Throat and Bullet Jump

[cosmic creepers]

Okay so I've gotten some good advice on here, thanks to some of you, and I've got my load for my .308

Shooting 190 grain Sierra Matchking
41.0 grains Reloder15
2.855" approximately [what I have is a homemade ogive comparator, but giving you guys that information would be irrelevant, so suffice it to say I am seating bullets off of an ogive datum point.]
Winchester LR primer
Starline Brass

The load shoots about 2455 fps and shoots about 5 to 6 inch groups at a thousand yards on a windless day at 3200ft elevation.

My seating depth seemed to ve very consistent actually getting better results closer to 2.845" so I should have a little bit of room. But I am absolutely at the maximum of my magazine's allowance.

My question is, typically, what kind of throat erosion do you guys get? (I.e. every 500 rounds adjust seating depth 0.003" etc..)

Just trying to do some preliminary research through some knowledgeable old timers.

 

[Straightshooter1]

Okay so I've gotten some good advice on here, thanks to some of you, and I've got my load for my .308

Shooting 190 grain Sierra Matchking
41.0 grains Reloder15
2.855" approximately [what I have is a homemade ogive comparator, but giving you guys that information would be irrelevant, so suffice it to say I am seating bullets off of an ogive datum point.]
Winchester LR primer
Starline Brass

The load shoots about 2455 fps and shoots about 5 to 6 inch groups at a thousand yards on a windless day at 3200ft elevation.

My seating depth seemed to ve very consistent actually getting better results closer to 2.845" so I should have a little bit of room. But I am absolutely at the maximum of my magazine's allowance.

My question is, typically, what kind of throat erosion do you guys get? (I.e. every 500 rounds adjust seating depth 0.003" etc..)

Just trying to do some preliminary research through some knowledgeable old timers.

Don't "chase the lands"!

Once you've found the load and seating depth that works, keep it there until you actually see that it's not working as well anymore. That could be well over 2,000 rounds and .033" of throat erosion (as it was for me in my experiment with my .308).

I like to keep track of various data just to keep an eye on what's gong on, so I do measure my distance to the lands after every cleaning using a Sinclair comparator insert for BTO (about every 100 to 150 rounds, though I feel that often is not really "necessary"). With a round count of 2,278 the DTL (Distance to Lands) with a 168 SMK that I save and only use for tracking this distance, it was 2.244". At 1,707 rounds the DTL, using that very same bullet, was 2.237". At 1,205 rounds, the DTL was 2.232". The powders and bullets I typically use for my .308 is AR-Comp and IMR-4064 pushing 168 and 169 SMK's. You're rate of throat erosion will likely be greater if you're using that heavier bullet all the time.

PS: Because bullet's BTO's can vary quite a lot from lot to lot, be sure to save and use the same bullet when tracking throat erosion.

 

[Zero333]

After going through many barrels I can tell you there is no set number. Too many variables that will affect erosion. Best thing is to get the Hornady OAL tool and the modified case for the cartridge and measure every time you load for it,... or youtube search for "finding the lands" method that doesn't require any $$ to find the lands.
And don't forget, different lots of bullets will vary in ogives ass well.

 

[gambleone]

5-6" groups at 1000 yards ain't bad. Can you tell us more about the rifle.

 

[Straightshooter1]

After going through many barrels I can tell you there is no set number. Too many variables that will affect erosion. Best thing is to get the Hornady OAL tool and the modified case for the cartridge and measure every time you load for it,... or youtube search for "finding the lands" method that doesn't require any $$ to find the lands.
And don't forget, different lots of bullets will vary in ogives ass well.

It's important to find where the lands is after mounting a new barrel to know where to start with the load for each bullet being used. Afterwards, since distance to the lands isn't very important (unless touching or jamming the lands is the objective), there's no real need to measure the distance to the lands . . . just try and keep the seating depth the same, even when changing lots of bullets that have very different BTO's.

 

[J.D.Erwin]

Don't "chase the lands"!

Once you've found the load and seating depth that works, keep it there until you actually see that it's not working as well anymore. That could be well over 2,000 rounds and .033" of throat erosion (as it was for me in my experiment with my .308).

I like to keep track of various data just to keep an eye on what's gong on, so I do measure my distance to the lands after every cleaning using a Sinclair comparator insert for BTO (about every 100 to 150 rounds, though I feel that often is not really "necessary"). With a round count of 2,278 the DTL (Distance to Lands) with a 168 SMK that I save and only use for tracking this distance, it was 2.244". At 1,707 rounds the DTL, using that very same bullet, was 2.237". At 1,205 rounds, the DTL was 2.232". The powders and bullets I typically use for my .308 is AR-Comp and IMR-4064 pushing 168 and 169 SMK's. You're rate of throat erosion will likely be greater if you're using that heavier bullet all the time.

PS: Because bullet's BTO's can vary quite a lot from lot to lot, be sure to save and use the same bullet when tracking throat erosion.

I agree with straightshooter don't chase the lands let the groups tell you when it needs adjusting Ive had some barrells erosion as mush as 60ths before I adjusted the load. Shoot it let it talk to you

 

[Rocketvapor]

This "let the groups tell you" only works if you shoot often.
I try and get one or two practice sessions in a month, then a monthly match.
If I find the groups have opened up due to erosion, and compensate, it means another practice session before a match. That or load long and bring a press/seating die with me. I don't want the throat to "let the groups tell me" one relay into a 60 round match.

 

[cosmic creepers]

5-6" groups at 1000 yards ain't bad. Can you tell us more about the rifle.

The rifle was a 400 dollar 1971 model 70 winchester that I bought used from a local gun store.

I couldn't make it shoot better than an inch and a half so I had a local barrel maker put a barrel on it. JCB Inc is his name out of Portland Oregon.

450 is his price for a barrel installed.

So I ordered an m40A1 contour barrel with an M118 chamber 1in10 twist. **Edit the barrel is 24"**

I spent an entire night with a sander and a hook knife and got the barrel to float, and then bedded the action with "Bedrock" with few wraps of electrical tape on it.

Initial load development was kind of a struggle had some help from guys on here and had it shooting bug holes with some 168 matchkings and rl-15. It was making about 4 inch groups at 700, but got unpredictable and difficult to dope at 1000, so I bought as many as I could afford 190 grain factory seconds matchkings 700 or so.

The gun seems to like reloder15 so I did a ladder, 2400 fps was my minimum velocity requirement, it shot a load pretty good at 41 grains so I went to a seating depth test started at 0.020" moved back in 0.005" increments and found three in a row that shot about three quarters of an inch or less.

Shot a 20 shot group of it and it was still 0.760"

So I took it to a thousand. My hornady 4dof dope was nuts-on first round within inches of a 1 moa plate.

Once I got it dialed it was consecutive hit after hit even in some lightly changing wind conditions with little adjustment.

Came out on a windless day and grouped it.

I only shoot this rifle prone off a bipod.

Can't say enough good about it. Once I figured out what I was doing wrong in the reloading room, it all came together.

The thing that really changed the game was pulling my seating stem and tapercrimping the cases as a complete separate step after I seat bullets. No idea why, I just heard Jeff siewart say to try it and now I do it to everything.

The trigger on it is a little spongy since I adjusted it a little lighter, so it might even be better if I put a level on my scope and had someone do the trigger. But I wanted to do it naked.

I like talking about this rifle so I liked this question. I'm really proud of what I've done with it. It was my first trip to a thousand with this rifle and it now feels like a routine outing to dink it and I only make minor adjustments to my original dope based on changing conditions.

I will probably always run 190 matchkings through it just so I can have one ammo, one dope, one zero one everything.

The basis of this question really stems from "how much ammo can I load for the damn thing without being concerned that throat erosion will outrun my loads before I get them shot up.

Thank you!

-Big Phil

 

[cosmic creepers]

This "let the groups tell you" only works if you shoot often.
I try and get one or two practice sessions in a month, then a monthly match.
If I find the groups have opened up due to erosion, and compensate, it means another practice session before a match. That or load long and bring a press/seating die with me. I don't want the throat to "let the groups tell me" one relay into a 60 round match.

I wouldn't let that be a concern. I train with this rifle often. Maybe not as much as a competition shooter, but enough that my 10 inch plate will ring first shot from a thousand in. I have my occasional errors, (usually when I make an environmental adjustment twice by accident. I'm still learning procedure and muscle memory)

But any advice helps even if it requires me to shoot every week. I've been dedicating a little more energy to offhand .223 AR shooting recently because I think it might be important soon, but when I pick up that .308, I think that rifle damn near shoots itself.

When my wife climbs behind it, she can do exactly what I do at a thousand (minus the dope evaluations) but as far as driving the gun, it drives itself I think.

 

[gambleone]

I'd say that's $ well spent for 400.00. Like the others above said, I wouldn't
worry about the lands until the groups start changing. Sounds like it's tuned
pretty good to do that at 1000 yds with a 24" barrel. What scope are you
using?

 

[cosmic creepers]

I'd say that's $ well spent for 400.00. Like the others above said, I wouldn't
worry about the lands until the groups start changing. Sounds like it's tuned
pretty good to do that at 1000 yds with a 24" barrel. What scope are you
using?

I got a vortex viper pst 3-15 [I think] dont have it right in front of me right now. Might be a 3-12.

It was just a sale deal from midway when I bought it and couldn't pass it up. Wish I'd have bought five of them.
I have it in a set of nightforce rings on a solid piece of picatinny rail that goes all the way across the top of the receiver.

The bolt is a little bit pockmarked from some primers blowing in the past, but I've thought about buying another long action model 70 just to steal the bolt from it.

It was a very good investment. Thanks for the advice from everyone about chasing the throat erosion. Much appreciated. I feel much better to load up 250 to 500 rounds of that exact load.

Thanks again, God bless.

-The Bill of Rights is my Bible