16:19 AM EDT
[Last Edit: 12/5/2007 8:36:21 PM EDT by XxSLASHERxX]
DEAR LENNY...Stop your trolling or get a timeout... I have had enough
DAVE

Your throat erosion gauge for AR was a great investment. I wouldn't even think of competing without one. Most people just piss away their money on pinned sights and tuned triggers. You spend it where it makes a difference.

Lenny
Link Posted: 12/1/2007 8:01:38 AM EDT
[Last Edit: 12/1/2007 8:02:45 AM EDT by wrangler]
On believing that ball powders had lower flame temps, this is probably the source I got it from. I for one actually believed this for a very long time!

This is a quote from Hodgdon reloading manual #22 copyright June 1974 page 188.

Spherical powders HP38, H110, H335, BL-C(2), H380, H414, H450, H870 burn at lower flame temperature, which means longer barrel life.

On the issue of calcium carbonate, I found this:

The following is a quote from Hodgdon reloading manual #25 copyright 1986 pg. 10

When the Olin St. Marks, Florida Plant went on line in June 1970, came with it a new generation of ball powder propellants. In the old East Alton process, calcium carbonate was used to neutralize final traces of acids in the nitrocellulose. This is why Ball Powder propellants are said to have an unlimited shelf life. During the late 1960's, a government study reveiled this additive as the culprit causing severe gas tube fouling in the M16A1 rifle. Handloaders were also experiencing a stubborn residue build-up in sporting rifle bores when using ball powder propellants.
The government went on to specify a reduction of 1.0 percent calcium carbonate content to .25 percent, but Olin went a step farther and eliminated it entirely from both military and sporting rifle powders. Long-term surveillance tests made by the government demonstrated that "Ball Propellant" stability was not impaired by this change.

Dave McGrath

Link Posted: 12/1/2007 8:08:09 AM EDT

Originally Posted By ocabj:

Originally Posted By BRONZ:
Did you think of measuring the throat before you shot it. I bet they weren't the same to start with.


Yes, bronz is right on.

The throat erosion gauges, especially for the M16/AR15, are comparative gauges. The value you obtain from the gauge, is for the most part worthless without the original reading from the barrel "as new".

Even if you have two barrels cut by the same gunsmith with the same reamer, it's not going to guarantee that the gauge will read anywhere near the same value (same ring) between the two. This is because the barrel extensions may be slightly different in length, and the upper receiver may have some anamolies at the thread area which will cause the readings between the two upper and barrel combinations to differ.


Thanks fella's. Point well taken!

Dave McGrath
Link Posted: 12/3/2007 10:40:14 PM EDT
Thanks !
I really learned a lot since I started this thread.

To sum things up, I learned that ball propellants are not lower in flame temps as one would be made to believe from their manufactures statements. Their claims are misleading.

I'll only take the throat gauge readings as being accurate only if I have gauged the barrel when new.

I also learned a lot about the character of those that replied (with the exception of the gentleman from New York) that there are a lot of very knowledgeable and educated individuals in our sport willing to share their insight for the benefit of all that visit this informative forum.

Dave McGrath
Link Posted: 12/3/2007 11:28:10 PM EDT
[Last Edit: 12/4/2007 4:07:43 AM EDT by Lenny]
Way to go on that gauge, Dave. Put those accurate readings to good use.
Link Posted: 12/4/2007 5:00:33 AM EDT
[Last Edit: 12/4/2007 5:01:06 AM EDT by bpm990d]
You're such a troll Lenny.

B
Link Posted: 12/4/2007 10:12:47 AM EDT
[Last Edit: 12/5/2007 8:37:48 PM EDT by XxSLASHERxX]
No more warnings Lenny.....slasher
Link Posted: 12/5/2007 10:02:23 AM EDT
Pressure is heat, plain and simple. Spherical propellents tend to peak faster but with moderation as to not exceed maximum pressures. In other words, sphericals tend to have a broader pressure curve. Remember, as pressure falls, so does temperature.

What this means is the 748 loads were probably much hotter in the first few inches of the bore where peak pressure is reached.

I was just looking through my Modern Reloading second edition and in .223 Rem, there are 2 sections, one rifle and the other pistol. No loads using 748 were listed but comparing Varget, H322 and H335 (the last being spherical double base) with a 40 grain bullet was interesting. All max charges are the same. Varget had the highest velocity at 3674 using 28 grains. Next was H322 at 3574 using 25.5 grains H335 was slowest at 3572 using 28 grains.

In a pistol length barrel, the highest velocity was H335 at 3231. Next was H322 at 3087 and finally Varget at 3069. Complete reversal.
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