Puzzled (rounds not chambering)

[SGK]

I don't believe this is a sizing issue based on what has been posted thus far.

I believe this is bullet seating issue. Measure about 5 bullets to determine the range of max COL. Selected the lowest measurement and back off .020 which should place you well off the lands even with variations in the bullet ogives.

The measurement method must be based on the bullet ogives not the overall length of the cartridge from the base of the case to the point of the bullet. I use a version of the Frankford Arsenal tool but any tool that measures off the bullet ogive will suffice.

The other issue is severe out of round bullet judging from the marks on the bullet, but I don't think that would cause excessive chambering issues.

I sorted all the bullets from a 500 box by BBTO. (All these rounds were loaded from the same BBTO lot.) I seat by measuring CBTO. I measured touch using the Wheeler method as 2.200". All using the same comparator. I've shot a lot of the 300 rounds so far (excl today) at or very near touch. With these rounds even 30 thou deeper doesn't resolve the issue.

 

[Mulligan]

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=12950

CW

 

[Mulligan]

Have you measured the diameter of a loaded round at the neck that will not chamber and compared it one that will chamber?

CW

 

[Willie]

The OP stated the fifty rounds were new. I would suggest the brass necks are not straight like you get on fired brass. The noticable scrapes on the bullets could be rubbing a carbon ring, but are more likely that the necks are off center, as new or possibly had a button pulled through them.

A really good cleaning to remove all the carbon and using fired brass should fix the problem. Of course, I could be wrong.

 

[SGK]

Have you measured the diameter of a loaded round at the neck that will not chamber and compared it one that will chamber?

CW

All the ones that chambered have been shot. But loaded rounds have a neck of 0.269" as noted above. Fired brass has a neck diameter of 0.2715" (versus chamber reamer dimension of 0.272").

 

[SGK]

The OP stated the fifty rounds were new. I would suggest the brass necks are not straight like you get on fired brass. The noticable scrapes on the bullets could be rubbing a carbon ring, but are more likely that the necks are off center, as new or possibly had a button pulled through them.

Once again. All brass is 3x Fired. 50 rounds were loaded from this 3x fired and prep'd brass. I have 48 cases of 3x Fired and prep'd brass I did not load. Run out on the loaded rounds is low (see above).

I will scrub some more but I have JB Bore Bright and not JB Bore Compound and certainly not JB Bore Paste

PS: loaded round case neck run out is less than 2 thou (and most often closer to 1)

 

[JLT]

Once again. All brass is 3x Fired. 50 rounds were loaded from this 3x fired and prep'd brass. I have 48 cases of 3x Fired and prep'd brass I did not load. Run out on the loaded rounds is low (see above).

I will scrub some more but I have JB Bore Bright and not JB Bore Compound and certainly not JB Bore Paste

JB Bore Brite is a polish. It will remove metal. JB Bore Compound is not a polish - the cleaning agent (diatomaceous earth) is softer than barrel steel and will not remove barrel steel if used as directed and with a bit of common sense. Aggressive scrubbing with Bore Brite may have unintended consequences. While it is possible to damage a barrel with JB Bore Compound, it's a LOT more work than with Bore Brite, all other things being equal.

 

[Willie]

I bump the shoulders 1-2 thou every time. Fired brass chambers easily. Unfired brass from which I loaded these rounds (FL resized, trimmed, chamfered/de-burred, annealed) chambers easily.

This is what I was going by.

 

[SGK]

Yeah you have to read the first post Later I was comparing the brass I had fired this outing (now 4x fired) with that which I had not (3x fired). But no worries.

Sounds like I need to buy some JB Bore Compound.

 

[Coyotefurharvester]

Sgk pulled the bullet from a cartridge that won't chamber, the brass DID chamber without the bullet. So the interference is with the bullet not the brass. So bullet/throat issue: seating depth, fouling, incorrect diameter bullet.

 

[SGK]

First thing I checked was bullet diameter and they read true. I find it odd that a carbon ring would affect some not all rounds. Some rounds chambered normally, some did with a push while at least one still doesn't chamber easily even after seating it 30 thou deeper. So perhaps it's a combination of carbon ring and the slope between the bearing surface of the bullet (.243 true) and the point where the bullets contact my comparator and/or bullet seater. Points in between those are very hard to measure. But all very odd. I will try to get rid of this carbon ring first.

 

[SGK]

I'm going to leave a couple of patches soaked in Bore Tech C4 on a jag pushed up snug overnight and see how it looks in the morning.

 

[bozo699]

This is what I have (The material is crimson in color)

J-B® BORE BRIGHT | Brownells

A micro-fine bore cleaning and finishing compound that works as both a cleaner and a final polish to help keep barrels free of fouling and shooting their absolute best. Regular use gives your barrel a mirror-like finish that helps prevent the buil...

www.brownells.com

There's JB Bore Compound

J-B® NON-EMBEDDING BORE CLEANING COMPOUND | Brownells

The original, time-proven formula developed by Jim Brobst and produced under exclusive license. J-B has been getting burned-on, caked-in powder residue and copper jacket fouling out of gun barrels since the 1960’s, and hasn’t damaged an inch of ri...

www.brownells.com

There is no product that I can find that is labelled JB Bore Paste.

I will scrub away some more tomorrow.

The second one you posted is the original bore paste or whatever they call it now. Idk but I’m pretty sure what you have is the same stuff only finer I’m sure it will work will just take longer. It’s obvious the barrel needs cleaned anyway so it’s a good time to attack the carbon. The method Lone Hunter mentioned should work very well. If you have a good bore guide I would for sure use it.
Wayne

 

[bozo699]

I'm going to leave a couple of patches soaked in Bore Tech C4 on a jag pushed up snug overnight and see how it looks in the morning.

I haven’t used that but I’ve heard good things about it. I normally use jb but CLR works well too but only on stainless barrels. Good luck my friend
Wayne

 

[Lone Hunter]

SGK, this is what I use. It works pretty good. I ordered from Brownells.

BROWNELLS J-B® BORE COMPOUND & KROIL | Brownells

Save money on the do-it-all combination that's been written up in several of the 'accuracy' publications: J-B and Kroil! Run a couple of patches soaked in Kroil through the bore to get under and loosen barrel fouling, then wipe away most of the cr...

www.brownells.com

I also use the felt patches also and they work great too. VFG Pellets.

 

[bozo699]

SGK, this is what I use. It works pretty good. I ordered from Brownells.

BROWNELLS J-B® BORE COMPOUND & KROIL | Brownells

Save money on the do-it-all combination that's been written up in several of the 'accuracy' publications: J-B and Kroil! Run a couple of patches soaked in Kroil through the bore to get under and loosen barrel fouling, then wipe away most of the cr...

www.brownells.com

I also use the felt patches also and they work great too.

Kroil is amazing stuff I’ve used a lot of it by itself and with jb . It’s a must IMO in every loading room!
Wayne

 

[bks22345]

I hope you can figure it out and let us know the final outcome. I have a similar problem with a 280AI. Difference with mine is the marks you note are full circumference. I’m thinking it’s a taper in the throat/leade area because like you I see “scuff” marks and not notches from the lands. It got worse with some Scenars with their long bearing surface. I may have missed it, what barrel do you have?

 

[JMayo]

I had some 30br giving me trouble. Turns out the cases were too long.
I shaved off another couple of thou and all is well.

 

[Stumpy1]

All the ones that chambered have been shot. But loaded rounds have a neck of 0.269" as noted above. Fired brass has a neck diameter of 0.2715" (versus chamber reamer dimension of 0.272").

SGK, If your measurements are correct, that only leaves 0.0025-0.003 of clearance. When I look at the photo on the bottom of page 1 here of the single round, I see a pretty good burr at the case neck mouth. If you can see the burr, it is more than a couple of thousandths, and could interfere greatly with chambering a round.

I would chamfer, inside and outside one of the cases, re-seat a bullet and try again.
Also, you could take a small file and just lightly remove the burr on the outside of the case mouth of a loaded round and see if it makes a difference.

Hope this helps,

Frank

 

[SGK]

Once again, cases (without a bullet) chamber easily as they are (I will de-burr more aggressively next time)


Barrel is a Bartlein .237 x .243 4 groove T syle 1-7.5 to 1-7.25 twist stainless steel #12 Heavy Palma