Standard chamber: Neck turn&bushings, or size up on a mandrel?

[Lukas_K]

Here´s a tricky one. On both my T3s (6,5x55) I have good results with Norma brass, very slightly neckturned (just taking off high spots) to .2925 loaded dia. Fired neck measures right at 0.299, so the chamber should be at .300 real dimension. I anneal after every firing and reload them with a .291 redding bushing (FS+bushing die). My ES is 3-4m/s, accuracy is great (0.5MOA).

 

The work involved, though, is daunting, as we loose and have to replace the brass pretty often.

 

I´m wondering where would it lead me if I stop neck turning, use a bushing according to the thinnest case (will be .292-.293 on un-turned brass) and run the cases over a K&M expanding mandrel to even them out before tumbling and seating the bullets.

 

Anybody practically compared the two approaches before?

[jcampbellsmith]

The advice I was given was to size the neck back down in two steps, ie using two different bushings in succession. Going down a max of 5 thou at a time. It worked fine for me on factory chambers and cleaned up brass.

 

Regards JCS

[Lukas_K]

On non-turned brass? Honestly one-step sizing this amount doesn´t give me any trouble, regular annealing may be helping with that. However if I stop turning the necks, after sizing all to one outside dia, the will all have a different inner dia, and therefore neck tension (plus concentricity issues, as the bullet will seat in the path of least resistance). Won´t use an expander ball in the die, but I guesstimate that expanding them on a proper mandrel could solve the uniformity between them.

[onehole]

7 thou of neck clearance is quite a bit?,,,,,,,to be honest a Lee neck die would do as good a job as any of making up a straight round,,,,,,,,,,,,not joking,,,,,,,,,O

[Chanonry]

Worked up loads with my mate on his T3 in .308. It shoots a lot better than .5 moa (off a rest) without any of your turning, annealing etc. To be fair that did surprise me, but targets are evidence.

 

There are a heap of things that you can do but no-one ever seems to perform any testing that is statistically valid to demonstrate that it is actually worthwhile on their system. Someone reads the F -Class boys say three prayers before seating the bullet so they start doing it on their Tikka Hunter. Not worth the effort generally.

 

The reloading steps you are applying are not addressing the limit in your system. Your ES is great but your precision (as opposed to accuracy) is not which implies your ammo is great but there are 'issues' elsewhere in the system.

 

You don't quote any numbers on runout? Not controlling that ??

 

So in answer to your question - try it. Try being even more minimalist. Just size the case load it, see where that goes. Load 20 of each. Shoot 4 groups of 5. Do more valid tests. I don't think that is statistically valid either but I am guessing you don't want to load 50+ of each. Then let us know what happened

 

You can either a) keep doing what you are doing. No harm in it, just not the limit in your system look to improve elsewhere barrel, bedding or bullet (or the shooting test itself). c) just leave out most of those steps and get the same results

[Lukas_K]

Honestly I don´t look for any improvement in accuracy/precision department. Reliable half minute is pretty much alright for me and my shooter/rifle combination; did 0.69 MOA at 500m yesterday, windy conditions, and shot on command - more than happy with the result. If you are used to do better than that on any day, on command (not waiting for conditions) and in competitions, well, more wins and glory to you

 

What I started this thread for was TIME economy in case prep in order to be the most time-effective while keeping the results on target, as I regularly loose 5-10% of my cases every comp.

[Lukas_K]

Anyway, talking new barrels with Nick over the weekend, I expect to be replacing these two over the winter. Can as well burn them out testing different methods.

[Lukas_K]

Went through some testing, tried as many combinations as I could, all on the same load and two OALs I know the rifles perform well at:

 

(1) neck-turned and appropriate bushing only;

(2) neck-turned, tighter bushing and expanded back up;

(3) neck-turned, standard die (way undersized neck) and expanded back up;

(4) no-turn with a bushing according to thinnest necks, expanded back up;

(5) no-turn with a standard die (way undersized neck) and expanded back up;

(6) no-turn with a collet die;

 

Here are the general conclusions:

 

1) To the question I set out in the beginning: yes, I would do fine without neck-turning. At least on shorter ranges.

 

2) Without regards to method used, thicker the neck = higher the velocity (if other variables are the same - load and OAL). Cannot find any direct relation to neck clearance, apparently once there´s enough, it´s only the grip on the bullet that changes with the thickness of the brass wall (lesser neck, lesser grip).

 

3) No-turn brass shot better at less jump; would need more testing to be sure, but i´d say here it´s not a question of the jump itself, but the grip on the bullet. That shorter bullet/neck contact on thicker case +- equals longer bearing contact in the thinner neck. Chrono agrees (same median number)

 

4) Without regards to method used, all neck-turned variants have better ES/SD numbers. Using a collet die gets closest to single digit numbers on no-turn brass.

 

The last point is what seals it for me - shoot over 500m all too often,

 

ES from best to worse according to method number above: (1), (2)+(3) equal, (6), (5), (4)

 

Sorry, no pictures, have only my notes hand-scrambled on a piece of wet cardboard.

[Andrew]

When do you find time to shoot? That's a lot of fuss for a factory chamber/ factory rifle. I don't have any problems hedging half MOA with out any of this.~Andrew

[Lukas_K]

Half MOA at what distance? I´m not really interested at 100m. Yes, I can load that without much extra effort, too. But further away? As in everyday repeatable performance, not choose the best group of the day?

 

I require consistent ES numbers and predictable velocity across a range of different temp & weather conditions. This - from last comp in Senica: 500m - 0,69MOA in gusting 3-9m/s wind. Shot on command, 5 rounds in a limit of 2 minutes.