Remington Sendero 300 Win Mag Constant Cleaning Possible Throat Erosion

[GunAddict]

Hello,

I am new to the forum. I feel somewhat out of place here. Although I have been shooting for most of my life, I have never owned an accurate gun or done done long range shooting. I have shot a couple of deer over 300 yds with a 7mm Rem Mag most between 100 and 200 yds. In Southeast NC, we have mostly small fields.

So down to the question. I recently found a Remington 700 Sendero in .300 Win Mag at a pawn shop. I got it cheap because they though it had trigger problems. It turned out there was some rust on the main spring and firing pin. With that fixed, I put a cheap scope I had laying around, leaned it, and headed to the range with some Hornady 150gr SST. I was pleasantly surprised with the .4-.5" group at 100 yds (see picture below far right is called flyer). So I wanted to put some decent glass on it. Ended up with a Sightron SII Big Sky 4.5-14x44. My groups went to 2-3" at 100 yds. Needless to say I was disappointed. So I put cheap scope back on and same thing. Decided to give a quick cleaning to remove carbon fouling. Went back to .5 MOA groups. Put Sightron back on and roughly .3 MOA (see picture below. Bottom group with far right fouling shot.)

So in summary the difference between .4-.5 MOA and 2-3 MOA was about 10-15 shots. So looking for answers I called Remington. First, gun was manufactured in 1995. I was told that I quite possibly have throat erosion and should replace the barrel. What I don't understand is that if this is a throat erosion problem, should cleaning carbon fouling bring back my groups? Or is this just an issue that I have never encountered and need to clean an accurate rifle that much? Sorry for the length, I try to be clear and sometimes just end up running long. Must be the engineer in me.

 

[dansig]

I have a sendero in .300 win mag. I run 50 rounds through the barrel without any problems.

Since you bought an old used gun you should give it a propper cleaning, solvent, brushing and oiling... Spend 2 hours on the barrel, let it soak in solvent and then brush it, 100-200 times and then wipe clean with pads.

If it still fouls then replace the barrel

 

[40X Guy]

I had exact same gun/caliber, my barrel was chrome moly and would foul after 15 shots or so badly. I was using RL-22 which the rifle loved but it is very dirty. This is before I owned a borescope so I never knew if I had gotten the carbon fouling out of it (one previous owner) after brushing etc. I sold rifle as I did not want to rebarrel. Long story short is find someone with a borescope and have it checked out, thats the only sure way to tell condition of barrel. The factory Sendero's do shoot well.

Frank

 

[Leaddog]

After thoroughly cleaning, use some USP bore paste in the barrel according to the directions. You'll find that this will clean up that bad carbon. Use it about every 200 rounds to restore accuracy. After using, make sure you clean your barrel and lightly oil. Before shooting the next time, patch out all the oil residue. I think you will find this will really help you.

 

[LRPV]

I have same rifle. I shot it a lot and it is very accurate. It fouls badly and is very hard to get clean. It copper fouls badly. I use it to hunt with mainly so i don't keep track of the number of rounds it takes but 15-20 sounds about right and it needs to be cleaned.

 

[Dans40X]

Each barrel shoots differently.
Each barrel cleans differently.

Thinking that you have that OEM Rem hammer forged barrel clean w/o verifying w/ a bore scope is fruitless,as it probably is not.

Once you figure when accuracy deteriorates in that hammer forged barrel-stop shooting for accuracy.
Possibly try shooting some moly or Hbn coated bullets.

That barrel will streak copper from beginning to it's useful end.

 

[kyreloader]

http://www.extremeguncare.com/index.php?main_page=index&cPath=2

Should fix it.