Ok, this one is driving me batty (short trip, I know)!



Gun is a Remington 40X Palma rifle, prone stock, etc. Brandy new Broughton 5C barrel put on by a well-known gunsmith, supposedly using a WTC Palma 95 .308 Winchester reamer w/ a .343 neck. Cases are new Winchester 'Palma' cases, roughly equivalent to Lapua, maybe a touch thinner and lighter. Trim, chamfer, debur, flash hole deburred, primer pockes uniformed, etc. Pretty much everything but neck-turned. Loaded on Redding Type 'S' F/L bushing die w/ .331 bushing, floating carbide expander button, etc. etc. etc. Redding Competition Seater die.



Measured jam length to the lands for a 155gr Nosler J4 w/ a Stoney Point comparator, number comes out at 3.193-3.194", for an OAL of 2.780", kind of short throated. Loaded some cases up w/ bullets set to 3.194-3.195", and an appropriate load of Varget, which pretty much filled the case up, so a slightly compressed load. Rounds still measure 3.194", chamber a round, feel a little resistance just as the bolt closes, open the bolt... Varget everywhere



Go back, remeasure everything, double and triple check, seat a bullet in a empty but primed case, it ejected fine w/ the bullet still in place. Even re-adjusted the die, so that loaded rounds were now 3.190", 3-4 thou shy of the lands. Put another loaded round in the chamber... and got to clean out the lug recesses and trigger and everything else *again* from Varget spilling all over the place. By now, I'm _really_ glad I'm not using a finer grained powder like Tac Checked the remaining loaded rounds to see if maybe the compressed powder is pushing the bullets back out to the lands... nope, the remaining loaded rounds still measure 3.190", several thou shy of the lands.



WTF? How in the blue blazes is the bullet 'sticking' and pulling free of the case (and it is dang sho wedged in the lands, have to plunk it free w/ a small caliber bullet down the muzzle) when I measured the jam length as being *longer* than what I'm seating the bullet to? Not exactly my first time around the block w/ the Stoney Point tool; I insert the bullet in the case, insert the case in the chamber, push the seating rod forward firmly until the bullet stops and lock it down, remove the tool, plunk the bullet free, reinsert it and take a reading using the comparator insert on my calipers (appropriately 'zeroed' for the insert). I take readings until I get 3 consecutive consistent readings, so if I'm really jamming that bullet too deep, I'm really really good at it ;p Also, how in the bloody heck is it that a loaded round pulls the bullet free and spews powder everywhere, but a round w/ no powder doesn't?!?



Really grasping at straws here...



Help!







Monte

Just a guess but it sounds like inadequate neck tension to me. Couple of your numbers confuse me a little, the .343 neck and .331 bushing but the culprit I would look at is the expander ball. What I do know is that engaging the lands with your bullet....well, there's more grip/traction there than you might think, and match bullets are built with thin jackets...read: 'soft'. If your neck tension is okay, just try seating a few thou shorter.

Thanks for the response. Any particulars on what about .343 and .331 is perplexing you? Standard SAAMI .308 Win chamber has a .346 neck, the Palma '95 chamber has a .343 neck; slightly smaller but not a tight neck by any stretch of the imagination. The necks are about 13 thousandths, so I went w/ .308+.013+.013=.334 loaded diameter. Figured w/ a .331 I'd have light, but not ridiculously light, neck tension and not be working the neck much as the expander went thru.

Thanks,

Monte

it is the compressed load doing it. My gunsmith had a compressed load in 7mm-08AI and he said he could load it,..then come back in a few hours and the load had started to slightly push the bullet foreward,..same symptoms as you have right now. HTH

That was my first guess as well... but please read the original post...

Quote:

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Checked the remaining loaded rounds to see if maybe the compressed powder is pushing the bullets back out to the lands... nope, the remaining loaded rounds still measure 3.190", several thou shy of the lands.

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Sure seems odd that if the powder is pushing the bullets out, they aren't showing it in any measurable way.

Thanks,

Monte

The pressure from the powder is "helping" the barrel pull the bullet out. It's not compressed enough to push the bullet quite by itself, but with a little bit of help, out she comes. HTH, Dutch.

Ok... that seems closer to making some sort of sense... next question is why is the bullet pulling out when by my (repeated) measurements, the bullet should have been several thou short of the lands?

Thanks,

Monte

Due to run-out or the pressure from the ejector, the bullet is forced into the lands on one side, creating enough "grip".

Try a smaller bushing, or leave the expander ball out, or use a drop tube/vibrate the charge to reduce the volume of the powder. HTH, Dutch.

What Dutch said. "Try a smaller bushing, or leave the expander ball out".

The puzzle for me was the large difference in dimensions. Not conversant with Palma requirements, but .010"-.012" release is generous. You said "about .013" on neck wall thickness. I'm still thinking inadequate NT. What is the PRECISE neck wall figure? What is the sized neck OD prior to loading, and after. Not your plans/expectations, but actual readings. A bushing of a specific diameter does not necessarily reduce the neck to that number because of springback in the brass.

It takes more than light compression of the charge to push bullets form a case.

The necks are *not* turned, so there isn't an *exact* measurement; some are a little more, some are a little less. Range seems to be about 0.0128-0.0137, using a ball mike.



Loaded up ten shorter rounds w/ a lighter load (42.0gr Varget), and took the gun to the range today. First 3 shots had me a little worried, being a shade over an inch, but things mellowed out after that. Last four rounds went into a group ~1/4" high x ~1/2" wide, w/ a 5-10mph wind from 7-8 o'clock, not the best for shooting groups. The barrel does show promise, though.



Think I found the problem, and it ain't neck tension, expander balls, etc. Found some marks on the case that shouldn't be there, and they only show up on fired rounds (at least I couldn't find definite marks on the other rounds w/ a magnifying glass). Nice bright deep scratch about 1/16" long, starting about 1/32" below the shoulder, and about 20 degrees around the circumference from that, a nice distinctive mark a little less than 1/8" long right at the case mouth that looks an awful lot like what a rifling mark on a bullet would. And no, before someone even goes there, the cases are not too long. Actually had to trim them short to 2.000" because someone had done a ham-handed effort at trimming and chamfering before me.



Guess it's time to really clean the chamber and throat out good, maybe w/ some JB, load up some more rounds, blacken the shoulders w/ a Sharpie, and see if it was just stray chips in the chamber and throat. Kind of doubt it, as the marks were in pretty much exactly the same place on all ten rounds, once I knew what to look for. After that... next stop... scope the chamber w/ a borescope?



Thanks,



Monte

Milanuk, Before you load more rounds with your newly cleaned chamber try smoking a loaded dummy round and see how much of the lands contact the bullet.
The case you get with the Stoney Point has a tolerance in headspace, the same as the cases and chamber your loading. The OAL maybe wrong depending on how the Stoney Point case relates to your chamber.(how deep the gage case inters the chamber before the shoulder stops it in relation to your sized cases) I would have a fired case drilled and threaded for the gage and use it with your rifle in place of the one that came with it. I have found a few cases that differ enough from my chambers to cause the bullet to seat a bit deeper in the lands then planned, The angle of the leade can be sharp enough that a thousanth or two inch can jam the bullet suprisingly tight.

JMO........Joe

Joe,

That is something else I've been looking at... the Stoney Point case body is about 3-4 thousandths shorter headspace than the cases I had F/L sized to a value safely shorter than SAAMI minimum headspace based on previous experience w/ this gunsmith. Wasn't sure if that could be adding in to things as well, figured it might. Still think the main problem is probably whatever the heck is in the chamber as far as burrs, chips, etc. Hopefully I will get a chance to clean things out and check everything out tomorrow.

Monte

I think Joe is on the right track. The Stoney Point case is different than the cases you are shooting, and when you are trying to get 1 or 2 thous. away from the lands, it's going to make a difference. Also make sure your primers are below flush and they aren't protruding slightly when you measure the round with the comparator. Bottom line is your loaded rounds are too long, regardless of what Stoney Point is telling you. Take an empty case that you have shot, seat a bullet, and blacken it or shine it up with steel wool so you can see the rifling marks. Then adjust your seating die until they go away. Also try loading a dummy round with a "snug" neck and the bullet seated way out, chamber it, and measure. Compare that length to the ogive with your other round you just worked up. They should be close. The chamber issue that is causing the scratches seems to be a separate issue to me. Stoney Point can get you started, but isn't necessarily exactly the most accurate.

Well... I do have a case from this batch that I'd be willing to 'sacrifice' (something boogered the edge of the case mouth). Guess I could neck-size it a few times to get the headspace as close to actual as possible, and then drill-n-tap it for the Stoney Point comparator... problem is that if the chamber is indeed boogered, and has to be re-cut, headspace now might not match headspace then. I could smoke the bullets and use that to establish the seating depth to the lands... but again, if the chamber is messed up and has to be re-worked, that value is going to be worthless again.

For now I think my priority is going to be figuring out just WTF is the matter w/ that chamber, and then I'll get back to worrying about the seating depth.

Thanks for all the ideas,

Monte