Throat erosion

[Crunchy]

I have read about chamber/throat erosion with increased rounds being fired through a barrel.  Anyone explain how this can or will affect your measurements for max bullet seating length?  I have notice that number is getting slightly smaller and was expecting it to get longer.  Maybe I need to do a little more scrubbing in the chamber or look at my Hornady OGIVE tool to make sure both are clean. I was at 2.702 kissing the lands and now at 2.696 I believe.

[Magnum_Willys]

Different bullets of the same type can still change the measurement also.  I try to save a dummy in a zip lock when new so I have a reference later.   If you use a different gauge its all different.

Ballpark throat erosion .004-.006 per 100 rounds.   (.060 in a 1000 rounds)

Its real easy to be off by .006 if you don't do 3 or 4 measurements.  I stick a cleaning rod down the muzzle so and I can push back and forth from both ends to feel the lands.

[Crunchy]

Yes, I did see a change from lot to lot of bullets.  But explain other than the bullet, shouldnt the number increase from 2.702 rather than decrease.  I just want to know what to expect if it is the bullet or throat erosion.

[Magnum_Willys]

Oh yea I would be scratching my head also.  Should be getting bigger if not then:

1. Operator Error
2. Different bullets
3. Different or worn gage
4. Carbon Ring or buildup.

Remeasure with other bullets - any bullets from prior load you could pull and measure?

[Crunchy]

Ok, I got another 500 bullets so I will start with a fresh measurement.  I lost my bullet seating depth sweet spot

[Magnum_Willys]

That happened to me.  I didn't write down jump - just ogive and COAL.   Then got new lot bullets and they were were different.  Then I decided maybe my ogive tool insert was wearing with that fine edge so I lapped it to a bullet.  Of course now measurements were all new.   I knew where sweet spot was measured by ogive but couldn't duplicate it now.   Arghh.  Not sure I ever did find that perfect spot again.

[jasnt]

I just had to change my seating depth. 243 is about toast again I’m thinking. Accuracy is great at 100 yards but now my speed is all over the place.  Es of 78
So I started load development over and started single feeding as the .015” off now won’t fit the mag.  No big deal but for 3 shot groups my best es was 38.  Still at about.25-.35 moa at 100 yards.   I’m going to clean it and see if it’s settles down. 

I have seen length to landes shrink with new lot of bullets.  They change out the dies in the bullet swag machine and bc changes and seating depth changes. 

[Magnum_Willys]

Darn throat erosion!  My new proof barrel showed up yesterday.  Sanding stock to fit then off to a shop and the throat erosion  problems will be cured for awhile. 

[Yondering]

Ok, I got another 500 bullets so I will start with a fresh measurement.  I lost my bullet seating depth sweet spot

If your seating depth is that sensitive, you didn't really have the "sweet spot".

It's not that hard to do a seating depth test again, maybe in finer increments this time if you think you know approximately where it should be. You should find a range of seating depth that shoots well, and you want to be in the middle of it. If a few thousandths change in the bullets or the throat ruined accuracy, maybe you were on the edge of that range instead of the middle.

[Angry Perch]

I just had to change my seating depth. 243 is about toast again I’m thinking. Accuracy is great at 100 yards but now my speed is all over the place.  Es of 78
So I started load development over and started single feeding as the .015” off now won’t fit the mag.  No big deal but for 3 shot groups my best es was 38.  Still at about.25-.35 moa at 100 yards.   I’m going to clean it and see if it’s settles down. 

I have seen length to landes shrink with new lot of bullets.  They change out the dies in the bullet swag machine and bc changes and seating depth changes.

You burned through another barrel?
Dang!

[jasnt]

I just had to change my seating depth. 243 is about toast again I’m thinking. Accuracy is great at 100 yards but now my speed is all over the place.  Es of 78
So I started load development over and started single feeding as the .015” off now won’t fit the mag.  No big deal but for 3 shot groups my best es was 38.  Still at about.25-.35 moa at 100 yards.   I’m going to clean it and see if it’s settles down. 

I have seen length to landes shrink with new lot of bullets.  They change out the dies in the bullet swag machine and bc changes and seating depth changes.

You burned through another barrel?
Dang!

im thinking it’s on its way out.  Cleaned it today and Es came down 24 for 5 shots but up to 56 for 10 shots.  And that’s after full new load work up.  Much earlier than I expected.  This started about 650 rds when I noticed vertical spread at distance.   
I’ve thread jacked enough

[buckfvr]

What bullet @ what velocity and twist, just curious as I run 105 vlds at 2960

[hogslayer]

If you set your measurement bullet aside and it’s shorter than you have excess carbon.  Which will effect accuracy and pressure.  I strip the bolt and removed firing pin and ejector to find lands.  I can get within .001.  I clean and check lands every 50 rounds.  This is why I like to buy 1k bullets of the same lot when I get a new barrel, or find a combo that I am going to run with.  Your going to buy them anyways.  Seems like staying on top of your barrel and bullets is enough work. I don’t like to throw different lots of anything in the mix.

[Mulie87]

Hey Magnum! That’s the same stock and barrel i’m using for my 6.5PRC build. What caliber are you building that around?

[Magnum_Willys]

Hey Magnum! That’s the same stock and barrel i’m using for my 6.5PRC build. What caliber are you building that around?

This is my 1100 yard rifle - 338 Lapua.  I run a 300 SMK same speed as Son’s 338-378 as his backup.   
Has worked well for us.  Had HCA 28” barrel and going to Proof 30”.

Thinking about a 6.5 PRC myself for a shooter as my next build.