Neck Tension Issue... I think

G'day team,

I've been discovering the highs and lows of reloading over the last 12 months or so.

My 7mmRM shoots pretty well. Recently I've been trying combinations of AR2217 and 162g ELD-X. Long story short, about 6 months ago I was doing some load development and had issues with excessive pressure when I was not expecting it so had about 30 bullets to "pull".

I pulled them all last night using the RCBS hammer thing. After a few, I noticed that about 1/3 of them were very easy to pull and the rest were very difficult. I'm looking for any thoughts on why this might happen and whether this could be the cause of the unexpected excessive pressure?

The bullets I pulled were loaded over two separate sessions with the same dies. I might have fiddled with the dies in between (it was a few months ago and I can't actually remember) but don't think I would have done anything too silly? Would I? All were loaded with twice fired Norma brass. All seated 0.020" off lands. All cases trimmed to whatever the right spec is. None were compressed loads. I can't think of any other variables off the top of my head? Oh, and no points for who can guess which of the projectiles below was harder to pull.

Thanks for any help in advance.

Elliott
Attachment 159086

Possible that one batch had been left a while before being reloaded. Sometimes the deposits inside the case neck harden and even corrode. Did you thoroughly scrub the insides of the necks before resizing and reloading?

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Originally Posted by Woody

Possible that one batch had been left a while before being reloaded. Sometimes the deposits inside the case neck harden and even corrode. Did you thoroughly scrub the insides of the necks before resizing and reloading?

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Didn't give them a good scrub, but they weren't left long before firing (couple of days max) and I had a good look inside the necks last night and they all looked in good nick - no corrosion just powder.

You say you may have set the sizing die diffently? If you developed your load initially with virgin brass did you actually run that brass in the sizing die before loading or not? If you did'nt, then on the second loading the sizing die may have produced different inside neck tension to the unsized virgin brass. Before resizing used brass it is a good idea to brush inside the case necks with a 7mm nylon or bronze brush. Also if you only resize the neck say half way down compared to full resize your neck tension will differ considerably.

Not the issue here but it is possible under the right conditions for bullets to "cold solder" themselves to the neck and that does cause pressure.
It was first noticed in the 20s with batches of experimental 3006 ammunition. It was known that tin not only prevented copper fouling in artillery pieces it actually removed it.
Tin washed projectiles were loaded to see if this worked in rifles and inital trials were good. Problems were encountered with stored ammunition producing excessive pressure, initally overcharging was suspected but pulling rounds showed that not to be true some had soldered to the case so the idea was dropped. The cfe powders incorporate a minute amount of metallic tin in the formula and that is sucessful.
Sorry it's a little off track but I thought it interesting

+1 for definitely running a brush down the neck before re-sizing. How many firings has brass been through ? have you annealed the brass ? After 2 or three firings the brass will harden & neck tension will get variable.
Did you by any chance weigh the powder aft you pulled the pills ? Worth doing for a few just to confirm you did not some how end up with variation in powder loaded.

Also, did you chamfer the inside of the neck mouth. If you trimned to length you must lightly deburr the inside and outside of the mouth. A good reloading manual will detail all the correct procedures.

Once an immunologist by any chance? Is the sizing die a bushing die or does it have an expander mandrel? You didn't change bushings or remove the mandrel (be pretty hard to seat into a case resized without the mandrel I'd imagine). Try seating a bullet back into the cases you pulled the bullets out of. Grab the press handle down close to the press to get a better feel of the resistance needed to seat a bullet. Pressure issues when you weren't expecting it? You didn't change primer brands or switch to a new batch of powder? are you keeping the brass trimmed regularly? you don't have a dodgy cheap electronic scale or a worn out old beam balance? Are you measuring your OAL off the ogive on all loads (i.e. OAL not creeping up)/checking for adequate shoulder bump after brass sizing.

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Originally Posted by Woody

You say you may have set the sizing die diffently? If you developed your load initially with virgin brass did you actually run that brass in the sizing die before loading or not? If you did'nt, then on the second loading the sizing die may have produced different inside neck tension to the unsized virgin brass. Before resizing used brass it is a good idea to brush inside the case necks with a 7mm nylon or bronze brush. Also if you only resize the neck say half way down compared to full resize your neck tension will differ considerably.

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Resized the virgin brass. But will definitely give the inside of the neck a good clean and make sure I'm resizing consistently, cheers.

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Originally Posted by chainsaw

+1 for definitely running a brush down the neck before re-sizing. How many firings has brass been through ? have you annealed the brass ? After 2 or three firings the brass will harden & neck tension will get variable.
Did you by any chance weigh the powder aft you pulled the pills ? Worth doing for a few just to confirm you did not some how end up with variation in powder loaded.

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Yeah will definitely brush the neck now, cheers. Two firings, brass not annealed. Powder weights were accurate.

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Originally Posted by Woody

Also, did you chamfer the inside of the neck mouth. If you trimned to length you must lightly deburr the inside and outside of the mouth. A good reloading manual will detail all the correct procedures.

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Yep, all well and truly deburred.

why are they seated so deeply????

also next time you go to pull some...seat them a TINY bit deeper first....it breaks any sealing tension and makes it a bit easier....I pulled 100 loads the other week...man some do take a few whacks till they let go.... most took 5-6 some 10....

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Originally Posted by Micky Duck

why are they seated so deeply????

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They're seated 20 thou off lands?

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Originally Posted by yerimaginaryM8

Once an immunologist by any chance? Is the sizing die a bushing die or does it have an expander mandrel? You didn't change bushings or remove the mandrel (be pretty hard to seat into a case resized without the mandrel I'd imagine). Try seating a bullet back into the cases you pulled the bullets out of. Grab the press handle down close to the press to get a better feel of the resistance needed to seat a bullet. Pressure issues when you weren't expecting it? You didn't change primer brands or switch to a new batch of powder? are you keeping the brass trimmed regularly? you don't have a dodgy cheap electronic scale or a worn out old beam balance? Are you measuring your OAL off the ogive on all loads (i.e. OAL not creeping up)/checking for adequate shoulder bump after brass sizing.

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- immunologist: once upon a time, yes
- dies are your stock standard rcbs dies
- none were Noticeably difficult to seat from memory, is there something that could cause some to be more difficult than others? How would I control for that?
- unexpected pressure in that I'd fired that charge before without any issue then that same charge caused very sticky bolt consistently after even though the charge was the same (yes, weighed extras from the same batch)
-primers and powder the same
-brass trimmed to spec
-beam scale is accurate as far as I'm aware. I calibrate regularly because science.
- measuring OAL off ogive for each bullet

Ammo exposed in hot sun or resting for long in a hot chamber may increase pressures.

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Originally Posted by Woody

Ammo exposed in hot sun or resting for long in a hot chamber may increase pressures.

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Yeah unfortunately neither of those either. Hot sun certainly isn't a regular occurrence down here.

From what everyone is saying, it sounds like I need to up my cleaning game a bit, which is definitely true. But that the neck tension might not be the cause of the excessive pressure.

I'm going to start that load development again with spring-cleaned rifle and brass, and see how we get on.

Thanks everyone for your thoughts, very much appreciated.

Elliott

Do a bit of research on "cold bullet weld". Longrange hunting.com,, should have some good reading on it...
Expander mandrels, do some research on them for setting your neck tension.... You can purchase expander mandrels from Sinclairs International, you will also need an expander die. Maybe "workshop innovation" in NZ has them in stock....

Are you using Brass from a single mfg/single batch of brass? If not there could be variations in seating pressures/neck tension between cases?

I once had similar problems with Remington Saum brass, (but I don't think it was neck tension-related). I switched to necked down 300 saum norma brass and no further issues. If you weigh 50 norma brass they generally fall within +/- 1 grain. The Remington was all over the show +/- 15 grains and there was big average variation between different bags of new brass too. I now only use norma or lapua brass for everything it is spendy but less hassles.

Usually the expander button on FL sizing die will clean a lot of the neck soot out once it has been pushed in and out again.

All you need to do is purchase some dry powdered graphite lube (the proper reloading stuff) and run a small amount inside the neck before you charge the case with powder.

This gives the projectile something to seat on which enables much better consistency and will solve your problem.

Google 'Imperial dry neck lube'

At the same time buy a proper VLD case chamfering tool as those ELD'x projectiles like a sharper chamfer angle to get them started and avoid shaving off copper jacket.

I asked about length because it sure looks to be deep in case.......most projectiles Ive loaded dont sit much below neck...boat tail normally sits at junction on neck and shoulder.

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Originally Posted by Micky Duck

I asked about length because it sure looks to be deep in case.......most projectiles Ive loaded dont sit much below neck...boat tail normally sits at junction on neck and shoulder.

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Right, well I'll certainly double check my measurements but my book says they were 20 thou off lands, which is pretty standard, and from memory the COAL was consistent with that. Will defintiekt double check though.

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Originally Posted by Woody

Ammo exposed in hot sun or resting for long in a hot chamber may increase pressures.

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was thinking simlar as a possibility.... fairly hot load in winter, now being shot in summer.

Dont know if its been covered but the inertia puller can be a tricky beast. Any alteration in orientation ( not perpindicular) when struck will result in more force or more whacks required. This could lead you to thinking neck tension variations are bigger than the fact.

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Originally Posted by Edunn

Resized the virgin brass. But will definitely give the inside of the neck a good clean and make sure I'm resizing consistently, cheers.

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Both anneal and resize virgin brass if you want consistency with later reloads. The making of the brass involves a lot of sizing operations, so safe to assume that virgin brass neck already has some work hardening present. I anneal before every resize. Since we know work hardening occurs with every resize and every firing it makes no sense to do it every 2nd or 3rd reloading cycle, who can keep track anyway.

Most (all?) manufacturers anneal as a final step once case totally formed.
Only the likes of Lapua leave the evidence. Others finish off with a polish that removes the evidence.
Cannot hurt to redo new brass though.
Yep, I anneal every firing. Never used to to. Seeing the difference with low and consistent ESs.

I've had a similar problem with both the 7Rem magnums I've owned and loaded for. No problem with w/w brass, but as soon as I started developing loads with Norma brass I started getting a few pressure spikes. Eventually found a projectile would easily slip into the neck of a fired w/w case, but not so with Norma cases. Further investigation revealed that the Norma cases either had "donuts" from new, or they appeared after the first firing. I initially solved the problem by inside neck reaming, but subsequently found that a Lee collet die would bring the donut to the outside and was easily skimmed off by outside turning. The longer VLD type bullets, such as you are loading are more inclined to bring the problem to the fore than shorter flat-based bullets, due to needing to be seated below the neck/shoulder junction. Also, the thicker Norma brass in a tight dimension chamber ( as mine both were), will elevate the pressure.
Hope this solves the problem. Cheers, John