.300 win mag...radical hyper velocities question do to copper build?

[Matches Malone]

So I "thought" I got all the cooper fouling out of my .Remy 700 .300 win mag...26" stock varmint barrel, which I know isnt the best...but I thought I'd run out the barrel before re barreling. I've only shot a little over 600 rds out of it. However I was getting some sticky rounds in the chamber then, and the copper build up was getting pretty ridiculous so I got some cooper solvent, hopps bench, and after a few days of running through the process, the barrel looked very good. I went to the range and rezero'd and chrono'd the new velocities for fed 180 gr match...i was getting hyper velocities...like 3078 and sometimes breaking 4000....I checked the brass and my bolt, no pressure signs, even though it was factory loaded. None of the rounds where sticking in the chamber though...so theres that. My previous velocities for these loads were in the 3015 range consistently with around a 7fps std. What do you guys think, barrel is done for?

 

[Dirty D]

You said "previous velocities for these loads were in the 3015 range consistently with around a 7fps std", what are your ES and SD since cleaning out the cooper?

 

[Matches Malone]

All over the place, like 70 std but i havent changed how I set up the chrono or how i shoot through it. at 100, it was maybe, 1 1/4 moa, but i used the data the chrono was giving me and took the ridiculous average and even using 3795 I was still shooting 2 mils high at 400....not consistently in the same area. Though some of that might be due to harmonics since i zero'd and chrono using bags and shot the 400 using a bipod...point was it was abnormally faster velocity if i was to go down range and start trueing.

 

[Matches Malone]

it was fine, before I cleaned out the copper...it wasnt shooting nearly as fast before the copper removal. Even with the build up

 

[cav has been]

If I read all this correctly you had a nearly 1000 fps variance. 3015 fps to 4000 fps. Throw your chrono over the bank it lies.

 

[Matches Malone]

yep. pretty much...what gets me though, is how high im shooting at other distances, from 300 to 500y...even putting that near 1000 fps difference increase into my dope and using those MV's...i was still shooting 2-2.5 mils higher...suggesting my MV is really even higher than that..hence why i dont believe it to be the chrono

 

[03psd]

If I read all this correctly you had a nearly 1000 fps variance. 3015 fps to 4000 fps. Throw your chrono over the bank it lies.

Yeah, I'm with this guy. No way in hell you are getting 4000fps with a 180gr pill out of a 300WM and live to tell about it.

 

[Matches Malone]

Idk, im on your side...like I said, it's why I checked for pressure signs and so forth, but the bullet doesn't lie...even if it was the chronograph, it still doesn't explain why using 3075 fps in a ballistic computer and still shooting a 2 mils high at 500..

 

[Dirty D]

...the bullet doesn't lie...even if it was the chronograph, it still doesn't explain why using 3075 fps in a ballistic computer and still shooting a 2 mils high at 500..

Bullet doesn't lie, I am naturally suspicious of those chrono readings but the bullet doesn't lie. I wouldn't think that you wore out the throat in 600 rounds but it is possible and we all know how Remington's QC is like playing craps at a casino so there is no telling. It sounds like it is time for a Criterion Remage conversion and if you can find a gunsmith with a bore scope I would be curious what the verdict is after taking a good look at the bore. That much powder right next to your face, play it safe and get a new barrel, tossing a factory barrel is nothing worth taking a risk on.

 

[niteshooter]

If the hope was to get 1000 rounds or so out of it might be best just to get started on a rebarrel. The cost of 400 rounds of factory ammo will go a ways toward that and probably a happier end result than chasing barrel/zero shift ghosts.
My vote is just rebarrel.
I wouldn't put much faith in that chrony either, it may have took a dump as well
OP post reminds me of an ass chewing I got as a kid for cleaning dads old filthy hunting rifle. Got that thing shining. But he was pissed about the ammo he wasted getting it zeroed back like he wanted.
No good deed goes unpunished.

 

[Matches Malone]

I wouldn't think that you wore out the throat in 600 rounds but it is possible.

I was thinking the same thing.

 

[BangBangBlatBlat]

Idk, im on your side...like I said, it's why I checked for pressure signs and so forth, but the bullet doesn't lie...even if it was the chronograph, it still doesn't explain why using 3075 fps in a ballistic computer and still shooting a 2 mils high at 500..

Ballistic computers lie too. Or don't take into account all factors. Sometimes, even with good data. That's why they usually have a truing function. I'm still struggling to understand it.

Here's an example. My 260 was launching a 142 Sierra Match King at 2850 according to a Magentospeed. Using a Kestrel, and inputting as accurate data I could get, I was hitting half a mil high at 1000 yards. The trued data gave me a velocity of 2950...I know that is wrong for actual speed, but it did make my come-ups match with what the calculator said.

The working theory I had at the time, is that the hole in the barrel is never drilled perfectly straight, and that slight curve was indicated so that it was in the up position at the end of the barrel. I know it's something my gunsmith does.

 

[Matches Malone]

yes, computers can lie if you put garbage into it. I use kestrel 4500 ab. but i do true my MV and with 4 shot groups and a micrometer put into a truing calculator. The issue isnt that it was 2- 2.5 mils high...its that it was high 2 mils at close to 4000 fps. Obviously meaning it was going faster than that velocity....I thought it would be interesting to get some insight from other shooters. I agree with dirty d and nitehooters post. Remington has a habit of having shitty barrels and i was using heavier loads before, is probably bad throat erosion and will need to be rebarreled which is fine, I was waiting for an excuse to move on to a custom barrel for this platform anyways.

 

[davisj3537]

This is fascinating to me. Genuinely interested in learning here. Let's put aside the numbers behind OP's velocity discrepancies for a moment. How would throat erosion spike velocity drastically like this?

 

[MtnCreek]

Throat erosion should reduce pressure and lower velocity.

If it's not showing any high pressure signs (on bolt lift, extraction & brass) shoot it enough to recoat the barrel and see how it does from there.

 

[Dirty D]

...How would throat erosion spike velocity drastically like this?

The rifling that we count on to spin the projectile causes drag so if you take away a significant portion of the rifling you can see velocity increases. The Army uses 120mm smooth bore barrels on the M1A and the Navy has some smooth bore guns as well. This is all a guesstimation until he has the bore scoped and a definitive answer is given, I would be very curious to see the results.

 

[Rob01]

Clean it very, very good and get all the copper out and then run some Tubb Final Finish bullets through it. It will help.

 

[Garyc]

yep. pretty much...what gets me though, is how high im shooting at other distances, from 300 to 500y...even putting that near 1000 fps difference increase into my dope and using those MV's...i was still shooting 2-2.5 mils higher...suggesting my MV is really even higher than that..hence why i dont believe it to be the chrono

Your chrono readings are wrong, trust me. I don't care what your elevation dope says, if you were getting 1000 fps more out of it then you wouldn't be here, you'd be in the morgue with a hole the size of a remington bolt through your forehead.

 

[sakobob]

Your Chrono is junk.... period,
180gr federal win mag match ammo?
How do you know your scope is tracking correctly
And what are you calling heavy fouling, how was it shooting at 100? , You would have to practically machine gun that thing to smoke a throat in 600rounds .

 

[Matches Malone]

Your Chrono is junk.... period,
180gr federal win mag match ammo?
How do you know your scope is tracking correctly
And what are you calling heavy fouling, how was it shooting at 100? , You would have to practically machine gun that thing to smoke a throat in 600rounds .

Your right, that was a typo on the grain.
190 grain gold medal match.

The scope tracking is fine, I run box drills on my scopes when i set them up, or when they come out of storage.

Fouling was barely being able to see the grooves in the barrel. After cleaning the copper out, it looks like the the grooves are really worn.

I admit that I've done some machine gunning with it a year or so ago. It's gotten pretty hot a few times, which is obviously not healthy especially for belted mags, but only a few times, and I'm talking only five rounds most in session. Not really enough to burn out the barrel that bad, but it's not a great barrel to begin with. I cleaned it out like i said in the beginning mostly because of the sticky brass. The copper cleaning helped with the sticky brass issue hence the why I just didn't let go messing with the fouling.

After taking sometime and looking at it with a bore scope its safe to say that there is some throat erosion, fire cracking was pretty apparent although I had to dig in there and dry out some of the solvent I had missed before I shot last, also there were some patches of copper in the barrel both which might explain some of the excess velocities...I suppose. The barrel still looks usable but I'm going to replace it anyways. The barrel quality isn't that great in a factory Remington barrel as it is. At 100 it still shoots 1.50 MOA, which is not nearly as good as when it was new, but that is to be expected.

I usually hand load as well. Usually 230 bergers, in a 300WM. That was what most of the action the barrel has seen in terms of loads.

I checked the Chrono with some load development yesterday, on an SPR build I just finished, I got a few errors so i changed the battery. Worked fine after. Idk.