Chambering question


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bob4
November 12, 2012, 09:18 PM
Just happen to notice this tonight. Never paid any attention before. Here's the scenario: Bolt action.
When chambering a rifle round let's say we just point the barrel down and drop a cartridge down the throat so it falls in place. Now lift that barrel up should that cartridge just slide right out?

And if it doesn't is there anything else other than the lands that might hold it? Lets say for sake of argument brass is brand new and correct length and has been full re-sized. And OAL is .20/1000 under just touching lands. Rifle clean and have cleaned the chamber.
I did note that store bought ammo does fall right out.

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Walkalong
November 12, 2012, 09:24 PM
Mark the case with a sharpie around the shoulder area and see if any scuffs off on chambering.

Are you sure the bullet is .020 off the lands?

Did you crimp? If so, did you buckle the shoulder a hair?

Did a sized case with no bullet seated drop in and fall out?

creeper1956
November 12, 2012, 09:50 PM
Based on your discription... yeah, it should fall out as easily as it fell in.

Just because it's full length re-sized however doesn't mean it's near minimum SAAMI spec. I'd consider Walkabout's references, especially the empty case check... and the possibility that your particular die set is on the larger end of SAAMI, and your particular chamber is on the smaller end of SAAMI. Measure a factory loaded round and compare it to one of your FL sized reloads... I'd bet yours have a few points where they are dimensionally larger.

bob4
November 13, 2012, 07:02 AM
Are you sure the bullet is .020 off the lands?Not 100% anymore now that the cartridge gets stuck. I measured by splitting a case with a dremel to the shoulder. Then with a bullet seated long , closed the bolt all the way, closed and not drop the bolt as to engage the catch then measured that cartridge. Did this 5 times and was back and forth @ 3.317 & 3.316 So set my OAL @ 2.295 and went all the way down to 2.265 to no avail.
When I say older box of bullets they aren't a month old

Did you crimp? If so, did you buckle the shoulder a hair? No on the crimp

Did a sized case with no bullet seated drop in and fall out? Yes. Slides right out. So I'm pretty sure I need to blame the bullet.

This morning for the heck of it I opened a new box of bullets ( box 3). This is my 3rd box. They fall right out at 2.275. Tried this twice with both bullets both times the new one fell right out were as the older one didn't.
When I opened the box the last box ( box 2) the ones that didn't fall out. I did notice that they weren't near as shinny as the last box but didn't think anything else about it. With only my calipers I measure them to be the same lenght and diameter. Go figure!

Measured my OAL with the split case and a long seated bullet and closed the bolt. 5 times it measured between 3.316 and 3.317. So obviously droping mine to 2.95 a bit over .020 didn't get them off the lands. I think I'll pick up a Hornady OAL guage today just to double check myself. Saw one in B/pro the other day.

NOTE: When I say older box of bullets they arent 3 weeks old yet.

Walkalong
November 13, 2012, 07:25 AM
Case too long, getting pinched in the throat with a bullet loaded?

MtnCreek
November 13, 2012, 08:14 AM
The cartridge case is tapered and when dropped in, it could slightly wedge itself in a little snug.

Is the cartridge headspace set the same on the test dummy as the loaded cartridges? If the test has more or less head clearance than the loaded cartridges, that will affect how close to lands your bullet really is.

bob4
November 13, 2012, 01:36 PM
Case too long, getting pinched in the throat with a bullet loaded? Wouldn't that get pinched with or without a bullet ? They are all under the rated 3.340

Is the cartridge headspace set the same on the test dummy as the loaded cartridges? I don't have a head-space gauge ...yet.. Guess that's next. All the brass is brand new so I'm hoping it's fairly close... And both the loaded cartridge and dummy are from the same bag of brass. I know that doesn't answer the question but the best I can do for now.

Unfortunately the big store was out of Hornady 270 modified cases so that's on hold for now.

jwrowland77
November 13, 2012, 01:42 PM
Do you strictly measure the OAL or do you measure from the Ogive as well?

In the reading and research that I've done, its much more accurate to measure to the ogive. I say that because each bullet is going to have its own unique profile. The OAL can very from bullet to bullet within the same box of 100. Once I started measuring from the ogive I got more consistent ammo which resulted in much more consistent accuracy. Just my .02 worth.

bob4
November 13, 2012, 05:19 PM
Do you strictly measure the OAL or do you measure from the Ogive as well?
Just bought a comparator tonight. Will be measuring Ogive from here on. :scrutiny:

rcmodel
November 13, 2012, 05:40 PM
You need a black magic marker worse then a comparator.

Color the cartridge and chamber it.

Where the ink rubs off is your problem.

rc

gamestalker
November 13, 2012, 06:36 PM
As RC stated, a black magic marker will tell you where the tollerance issue is without having to continue guessing, or using a process of eliination, it works every time.

However, from the sounds of it you may have olgives that are getting into the lands, or mouths getting pinched in the throat, as in they need trimming, or bodies that may need to be run through a FL die. I would doubt it has anything to do with shoulders as they wouldn't be likely to cause any binding prior to closing the bolt, thus a cartridge should just drop right back out of the chamber by gravity alone, regardless of head space. But a magic marker shoudl quickly tell the story without further guess work.

Even new brass will have inconsistencies in neck lenghts, as well as other critical areas. New brass is manufactured to a one size fits all specification, dimensionally speaking.

GS

Walkalong
November 13, 2012, 07:32 PM
Wouldn't that get pinched with or without a bullet ? No, the neck is wider with no give with a bullet seated.
They are all under the rated 3.340Then that probably isn't it. Got a sharpie yet? :)

bob4
November 13, 2012, 09:12 PM
Thanks all,

First off what I thought I found this morning with the 2 different boxes of bullets fell apart this eve. :cuss:

Broke out the sharpie ( permanent). Painted it black to the shoulders. No discernible marks. Even lengthened the OAL to be sure it got stuck too. Kinda frustrating. Also engaged the bolt. :banghead:

What I did do because this brass was new ,was to take apart a factory load and stuff my bullet in it. Same thing got stuck as I set it to where factory had it from the Ogive. Then I took one of my new pieces of brass to my buffing wheel and chamfered a 45 angle lightly on it and set it again to where the factory ammo was bt Ogive length. BINGO! Slides right out.
I'm just not sure enough as to where my lands are anymore.

Measured my OAL with the split case and a long seated bullet and closed the bolt. 5 times it measured between 3.316 and 3.317. Now when I measured this I measured the cartridge OAL. Didn't have a comparator yet. Is this a reasonable way to measure to the lands?

MtnCreek
November 14, 2012, 08:14 AM
Just by chance, your bullets aren't marked .284 are they?

jwrowland77
November 14, 2012, 08:52 AM
Just by chance, your bullets aren't marked .284 are they?

Good call. I know the .284 bullets I load, my OAL is around 3.290 or 3.300, but that's just for the specific bullets I use.

bob4
November 14, 2012, 06:56 PM
Everyone has been such a big help here thanks! :D

Just by chance, your bullets aren't marked .284 are they? No. The bullets them selves aren't marked. They are Sierra Game king 130gr BT # 1820. Diameter is real close by my calipers and OA/ length averages 1.100- 1.150

Everything seems good now. I came home today with plenty of time and went to work. Attached is a pic of my doings. Although not completely scientific it seemed to work for me today. Came down to alot of slightly pressing on the press and getting close to my goal for the next test and going with the Ogive length that came out. As long as it was in .005-.010 I was happy to try. My Ogive length is settling on 2.790 and OAL 3.265 I am not sticking in the chamber anymore.
My biggest concern now is my seating depth. I have it figured to Approx. .350. Much of the reading I've done says it should be close to the diameter bullet. "Close" is such a relative word.
So I am interested in some thoughts on seating a .277 @ .350

So much to learn this is really fun.

http://www.bob-4.com/storage/pics/270_case.jpg

MtnCreek
November 15, 2012, 08:37 AM
Much of the reading I've done says it should be close to the diameter bullet. "Close" is such a relative word.
So I am interested in some thoughts on seating a .277 @ .350

That's a standard min. to insure you have enough bullet / neck contact. A lot of the ammo I load has the bullet base well below where the shoulder meets the body (i.e. 308win / 178 a-max).

Those GK's should not be sensitive to jump to lands. I would maintain at least 0.020 to lands. As you close the gap from about 0.015 to lands, small variations in bullet construction can cause large variations in velocity.

Typically, I load hunting bullets to mag length less ~0.100 or at least 1 cal in the neck, whichever is less, with no regard to lands.

fguffey
November 15, 2012, 08:59 AM
“When chambering a rifle round let's say we just point the barrel down and drop a cartridge down the throat so it falls in place. Now lift that barrel up should that cartridge just slide right out?”

Yes it should. I make chamber gages, not like the ones offered on the Internet, real ones, not bad copies of the L.E. Wilson case gages.

Then there are bad habits and or giving the case a reason for not falling out. Again, I am the fan of ‘time is a factor’, I want nothing but air between my case and chamber, not a lot of air just a little air.

F. Guffey

popper
November 15, 2012, 12:53 PM
So you mik'd the neck OD of rounds that fall out and compared to your reloads? Most new brass I've seen needs the mouth cleaned up by chamfering inside and out. Obviously you are not stuck in the lands. If with an open bolt it doesn't slide right out but does if you drop the butt on the ground, you should be good to go. Pulling a bullet and reloading the case will distort the mouth - did you crimp it?

bob4
November 15, 2012, 03:40 PM
No on the crimp. Rifle seemed to do OK today.

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