OAL and throat/land erosion

[joeb33050]

My Savage Striker 308 Win., required 311/314299 bullets seated such that the base of the bullet/gas check was below the case neck. In some 1219+ shots the throat and land tops have eroded until the bullets can now be seated to an OAL of 2.965" for the 311s, and 2.888" for the 314s, about .125" or more longer than at the start. Now the GC is well up in the neck.
I don't slug the barrel to get bullet fit, I seat bullets out as far as they will go and look for a seal from the (maybe top) band to the throat.
OAL is fuzzy. As bullets get harder or bigger, they get harder to push in. Thus OAL is a complex business of
How hard is it to push the ctg. in?
Will the ctg. de-bullet if it's taken out?
Sizing diameter
Nose diameter
Alloy

I've known that throats and lands erode over time, but this is the first time I've counted shots to see that erosion.

Groove diameter is .3065"/.307, on the Striker. Land diameter is very little over .300", at the rear. There is little to no nose engraving on the 311299 nose at .3015" max.

joe b.

[swheeler]

Well .125" seems a bit excessive to me for the 308 and cast @1200 rounds, that is about what a 300 rum I had erroded in 400 rds. But different barrels/barrel metal/manuf, tooling marks or lack there of in the throat when new, antimony content in your alloy, powder choice and load, shooting habits, cleaning habits and on and on all come into play. I just happen to have measured errosion on a 308, but an A&B barrel, first 1K rounds were 168 Nosler custom comp moly coated(my moly) and next few hundred were SMK and what ever-all moly coated. So just for you from my book 2002 HLEP new 2.230-1480rds fired HLEP 2.254 so I only used up .024" throat in 1480 rds, therefore 5 times that amount of erosion from firing approx 260 rounds less ammo seems excessive. Kinda makes you wonder if moly isn't a little better than most think on reducing throat errosion. You asked I answered.02

[HORNET]

Joe, Kinda wonder if that might have had some burrs or a tight spot that cleared up. IIRC, you're not pushing those very hard or using a high antimony alloy so I wouldn't expect anywhere that amount of actual wear, even if some claim that Savage barrels tend to be soft. You might want to check it again in about 500 rounds. That even sounds like a lot of wear for firewalled j-bullet loads.

[joeb33050]

Well .125" seems a bit excessive to me for the 308 and cast @1200 rounds, that is about what a 300 rum I had erroded in 400 rds. But different barrels/barrel metal/manuf, tooling marks or lack there of in the throat when new, antimony content in your alloy, powder choice and load, shooting habits, cleaning habits and on and on all come into play. I just happen to have measured errosion on a 308, but an A&B barrel, first 1K rounds were 168 Nosler custom comp moly coated(my moly) and next few hundred were SMK and what ever-all moly coated. So just for you from my book 2002 HLEP new 2.230-1480rds fired HLEP 2.254 so I only used up .024" throat in 1480 rds, therefore 5 times that amount of erosion from firing approx 260 rounds less ammo seems excessive. Kinda makes you wonder if moly isn't a little better than most think on reducing throat errosion. You asked I answered.02

What is "HLEP"?
The max OAL change and erosion of throat and lands depend on geometry, as well as other factors. Imagine a tapered bullet and throat that match. I'd suggest that zillions of shots would be required to change max OAL much. On the other hand, imagine a 314299 and chamber that fit well on nose and lands, but have some slight interference at the top band and throat. Here, not many shots will erode the throat enough to allow that top band to fit the throat, and max OAL to increase quite a bit.
Max OAL change is a poor indicator of throat wear per shot, but it's all I've got.
The only other record I have, and it's now just a memory, is that my wife's M700 Varmint 222 Rem went from bullet-way-in-the-case to bullet-doesn't-touch-rifling when seated out to max OAL.
I'm a little interested in other's experience, shots fired vs. change in max OAL, with cast bullets.
I'll keep your data also. (I klnow I'll feel stupid when I find out what HLEP is.)
Thanks;
joe b.

[swheeler]

Head to Land Engagement Position. I do believe Savage barrels may be a little softer than others, on my Savage 223 I had to lengthen the magazine box by .250 after firing 2500 rds to chase the rifling, now it is beyond hope of ever getting close to a land even with the heaviest pointed bullet I can load.

[Ricochet]

HLEP isn't a bit of terminology I'll pick up. I still think it's bizarre and befuddling to hear someone refer to a bullet/boolit as a "head." That's the closed end of a cartridge case.

[StarMetal]

Head to Land Engagement Position. I do believe Savage barrels may be a little softer than others, on my Savage 223 I had to lengthen the magazine box by .250 after firing 2500 rds to chase the rifling, now it is beyond hope of ever getting close to a land even with the heaviest pointed bullet I can load.

They are softer Scot.

Joe

[swheeler]

HLEP isn't a bit of terminology I'll pick up. I still think it's bizarre and befuddling to hear someone refer to a bullet/boolit as a "head." That's the closed end of a cartridge case.

My goodness! Head(as cartridge head of case) to land(as lands inside a barrel) engagement(as in making contact/touching) This is how a measurement is taken with a bullet comparator. If I am interested in recording throat errosion on a barrel, I take a once fired case from that rifle and seat a bullet until it just contacts the lands, I get a HLEP measurement and record it- then PUT THIS CASE/BULLET COMBO AWAY, then after I fire 1K rounds(or how ever many) I take the same case/bullet combo and with my inertia puller knock the bullet out .125"(or whatever amount is needed to exceed) repeat first step. Then you just subtract the short one(smaller number) from the long one (larger number) and this tells me how much the throat has moved forward, BUT IT DOES NOT TELL ME HOW MUCH THE LANDS HAVE ERRODED TO INCREASE BORE DIA IN FRONT OF THE THROAT SPECIFICALLY. It is not my terminology, Layne Simpson? Sinclair International? GD Tubbs? couldn't really tell you as its been awhile since I've seen it in print. I find it scribbled in my Hornady 3rd edition on several pages and am not confused in the least, but then I've never called a bullet anything but a bullet/projectile! No pipes, tubes, pills or HEADS in my vocabulary.

[swheeler]

They are softer Scot.

Joe

I believe you are correct Joe. In college I rebarreled a 1916 Spanish mauser, cut 3 inches off muzzle end of the old barrel, split it in half and tested for hardness on inside, 10 R C IIRC. Later I rebarreled a P14 to 375 H&H, Wilson barrel 26 inches long, I didn't want a 26 inch bbl so I shortened to 23 inches, did the same test with the Wilson barrel, it tested 22 IIRC on the C scale(these numbers could be off by a point or two, its been over 15 years, but it is written down here somewhere). I have a couple spent Savage barrels here, just might have to take a trip to school. I now have a A&B barreled Savage 06AI because my cast shooter 06-same rifle- did what Joe B was asking about in start topic, but it kept moving and moving and moving forward until my .301 bore rider would just drop in at the muzzle. I can't give him any numbers because I never recorded the rounds, but a real world guess would be 5-6K based on primer usage. I have quit alloying up with Linotype so much though as that was my first thought as to the fast wear, I still have thousands of those 7/3 17BHN bullets(or should I say pills or heads) in various calibers tucked away-SOMEWHERE.

[HORNET]

swheeler, so HLEP is basically the same as jam length?

[Ricochet]

Ok. :d

[swheeler]

swheeler, so HLEP is basically the same as jam length?

As in jam the thing in there, or Just Another Measurement

[joeb33050]

My goodness! Head(as cartridge head of case) to land(as lands inside a barrel) engagement(as in making contact/touching) This is how a measurement is taken with a bullet comparator. If I am interested in recording throat errosion on a barrel, I take a once fired case from that rifle and seat a bullet until it just contacts the lands, I get a HLEP measurement and record it- then PUT THIS CASE/BULLET COMBO AWAY, then after I fire 1K rounds(or how ever many) I take the same case/bullet combo and with my inertia puller knock the bullet out .125"(or whatever amount is needed to exceed) repeat first step. Then you just subtract the short one(smaller number) from the long one (larger number) and this tells me how much the throat has moved forward, BUT IT DOES NOT TELL ME HOW MUCH THE LANDS HAVE ERRODED TO INCREASE BORE DIA IN FRONT OF THE THROAT SPECIFICALLY. It is not my terminology, Layne Simpson? Sinclair International? GD Tubbs? couldn't really tell you as its been awhile since I've seen it in print. I find it scribbled in my Hornady 3rd edition on several pages and am not confused in the least, but then I've never called a bullet anything but a bullet/projectile! No pipes, tubes, pills or HEADS in my vocabulary.

I have guns that allow a cartridge to be chambered and have ~.15"-.2" of the nose well engraved-cast bullets I'm talking about. Most of the time the front of the top band hits the throat. Maximum OAL is what I call the max length of a cartridge that will go in the chamber without undue force, OR, for those of you who take a ctg. out of the chamber, the max length of a ctg. that will go in and come out without de-bulleting.
Just my definition, but undeniably correct.
joe b.

[Ricochet]

I agree with Joe.

[swheeler]

Joe; I fully understand, I just gave you an actual measurement of how much the throat on my 308 moved forward after shooting 1480 jacketed rounds, acurate and undeniably correct. So I just gave you a number, I AGREE WITH THAT

[StarMetal]

I believe you are correct Joe. In college I rebarreled a 1916 Spanish mauser, cut 3 inches off muzzle end of the old barrel, split it in half and tested for hardness on inside, 10 R C IIRC. Later I rebarreled a P14 to 375 H&H, Wilson barrel 26 inches long, I didn't want a 26 inch bbl so I shortened to 23 inches, did the same test with the Wilson barrel, it tested 22 IIRC on the C scale(these numbers could be off by a point or two, its been over 15 years, but it is written down here somewhere). I have a couple spent Savage barrels here, just might have to take a trip to school. I now have a A&B barreled Savage 06AI because my cast shooter 06-same rifle- did what Joe B was asking about in start topic, but it kept moving and moving and moving forward until my .301 bore rider would just drop in at the muzzle. I can't give him any numbers because I never recorded the rounds, but a real world guess would be 5-6K based on primer usage. I have quit alloying up with Linotype so much though as that was my first thought as to the fast wear, I still have thousands of those 7/3 17BHN bullets(or should I say pills or heads) in various calibers tucked away-SOMEWHERE.

I talked to my Lothar Walther friend about Savage barrels once. He said they were very accurate factory barrels and I mentioned that I heard they were soft and he said they were, but that didn't matter for the average hunter. Only the big time shooters who put lots of ammo through them.

Joe

[felix]

Molybdenum is the component of steel that is used on the scraping edges of graders, cats, utes, draglines, etc. This is also the primary reason why it is used in normal gun barrels. Unfortunately, that is also the reason it is difficult to machine, which makes sense, right? Accuracy barrels have a low amount of this constituent, and perhaps machine gun barrels have it over the top. Probably, we can measure the content of moly within the steel by the number of shots it takes for the throat to wear a predetermined length. ... felix

[swheeler]

Felix that does make sense. I have a new Savage 308 barrel, almost new think I've put 50 rounds through it. A good test would be to shoot 1480 rds of moly coated bullets through it and see how much the throat moves forward. On second thought I think I will just shoot it, enjoy it and forget all the measuring.

[StarMetal]

Molybdenum is the component of steel that is used on the scraping edges of graders, cats, utes, draglines, etc. This is also the primary reason why it is used in normal gun barrels. Unfortunately, that is also the reason it is difficult to machine, which makes sense, right? Accuracy barrels have a low amount of this constituent, and perhaps machine gun barrels have it over the top. Probably, we can measure the content of moly within the steel by the number of shots it takes for the throat to wear a predetermined length. ... felix

You're dead on about moly Felix. The newer generation of grader blades, for example, have gone to high carbon steel, carbide and tungsten carbide. Most often they are inserts. There is also a carbide impregnated edge.

I was at molybdenum mine in Colorado once. They are very high in the mountains. Funny how you find different metals at different levels.

Joe