Reduced loads for fireforming

[chas442]

I am the process of fireforming 7.62x39 to 6.5 grendel. It appears the general consesus is to go to the minimum advertised powder charge. I did some measuring using AA 9 as it is a fine grain powder.
Brand new unfired Starline 6.5 grendel would hold 33 gr of AA 9.
Unfired but formed 6.5 grendel ppu using ppu 7.62x39 would hold 30 gr of AA 9.
Fireformed 6.5 grendel ppu from above would hold 33 gr of AA9.
This was done with overflowing the case and using a playing card to scrape off the excess.
I did not report the 10ths of a grain. All measurements exceeded the posted weights.

Referencing Hodgdons load data, it appears that if you use the minumum load data of a given powder you might be at or over maximum charge when fireforming.

With this info, it would appear the general consensus will not apply in all cases.

I would appreciate any and all comments

TIA

 

[AJC1]

Most people fire form with a very small charge of a fast pistol powder like red dot or bullseye

 

[Mr_Flintstone]

I have fireformed carcano brass by using a large pistol primer, 5 grains of Titegroup, and top off with corn meal and plug with paper towel. It may not be the preferred method, but worked for me.

 

[Nature Boy]

I fire form my 6BRA with a load suitable for its parent case, the 6BR, which is a couple of grains less. This is for using a same diameter bullet and not corn meal.

 

[AJC1]

I fire form my 6BRA with a load suitable for its parent case, the 6BR, which is a couple of grains less. This is for using a same diameter bullet and not corn meal.

If he has the ability to create a false shoulder to align the case this would be my preferred plan. Some people have the tools others dont.

 

[FROGO207]

I initially fireform using 5 or so grains of any fast handgun or shotgun propellant I have left in a canister and cream of wheat over that with a wax plug in the mouth. Worked well for years so far.

 

[Walkalong]

I fire form my 6BRA with a load suitable for its parent case, the 6BR, which is a couple of grains less. This is for using a same diameter bullet and not corn meal.

I did basically the same thing, but I used a couple of grains short of what would be my full charge for 6 Dasher to fire form 6 BR cases into Dasher cases.

If you use reduced charges to fire form, it's generally not fully formed, especially in the shoulder.

 

[codytrucker]

I can't tell you the best way to fire form cases , but I ordered 6.5 grendel cases from starline monday on backorder and they already shipped , supposed to be here monday .

 

[Varminterror]

If he has the ability to create a false shoulder to align the case this would be my preferred plan. Some people have the tools others dont.

Converting 7.62x39 to 6.5 Grendel, we don’t need a false shoulder - we’re pushing the shoulder back anyway, so we have almost all of the finished shoulder where it will end up - but the body taper needs blown out to fill in the OUTSIDE of the shoulder of the Grendel chamber. So he can largely use just a mild load and blow out just fine. No corn meal, no wasted primers, no bullet jam or false shoulder. Much more like fireforming AI cartridges, not really like blowing shoulders forward like Dashers.

 

[AJC1]

Converting 7.62x39 to 6.5 Grendel, we don’t need a false shoulder - we’re pushing the shoulder back anyway, so we have almost all of the finished shoulder where it will end up - but the body taper needs blown out to fill in the OUTSIDE of the shoulder of the Grendel chamber. So he can largely use just a mild load and blow out just fine. No corn meal, no wasted primers, no bullet jam or false shoulder. Much more like fireforming AI cartridges, not really like blowing shoulders forward like Dashers.

Sounds like a minimum charge and a range day situation.