308 throat erosion: 0.034 after 1000 rds typical?

[Kevin1]

I just notice that I have a throat erosion of 0.034 since last year when I purchased my 308 Savage 10FP and after putting around 1000 rounds.
The average OAL of a bullet touching the rifling went from 2.801 to 2.835 (with 175G SMK).
Measurement method: Load a round with an OAL of around 2.85, chamber the round, eject it carefully, and re-measure the OAL.

I have 3 questions:
1.Is this erosion typical? Keep in mind that my loads have been pretty mild.
2.At which point I need to consider swapping barrel?
3.Will the erosion rate slow down and how much? I’m pretty sure the erosion is faster at the beginning and will slow down, but just wanted to confirm.

 

[motodog]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

tag

 

[EROCO]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

yes, that sounds about right. The first few hundred you can easily see as much as .030, ofcourse depending on how hot the loads are.

It slows down a little from there, but you still have to keep chasing it down..

 

[Kevin1]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EROCO</div><div class="ubbcode-body">yes, that sounds about right. The first few hundred you can easily see as much as .030, ofcourse depending on how hot the loads are.

It slows down a little from there, but you still have to keep chasing it down.. </div></div>

Thanks. This is reassuring. This means that the FGM rounds would make a jump of over 0.030 only after 1000 rounds and it will keep increasing. I wonder how can people who don't reload and follow the throat erosion maintain a good accuracy with match ammo. Maybe 308 match bullets are just forgiving on the OAL lenth. This might be one of the reasons why the barrel life of the 308 is much longer (since the accuracy might not be that much affected by the OAL). But I might be wrong....

 

[Doeboy]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

In my opinion, i would not go by O.A.L. the length of the bullets will have variation. I go by the Ogive to measure throat erosion.

 

[Kevin1]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Doeboy</div><div class="ubbcode-body">In my opinion, i would not go by O.A.L. the length of the bullets will have variation. I go by the Ogive to measure throat erosion. </div></div>

I know. But since I don't have the device, I go by the average of several OAL. It might not be as accurate but still gives you an idea.
To set my dies, I chamber a longer round, then I take it out and ajust my die to the proper length (to get for example -0.005 compared to the initial length of the round previously chambered touching the rifling). As you can see, with this method, I'm also relying on the ogive length.

 

[grayghost]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

How easy was it to eject the round, as on my 10fp w/800 rounds through it will unseat the bullet from the case if I go to 2.83 oal and are tight at 2.81.

 

[clmayfield]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kevin1</div><div class="ubbcode-body">

I know. But since I don't have the device, I go by the average of several OAL. It might not be as accurate but still gives you an idea.
To set my dies, I chamber a longer round, then I take it out and ajust my die to the proper length (to get for example -0.005 compared to the initial length of the round previously chambered touching the rifling). As you can see, with this method, I'm also relying on the ogive length.

</div></div>

Get this:
http://www.sinclairintl.com/.aspx/pid=34262/Product/Sinclair-Hex-Style-Bullet-Comparators
It is an absolute must for a reloader.

 

[Kevin1]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hogrider2003flht</div><div class="ubbcode-body">How easy was it to eject the round, as on my 10fp w/800 rounds through it will unseat the bullet from the case if I go to 2.83 oal and are tight at 2.81. </div></div>

It's pretty easy. You need to put just a little tension on the neck. Just enough to make sure the bullet isn't pulled (giving the wrong measuring) when you extract. Adding a little gun oil to the bullet can also help.

 

[Kevin1]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

What I do isn't an exact science. I'll probably end up buying a Hornady LNL OAL Gauge and Bullet Comparator.


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Carter Mayfield</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kevin1</div><div class="ubbcode-body">

I know. But since I don't have the device, I go by the average of several OAL. It might not be as accurate but still gives you an idea.
To set my dies, I chamber a longer round, then I take it out and ajust my die to the proper length (to get for example -0.005 compared to the initial length of the round previously chambered touching the rifling). As you can see, with this method, I'm also relying on the ogive length.

</div></div>

Get this:
http://www.sinclairintl.com/.aspx/pid=34262/Product/Sinclair-Hex-Style-Bullet-Comparators
It is an absolute must for a reloader. </div></div>

 

[turbo54]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

Using COAL for this procedure (determining erosion) is completely satisfactory, provided you hang onto/keep the same bullet for the purpose.

 

[totenkopf]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Doeboy</div><div class="ubbcode-body">In my opinion, i would not go by O.A.L. the length of the bullets will have variation. I go by the Ogive to measure throat erosion. </div></div>

Well said, bullets have varied lengths if you measure from the meplat, as stated use the ogive to base.

 

[EROCO]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

Standard procedure for me with a new rifle is to measure seating depth to lands for each bullet I will be using. I use the RCBS precision mic which works pretty good and repeatable. I record this number into my data book along with the maximum brass length using the Sinclair tool.

 

[JWV]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

I personally kept shooting mine at the same c.o.a.l. until accuracy declined. Then I started chasing the lands a bit. The 308 is generally a jump friendly round with the smk and amax I have found.

 

[gme]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

the only way the numbers you have would be any value would be if you kept the original bullet you took your initial measurements with and used it to take your later measurements, lot to lot variation on the bullet OAL would be enough to invalidate your measurements, as stated above you must use the ogive length in order to have good data, that said I would say that .034 over 1000 rounds on a .308 is far more than you would expect, I have four .308 rifles and right now my oldest rifle (3800+ rounds) has about .035 erosion.

 

[skinnypitt]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

I have to agree with GME, that is possibly what I might expect from my 260 running med-hot loads after 1000 rds.

 

[turbo54]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

I agree that .035" is too much for 1000 rounds.

However, the most ogive length variation I'd expect to see from an SMK is about .015"....MAX. So even the bullet used initially was the shortest, and the bullet used recently was the longest, that would still mean .015" erosion, which STILL sounds like too much for 1000 rounds.

My Savage has 5000 through, and still touches at 2.815 with a 175smk...just like it did at 500 rounds, 1000, 2000, 3000 etc etc.

 

[Doeboy]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">I agree that .035" is too much for 1000 rounds.

However, the most ogive length variation I'd expect to see from an SMK is about .015"....MAX. So even the bullet used initially was the shortest, and the bullet used recently was the longest, that would still mean .015" erosion, which STILL sounds like too much for 1000 rounds.

My Savage has 5000 through, and still touches at 2.815 with a 175smk...just like it did at 500 rounds, 1000, 2000, 3000 etc etc. </div></div>I wounder how hot his loads are? and what powder he's useing? He didn't say..hmmm?

 

[turbo54]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Doeboy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">I agree that .035" is too much for 1000 rounds.

However, the most ogive length variation I'd expect to see from an SMK is about .015"....MAX. So even the bullet used initially was the shortest, and the bullet used recently was the longest, that would still mean .015" erosion, which STILL sounds like too much for 1000 rounds.

My Savage has 5000 through, and still touches at 2.815 with a 175smk...just like it did at 500 rounds, 1000, 2000, 3000 etc etc. </div></div>I wounder how hot his loads are? and what powder he's useing? He didn't say..hmmm?

</div></div>

The last 3000 or so have been 45.5gr Varget, CCI BR2 and 175smk - mostly in Lapua brass, going between 2650 and 2700fps.

 

[Kevin1]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

My measurements were wrong !
I bought the Hornady LNL OAL Gauge http://www.midwayusa.com/product/570611/hornady-lock-n-load-overall-length-gage-bolt-action

I measured the OAL with a few different SMK 175 bullets and it gives an average of 2.826
Now I'm going to keep one bullet to follow the throat erosion.

Mistake I made:
By chambering a longer round, the pressure of closing the bolt pushes the bullet into the rifling. That's why the results are not only inconsistent, but are also longer than the actual OAL touching the rifling.

The Hornady LNL OAL Gauge is the way to go to follow the throat erosion and to correctly set the dies.

 

[turbo54]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kevin1</div><div class="ubbcode-body">My measurements were wrong !
I bought the Hornady LNL OAL Gauge http://www.midwayusa.com/product/570611/hornady-lock-n-load-overall-length-gage-bolt-action

I measured the OAL with a few different SMK 175 bullets and it gives an average of 2.826
Now I'm going to keep one bullet to follow the throat erosion.

Mistake I made:
By chambering a longer round, the pressure of closing the bolt pushes the bullet into the rifling. That's why the results are not only inconsistent, but are also longer than the actual OAL touching the rifling.

The Hornady LNL OAL Gauge is the way to go to follow the throat erosion and to correctly set the dies.

</div></div>

That makes more sense.

I keep a master bullet, and use a hex-style bullet comparator. I use FLSd brass that EASILY fits in/drops out of the chamber. I put a cleaning rod in the bore from the muzzle. I seat a bullet long and insert (by hand) it in the chamber. I give a gentle "push" with my finger to seat the cartridge. If it won't drop out of the chamber simply by tipping tge muzzle up, I pop it out with the cleaning rod, seat a little deeper, and try again. After a few adjustments, you can NAIL down the perfect length it takes to *just* touch the lands.

 

[cmh2007]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

Throat??? I have serious doubts that my reloads could even touch the lands any more. 5000 rounds down the tube and i now only have to neck size the last 1/8" of the neck of my cases. It still shoots decent, but gets progressively worse every time i take it out.

Ps 3000fps with a 155 scenar is a barrel burner

 

[Kevin1]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: seaaggie</div><div class="ubbcode-body">Throat??? I have serious doubts that my reloads could even touch the lands any more. 5000 rounds down the tube and i now only have to neck size the last 1/8" of the neck of my cases. It still shoots decent, but gets progressively worse every time i take it out.

Ps 3000fps with a 155 scenar is a barrel burner</div></div>

Do you have the factory barrel? If so, and with a 1:10 twist, I didn't know you could have good results with 155g bullets.

 

[cummins cowboy]

Re: 308 throat erosion: 0.034 after 1000 rds typical?

I don't wanna have to worry about exactly where the lands are so on a field rifle unless I have to I don't go chasing lands and the last thing I want is to have to shoot a bullet that is jammed into the lands, because the bullet could get stuck and powder dumping everywhere.

OAL is a terrible way to know thats going on, a stoney point setup is like $40 bucks, heck thats a box of ammo. Ogive is what you wanna measure, OAL can actually vary alot and that is normal, ogive should be within .003 or so +or-