Anyone measured throat erosion ?

[dvdt]

Can anyone help me out with some throat erosion numbers over a barrel's life ? I'm interested in .308 and 6.5CM if anyone just happens to have those.

I'm trying to decide if I want to get Alpha Type I or Type II mags (2.850 vs 2.985).

I may be over thinking this, but I'm curious if after X number of rounds I wouldn't be able to load 0.010" <span style="font-weight: bold">off</span> the lands b/c of throat erosion + mag length.

My rifle is chambered in 6.5CM (custom build) and factory rounds measure 2.800" on average. I have no idea how much throat erosion I might see over the life of this barrel. In other words, is 0.050" of erosion unheard of or is that something I might see towards the end of it's life ?

I'll be measuring my rifle soon but my OAL gauge is in the mail. However, trying to future proof myself for a possible .308 build in the future.

Thanks!

 

[Brasscow]

Re: Anyone measured throat erosion ?

I figure on (and have seen) .007" - .008" per 1000rds for .308.

 

[bohem]

Re: Anyone measured throat erosion ?

My 6.5-06, as life progressed, was burning 0.009"/100 rounds.

I'd run with the longer magazines, this way if you want to use a different case or longer bullet or something in the future you've got the extra space and it won't affect feeding anyway.

 

[sniperaviator]

Re: Anyone measured throat erosion ?

It's not just magazine length, but also how long a round will your action chamber? And of course it is not just OAL, but where the bullet touches the lands. Bergers have their ogive about 0.1 further back than Lapua Scenars for instance, making the Berger a pretty long OAL if you want to touch the lands with it.

The best solution, in my limited opinion, is to decide on a bullet ahead of time and throat the chamber to minimum length OAL for that bullet (with the bullet maybe .02 off the lands). That should give you maximum amount of room to load longer as the lands move out.

As for the magazine, get the longest one that you can find that will still chamber your rounds reliably. .308 guns use AICS mags and short action Rem 700's will only chamber a round slightly longer than the 2.88" they hold, if I recall correctly. Then there are the AW mags and the longer (Defiance?) actions that accept them.

It's a sticky wicket. Someone like GAP has most of the answers from what I hear, as they deal with these issues constantly. Sako magazines hold 2.95" rounds and the Sako chamber is medium throated, about right if you ask me. Not that Sako is all that picky on how close to the lands you load. It shoots pretty good no matter where you load it.

 

[vman]

Re: Anyone measured throat erosion ?

Mmmmm Alpha Type 2 and if that feed ramp sticks out get it trimmed back.

Depending on the type of shooting you do will determine how fast that throat errodes. Long stings on hot loads will quickly wear out the throat.

I prefer not to clean often and when i do i use a lucas bore guide. loads arent too hot.

I cant even recall if my throat has moved back much over the past 1000 shots... but if and when it does get to a point that its beyond alpha type 2 mags max length, and accuracy deminishes, i will then rebarrel with a decent reamer.

 

[427Cobra]

Re: Anyone measured throat erosion ?

Go long, in 1400 rounds my 260 has grown .060, and it seems to be excellerating.

 

[nova-birdman]

Re: Anyone measured throat erosion ?

Not the caliber you want, but some good information anyway, I'm keeping close track of my 338lm erosion (savage 110ba), and have measured 0.002-0.003" per 100 rnds. The question I have, is how much erosion is typically seen before accuracy starts to wane? I'd like to have some idea of barrel life to be able to plan ahead. Anyone?