Would S type Bushing help in Lowering ES

[merbeau]

Currently I am loading for a 6.5 x 55 SE using Lapua brass, an RCBS FL X die and Forster competition seating die. After firing, the resizing die is set to bump the shoulder back 0.0015 inches. The load consists of 46.5 grains of RL 22 using Lapua Scenar 136 grain bullet seated off the lands by 0.002, and CCI BR2 primers. This load is shot from a custom rifle set up for long range shooting and produces groups of 0.4 inches center to center at 100 yards and will hold less than 1 inch at 300 yards.

The velocity is 2850 fps with an ES of 18 which may be ok for the ranges shot to date but may not be suitable for long ranges, say from 600 to 1000 yards. I want to try to see if I can get the ES lower. Would going to a S type neck type bushing die help in that regard? I have read that there is no need if using Lapua brass.

Thanks

Robert

 

[ShtrRdy]

Is the brass still new, or has it been once fired?

 

[SealT5]

OP can you measure how much neck tension the FL die giving you?

 

[merbeau]

Thanks for replying.

The brass is once fired. I typically fire form my new cases using cast bullets and loads found in the Lyman Cast bullet manual.

According to Redding the neck diameter range for the 6.5x55 is 0.288-0.296. The diameter of the Lapua brass plus bullet is 0.2950 for my combination. The numbers are consistent only varying in the 10 thousand decimal. It would appear my round is at the upper end of the 'normal' range.

Thanks

Robert

 

[Mikecr]

I suspect that bushing sizing of the neck will provide far more consistent neck tension. This should help with ES.
You may need to shoot another ladder & adjust your powder load with this sizing change.

The whole notion of brass brand making a difference is hogwash. By your neck OD measure your necks are 15.5thou thick, which is a lot. The thicker necks are, the higher the tension, and the higher the variance of tension. Probably not what you'd want to here.
But I would not change anything, extra annealing or neck turning, until fully exploring the neck thickness and clearance you currently have. Your results might be really good just like it is.

 

[Greyfox]

For optimizing ES from the sizing die standpoint I will measure runout and neck thickness/tension consistency. With S dye bushings, I like light seating pressure and select a bushing that gives .0015" of neck tension. Also, do not tighten down on the bushing. Back off a bit do you can hear a faint clicking when shaking the dye. This can make a difference in runout which I try to keep under .002" or less. Make sure the lettering in the bushing faces the bottom of the dye. Neck wall thickness with Lapua Brass is very consistent. While other factors come into play for achieving single digit ES, I have had goo success with the Redding S dyes in this respect.

 

[merbeau]

Thanks for the information - the neck thickness of the Lapua brass is thicker and the water holding capacity is about 1 grain less than for Norma which I have a limited number of pieces.

Thanks GreyFox for the tips. I will try using the neck tension suggested and for setting the bushing inside the die. Mikecr, yes it may require adjusting the load after reducing the neck tension.

 

[J E Custom]

The main advantage to the bushing dies is the ability to size the necks to exactly the dimension/ tension you want without altering the expander ball. the other advantage is that if you remove the expander before you size the necks, you will cut the work hardening in half and brass life will be better.

A mistake some people make is to size the neck with the expander ball still in the die and the bushing sized neck is then expanded when the expander ball is pulled through the neck on the up stroke. negating the benefit of the bushing.

There is nothing wrong with ether method as long as they are not combined.

J E CUSTOM

 

[Remmy700]

I found the best ES using bushing dies with expander completely removed. In most instances I can keep SDs below 5 usually around 2. While that is not the end all be all of gaining low numbers neck tension does play a great part of that. I have in the last few months went to using Sinclair expander mandrel with NT mandrel installed. Since I have done this it seems despite what die I use whether whidden, redding, forster, or hornady by adding the mandrel as my final step have been able to achieve super low numbers also. I can feel the consistency on bullet seating. As mentioned this neck tension is not completely the answer but a large part of the equation. The other large part is super consistent powder charge. I run a A&D Fx 120i and after moving to that from a chargemaster I also seen drastic drop in my ES numbers. With all this coupled together I feel as though I have found my recipe to making the best possible loads I can on my Co-ax. Despite the die on my bench, not a single one of them has an expander installed.

 

[Greyfox]

I have had several cases over the years when my run-outs/ ES were better with the expander then without. When I do there is usually only a slight resistance that is felt when the expander passes through the neck. I will generally use the dye without the expander but if I'm seeing issues with runout or ES will try the expander. My current 6.5x284 custom is a case in point. My runout is 0-001", ES <8FPS, with .25MOA accuracy. The bushing applies .0015" of neck tension with Laoua brass. I never say never!

 

[merbeau]

Sounds like the word Experiment is the answer. Start with no expander and purchase several neck tension bushings. Test those combinations and then if no significant results, then try the Sinclair mandrel combination. I should mention that I have tried an alternative primer, Winchester standard large rifle and ES was 20 and the resulting group did not change. I still can not find Federal or Russian primers in my local supply stores or the Internet for that matter and have essentially abandoned that avenue. I also tried using the gram part of my scale which gives an extra digit of significance. I measured and weighed the Lapua bullets which are extremely consistent - the only complaint is the meplat on the bullets which are terrible. I use a Hoover trimmer.

 

[lancetkenyon]

What about using your standard FL non-bushing die and then running them through an expanding mandrel with a .262" pilot? Should give you consistent .002" neck tension.
And anneal the case necks of course.

 

[Remmy700]

That is what I do a great deal now. Use regular FL non bushing die with all the guts ripped out and then use the NT .262 mandrel. I am not using a bushing to set the next tension but I am using the mandrel so why have a bushing. Works very well

 

[merbeau]

Following up. Sinclair offers both a 0.263 and 0.262 mandrel. Why the 0.262?