Thread: Neck Tension Issue... I think

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

Originally Posted by Woody

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

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.

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.

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.

Originally Posted by Woody

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

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.

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.

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