Home Forums Hunting & Shooting Ask The Gunwriters Neck Sizing and Chamber Fit

New to neck sizing.

I re-barreled a Mex Mauser to 250 Savage with minimum headspace. The first 5 pieces of brass I used to check fire function I then neck sized. They chambered, without bullets, fine. They were a bit tight trying to extract however and didn't really pop loose until the bolt bevel hit the receiver extraction cam. They look fine with no discernible markings . Full length sized and unfired brass worked as expected.

Is this usual with neck sized brass?

Thanks

You chambered unfired brass that was neck sized and you didn't fire the brass in the gun. Those necks should almost fall out of there. When fired the necks expand and would be tighter that unfired brass. Actually, if it's neck sized or full length it shouldn't make any difference. When you size a case you make it smaller. Until you fire the round it should be relatively loose in the chamber.

To be clear - the 5 cases were fired in the rifle, then necksized. I guess I thought the body of the cases would have sprung back after firing enough to make extraction easier.

Not an expert but more shooters are going back to a bump or full length sizing with each firing. I would concentrate on setting the sizer to bump the shoulder back 0.001-2" each loading, after spring back. I also like to use the Lee Collet dies with this method and opened up the necks on some of my FL dies so I am not double sizing them. For me any additional extraction effort needed indicates the cases need a bump or minor resizing. This is not surprising with minimal chamber dimensions.

I drank the neck sizing Kool - aid a while ago, had trouble chambering founds after 3-4 neck sizings. Went back to FL sizing and no problems, didn't see any advantage to neck sizing. No improvement in accuracy, case life, nothing.

Ah ok, that makes things a lot more clear. To me since you're neck sizing and shooting cartridges in a chamber with very minimal head space things are getting pretty tight in your chamber after the brass tries to expand upon firing. I think you'd do better to full length size them.

I quit neck sizing about 10 years back. I got tired of having to bump back the shoulder after a couple resizes anyway, might as well do it right the first time.

I too mostly FL resize. The Redding shellholder sets that allow you to control shoulder bump while still adjusting your die so the shellholder contacts the die firmly is a real help in my opinion. I have the Hornady kit to measure case length to a datum line on the shoulder, and measure a few cases after firing, then choose the shellholder that bumps the shoulder where I want it, usually .001 to .002" as Tejano said for varmint and target loads, and .002-.003 for hunting loads.

Bumping the shoulder back near as I can tell is FL sizing but sizing to fit you chamber. Neck size till the case's won't chamber any more then start adjusting the die down until the case chamber's easily. You will have FL sized just to fit that one certain chamber. I have 2 234's and both have their own dies set up this way and locked in. Another term is partial sizing, make the case fit the rifle it came out of!

The sized cases chamber fine. The rifle's action is designed to use the camming surface to start the extraction. I'm not seeing a problem.

If on the other hand, the cases chamber fine, but it is hard to get the bolt open, that does not indicate a problem with the brass. It may indicate a problem with the action - perhaps as simple as a bit of grit, a burr, or a stiff mainspring, but there are other possibilities.Have you tried taking the striker assembly out of the bolt and cycling the brass using just the bolt body with extractor?

FWIW I only ever neck size. I like Lee's Collet die for the purpose. I have had batches of brass go literally dozens of loading cycles without FL sizing, in a range of calibres and actions.

A case comes out of the chamber small enough to go right back in again, unless for some reason it is bulged or out of round perhaps. Other than those situations, if it won't go back in after sizing it is because of something you did to it in sizing.

Conventional neck size dies do not support the body and can induce runout. I had a 308 neck die that put .006-.007 runout on straight cases. Now I use only Lee Collet neck sizers. Also partial full length sizing accomplishes minimal case working and you can always FL size when needed.

I agree. My runout numbers went down rather drastically after using Lee Collet neck sizing dies. I'm a big believer in them. As you say, when the need arises, now I just use a body die to bump shoulders a touch. My brass most definitely lasts longer than FL sizing every time.

A sticky case can also be caused by higher than normal chamber pressure. I've had to knock a few of 'em open with a mallet when I got a little too close for comfort. When firing neck sized only brass only the neck expands and contracts much upon firing because the case body nd shoulder were never resized and fit the chamber pretty much exactly. So the case can be a little sticky upon extraction, but not to the point you need a mallet or some other aid to open the bolt. If you have to knock the bolt open you're probably developing higher than normal chamber pressure. If that happens you need to look at your primers to see if they're flattened or check your primer pockets to see if they enlarged.

I have a .250 Savage that I had built on a Howa action that I worked a load up for. I knew I was getting close but kept trickling more powder in every time I reloaded because I wasn't seeing anything to stop me. I had gotten up to 41 grans of RL-17 with absolutely no sign of excess pressure, no sticky bolt, no flattened primers and accuracy didn't seem to be affected. However, I stopped there because I was approaching 3100 FPS with a 115 grain bullet and knew this was getting past the edge of the normal envelope with the .250 with other powders for this weight bullet.

Anyway, when I finished shooting that batch of 10 rounds and went to reload that brass, when I was priming the cases (I use a lee hand priming tool) I noticed the primers felt loose. That keyed me on to the first sign of excess pressure. Up to this point nothing seemed out of line, then all of a sudden the primer pockets were loose? Why? I figured I would have seen other signs before this. Anyway, I discarded that brass and when I loaded up another batch I backed the load off a whole grain of powder. At 40 grains I was still getting 3000 FPS but the primer pockets weren't gettng loose.

However, even so, I did further rethink my operation and figured it prudent to back it off another grain to 39 grains of powder just for good measure. With that I still get over 2900 FPS with a 115 grain Combined Technology Ballistics Tip and 39 grains of RL-17. For a .250 Savage that's a smokin' hot, but safe load. It's accurate there and it doesn't loosing primer pockets or show any other signs of excessive pressure. I learned a valuable lesson with this. Always pay attention to your primer pockets when working up a load, even though everything else looks good. Be sure they're not getting loose. If they are it's probably a good a sign your case head is expanding due to high pressure.

Now as for my load, some of you experienced guys may be thinking that 2900+FPS with a 115 grain bullet still sounds a little hot for a .250 Savage, but you gotta remember I'm shooting through a 26" barrel with a long throat. A more normal chamber and shorter barrel probably wouldn't yield much over 2800 fps safely, if that.

Correct me if I am wrong but to me a 0.001" bump each time works the brass less than letting it get 0.004" out and then sizing it back down. May turn out to be even if this only happens after 4 or more loads. Maybe someone smarter will comment on this?

Filaman what I have seen is the more progressive powders usually don't show traditional pressure indications until you are right up there. My theory is the progressives reach peak pressure further down the barrel so less effect on the case. This seems true of R26 and R16, I have not used R17. But this is also why initially people got crazy high velocities when R17 came out but there was no published data, people were putting the pedal to the metal and getting astounding results like 3,400 fps with 105s in the 243. Alliant is now showing 3,044 for the Speer 100 grain bullet, they took the pixie dust out of R17 darn lawyers.

Have covered this subject considerably elsewhere, but in general if you don't want to bother with sorting or turning case-necks, Lee Collet dies are the best deal.

If you want the absolute best accuracy, however, some sort of bushing die works even better--IF you sort or turn case necks, and do NOT use the expander ball.

From my experience I'll add another IF:

If you aren't having to size the necks down more than 4 or 5 thousandths.

For sure!

I normally use a bushing that only resizes the necks no more than about .002.

So, you're playing with empty brass to check fit, feeding, etc? You have three batches of said empty brass:
1) full-length sized
2) unsized
3) neck sized

#1 and 2 seem to be fine.
#3 is messed up.

If you are using a separate neck-sizing die, then it is out of alignment making either crooked necks or crooked bodies, thus causing a "tighter" fit than you started with.

Possibly its expander ball is much too large and is making the necks too fat upon withdrawal. Try the neck sizing without any expander ball at all, and see if those cases fit well.

Please forgive a possibly dumb question: Do you mean .002" below loaded diameter or the fired brass only comes down .002" from its fired diameter?

What I'm getting at is a situation common in 308's with factory chambers. Fired necks come out .344" or thereabouts. But Winchester brass necks are typically .012" thick, so their loaded diameter is 2 times .012 + .308 for .332". So they need sized to .330" for .002" below loaded diameter. But the amount of sizing is .344" - .330" = .014", and that's the "having to size more than 4 or 5 thousandths" I'm talking about.

So last week I sorted some .257 Roberts brass that I bought several years ago and culled about 30% that varied more than 0.001 in neck thickness. I use a Lee Collet to size the necks. Did I waste my time (and useable brass)?

Yes