If your accurate load in your rifle isn't anymore, you better check throat erosion.


I've got about 1000 rounds through this rifle; about 300 since I settled on a load and depth. Since then accuracy has gone all to hell. Checked the MOAL and it had increased by .075"!

Wow.

Ran a depth test this morning from the lands then off by .030" for each 5 shot group. Shot the groups in round robin fashion.







Top left is the original depth. It used to be .015" off of the lands and now with the erosion it is .090" off. The next group to the right is .030" longer.







The center group is my buddies ammo loaded with a different powder, but the depth is comparable to my loads "good" depth. Strange that his ammo groups great in my rifle even though it is about 200 fps slower and loaded with a different powder. The OAL's between our ammo (same bullet) only differs by .007".......

Could be barrel vibration. He hit the sweat spot and your loads miss by a touch.

It's definitely harmonics and I'm sure that making variations in the seating depth changes the pressure curve.

The size of the two groups is virtually identical.

The major factor differing between the two loads is the propellent and the velocity it gives. POI is about a minute and a half lower for the lower velocity, but still accurate load.

Same bullet, same primer, same case, similar depth.

I'd think about switching powder?????

Hey R, That should be covered in Seating Bullets: Converting OCL to ODL.

I agree the Group will change as the Throat moves forward. When people shoot enough and keep good Records, they can see it for themselves.

Just as you saw, it is Reality.

I may switch powder. I'm getting better velocity with the RL-17 though so I'm gonna stick with it if I can tune some accuracy into it.

Great link HC; I've read it before

I'll be checking MOAL every 100 rounds or when accuracy sucks from now on!

Have you looked inside with your borescope? That's the only way to really tell what's going on. They're not as expensive as they used to be, so anyone who is really serious about accuracy should have one now.

Yes, I've used a borescope

If you do the cleaning rod method with the same bullet like HC says, it's easy to tell how much erosion has occured

I've never owned a bore scope but I do own a Chrony. With my main Pdog rifle, a 700VS in 22-250, I would check the throat each spring and adjust my COL AND THEN I'd add powder until I had the same velocity as the original load.

quote:

Originally posted by amamnn:
Have you looked inside with your borescope? That's the only way to really tell what's going on. They're not as expensive as they used to be, so anyone who is really serious about accuracy should have one now.

How do you know how much the "change in measurement" is for the Seating Depth, as the Lead moves forward, by using a Bore Scope - since "That's the only way to really tell what's going on."???

Perhaps amamnn is still trying to figure it out.

OK, I thought it would turn out this way

quote:

Originally posted by amamnn:
...borescope? That's the only way to really tell what's going on. ...

I'm using RL-17. My gunsmith scoped the bore recently and was shocked to see that with only 1000 rounds down the bore how rounded off the lands in front of the throat were, some firecracking, and my findings of erosion.

I've heard this may be a problem with high energy powers like the RL line and the Vhitavouri.

Anybody else experience this?

quote:

I've heard this may be a problem with high energy powers like the RL line and the Vhitavouri.

Anybody else experience this?

Heard or read about it. Looks like you are useing 4350 though,,,? What cartridge?



H.C., maybe try some platform shoes

.

quote:

Originally posted by rcamuglia:
I'm using RL-17.

6.5 Creedmoor

quote:

I'm using RL-17

OK,

I was shooting R22 and R19 in a 6.5x55 barrel several years ago, and had noticed my throat had worn also. Started useing H 4350/4831 after I heard rumors about "high energy powder" and throat erosion...
Might have been 6mmbr.com forum where I read about it

quote:

Originally posted by Hot Core:
OK, I thought it would turn out this way

quote:

Originally posted by amamnn:
...borescope? That's the only way to really tell what's going on. ...

Hotsh#t raises his family flag again.


BS= Buttshooter

Yep.

Do you think it's worth changing at this point?

I wonder what the difference in barrel life would be. I like the 200 fps gain with the RL-17.

RCAMUGLIA, everything has a price. The question is, is it worth it to you? And the question that can't be answered is how much will it shorten your barrel life? If any.
I read an article once about looking thru barrels with a bore scope. According to the article (I don't know who wrote it), in very short order, you will see heat checking in the barrel and throat erosion. Enough so that with the proper amount of snake oil, you could be sent running to the new barrel store. But, after a certain amount of barrel degradation, the author learned, the problems stop or slow down to a small amount.
I took this article to heart and I don't look down my barrels with a bore scope. And I let the rifle's performance determine when I am going to re-barrel. Like you, I will adjust my col and juggle my powder around in my rifles that see heavy use. I don't motor my rifle at the top end but I certainly don't reduce the amount I use them nor would I change a load based on the amount of barrel erosion it was causing.
I guess, beyond that, I truly believe ignorance is bliss.

Thanks wasbeeman!

Great analysis.

Before your reply I talked to my gunsmith about it. He said either way. I've got 5 more #s of the RL stuff and I like the velocity so I had already decided to stay with it, keep an eye on accuracy and adjust accordingly.

quote:

Originally posted by amamnn:
Have you looked inside with your borescope? That's the only way to really tell what's going on. They're not as expensive as they used to be, so anyone who is really serious about accuracy should have one now.

I might buy one one day.I can go longer without one but I am sure you can learn alot with one.

Perhaps JD and his buddy teenScum could help amamnn and describe to all of us (especially me) how using a Bore Scope will tell us how much, in 0.xxx", the Throat has moved. My bet is it is time for a second Flag, or two - one for each of them.

But you're slipping...you forgot your usual comment about it being a total waste of $$$. That's what it's really all about, isn't it?

Dang ankle biter H.C.

You might be able to observe some erosion with the scope and other wear, but the only way to measure how much it has actually eroded is to use some kind of "thingy".

You don't have to spend a lot for this "thingy" if you don't want to. You can buy the Stoney Point OAL gauge or you can do what I have learned from HC and Woods.

I use the cleaning rod method with some Sinclair cleaning rod stops (3.00$ each, you need 2)

1. Put a plastic jag on the end of your cleaning rod and snip off the pointed tip
2. With the bolt in the gun, put both rod stops loosely on the rod and run it down the bore till it touches the bolt face.
3. Tighten the rod stop on the outside after snugging both against the muzzle.
4. Remove the bolt and drop the bullet you have used for this initially down the chamber till it stops against the lands. You have used this bullet before, saved it in your die box, and will always use it to check for erosion. It's important that you use the same bullet as ogives between bullets vary slightly.
5. Use a pencil or pen to gently hold the bullet against the lands then run the rod back down the bore to touch the bullet tip.
6. Make sure the second rod stop is against the muzzle and tighten it to the rod.
7. With your calipers, measure the distance between the rod stops.

This is your MOAL for this bullet.

Do the measurement a couple of more times to double check.

I have compared this method to the Stoney point tool and the outcome is identical.

quote:

Originally posted by onefunzr2:


But you're slipping...you forgot your usual comment about it being a total waste of $$$. That's what it's really all about, isn't it?

Actually, a Bore Scope is an EXCELLENT (non-Thingy) Tool and well worth the cost " if " you have a need for one. However, it hasn't got spit to do with seeing how far the beginning of the Lead has moved, nor how much to change the Seating Depth.

Since JD responded, he missed out on a Flag.

However, it gives me the chance to give two to teenScum -

You guys are doing it all wrong!
I NEVER chase the throat!

In my Open F-Class rifle, as soon as I see a change in POI I chrony the load, normally it will have lowered velocity, which tells me that the throat has eroded further.
I then load back up to the same velocity I was getting before, which doesn't alter barrel harmonics, and surprisingly the accuracy to date has stayed the same!
I do remeasure the distance to the lands from time to time, and have set my limit of erosion to 2", once that is reached I replace the barrel with a new one. I used to dock and rechamber, but found it never really shot the same after doing this.

What "rcamuglia" said is 100% correct, I too have used both methods of determining the origin of the lands and it works within a hair of the gauge. I also use the ogive to base method, which is a little more precise than working off the tip as a MOAL.

416 Rigbyhunter...."load back up to orginal velocity..."
Bingo!!
This isn't something you would recommend to a beginner but a competent reloader with a Chrony can do this and get quite a lot of additional service from a barrel. You can/will be venturing out of the book but the circumstances of the elongated throat keep you safe.
Whatever you do, when the first accuracy starts to loosen up, DON'T look down the barrel with a bore scope.

Great info guys.

Hopefully I can get a couple more thousand out of the barrel.

quote:

Originally posted by Hot Core:
Perhaps JD and his buddy teenScum could help amamnn and describe to all of us (especially me) how using a Bore Scope will tell us how much, in 0.xxx", the Throat has moved. My bet is it is time for a second Flag, or two - one for each of them.

Amazing that a man who is out killing 'thousands of deer', still has the time to come onto AR and piss on everyone who doesn't agree with him...

Evidently he must be using an Automatic Weapon illegally, to be able to kill so many deer and still have all of this time to come on to AR and piss on his fellow forum members.. who don't have the 'advantage' of his vast experience and 'knowledge'....

Don't you guys wish you could learn more in 5 minutes, than the average person learns in a life time? and always be right... when everyone else is wrong.. of course unless they agree with every word you say, and think you are as big of a hero as your ego thinks you are?

So its noon HotBore.. how many Bambis have you machine gunned today?

Did Hot Bore tell ya about his 1200 lb 'doe' yet? ......

quote:

Originally posted by seafire/B17G:
HotBore.. how many Bambis have you machine gunned today? ...

How many "other" people have you allegedly SCAMMED today? I really thought EVERYONE could see through you by now.