Does neck sizing only create more pressure?

[lugerstew]

I shot some 243 loads today that were overpressure, ie, hard bolt lift, ejector mark and cratered primers, the problem is, the loads were exact duplicates that I had shot last week with new starline brass, H4350 powder, cci large rifle primers, same coal, same powder charges, only difference was I used the fireformed brass from last week and only neck sized them with about a .002 fit.
With the new brass last week there were no overpressure signs at all.

[Bart B.]

No, it doesn't.

Something in your resized cases probably caused the problem.

Too long of case necks can get jammed into the chamber mouth which crimps case mouths into bullets. Or no expander ball was used.

.002 fit where?

[sparkyv]

I agree with Bart.

Originally Posted by Bart B.

Too long of case necks can get jammed into the chamber mouth which crimps case mouths into bullets. Or no expander ball was used.

[lugerstew]

Powder charges were the same,cases , and I always check that the brass is under max length, if it isn't, I trim it a few thousands less than minimum., I do have additional info, I was using 40.5, 41 and 41.5g of h4350, it was over in the hornady book but I used up to 42 grains the first time from the Hodgdon website,, although, not exact 95 grain bullet, I must also confess that I was loading all these loads at .020 more seating depth than hornady recommended, mainly because im trying to match some factory black hills gold ammo that was seated 2.610 and hornady recommends 2.630. Was no problem with the first test loadings, in fact I went to 42 grains and had no overpressure. This brass is new and I have only neck sized it one time.

[lugerstew]

True, on the one comment of no expander ball used, I was neck sizing with Lee collet neck sizer,, and .002 interference fit or whatever the official name for it is is all I could get for a bullet seating tightness, sorry I cant remember the proper terms.

[jpx2rk]

What was the bolt closure like on the reloads? Similar or close to the new/zero fired or was it on the stiff side when closing the bolt??

[lugerstew]

Bolt closure was normal, did not notice anything different than I ususally have, I have been reloading only about 5 years, but shooting for over 50 years, I am no expert with this reloading stuff, but I appreciate all the advice from you all.
Although I have to admit, I started reloading 12 gauge shotgun shells when I was 8 yrs old with my dad, to make some awesome goose hunting loads, but pistol and rifle, from what I have read, learned and experienced, will be a long time, life learning experience.

[hounddawg]

Just me but I like at least .003 difference from unsized to sized neck OD with the bullet inserted. If my neck is .271 after firing and .012 thick I will use a .264 bushing so that when the bullet is seated I have a neck OD of .267. That gives the brass .004 to expand on firing and .003 of compression force on the bullet by the neck brass. Works on my 6BR and 6CM

edit - I quit trusting the Hogdon site. I can think of at least two different rifles/powder/bullet data where I can't get anywhere near their max w/o pressure signs

edit 2 - Tips for using a Lee Collet Die

John Kielly uses this method (post 19) http://forum.accurateshooter.com/thr...#post-36644901

[std7mag]

Luger,

Collet sizing uses a mandrel in the center of the die. The case neck is essentially pressed inward to fit the center mandrel.

What do you mean by "not exactly 95gr" bullets?
Heavier?
Lighter?

The 0.020" deeper seating of the bullets will raise pressures, but usually not by that much in a bottle necked cartridge. (Note, don't try doing that with a pistol cartridge & think you'll get away with it. Too small of a case capacity & faster burning powders.)

[Unclenick]

Lugerstew,

How did you load and transport the ammunition? Same orientation during the trip, or might it have been upright the first time and on its side the second time? Long ago one of Precision Shooting's authors had a load that shot great when he loaded it at home, but that gave him sticky bolt lift when he loaded it at the bench on the range. He finally figured out the vibration of being carried and driven and carried some more at the range was settling the powder. With stick powders, settling can decrease burn rate by making it harder for the flame front to move between the grains. How much effect this has varies with the particular powder. This is one advantage compressed loads of stick powders have; they tend to lock the powder in place so vibration doesn't pack it down any. The Federal GM308M load is an example, and its reputation for consistency is very good. I would expect cartridges transported on their sides to pack less than those transported upright.

A second orientation factor, if your loads are not compressed, is the powder position at firing. Years ago I had occasion to shoot some 1964 National Match ammunition in several club Garands and intentionally tipped them either down or up before leveling the guns to fire them over my chronograph. The charge of IMR4895 in those old loads only filled the cases about 82%, so the powder shift was significant. Powder forward and away from the flash hole shot 80 fps slower than powder back over the flash hole, and powder forward produced nice rounded primers while powder back gave a fairly flat primer. So powder position can matter to pressure reached, too. If you kept your ammo in a box nose-down for the first loads and nose-up for the second set, that might encourage a similar effect.

Keep in mind the Hodgdon data is for their guns with their component lots. They have a ±3% tolerance for the burn rate of their extreme line of powder, and yours could be at the faster end. (Were you using the same lot of powder in both instances?) They use Winchester cases most of the time, which, in most chamberings, tend to be on the large end of the capacity range; i.e., larger than Starline, Remington, Federal and most others except sometimes Hornady. So if you don't use Winchester cases, that can be the issue. I note, too, that Winchester has changed a bit over time, with their .308 Win cases weighing more now (around 166 grains) than they did fifteen years ago (around 156 grains), so old data in Hodgdon's charts may err on the high side. They often use a Winchester or a Federal primer. Federal standard primers are among the mildest, while their magnum primers are among the hottest, so if you substitute a Federal magnum primer for about anything else, including Hodgdon data with a Winchester primer, you may raise pressure some (this varies with a number of other factors).

[lugerstew]

Sorry didn't explain the same bullet part, im shooting a 95g hornady sst, and the Hodgdon website data is for a nosler 95g partition bullet, that's why I went about 2 grains higher the first time with my ocw load testing, and yes I agree with you on how a collet neck sizer works and also would try to stay away from seating pistol bullets .020 deeper, im still not sure what caused the overpress, but I had 1/2 moa with 5 rounds at 200 yds, with the 40.5 grains, so im going to keep that in my log as a good ocw and scratch the higher loads off as over pressure, again thanks for everyones advice.

[lugerstew]

Thanks unclenick
The powder I was using was the same container and also I use the nice plastic 50 round boxes and keep them upright to the same range, same route every time. That's interesting about tilting the cartridges and getting different velocities, I wouldn't have ever thought that. These rounds are definitely not compressed so maybe that is some of my problem, as I learn here, it seems that I like to look now for loads that fill the case nicely instead of sloshing around, it just seems more consistent, also I probably need to be careful of even the 40.5 grain load that shot nice while it was 25deg, for when I take it out on a 80 deg day. I could maybe see some overpressure with that scenario.

[Unclenick]

Try the trick of getting the powder forward and backward to look for differences in both pressure signs and velocity. When people follow the SAAMI test protocol, they are careful to handle the cartridge to ensure the powder is over the primer. That maximizes pressure, thereby representing the worst case.