Need Some Help

462

California's Central Coast Amid The Insanity
At the range, yesterday, I experienced a new-to-me problem.

Qualifiers:
Rifle: 03A3 with a barrel date of 2-43.
Case: Winchester previously fired with RCBS 30-180-SP and 13.5-grains of Unique, then re-sized with a Lee collet neck sizing die.
Bullet: Sierra 165-grain SBT seated with a Forster Ultra Micrometer die to 3.315” for reliable feeding from the magazine. (Sierra’s recommended OAL is 3.330”. Seated to engage the lands, cartridge length is 3.450”.)
Load: 56.0-grains of IMR 4831, though it is of no consequence to the problem. (A picture of two previous 50-yard, three-shot groups attached. Wahoo!! groups for me, considering my screwy vision and issued sights).

Problem:
Eight of the rounds took considerable effort to close the bolt, and I didn’t fire them. The difficulty was akin to seating a cast bullet to engage the lands, only more so. Several rounds required much less effort, and the remaining had the bolt close as if the chamber was empty.

I’ve spent a lot of time measuring various areas of yesterday’s unfired and fired cases, the effortlessly ones, and those that have been full length and small base sized. I can’t find any difference between any of them, other than yesterday’s unfired and fired heads -- measured at that faint ring -- measure .463”, while rounds that chamber effortlessly and full length sized measure .462”, and small base sized measure .461”.

Now, before I see which of the 400-round stash chamber easily, and which ones will have to be torn down and full length/small base sized, does anyone have any idea what is going on, other than an undersize chamber?

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Cherokee

Medina, Ohio
I had something like that happen to me with 9mm years ago. Turned out the bases were too big for the chamber and I had to change my sizing method. Doesn't take much.
 

Ian

Well-Known Member
Something I almost never do with jax: Neck size without bumping the shoulder at least .001" back from the measured headspace dimension.

Failure to bump the shoulder increases bolt thrust load dramatically, reference Glen Zediker's small tome on loading for the M14 and the exhaustive investigations by Harold Vaughn. Bolt thrust is of little consequence with a 20K psi load with cast bullets, but it matters a lot more as you near the top end.

Then obviously there is the functional benefit of giving your loads some headspace....odds are they'll still chamber six months from now when the brass has had a chance to relax.

Why do some fit and some not? Hard to say. I didn't see mention of checking them all either in the rifle or in a case gauge when they were first reloaded, so you may have a growth problem at the datum point some time after collet sizing and seating a bullet or the process itself was causing some deformation. Another consideration is some of the brass may have a donut forming or the collet didn't get emough of the neck base squeezed down to chamber. Examine a cartridge you attempted to chamber for contact points using a sharpie marker or soot and back-track from there.

A Wilson case gauge, shoulder-bump neck bushing die, and a good 2-3" micrometer, and setting your headspace at .001 to .0015", should solve your fitment problems. Hopefully doing so doesn't adversely affect those stellar groups!
 

RicinYakima

High Steppes of Eastern Washington
Were the cases of the same lot? Lee Collet dies can become an issue with brass that expands differently. Since they only squeeze the neck down, every other piece of brass fired in a different chamber, will not work. What it sounds like to me is the very common problem of varying cases resized with collet dies from different chambers or case lots. The other factor may be which had sizing lube or not one them when fired, allowing differing streahing. FWIW
 
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Ian

Well-Known Member
Here's a good shoulder bump neck bushing die that will enable you to precisely and minimally control headspace and neck tension as well as how much of the neck length you resize while leaving the case body fireformed perfectly to the chamber. The less headspace you have, the closer you want the body of the case to fit the chamber so it grabs the chamber wall immediately and takes stress off the bolt face. Yes, that means the case body stretches some each firing and you'll get a neck donut and head separation eventually, so you must be aware of and be monitoring those things, but at high pressure brass doesn't last forever no matter what you do.

The Wilson case gauge and a micrometer (not calipers!) work together as an excellent headspace measuring set so you can check each case as you size it and sort/resize as required to ensure uniformity.
 

Rcmaveric

Active Member
Never had that problem with aged ammo, definitely had chambering issues from freshly loaded cartridges in a couple of cartridges. I always full length size. I measure my COLs so i knew that wasn the problem. Smoking the brass and chambering it gave the shoulders away. I had to polish my dies bottoms.

See if you can find a loaded one that causes problems. Pull the bullet, dump the powder and knock out the primer. Then smoke the case and chamber it. The brass will give its secrets if you know how to listen.

Then you will know if its the neck, shoulder, base or bulge.
 
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Cherokee

Medina, Ohio
I missed the neck sized comment in my first read, agree with others that shoulder is probably the problem. I always FL size brass.
 

462

California's Central Coast Amid The Insanity
Thanks for the replies and suggestions.

Ian: Can't remember exactly when the rounds were loaded, but the 400 were done over a long period of time, and those I took to the range are at least six months old.

Ric: All cases had been previously fired in this rifle, with cast bullets and that above Unique load. Also, they are all Winchester and a combination of purchased new and once fired range pick up, and all had been full length sized prior to being loaded and fire formed with cast bullets.

Rcmaveric: I painted the neck/shoulder area with a Sharpie and chambered it, but there was not any indication of interference. However, I'll do as you suggest.

Because all the cases had been previously fire formed, in this rifle with reduced cast loads, would that not provide the proper headspace dimensions?

Testing, measuring and comparison will continue as time allows.
 

Ian

Well-Known Member
Because all the cases had been previously fire formed, in this rifle with reduced cast loads, would that not provide the proper headspace dimensions?
NO. That will give you zero headspace at best. What is "proper?" You're loading jax with a medium load of slow powder, my opinion is you need some headSPACE to reduce the bolt thrust load at these pressure levels. If you were loading 10 grains of Unique and a 150-grain cast bullet you can get away without setting the shoulder back.

If the cartridge won't easily chamber, it's binding SOMEWHERE. You need to find where, look for a tiny, shiny ring at the base of the neck, or possibly the body/shoulder junction, or maybe just back from the body-shoulder junction on the body of the case, or maybe the whole shoulder is contacting the chamber (since these were fireformed) and not leaving any particular mark.
 

popper

Well-Known Member
I’ve spent a lot of time measuring various areas of yesterday’s unfired and fired cases, the effortlessly ones, and those that have been full length and small base sized. measured at that faint ring -- measure .463”, while rounds that chamber effortlessly and full length sized measure .462”, and small base sized measure .461”.
Did you check near the case head with sharpe?
What kind of crimp?
 
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Ian

Well-Known Member
I can't imagine that the back of the chamber isn't at least .475" but Popper might well be right.
 

462

California's Central Coast Amid The Insanity
Update:
Sharpie blackened an entire case and chambered it, but could not find any areas where the black was removed, except where its bottom slid along the magazine follower.
Made dozens of more measurements, and other than an approximate .001" to .002" difference at the faint ring at the top of the head, the easily chamberable rounds measure the same as the difficult to chamber ones.
Trimmed a case .010" under minimum dimension and it chambered no differently than before trimming.
Thinking the Timney trigger might be causing some interference, I installed the issued trigger, but again no difference.

Then my memory started working:
I remembered that, when I bought the rifle, the bolt would not close on a borrowed GO gauge. But, then I couldn't remember if I had stripped the bolt prior to inserting the gauge, or not.
Remembered, too, that I have some new Winchester brass, and the pressure to close the bolt on one is the same as closing the bolt on an empty chamber.

Because of an upcoming road trip, I have to forego any more work till after we get back.
In the meantime, though, could it be that, for some unknown reason, the chamber just happens to be on the short side?
I've never experienced any difficultly in lifting the bolt handle, or extraction, or any shiny spots on the ends of cases, or other signs of excessive pressure. I have a Wilson headspace gauge sitting in my Brownells, Midway, and Amazon shopping carts.
 

Ian

Well-Known Member
Headspace or case gauge? The Wilson case gauge can be used to set up your sizing die to bump the shoulder a known amount even though it isn't intended for that. If I had more time at the moment I'd do a pictoral essay on how I use the case gauge to set my sizing dies, but basically it involves using the gauge and a micrometer to check head protrusion of a fired case from the gauge and recording the number, then bumping the shoulder a thousandth or two or three (depends) and locking down the sizing die. The actual measurement is only a reference measurement and not a true headspace measurement like chamber gauges will give you but all you need is a reference to positively measure the amount you push back the datum point on the case with your sizing die. Bumping the shoulder more than once ruins the measurement due to springback being less after the first go, so use a fresh, fired case to check each sizing adjustment until you get what you want. Figuring the thousandths per turn of 14-pitch threads is helpful here.
 

CZ93X62

Redlands, Kalifornistan
Some people get good results having their jacketed bullets snugged up into the leade. I NEVER DO THAT. My J-words get seated with a minimum of .020" of leade clearance from the bullet ogive, usually more like .025"-.030". Bias alert--I am not a target-oriented shooter. I am a hunter, and (God forbid....) a defensive shooter. Feeding, chambering, and extraction/ejection reliability are my focus, and I will trade off a bit of accuracy (and likely do) to get that worry-free functioning.
 
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Spindrift

Well-Known Member
My suggestion would be first to focus in the COL. I load heaps of jacketed bullets using the Lee collet; works like a charm. But I always load with a bit of bullet jump (no problem with that, either).

It is quite common to have COL variability during the same loading session, with the same bullet seater and- adjustments. If you are loading to zero jump, the cartridges in the «long» end of your production tolerances may not chamber.

The LCD usually gives low neck tension. ANother possibility is, the COL increase a bit during recoil. Do you remember if the cartridges giving problems where fed from the magazine during a group, or if they were «first shots?»
 
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Ian

Well-Known Member
If I read his numbers right, Michael loaded all those with about .120" of bullet jump, no chance of jam interference. Cartridges in a box magazine with insufficient neck tension should shorten under recoil, not lengthen. I still think the whole datum point is too long and mixed brass history accounts for that even after FL sizing and fireforming with a cast bullet load prior to collet sizing and loading the jax. It's hard to see a rub mark on the shoulder if the whole shoulder is contacting the chamber. Perhaps a pinhead-sized bit of plasticine, bullet lube, or plumber's putty on the shoulder halfway between the neck and body junctions would reveal a tight jam condition in the same fashion that Plastigage is used to check engine bearing clearance.
 
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462

California's Central Coast Amid The Insanity
Allen: bullets are seated to feed from the magazine, so there is an abundance of bullet jump, in the long throat.
Spindrift: I single-round feed, and apologize for not mentioning that in the original post. COL is set for magazine feeding, if that were ever to be an option.
Popper: bullets are seated without any crimp.
 

CZ93X62

Redlands, Kalifornistan
Arrgghhh......BRAIN FADE. I read as far as "Seated to engage the lands......" and went into immediate vapor lock. Sorry about that.

Back in my 308 bolt rifle shooting days, I got into the neck-sizing regimen rather passionately. 308, 223, 222, you name it--it got neck-sized. And very reliably, after 3-4 firings the loaded ammo started becoming hard to chamber. I went to the opposite extreme with small-base sizer dies, since I had gas guns in 223 and 308 at the same time. That fixed the chambering issue OK, but I got the idea (possibly valid) that I was inducing error with the cartridges all lying at the bottom of the chamber now. Well, crud.

These days with most bolt rifles I use the OEM full-length sizing die, but don't screw it down so that the press mechanism "cams over" after firm contact between the die end and shell holder--that bit about screwing in the die until it touches the shell holder, then giving it 1/10- to 1/8-turn in. I just screw the die in to touch the shell holder firmly, and set it right there. Everything feeds--gas guns, bolt guns, single-shots. Case trimming requirements are not excessive, either. With tungsten-carbide pistol dies, I screw it down to just touch the shell holder, then back it off about 1/16-turn. No more chambering issues with handgun ammo now, either. 44 Magnum and 45 Colt sizing gets done in steel dies now, the T/C dies make short-lived "Coke bottles" out of cartridge brass IME.

I would need far better rifles AND skill set to exploit the alleged advantages any of these sizing tweaks might offer. The reliance upon accuracy "suggestions" made in gunrag text and elsewhere was successful in one regard--it got me to buy sizing die variants whose useful character ranged from superfluous to unnecessary. RCBS got my money, those hairballs. :)
 
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462

California's Central Coast Amid The Insanity
No need to apologize, Allen -- I'm guilty of doing the same.
 

popper

Well-Known Member
.001" to .002" difference at the faint ring at the top of the head You Fl sized, then fireformed, My guess it's the base. I found identicle rifles had different HS & chamber (243 weatherby). I use the wilson and feeler gauge to set HS on the FL die. For minor binds, smoking works bettter than sharpie & gently drop into chanber then close the bolt. Use a fire formed case. As you have the shiny ring, check the inside for case separation.