6mm Creedmoor (Possible) Troat Erosion or Freebore Issue

[riverrat13]

I recently picked a 6mm Creedmoor on a trade, and measured the COAL OGIVE today. I am using 105 Berger Hybrids, and if I seat to the lands then my COAL measures 2.900. I would of expected that number to be closer to 2.800. Sammi Spec is a max of 2.800.

I was told the rifle was only fired 350 rounds, and I believe the guy I traded with. That is way to much throat erosion for 350 rounds right?

PVA Rock Hill Barrel on a Curtis Curtis Custom Action. I don't know the reamer, but I was told it was chambered for SMK 110. I used a Hornady OAL Gauge with Modified Case and Berger 105 Hydrids.

I just seated some at 2.880 OAL and I could pull the bullet loose with my hand. Peterson Brass that is unfired, but I ran it through a Redding Full Length Bushing Die with .270 bushing sizing for .002 - .003 shoulder bump.

I’m considering getting it set back and rechambered (26” barrel now), or just rebarreling it.

Thoughts or guidance??

 

[rhovee]

Have you shot it yet?

 

[riverrat13]

Have you shot it yet?

I have not shot it yet.

 

[Thud]

Get a bore scope

 

[beemanjohn]

The 110 SMK is a very looooooong bullet. If it was chambered for that bullet, it will have a lot of freebore.

 

[lawrence97]

First off, who chambered the barrel and what are the specs of the reamer used?

You are measuring with a 105 hybrid and the chamber was setup for a totally different bullet which is the Sierra 110 which is heavier, longer and most likely has more bearing surface than a hybrid which is why the chamber/throat may seem long when measuring with a 105.

Use your tool and measure where the 105 touches and then back the bullet off -.015 (15 thousandths of jump) and go shoot some groups testing powder charges. If -.015 isn’t enough then seat to the point were the bullet pressure ring (point where boat tail meets major diameter of bullet)is at least half way down the case neck for starters.

Don’t pay attention to saami oal!

 

[riverrat13]

First off, who chambered the barrel and what are the specs of the reamer used?

You are measuring with a 105 hybrid and the chamber was setup for a totally different bullet which is the Sierra 110 which is heavier, longer and most likely has more bearing surface than a hybrid which is why the chamber/throat may seem long when measuring with a 105.

Use your tool and measure where the 105 touches and then back the bullet off -.015 (15 thousandths of jump) and go shoot some groups testing powder charges. If -.015 isn’t enough then seat to the point were the bullet pressure ring (point where boat tail meets major diameter of bullet)is at least half way down the case neck for starters.

Don’t pay attention to saami oal!

PVA. And I do not know the actual dimensions of the reamer.

I measured to the OGIVE with the Hybrids. To keep everything relative, a -.015 thousandths of jump would put my OAL at 2.885. I tried seating some at 2.880 and I could pull the bullet out of the case with my hand. It wasn't close to half way down the neck. I am thinking I would have to jump the bullet .075 or so to reach half way down the neck. That number will continue to get larger to as the throat keeps eroding.

I guess I should of just bought the SMK 110's but I never thought it would make a .075+ seating difference... However I went with the Bergers so I could use the 105 Hybrid for Target and the 105 VLD Hunter for yotes with a minimal POI change. I don't believe Sierra makes a hunting equivalent of the SMK 110.

The conclusion I am figuring out is that I am going to have to switch to the SMK 110 's or get the rifle re-chambered or re-barreled.

 

[Zero333]

Make sure the hornady modified case is going in all the way. You never know.

Try using the Wheeler method of finding the lands.

 

[lawrence97]

PVA. And I do not know the actual dimensions of the reamer.

I measured to the OGIVE with the Hybrids. To keep everything relative, a -.015 thousandths of jump would put my OAL at 2.885. I tried seating some at 2.880 and I could pull the bullet out of the case with my hand. It wasn't close to half way down the neck. I am thinking I would have to jump the bullet .075 or so to reach half way down the neck. That number will continue to get larger to as the throat keeps eroding.

I guess I should of just bought the SMK 110's but I never thought it would make a .075+ seating difference... However I went with the Bergers so I could use the 105 Hybrid for Target and the 105 VLD Hunter for yotes with a minimal POI change. I don't believe Sierra makes a hunting equivalent of the SMK 110.

The conclusion I am figuring out is that I am going to have to switch to the SMK 110 's or get the rifle re-chambered or re-barreled.

There isn’t anything wrong with jumping those 105’s! You might be surprised with how they shoot. Ultimately these measurements don’t matter if the rifle will shoot accurately and you won’t know that until you put some rounds down range.

 

[Don_Parsons]

I agree, there are mult millions of bullets to Chambers that don't meet the specs,,, don't let this prevent you from loading up some bullets and go shooting.

You might be suprized how accurate it is.

Seat you bullets 15 or 20 thou off the lands and lunch some down range,,, start with a tested accurate powder change,,, then try a few different charges when you do your ladder test.

One thing about those 6 Mills, the majority of them are very forgiving ,,, of course this is also true for most cartrages.

Don't over think it till you see what it does on paper.

 

[riverrat13]

I agree, there are mult millions of bullets to Chambers that don't meet the specs,,, don't let this prevent you from loading up some bullets and go shooting.

You might be suprized how accurate it is.

Seat you bullets 15 or 20 thou off the lands and lunch some down range,,, start with a tested accurate powder change,,, then try a few different charges when you do your ladder test.

One thing about those 6 Mills, the majority of them are very forgiving ,,, of course this is also true for most cartrages.

Don't over think it till you see what it does on paper.

If I seat at .015 or .020 off the lands then I would have a COAL of 2.880. I have already seated bullets at that length, and I can pull the bullet out of the case with my hands. I would have to seat a couple hundredths deeper at a minimum.

 

[JBT47]

If I were in your shoes I would shoot the rifle to determine accuracy. After putting a little effort into load development those results would determine what to do next. If it doesn’t shoot accurately, I would rebarrel.

 

[Dusty Stevens]

Ive seen them shoot at .125 jump before as well. Another solution is get a different bullet more suited to your chamber or get a chamber suited to your bullet. Dont waste your life trying to make something work that doesnt. I wouldnt do anything until i seated them where i like em then go try it. Ive shot a ton of 68gr bullets in a .125fb which is about a .125 jump and they shot fine

 

[riverrat13]

Ive seen them shoot at .125 jump before as well. Another solution is get a different bullet more suited to your chamber or get a chamber suited to your bullet. Dont waste your life trying to make something work that doesnt. I wouldnt do anything until i seated them where i like em then go try it. Ive shot a ton of 68gr bullets in a .125fb which is about a .125 jump and they shot fine

Not sure I know a bullet more suited for my chamber, I think my chamber has been cut to large. If i went with the 110 SMK that is was "chambered" for and seated them .02 off the lands then I would have to single load as they would be longer than my mag length.

Just a frustrating circumstance. I am very OCD when it comes to reloading, and I hate "settling" in anything that I do. I think I am just going to re-barrel so I don't have to deal with this...

 

[AKShooter]

I don’t know if you can make the claim your chamber was “cut to large” that suggests a deficiency. You simply bought a barrel with too much freebore....Or too much freebore for the bullet you wanted to shoot


Plenty of other bullets out there with long bearing surfaces, do some searching, or shoot a 105 out of it like many folks have posted

Not a creed, but my 6mm was cut for 105’s. I’d love to try the 95 game changer. But it same boat. I’d really have to jump it to get proper seating. Just the way it goes. Still will shoot some. See how it goes.

 

[PatMiles]

[QUOTE="riverrat13, post: 37375879, member: 1307671
I think I am just going to re-barrel so I don't have to deal with this...[/QUOTE]

That's an expensive alternative to trying different bullets in your gun, but it is your $$$$.

 

[riverrat13]

I don’t know if you can make the claim your chamber was “cut to large” that suggests a deficiency. You simply bought a barrel with too much freebore....Or too much freebore for the bullet you wanted to shoot


Plenty of other bullets out there with long bearing surfaces, do some searching, or shoot a 105 out of it like many folks have posted

Not a creed, but my 6mm was cut for 105’s. I’d love to try the 95 game changer. But it same boat. I’d really have to jump it to get proper seating. Just the way it goes. Still will shoot some. See how it goes.

I agree with you first statement.

 

[M-61]

Shoot it. See what it does.
e.g. I have a 222 Remington that I had made in the early 70's for benchrest 100 yard shooting. Shoots extremely well. There isn't a 224 bullet long enough to come close to the lands. Does this concern me? Not one bit...I look at the targets and smile. Almost 50 years ago....that's upsetting!

 

[riverrat13]

[QUOTE="riverrat13, post: 37375879, member: 1307671
I think I am just going to re-barrel so I don't have to deal with this...

That's an expensive alternative to trying different bullets in your gun, but it is your $$$$.[/QUOTE]
Yep it is... It is an 8 twist and I am shooting at sea level so I cannot shoot the bullets it was chambered for (110 SMK). Also, I if was to shoot that bullet then I would be maxing out my magazine as it is. With more throat erosion 250 or so rounds later, I now have a single shot.

But if I re-barrel, it will be the barrel I want, with the twist I want, and chambered for the bullet I want.

I shouldn't of made the trade, but hindsight is 20/20. I will learn from it and move on.

 

[riverrat13]

Talked to PVA today, and they were extremely helpful.

Apparently the rifle was chambered for Factory Hornady ELD ammo. The 108 grain hornady bullets nose is much shorter and it has larger bearing surface than the 105 Berger Hybrids. That is the reason I am having to seat the Bergers so long. Another interesting note, the difference between the two bullets is so large that if I had the rifle chambered for the Bergers, I wouldn't be able to shoot the factory ammo as it would be shoved into my lands.

Just wanted to post that in case someone else encounters a similar issue.