How far to jam projectiles when fireforming 6BRX?

[Fordnutter]

Hi Guys,
I'm due to get my 6BR back from the gunsmith this week rechambered to the 6BRX. My go to load in it's previous 6BR life was 29.8gr Varget, CCIBR4 primer & a Berger 95gr VLD jammed 0.010" into the lands with a .268" bushing (neck is .271"). I'm figuring I'll use exactly the same load but with the projectile jammed further into the lands for the purpose of fireforming & hopefully still be accurate enough for some varmint blasting. The question is how far should the projectile be jammed to ensure the case is kept hard against the bolt face during fireforming?
Any advice is greatly appreciated

 

[uncleduke]

On the main site page go 6br improved. There's a lot of info.

 

[Fordnutter]

Yeah had a good read of that but it didn't really say how far to jam projectiles if you were relying on the projectile only for headspacing. I were thinking 0.030" into the lands should be allright but I have read posts of 0.060 or even 0.100" into the lands. Is 0.030" enough of a jam or will I likely need more?

 

[limbic]

Hard to say. I would use a tighter neck bushing to make sure that he bullet doesnt ride back into the brass. I tried the "jamming the lands" approach but was quite unsuccessful. I got an expander mandrel and die from Sinclair and began to use the false shoulder method. It worked like a champ.

I don't know what my problems was. I think that it was a combo of not knowing exactly where the lands were as well as not enough neck tension.

Personally i've never jammed a bullet more than .040 into the lands. No specific reason but I usually find something else that works better (change primers, ect) than jamming further into the lands.

 

[Ackman]

Like with an AI, jamming the lands isn't the right way to blow a shoulder forward. And that shoulder goes forward a considerable amount. I'd never ever try to form that case by jamming the lands. Do it right and neck to .257, then back down to 243 and headspace on a false shoulder.

 

[jr600yd]

I know a lot of shooters don't like the "Jaming" method to fireform 6BRX brass. I'M not one of them. I fireformed 300 cases of 6BRX by "jaming" the bullet and didn't lose a case. My load was 29.5grs of Varget, Lupua 6BR case, rem 7 1/2 primer, Berger 105 VLd's. I fireformed these in several 600yd matches and placed very well. Rifle is a Remmy SA with a 30" Krieger 1/8 twist.

Good shooting, Jim

 

[Klong]

Fordnutter, I have fireformed around 100 cases that way with no issues. The right amount of jam is enough to make the round go boom! The purpose of the jam is so the case does not move forward at the primer strike. Since you are not headspacing on the short shoulder , you have to headspace on the jammed bullet.

I currently have 100 cases with the false shoulder method sitting in the reloading tray to load up. I will see if there is a difference.

 

[Fordnutter]

Thanks for all the advise guys.
Well I loaded up 25rounds using a .267 bushing, 95gr VLD jammed .035" with 30gr Varget & had great success in the field fireforming on some varmints. Didn't get a chance to accuracy test load but can't be too bad as were still head shooting rabbits at 200yds. I did have two miss fires but I did notice when seating the projectiles the neck tension felt less on these - by easing the bolt open & back slightly must have drawn the projectile out enough to then happily fire once closed tight again. I think some lube may have sneaked into those necks. Judging by the cases I think I could still bump the powder charge up slightly for a sharper shoulder.

 

[6BRLongRange]

I used .003 neck tension, .050 into the lands and fireformed 300 pcs without any issues.

 

[nfa1eab]

There have been posts by a very knowledable gentleman on this forum explaining the reasons why using the false shoulder method plus bullet jamming is far superior to simply jamming. Had to do with the case moving forward and stretching at the body above the web which is bad JuJu. Could not find fault with his logic or personal experience. People have had success just jamming, but I deferred to his logic and knowledge. I have used this combo method very successfully and have not lost a single case in more than three hundred formings. I formed with 107 Sierras and 30.5 gr. Varget. Quite accurate as well while forming. I used a .267 bushing in a Type "S" FL die for good grip on bullet. Mine is a Remington action and I had Gretan bush the bolt with the .062" firing pin. This eliminated primer piercing concerns entirely. I would highly recommend it. Good luck with the BRX. It is a phenomenal cartridge and drives 107's and 105's at 3,025-3,035 with accuracy and good case life. They go where you point them. You will enjoy it.

Favor Center,
Ed

 

[rcw3]

I think the optimum technique to be used to fire form (bullet jam only vs false shoulder) is somewhat dependent on the equipment you have as well. For example I have a Barnard P action with a 6mm Dasher barrel on it and I bullet jam only and it works great and the cases come out very consistent as to each other in OAL, etc. That action has no ejector (i.e. pick the case out after each shot) and it has a Sako style extractor that pops over the rim of the case easily when you chamber a round. That set up makes the bullet jam technique very feasible. Now if you have an action with a stiff plunger style ejector and an extractor that is hard going over the rim of the case, it can push the case forward hard enough to make the bullet jam only technique not optimum, in which case the false shoulder technique may be better. I personally don't like doing false shoulders because it overworks the neck brass a lot (i.e. expand it way up then take it back down again to load it for fire forming).

I used .025" jam for fire forming my Dasher with no issues.

Robert Whitley

 

[jr600yd]

Robert has a good point about bolts wth ejectors like a Remington. When I fireform for my BRX I remove the ejector from the bolt. I don't know if this has stopped problems from starting or not but I haven't had any and this has turned into my preferred method. I also found having the bolt "Bushed" eliminates almost all primer failures when I do my part in case prep.

Good shooting, Jim