Possible chamber issue - short throat maybe?

[rookie7]

Good afternoon,

I have a Ruger American Predator Gen 2 in 6 arc.
About three weeks ago after hunting I removed the chambered round - bullet stuck and powder everywhere.

Once fired Starline brass, full length sized, neck turn mandrel to expand and brass was annealed. The COAL for that hunting round using Sierra 85 gr bthp GameKing was under recommended coal.

I cleaned it well after. However, every round I chamber in the rifle comes out with marks on the bullets. My hand loads and factory Hornady 108 eld and factory Hornady 105 black.

My guess short throat. The 108s come out with rifling marks on the bullet- or did.

Attached is a pic. Now, marks only on one side of the bullet. I don’t have a bore scope nor do I know how to measure if the chamber is cut correctly.

Just trying to determine do I remedy or send back to Ruger. Thanks in advance.

 

[rookie7]

Trying to upload the pictures but having issues.

Ah, ha! Worked!

 

[rookie7]

The blurry photo is the clean side of the bullet with no marks.

 

[243winxb]

recommended coal.

2.260" ?

Load to a shorter COL & increase neck tension/bullet hold on reloads. .002" minimum, NT.

Google - "hornady 6 arc. load data bolt gun" Note the short COL.

I have seen Hornady 6.5 CM factory ammo to long col to chamber in a Savage.

 

[243winxb]

sierra 0.243

85.0

HPBT (GameKing)

0.930"

Sierra bullet is shorter.

Horhady 0.243

87.0

Boat Tail Hollow Point

1.053"

https://jbmballistics.com/ballistics/lengths/lengths.shtml

 

[Ackman]

Good afternoon,

I have a Ruger American Predator Gen 2 in 6 arc.
About three weeks ago after hunting I removed the chambered round - bullet stuck and powder everywhere.

Once fired Starline brass, full length sized, neck turn mandrel to expand and brass was annealed. The COAL for that hunting round using Sierra 85 gr bthp GameKing was under recommended coal.

I cleaned it well after. However, every round I chamber in the rifle comes out with marks on the bullets. My hand loads and factory Hornady 108 eld and factory Hornady 105 black.

My guess short throat. The 108s come out with rifling marks on the bullet- or did.

Attached is a pic. Now, marks only on one side of the bullet. I don’t have a bore scope nor do I know how to measure if the chamber is cut correctly.

Just trying to determine do I remedy or send back to Ruger. Thanks in advance.

Make yourself a split neck case using a Dremel cutoff wheel. Cut it lengthwise and down into the shoulder. Put a bullet in and chamber it. Unchamber then measure using an ogive gauge from Sinclair. That's your seating depth to the bullet touch point. Very simple.

 

[rookie7]

I appreciate the tips so far, but my COAL with the 85 gr Sierra is 2.104 and my BTO is 1.739

Way under spec and I’m seeing marks on the bullet which is why I think it has a very short throat.

 

[DaveTooley]

I don't see square/rectangle land marks. Am I missing something?

 

[Rocketvapor]

and marks on the smaller diameter ogive.
touch marks:

 

[DShortt]

Have you fired the rifle much at all or is this a relatively new purchase?

The reason I'm asking is I have encountered rapid carbon build up/carbon ring with some powders. Varget in particular tends to do this in my personal experience. Also, based on your first post, it seems the problem improved at least some when you cleaned it.

 

[FeMan]

I also suspect you might have a carbon ring in the freebore area or lead. If so, you will need to clean the lead aggressively with solvent/brush and/or JB/Isso. Carbon rings in the lead aren't likely to respond to normal cleaning regiments.

 

[243winxb]

BTO is 1.739

Free bore. 1.6057" The bullet, when chambered has .0005" diameter clearance. Looks like your Case  Base  To Ogive* is to long for the free bore.? 1.605"

 

[243winxb]

This 6ARC Hornady cartridge was made for the M16 or AR 15 rifles. COL needs ro be short to fit the M16/AR15 magazine.

From what i read online?

 

[FeMan]

If the above is accurate for your chamber, you would definitely be jamming the bullet at a CBTO of 1.739 in a fresh chamber. My guess is touch would be around 1.670 in a new chamber. Unless you have around 70 thousandths of throat erosion, you are jamming the bullet based on the above.

 

[Bill Norris]

If the above is accurate for your chamber, you would definitely be jamming the bullet at a CBTO of 1.739 in a fresh chamber. My guess is touch in a fresh chamber would be around 1.670 in a new chamber. Unless you have around 70 thousandths of throat erosion, you are jamming the bullet based on the above.

With this much jam on a new chamber especially, it would be enough to pull a bullet from an unfired load.

 

[rookie7]

I appreciate all the help and input. It’s been a busy week from the word go, so I haven’t thought of checking forums at all until today.

I’ll check my CBTO length with a cut piece of brass as recommended.

This is a new rifle with now only 102 rounds down the barrel. I’m using Leverevolution powder, and I have heard it is a dirty powder.

I don’t have any JB bore paste, but will order some.

The rifle shoots well, but a few times I’ve had a moment of what the heck. I changed scopes Sunday because of it. I had a Zeiss conquest 3-9x40 on it and switched it out for a Sightron S2 Big Sky in 3.5-10x42. It sits in Vortex rings and shot well after the change. I think something may be wrong with my Zeiss windage turret b/c 4 clicks gave me 2.5 inches at 100 instead of 1”.

 

[Bill Norris]

I appreciate all the help and input. It’s been a busy week from the word go, so I haven’t thought of checking forums at all until today.

I’ll check my CBTO length with a cut piece of brass as recommended.

This is a new rifle with now only 102 rounds down the barrel. I’m using Leverevolution powder, and I have heard it is a dirty powder.

I don’t have any JB bore paste, but will order some.

The rifle shoots well, but a few times I’ve had a moment of what the heck. I changed scopes Sunday because of it. I had a Zeiss conquest 3-9x40 on it and switched it out for a Sightron S2 Big Sky in 3.5-10x42. It sits in Vortex rings and shot well after the change. I think something may be wrong with my Zeiss windage turret b/c 4 clicks gave me 2.5 inches at 100 instead of 1”.

WOW Yea sounds like the scope may need some attention.