I did a lot of load development and accuracy testing with my new 6.5 PRC in the first few weeks of owning it and at around the 250rd mark accuracy fell off from consistently .5min to consistently 1.25.min. At first I suspected the scope, but nope, swapping it out with a proven scope yielded the same results. Barrel fouling was not it, as I stay on top of that.
Turned out to be .040" of throat erosion, so I seated the bullets out further to match the original .020" jump and accuracy immediately went back to .5min (or less)
Does this seem excessive to anyone? I am at rd. count 347 now and all is still good...
How about it MuleDeer; ya got any theories? I can't say that I have ever seen this happen so suddenly before. Rifle is a Fierce Fury with a McGowan barrel. Thanks fellas

Since I bought a bore scope I have changed my thought process more to a throat firecracking than to eroding, cant imagine the lands moving out .040" with a 6.5PRC

But then by far the worst custom barrel I have ever owned was a Mc Gowen

What bullets were you using? Were they all from the same lot#. Sometimes you get variations from lot to lot...

Yes, all bullets used in this development were the same lot #

McGowan steel has nothing to do with this issue. You are shooting a lot of powder.

Now you start to understand the importance of throat geometry on a new chamber(reamer design), Max OAL of magazine, plan accordingly.

Measure your leade growth on a regular basis.

Thanks Keith,
This rifle has a long action, so seating depth is not a problem.
The 147gr Eld-m is what I'm shooting mostly, but the 140 NoslerPartion is working great as well, which will be my primary hunting load with this rifle.

Yep. I'd be interested to see how the PRC compares to the creedmoor in that department. I'm thinking the PRC is going to be more like the old 264 winchester though. My Creed has burnt its throat back .025", but after 1,140 rounds downrange....and that is a cheap azzed rough savage barrel to boot...

bsa,

The PRC has just about exactly the same powder capacity as the 6.5-06, so I doubt it will burn throats anywhere as fast as the .264.

You know powder capacity is only part of the equation. Neck length also comes into play. If the op is correct about how much his throat has erroded, it seems like a barrel burner to me. As is/was the 264... If someone has done a side by side comparison between the 6.5 PRC, Creed and 264WM, I'd like to see it... This info is also intriguing as well because I have a 7WSM sitting idle, that a friend keeps telling me I need to turn into a 6.5 PRC. I'm still weighing the pros and cons...

Looks like that happened a bit early. I have a 26 Nosler and have a Hawkeye borescope.

After 500 rnds I see some throat erosion but the gun still shoots half MOA. I would think the 26 Nos would eat a barrel faster than the 6.5 PRC. Mine has a Shilen SS.

DF

bsa,

Yes, powder capacity is only part of the equation, Longer necks help, but shoulder angle has a major effect. The 6.5-06 has a .321" long neck, but the relatively shallow shoulder angle directs hot gas in FRONT of the case mouth, which also has a major effect on throat erosion. In fact, it's why the .243 Winchester tends to fry throats quickly: The shoulder angle directs gas in front of the case mouth.

The 6.5 PRC's neck is .272" long, but the should angle directs gas just inside the case mouth. (The. 264's neck, by the way, is .254" long.)

My 6.5 PRC has almost 200 rounds through it and through my Gradient Lens Hawkeye there MIGHT be a a very slight amount of erosion on the sharp edge of the chamber just in front of the case neck. But there's none in the throat itself, much less the rifling.

Thanks all for your wise input- it appears to have settled down and in the last 130rds or so I haven't been able to detect any change.......Because I didn't want to roast it out in a year I've went back to the Creed and a new SuperGrade 70 in the grand ole .30/06 to satisfy my shooting addiction. John was right as usual about the 185 VLD and 58-59 grs. of Hunter,
A solid performer in both of my '06's. Thank you for that.....

So with these throat eater type chamberings, is the erosion rate linear throughout the barrels life? Or is there a point at which the erosion slows? Just an S&G, curiosity type question.

Is it possible your measurement was off to begin with?

What powder and primers are you using?

Rate of fire?

Don't think the original measurements could be off- I'm pretty anal about this stuff.
The best performing loads use RL-25 and MRP. As to primers, the best have actually been the old Winchester white box type that are marked " For standard OR magnum rifle loads"
Remember those? These I have had vac-packed and rat holed since the pervert (Clinton)
was in charge. Rate of fire is slow, with a lot of cooling time. I am new to the forums, but I am not new to hand loading or shooting little bug hole groups. It's just that in 40 yrs of doing this game I have never seen this before.
Now I have seen very rapid erosion happen to 3 barrels at the very end of their life- barrels that you expected to die some time back, but manage to hang on, and then suddenly you can't find the throats without a scope. Now you have a nice long tent stake.....

To all the gun owners who don't support the 2nd Amendment protection groups:
You are getting very heavy...........