loaded round chambering issue

[thexman]

I got a batch of loaded 6 dasher using 3 times fired(from my rifle) alpha 6 dasher brass. About half of the batch started having chambering issue today.

The problem is the bolt cannot be closed.

70% of the unchambered rounds can be extracted using the bolt's extractor, the rest 30% need to use cleaning rod or some kind of tool to pull from the back.

I compared FL resized brass with fired brass, 0.002inch difference, so I reckon resize part should be good.
Then I measured neck diamater(outside the neck), it is almost identical between unchambered round and round can be chambered.
I also checked the ogive between rounds can be chambered and cannot be chambered, it is.the same.
Lastly, I checked the outer diameter close to the extractor grove between fired and unchambered, it's almost identical.

Same load has been fired in the same rifle few months ago.

And same thing happened on a 308win rifle too, only differenc is on the 195gr ELD bullet of the 308 unchambered rounds, there is some scratches, which I thought could be seating depth issue, but will need to verify this shortly. No marks on the 6 dasher ELD 108gr bullet.

But for the 6 dasher's chambering issue, any suggestion or direction would be really appreciated.

UPDATE:
I also pull the bullet out of a loaded round but could not chamber, compared the headapace it is same as FL resized brass, but even the unloaded brass with only primer can not be chambered, so it was able to fire last time, but after resize 0.002inch, it.can not be chambered, how does this make sense?

UPDATE 2:
So I pulled all of the unchambered rounds, FL resized, check chambering, no problem, expand using .242 mandral, chamber no problem, charge then seat the ELD 108gr bullet about 0.025inch from lands, check chambering, some still could not chamber.
I don't get it, how could seating bullet causing loaded rounds not chambering? And it seems this only happened randomly within the same batch.

 

[mheimer_45]

I’ve had this happen and it because I hadn’t pushed the shoulder back enough in a new barrel.

Try coloring the brass with a sharpie or candle flame and try to chamber and eject. It’ll show you where it’s touching.

 

[thexman]

I’ve had this happen and it because I hadn’t pushed the shoulder back enough in a new barrel.

Try coloring the brass with a sharpie or candle flame and try to chamber and eject. It’ll show you where it’s touching.

I have not made any change to the rifle, so same barrel under 600 rounds, I even tried resizing additional 0.001inch, so 0.003inch in total, the brass from unchambered round still cannot be chambered without bullet. But I will give it a try using marker.

The only difference is I used a 267 bushing instead of 268 bushing, but still the same 242 mandral.

 

[JS/]

Check length of resized brass. I had this issue with some rounds of .30-06 for a hunting rifle and found the brass needed to be shortened to minimum trim specifications.

 

[thexman]

Check length of resized brass. I had this issue with some rounds of .30-06 for a hunting rifle and found the brass needed to be shortened to minimum trim specifications.

All the brass are under the max length 1.560onch, within +/-0.001 of 1.5365inch

 

[B y r o n]

Measure the diameter of the case just above the extractor groove. My guess is the rounds that will chamber are smaller than the rounds that will not chamber.

Brass stretch in this area and unless you have a small base die, regular dies will not size the case enough to chamber.

 

[GreenGO Juan]

Are the necks aligned with the body, concentric

Roll them on a flat surface is a quick way to see.

 

[J McGriddle]

I have seen this before. The culprit in my case was at the body/shoulder junction. I gave the shoulder an extra .002 (.004 total) bump and problems went away. I chalked it up to a slight variation between my chamber and die for the body taper angle.

 

[thexman]

Measure the diameter of the case just above the extractor groove. My guess is the rounds that will chamber are smaller than the rounds that will not chamber.

Brass stretch in this area and unless you have a small base die, regular dies will not size the case enough to chamber.

Both are almost identical, 0.469inch +/-0.0005, I think that is within the spec.

 

[thexman]

I have seen this before. The culprit in my case was at the body/shoulder junction. I gave the shoulder an extra .002 (.004 total) bump and problems went away. I chalked it up to a slight variation between my chamber and die for the body taper angle.

I will give another try. But seems this only happens.after I seat the bullet, FL resizing, expanding would not stop the brass chamber.

 

[J McGriddle]

Your seater die could be in too far and deform the case. I have done that too. The only way i figured this out was by using a body die on a loaded round.

If a sized case will chamber but a loaded round won't, then back the seater die out a revolution and compensate with the stem.

 

[thexman]

Your seater die could be in too far and deform the case. I have done that too. The only way i figured this out was by using a body die on a loaded round.

If a sized case will chamber but a loaded round won't, then back the seater die out a revolution and compensate with the stem.

I am able to fit the loaded round into the FL sizing die with the central rod removed. And I also tried to back the seating die for one revolution and adjust the micrometer down to seat the bullet, still the same. I started thinking it might be the chamber having some kind of issue.

 

[DellaDog]

After only 3 firings it’s unlikely, but I had a similar issue and was completely stumped. Turned out my issue was peened necks from wet tumbling were a few thousandths wider than chamber. You’ll only notice *after* seating the bullet because it pushes the imperfection outside once seated.

A quick turn of the damaged case mouths solved the problem.

Soft, annealed, wet tumbled case mouths will eventually peen to the point of not being able to close the bolt.

 

[thexman]

After only 3 firings it’s unlikely, but I had a similar issue and was completely stumped. Turned out my issue was peened necks from wet tumbling were a few thousandths wider than chamber. You’ll only notice *after* seating the bullet because it pushes the imperfection outside once seated.

A quick turn of the damaged case mouths solved the problem.

Soft, annealed, wet tumbled case mouths will eventually peen to the point of not being able to close the bolt.

Thank you for your advise.
Would bushing and expander mandral helps reduce the chance having the damaged mouth?

My gunsmith told me the reamer is no turn with .272 internal diameter, I measured the neck outside diameter is about .269 and other dimensions are within SAMMI spec. So I thought unless it is really obvious dent around the neck, I don't have to worry too much about the neck?
But I will give it try to turn the neck.

 

[TheOfficeT-Rex]

Have you actually sharpie'd a round like the first post suggested? We'd like to see a picture of it after you've coloured and tried to chamber it.

 

[thexman]

I’ve had this happen and it because I hadn’t pushed the shoulder back enough in a new barrel.

Try coloring the brass with a sharpie or candle flame and try to chamber and eject. It’ll show you where it’s touching.

Have you actually sharpie'd a round like the first post suggested? We'd like to see a picture of it after you've coloured and tried to chamber it.

Yes, I managed to use marker to colour the brass and bullet, then tried to chamber. Not something really obvious, but it might provide some info.

Both rounds cannot be chambered, I cannot tell there is any obvious mark removed or scratch.

But on another unchambered round, I found some light scratches on the bullet, not sure if it happened when I hand feeding the round into the chamber. But bullet seating depth is same as those can chambered.

 

[mheimer_45]

The second pic looks like that is from the ejector scraping it along side the chamber. Now color just above where your hand is and try again. I know you don’t think it’s down there but try it anway.

 

[37L1]

Right in the area where your sizing die stopped above the extractor groove.

 

[4O6shootist]

Likely swollen at the web, not getting sized back. Need get a harrels D3 die, they act like a small base die but with neck bushing. Run dasher at 2950 node and you'll get that after 3-4 firings. Wilson/Harrels dies are tighter at base than redding and other brands. I recently purchased 400pcs lapau 6br 3x fired cases. The web measures 4705, which will not get sized down far enough with standard dies. My alpha 6bra brass run at 2950fps(28" pipe H4350, water safe in my rifle) after going through my Wilson bra die only measures 4685, fired is 4695.

 

[TheOfficeT-Rex]

First picture looks like they're hitting at the case neck.
Sharpie the whole case to see if it is near the web. Does it come out of the die with all that layer cake scuffing on the body?

Also, your seating stem is crushing those bullet tips.

 

[DellaDog]

First picture looks like they're hitting at the case neck.
Sharpie the whole case to see if it is near the web. Does it come out of the die with all that layer cake scuffing on the body?

Also, your seating stem is crushing those bullet tips.

Agree, case mouth. Carefully measure midway down the neck and exactly at the mouth. May be a few thousand more at the mouth. Are you wet tumbling?

 

[thexman]

Likely swollen at the web, not getting sized back. Need get a harrels D3 die, they act like a small base die but with neck bushing. Run dasher at 2950 node and you'll get that after 3-4 firings. Wilson/Harrels dies are tighter at base than redding and other brands. I recently purchased 400pcs lapau 6br 3x fired cases. The web measures 4705, which will not get sized down far enough with standard dies. My alpha 6bra brass run at 2950fps(28" pipe H4350, water safe in my rifle) after going through my Wilson bra die only measures 4685, fired is 4695.

I am guessing this could be my case. Yes, my MV is about 2940 with 31.8gr varget, 28inch barrel. I measured the diameter just above the extractor groove(probably same place for web?) for both chamber and unchambered rounds, both are about 0.469inch, which I believe this is within SAMMI spec's 0.472inch?

So if I am not mistaken, the problem is after few firings the web area of the brass would get thicker/ increase of diameter, and Redding's die does not size where the web is. Then when I tried to chamber, the web of the brass stops the loaded round getting pushed into chamber, correct? If this is the case, would use redding competition shellholder to increase shoulder bump say 0.008inch helps?
And I still don't understand why a resized but not seated brass can still be chambered if the web is not getting sized? Because I would expect it should have chambering issue straight after I FL resize, not after seat the bullet.

But thank you very much for your information.

 

[4O6shootist]

I am guessing this could be my case. Yes, my MV is about 2940 with 31.8gr varget, 28inch barrel. I measured the diameter just above the extractor groove(probably same place for web?) for both chamber and unchambered rounds, both are about 0.469inch, which I believe this is within SAMMI spec's 0.472inch?

So if I am not mistaken, the problem is after few firings the web area of the brass would get thicker/ increase of diameter, and Redding's die does not size where the web is. Then when I tried to chamber, the web of the brass stops the loaded round getting pushed into chamber, correct? If this is the case, would use redding competition shellholder to increase shoulder bump say 0.008inch helps?
And I still don't understand why a resized but not seated brass can still be chambered if the web is not getting sized? Because I would expect it should have chambering issue straight after I FL resize, not after seat the bullet.

But thank you very much for your information.

Can you get a reamer print from your smith? 469 web is okay to a 471 chamber @ 0.200" line. Brass cannot really flow into the web from the case head, usually it flows from from body to shoulder then into neck. The 40° shoulder of the dasher arrests a lot of that. Web ares work harden, and if you don't get a tight spec die, it'll harden in the larger state and resist sizing. Typically a dasher is 272 neck for lapua brass. know my alpha 6bra and 6gt are 269 loaded, with 274 chamber necks. I don't see any chamber wear on your sharpied cases, so likely not the neck.
Take a fired piece of brass, size it 002 bump. Strip the ejector anf firing pin assembly from your bolt. Insert case and see if bolt drops closed freely. If not, bump another 001-002. Once you find proper bump, seat a bullet at least 10k off lands. See if bolt drops shut. It should, if not, its lands or neck is tight. I hope this can help!

 

[mheimer_45]

You don’t understand the web. As you fire more rounds and you don’t resize the web the web stretches and gets thinner. That’s were case head separation comes from. If it’s thin enough and you have resistance seating bullets it is possible to expand this area. (I think). Think of it as the weakest link.

But also I could be way off track. Been known to happen.

 

[cwinner]

Never said if your wet tumbling but case mouth peennng looks like your issue...... I've seen it numerous times.

Give them a generous outside neck chamfer and I bet it solves your problem.

Typically if you had swelled bases you would have a hitch when you open your bolt from a fired round and most typically seen when using fired brass in a new chamber.

The area in red is your issue....

 

[TheOfficeT-Rex]

It's the neck. Best guesses from most to least likely culprits:
1. Neck flared because you bottomed out the expander mandrel - screw the die up/out a full turn
2. Peened the necks wet tumbling - run a debur tool after the tumble
3. necks too long and bottom out on chamber - double check trim length.

I don't think it's the web. 3x fired is pretty low unless its a hot rod, and you hopefully would have noticed a clicker on the last firing.

 

[thexman]

The second pic looks like that is from the ejector scraping it along side the chamber. Now color just above where your hand is and try again. I know you don’t think it’s down there but try it anway.

3/4 of the unchambered rounds can be chambered now, I need to push harder, some would need using both hands. Really strange.

But still have last 5 rounds cannot be chambered no wonder how hard I tried to push.

And here is the fully coloured round from the last 5 left, I couldn't tell any obvious mark except a few tiny scratches which could be from the marker or top edge of the magazine.

 

[thexman]

Can you get a reamer print from your smith? 469 web is okay to a 471 chamber @ 0.200" line. Brass cannot really flow into the web from the case head, usually it flows from from body to shoulder then into neck. The 40° shoulder of the dasher arrests a lot of that. Web ares work harden, and if you don't get a tight spec die, it'll harden in the larger state and resist sizing. Typically a dasher is 272 neck for lapua brass. know my alpha 6bra and 6gt are 269 loaded, with 274 chamber necks. I don't see any chamber wear on your sharpied cases, so likely not the neck.
Take a fired piece of brass, size it 002 bump. Strip the ejector anf firing pin assembly from your bolt. Insert case and see if bolt drops closed freely. If not, bump another 001-002. Once you find proper bump, seat a bullet at least 10k off lands. See if bolt drops shut. It should, if not, its lands or neck is tight. I hope this can help!

I will ask if the gunsmith would share the blueprint, but this is some basic info"
The chamber is a .272 neck no turn neck with .104 freebore", sounds pretty standard to me.

My standard reloading process is bump 0.002 and find seating depth from 0.015, for ELD bullet loads, it's about 0.025 from lands.

Also I measured one of the last 5 unchambered rounds(able to push some into chamber this morning with harder force), seems all under Specs.

Above extractor grove, body just under shoulder, neck above shoulder and neck at mouth

 

[thexman]

Never said if your wet tumbling but case mouth peennng looks like your issue...... I've seen it numerous times.

Give them a generous outside neck chamfer and I bet it solves your problem.

Typically if you had swelled bases you would have a hitch when you open your bolt from a fired round and most typically seen when using fired brass in a new chamber.

The area in red is your issue....

I tried chamfer and debur, it didn't help. Plus my loaded rounds neck OD at mouth is 0.003-0.004 less than chamber ID from reamer spec.

I only notice the bolt lifting has slightly resistence after firing, I thought that is normal?

 

[thexman]

It's the neck. Best guesses from most to least likely culprits:
1. Neck flared because you bottomed out the expander mandrel - screw the die up/out a full turn
2. Peened the necks wet tumbling - run a debur tool after the tumble
3. necks too long and bottom out on chamber - double check trim length.

I don't think it's the web. 3x fired is pretty low unless its a hot rod, and you hopefully would have noticed a clicker on the last firing.

Thanks.

I checked and tried, debur chamfer and trim doesn't help, I ran the expander with my fingers to top of the press, so it would stop after the mandral pass the neck and would not touch.the mouth. I wish it would be as simple as a over expander mouth problem.

Will see what my gunsmith will find out later this week. Seems really strange issue to him as well.

 

[cwinner]

I tried chamfer and debur, it didn't help. Plus my loaded rounds neck OD at mouth is 0.003-0.004 less than chamber ID from reamer spec.

I only notice the bolt lifting has slightly resistence after firing, I thought that is normal?

Based on your base diameter of .468" I'd say you should be good to go and your neck diameter is fine..... my guess is still a slight peening of just the mouth of the case causing the issues.... I know you said you have chamfered the outs side neck diameter but sometimes it takes quite a bit.... based on your original pictures the only shines spots are right at the end of the neck which makes me think that's your problem.... I have never seen a case base expand enough from when fired from the same chamber to cause issues, old brass in a new chamber sure thing but not from existing.

Please let us know what you ultimately determine.....

 

[DellaDog]

None of those pictures shows actual case mouth measurement. Use the fatter part of the caliper blades and measure the exact top of the case neck. Also, if you slide the calipers up the neck, if the mouth is peened, the blades will catch on the peen. You’ll feel it.

 

[thexman]

I actual start thinking if this could be caused by carbon build up between the case mouth and the lands.

I noticed that I have a shorter brass(box A) at about 1.536-1.538, the virgin Alpha brass I measured from another box(box B) is between 1.541-1.544. As I only shot about 400 rounds with this new rifle using brass from box A, I didn't expect it needs that much cleaning, even I do run patches through the barrel every time I go to the range(50-70 rounds each time), but I never pay attention to the carbon(I came from 308win and 6.5creedmoor, never had this problem after shooting thousands rounds).

As I mentioned at #27, I managed to apply more force to push quite a few unchambered rounds in, the first time say I use 20lb force, but if I tried to chamber it 2nd time, it goes much smooth and have much less resistant. So something must changed inside.

Unfortunately, I don't have a bore camera, I guess what I can do now is to do some cleaning in the chamber just before where rifling starts, and see if that would make any difference.

 

[4O6shootist]

I actual start thinking if this could be caused by carbon build up between the case mouth and the lands.

I noticed that I have a shorter brass(box A) at about 1.536-1.538, the virgin Alpha brass I measured from another box(box B) is between 1.541-1.544. As I only shot about 400 rounds with this new rifle using brass from box A, I didn't expect it needs that much cleaning, even I do run patches through the barrel every time I go to the range(50-70 rounds each time), but I never pay attention to the carbon(I came from 308win and 6.5creedmoor, never had this problem after shooting thousands rounds).

As I mentioned at #27, I managed to apply more force to push quite a few unchambered rounds in, the first time say I use 20lb force, but if I tried to chamber it 2nd time, it goes much smooth and have much less resistant. So something must changed inside.

Unfortunately, I don't have a bore camera, I guess what I can do now is to do some cleaning in the chamber just before where rifling starts, and see if that would make any difference.

A teslong Amazon bore cam was 80$ last time I purchased one few years ago. Best cleaning aid I've invested in. Dont use it for looking at the chamber/bore on a new barrel unless you're having problems. It's not a device for qc a smiths work unless accuracy or chamber issues become apparent. I've observed crooked barrels with rough chambers and ugly bore/groove shoot as good as one that looks pristine.

 

[thexman]

A teslong Amazon bore cam was 80$ last time I purchased one few years ago. Best cleaning aid I've invested in. Dont use it for looking at the chamber/bore on a new barrel unless you're having problems. It's not a device for qc a smiths work unless accuracy or chamber issues become apparent. I've observed crooked barrels with rough chambers and ugly bore/groove shoot as good as one that looks pristine.

Yeah, I am doing research on Teslong at the moment, trying to decide if I should choose the 45inch flexible one or the 26inch rigid one. Barrel is 28inch and I prefer to have some buffer in case I want to have a 30 or 32 inch barrel in the future, seems like 45inch is the only option for me.

 

[4O6shootist]

Yeah, I am doing research on Teslong at the moment, trying to decide if I should choose the 45inch flexible one or the 26inch rigid one. Barrel is 28inch and I prefer to have some buffer in case I want to have a 30 or 32 inch barrel in the future, seems like 45inch is the only option for me.

45" flexible for sure. I run the USB Cam pro ap with mine plugged into my phone. The flex cam can be used for a lot more than just rifle barrels. Engines, tight spaces what not.

 

[thexman]

After investigation with my gunsmith, here are some result I want to share:

1. First, I want to apologize that I made a mistake when I was measuring the neck OD at the mouth. From the photo I included in the post, I should use the middle/thicker part to measure the neck mouth, not the thin part of the caliper, so that causes the problem at first place.
2. So the actual neck OD at mouth is between 0.269-0.2725(most are up to 0.271, a few extreme case goes to 0.2725, which for sure wouldn't chamber to a 0.272 match chamber), also my caliper probably needs a upgrade to either Mahr or Mitutoyo, I had some reading issue yesterday, it gives funny numbers.
3. Not much carbon built up in the chamber before the rifling starts after look through a bore scope, so that is not the root cause for my case. But I did learn something about carbon ring and what need to do for regular maintenance when shooting for groups.
4. So before the neck turning tool arrives, I guess I will use some 320 sanding paper to "turn" the neck for now. And will also try a new box of Alpha brass to see if there is any problem for the neck thickness from the factory.

Will update the post if the neck turning or the new brass still not solve the problem.

Thank you very much for the help.

 

[thexman]

Just curious, especially for alpha OCD 6 dasher brass user, how much neck grow did you experience after x number of firing in the past?

It seems the neck does not grow longer enough or at all, but more thicker, I've been told this might be related to wet tumbling especially without SS pin.

 

[DellaDog]

Just curious, especially for alpha OCD 6 dasher brass user, how much neck grow did you experience after x number of firing in the past?

It seems the neck does not grow longer enough or at all, but more thicker, I've been told this might be related to wet tumbling especially without SS pin.

Don't know about the Dasher, but that's part of the problem with the 6 BRA (and probably Dasher). The brass hardly grows at all, and using a Girauld trimmer the case mouths are hardly touched at all, unless you're willing to trim a couple thousand each reload.

I've taken to neck turning the peen off after a few reloads. Gave me an excuse to get a 21st Century powered lathe

 

[thexman]

Don't know about the Dasher, but that's part of the problem with the 6 BRA (and probably Dasher). The brass hardly grows at all, and using a Girauld trimmer the case mouths are hardly touched at all, unless you're willing to trim a couple thousand each reload.

I've taken to neck turning the peen off few reloads. Gave me an excuse to get a 21st Century powered lathe

Thank you.

Yeah, I am on the same boat for the 21st Century lathe.

But I found push little bit harder on the chamfer and debur gauge helps in my test today. I guess it is only the mouth part is getting thicker.

 

[lash]

As was suggested, but perhaps missed, if you both ID and OD chamfer the neck every time, after they are tumbled but before sizing, it helps to slow down growth in thickness at the case mouth. Every time.

 

[thexman]

As was suggested, but perhaps missed, if you both ID and OD chamfer the neck every time, after they are tumbled but before sizing, it helps to slow down growth in thickness at the case mouth. Every time.

Lesson learned.

I normally resize then chamfer and debur if I trimmed the brass, but not every time. So I guess for dasher like caliber, the neck does not grow that much, I would need to debur and chamfer every time.

 

[lash]

Yes. It does help.

 

[Molon]

You don’t understand the web.

You're the one who doesn't understand what the web is and that picture that you posted is flat out wrong. The illustration below shows the correct location of the web.

 

[Mormegil87]

Have you tried dry tumbling in a vibratory cleaner instead of wet tumbling? It might prevent the issue.

 

[cwinner]

Thank you.

Yeah, I am on the same boat for the 21st Century lathe.

But I found push little bit harder on the chamfer and debur gauge helps in my test today. I guess it is only the mouth part is getting thicker.

Glad you figured it out...... it takes more chamfer than you'd think.... I've seen it many times and have been bitten myself.

I now run each case through my giraud trimmer every time...... I have also really reduced my wet tumbling time, usually no more than an hour before I anneal and I use dry media exclusively after sizing.

 

[JoshPutman]

Just saw this, and have a few thoughts.

1. Like was said, use the calipers up into the jaws more. You will get more accurate measurements.

2. In the pics, it appears you are squeezing the calipers tight enough to hold the rounds without them sitting on the table. You are squeezing them harder than necessary. This can give false readings. A light touch is all you need.

3. You mention you are looking at Mitutoyo as an upgrade. Excellent choice. I work in a machine shop, and I'm still using the same Mitutoyo 8" dial calipers I started with twenty years ago. I have a 6" set at home for reloading.

 

[secondofangle2]

how deep is the seating die screwed in? Is it deforming the brass at the top of the stroke?

And if you have a tight chamber, case mouth deformities can def cause this

 

[lash]

how deep is the seating die screwed in? Is it deforming the brass at the top of the stroke?

And if you have a tight chamber, case mouth deformities can def cause this

I had this happen on one of my .260 barrels, now long gone. I had the smith open the neck part of the chamber to just under max specification since it was a competition rifle. I needed it to feed every time without fail. That is when I discovered the importance of ID/OD chamfering during the reloading process.

 

[thexman]

how deep is the seating die screwed in? Is it deforming the brass at the top of the stroke?

And if you have a tight chamber, case mouth deformities can def cause this

I tried back the seating die one revolution and only adjust the seating stem down to seat the bullet. It is still the same.

I have to conclude it is caused by trimming most likely, will try to measure the mouth thickness before and after trimming the brass next time.