Home Forums Hunting & Shooting Competitive Shooting 1000 yd BR - Ruined the Throat

To recap..........

I showed up at the Tucson 1000 yd range with a varmint rifle in 6mm Rem. 14x Leupold scope, HS Precision stock, trued 700 long action, Pac-Nor #5, 27" long with a 1x8 twist and in a three-groove rifling configuration. I shot off my Hoppes front rest and Protektor rear bag on 8 Jan. I became hooked.......

Since the barreled action was showing promise, and I needed to limit my budget since we are building a new house, I thought about how I might ease into this in a cost effective manner. I have now learned that like all other shooting pursuits I have engaged in, there is no cost effective way to "ease in" to this.

The plan was front rest, stock, scope, and a load with 115 grain MKs. I figured that would get me through the year. Well, I did all that and pushed my original budget a bit, but it was all working. Then last night, after mounting the scope, I started in with the new bullets. I started by checking seating depth. I started with some 107 MKs to see how much the throat had moved. I figured there would be some erosion, and I wanted to see how much.

Would you believe .300"? That is not a typo. The throat had eroded a full 3/10ths of an inch in the barrel's 200 round life. I assume most of that happened at the match, when I was shooting 10-shot groups in heavy rifle.

I was stunned. The barrel now has as much freebore as if I had bought a 240 Wby. I realize the 6mm Rem is a tad high case capacity for a 6mm, and I know Pac-Nor barrels are soft, but come on, .300" in 200 rounds?

Fortunately, Jerry (the local 1000 yd rifle machinist who is moving in a month) hasn't packed his lathe up yet, Bruno's is only a 2.5 hour drive, and Bruno's had a Krieger 6.5mm, 1x8.5 LV barrel blank in stock--along with some 6.5x284 brass and most of the other stuff I need.

If I had checked this rifle's throat right after the match, I wouldn't have even ordered the scope and stock. I would have bought another Tucson shooter's 308 Patriot light gun (on a 700), and then bought a much lower end scope. Such is hindsight.............

Oh well, I guess I'll be better off with a new Krieger barrel in 6.5x284 and the Nightforce scope, right? (Just say yes, I don't even want to consider the alternative.)

All this bring up some thoughts on throat erosion.

Three times now I have fired strings and gotten barrels hot, and each time the throat has eroded excessively.

The first was several years ago, a factory Rem SS Sendero in 7mm Rem Mag. I started shooting 5-shot groups. I'd shoot five in a row, then let the barrel cool. In 400 rounds the throat moved about .040". I heard that is not uncommon for that chambering. I got rid of the rifle and got another SS Sendero, this one in 300 Win. After 825+ rounds, the throat had moved maybe .010". I started shooting three-shot groups and didn't shoot the barrel when it was more than lukewarm.

A couple years ago I was messing around with a 338-06. It too was a Pac-Nor barrel. The 338-06 isn't know for throat erosrion, but when I kept it hot for a few rounds it too erodoed noticably (like .010 in 80 rounds), whereas when I kept it cool, the throat didn't move. On this barrel, I was careful and stopped the experiment after noticing the throat movement, and kept form hurting the barrel.

I guess my issue is whenever I shoot barrels when they are hot, I seem to erode the throat excessively.

Several years ago I started using Rem Bore Cleaner, which like JB Bore Paste, is a non-embedding abrasive cleaner. I have very good luck using it with several rifles. I remember reading a test in Precision Shooting a while back how that RBC was so fine that all it did was polish the 600 grit lapping marks, and as such the author said it would not harm a bore.

Now I am wondering if I should be routinely using RBC or JB Bore paste.

Thoughts?

Blaine

Just copied this from the Krieger Website..............

"Abrasive cleaners work very well. They do not damage the bore, they clean all types of fouling (copper powder, lead, plastic), and they have the added advantage of polishing the throat both in "break in" and later on when the throat begins to roughen again from the rounds fired. One national champion we know polishes the throats on his rifles every several hundred rounds or so with diamond paste to extend their accuracy life. "

How much pressure are you operating at with the 6mm?

I use both and they wont hurt your barrel, especially if you have a good bore guide. You probably dont have to use them that often. I use butches bore shine. 2 wet patches, soak the brush and five in and out soak the brush again 5 in and out, let it set about 10 minutes and then patch it out. one patch damp with kroil and one dry patch. firtst two shoots into the backstop and your ready to go. If you start to see copper then hit it every so often with the Rem or JB. But a little copper wash is not necessarily a bad thing. Re: heavy class: its real easy to shoot several sighters- and then several during the 2 or 3 minute time when they mark the targets, and then when you fire your ten for record your barrel is really smoking! I try to keep my sighters to a minimum and take fairly aggresive clicks to get on the clay bird or gong right away and stop. Then shoot the minium shots during the marked sighter period, but always fire one just seconds before the end of marked shots end. See where this hits, hold on or off accordingly when the record targets come up and start firing immediatly before conditions change. If you get all sighted in nice and the have a wait till the record targets come up conditions might change and you will be lost, maybe even off target! Been there! If your last shot at a marked target was off the X just hold off for it and get those shots off downrange with your best guess for hold off. I am no means real good at this and work wont let me shoot as much as I like but this has worked for me and have won most relays (not matches) I have been in.
I wonder if your barrel is really shot? Look into it with a bore scope. Shoot the hell out of it till it quits. I have seen barrels where the first 2 inches looked like charcoal but they still kicked butt.

Lefty

Blaine, I have burned out a few barrels in my lifetime and I have drastically changed the way I reload for a match rifle. I have found that by loading down to 10 to 15% below max pressure I increase barrel life dramatically. I don't shoot 1000 yards but I know you have to stay supersonic, so maybe look for a load that will get you there without as much pressure.

I think a heavier barrel will also help you, something like a HV #7 gives a lot more area for heatsink.

As an example, I use a 22-250 for 300 yard prone where we fire 2 strings of 20 rounds 20 minutes each. I have put close to 600 rounds through this barrel and the throat has barely moved and shows almost no fire cracking under the bore scope. I only run it at about 3350fps with 52 grainers and it just hums along without getting excessively hot. This barrel is a HV #7 shilen. I also use ball powder which is supposed to have lower flame point than extruded though not by much.

I don't know that much about it but isn't that the main point of fluting, to give more surface area too cool off?

Blaine,
The obvious answer is to choose a large bore with a smaller case capacity. I think that a short 300 Magnum might do the job.
It all depends on your budget. I know shooters who rebarrel every year. I can't afford to do that so I don't shoot 1000 yds. When you shoot a three gun 1000 yd match you are really talking about well heeled shooters. 30 caliber is pretty popular because if you go any bigger the recoil becomes a problem and any smaller than that and bore erosion becomes a problem. There is always a tradeoff. A 308 Winchester is very accurate at long range, talk to some Palma shooters.
Great White North

Portagas, yes you are correct, fluting is supposed to help cooling. I have never used a fluted tube so I really have nothing for comparison and don't know if it really works as described compared to an unfluted tube. I pretty much stick with what I know, and a big fat barrel with mild powder charges and pressure makes for lots of shooting.

Shane,

The 6mm Rem is a standard 65,000 PSI chambering, like most are. My load was generating 3060 fps from a 27" barrel, which is about right. There were not any high pressure signs of any kind.

Lefty,

Your method is exactly how the other guys have coached me to shoot. The 6mm barrel may be reusable if I cut 1/2" off the shank and rechamber, but I am leery about spending money on something that may not work.

TBS,

I try to keep loads under the max as well. High pressure signs just started to show up at 3200 fps with this load, and I thought backing it off to 3060 was a significant reduction. With the 6.5, I certainly will not push it....

GWN,

The 6.5 / 284 has a better case capacity to bore ratio, though when I start from scratch I will probably build a 300 WSM.

I like the the .300 wsm and shoot it in the light class and it has a brake..the only disadvantage is if I am going to shoot it in the heavy class to I would have to remove the brake. Not that it hurts you or anything w/o the brake but it moves around a bit and you have to spend a bit more time getting back on target dicking around with the rest. with a lighter recoiling rifle it will track the bags well and let you shoot a little quicker. What would be ideal is something that recoils like a 6BR but bucks wind like a .300 with 220 gr. matchkings!
When you find it let me know!

Lefty

Lefty,

The biggest thing I noticed at my first match was how much even a 11 lb 6mm moved around on the bags. What a pain! My 6.5x284 will come it at just under 17 lbs. It has a proper stock and I now have a proper rest. That should make a huge difference.

Blaine

Lefty the round you may be looking for is the 6XC. It is ment to drive the 115 gr tubbs bullets to 3100 and change with great barrel life. BC of said bullets is in the mid 580's and the smith that is building mine says 2500 rounds. Although F class is more forgiving on the accuracy requirements and rapid strings. The round has been doing well against the 6.5's locally and they are what is supposed to beat the big winney ballistically.

Will know for sure in about 45 more days. Should be blasting by then.

I actually have thought about it.....but the last thing I need now is to start with another rifle, dies, barrels, bullets load development etc. divorce is very expensive. I do think the cartridge will be a winner though. Love to hear about yours as soon as you get it going.

Lefty

Sounds really good. Would be nice if you could get to the World Open at Williamsport pa. this summer. Pretty good shoot. Last year a 6.5X.284 took it all both light and heavy. If you do compete in Williamsport your rifle will have to weigh in under 16 1/2 lbs..Pain in the butt, but Williamsport started it all and they go by their rules. Let us know how your rifle does when you get it.

Lefty

" I know Pac-Nor barrels are soft, "

I'm surprised that quote went unchallenged. I can't say one way or the other but I hope your wrong.

I posted asking about it being the heat treatment being softer, or the actual type of metal. Also about using 4 ought steel wool around a brush as a cleaner. That was in between the first and second post. Don't know what happened, or why it aint there.

Nobody really stepped up and explained or really bit on it. Confused like the rest.

I didn't intend this to be an inditement against Pac-Nor, but here is my experience with them. I have had 5 Pac-Nor barrels, and three were outstanding. With that said:

More than one rifle builder has told me Pac-Nor barrels are soft, and that is based on their experience machining them. I have also noticed how easy it is to scratch one up when hunting, and then am amazed at how well the scrathes will polish out with steel wool. All this leads me to believe they are a bit soft.

Pac-Nor seemed to have struggled a while back with quality, and I know many hunters, shooters, and a couple rifle builders that quit using them. Please don't ask me to name names, because the builders especially want to remain anonymous. I bought this 6mm barrel around the time of the uncertain QC.

Maybe Pac-Nor got a bad lot of steel, like what happened to me last month when I was 170 miles from home and an aftermarket (to the lift kit) suspension component broke, completely settling my truck's suspension on the right side. This was due to improperly heat treated steel, so I know personally "bad steel" can happen to anyone.

Of the two 3-groove Pac-Nors I have, the 6mm shot well with one particular seating depth. Move it .005 either direction and it didn't like it. The 30 cal Pac-Nor three-groover I have is a bit more fussy, and I haven't found what it likes. After 750ish round when chambered in 30-06, I could not find a load with a hunting bullet that would not ocassionally open three-shot groups up to 1.125". Many feel that is acceptable for a #4 contour barrel in a hunting rifle, and if it hadn't been a fully accurized rifle built on a 700 in good stock, it would have been. I had it rechamberd to 300 Win, and so far it seems to be shooting a bit better, but I have not sorted it out yet. Needless to say I am almost completely soured on Pac-Nor three-groove barrels.

It is possible that a 1/2" could be cut off the 3" shank of the 6mm barrel and it could be rechambered. However, I am not enthused about putting more money into something that may not last. Been there done that too many times, like with those suspension components that failed. That was the second set of I had problems with.........

Realize I am not anti Pac-Nor. My favorite rifle still wears a Pac-Nor, and I still have high hopes for my 30 cal Pac-Nor. I had a 338 RUM and a 300 Win, both with Pac-Nors, that were extremely accurate, and when shooting them like the hunting rifles they were (never when hot), the throats showed very little erosion.

Blaine

Blaine,

Thanks for the very informative thread. Your attention to detail always amazes me, even though it shouldn't, given your profession.

Anyhow, what are your thoughts towards Lothar Walther barrels, as Celt seems to prefer.

3 Groove are picky. That is the word I hae heard about anybodys 3 groover.

Blaine, I still find your way of measuring throat erosion in question. You simply need to get a BORE SCOPE and stop farting around with Stoney Point OAL guages as THE way of measuring throat erosion. They work great for some things, but you can't tie throat erosion to bullet jump. They aren't the same. Case in point, the "lead" or "throat" angle of a barrel changes very quickly and dramatically in the first 200 rounds of being shot. Pac-Nor barrels have VERY steep, sharp leads that wear VERY quickly, but it isn't "throat erosion". This gives many individuals the idea that the throat is wearing prematurely, which isn't the case, even though I have found Pac-Nor barrels to wear rather quickly. The throat needs to be looked at under a microscope or bore scope to REALLY determine throat wear, which looks like a dried up lake bed. With your method of shooting a barrel cool, I, as well as many others aren't getting ANYWHERE near the throat 'erosion' you are and we shoot our rifles hot and with a LOT more rounds down range before the barrels puke. Get a bore scope!

Just because the throat "seems" to be advancing, doesn't mean the barrel is anywhere NEAR being shot out. I have personally owned and seen barrels with NO riflings, lead, or throat for 1-2 inches pound out 3/4" groups with boring regularity. One in particular, a .22-250 went 4,500 rounds and it wasn't taken care of when in a hot prairie dog town. When it quit shooting, it quit abrubtly. Many AR-15 or M-14 shooters go 6,000 + rounds and notice NO deterioration in accuracy, even though the throat may have advanced over half an inch. All I am saying is, there is a LOT more to the equation here than you know. You are detailing a small piece of what is really going on here. Just trying to clear some things up for shooters that might be wondering about throat erosion. Flinch