Fireforming Brass

[hardy]

Hi All, when fireforming once fired brass from another rifle with a larger chamber I FL size until I can just close the bolt with a slight resistance.Now,I never shoot full house loads in my old military rifles so I fireform using a "medium"chargeof 10 grns Unique under a 180 grn boolit seated out to just engrave the rifling in my #4 Mk1.Then I,ll use 12 or 13 grns for my shooting loads,same boolit wt. These shooter loads chamber easier than initial sizing???.Am i not using a warm enough F/F charge?They shoot fine.Then I neck size only and they shoot likewise.What,s the collective thinking?If it aint broke,dont fix it,eh? Thanks,Mike

[405]

I'd think if it ain't broke- don't fix it. Hard to say why you're feeling resistance on the second firing. I fire form brass in much the same way but use hard cast bullets crimped and seated for firm contact into the lands when chambered. I use medium charges of something like 4895... yielding about 30-35K PSI. That way I know, for bottleneck type cases, the head is held firm on the bolt face and the case is forming completely where it should- in the upper body and shoulder area.

The body of your pick up brass may be hard or is work hardened and taking a "set" to your chamber. The resistance you feel on chambering the second firing may be a little contact with the shoulder or just the body taper of the case and expanded lower body- if it has taken that "set".

Now, the one thing to check that I can think of that may be broken and needs fixin' would be case length that is too long. You could take one case that shows the resistance when chambering and trim maybe .010" off the neck. Shooting rounds where the case mouth is crimping in the bullet as the case runs into the end of the chamber is not good-- not likely but possible. So, not at all sure the reasons- just some guesses.

[220swiftfn]

Hi All, when fireforming once fired brass from another rifle with a larger chamber I FL size until I can just close the bolt with a slight resistance.Now,I never shoot full house loads in my old military rifles so I fireform using a "medium"chargeof 10 grns Unique under a 180 grn boolit seated out to just engrave the rifling in my #4 Mk1.Then I,ll use 12 or 13 grns for my shooting loads,same boolit wt. These shooter loads chamber easier than initial sizing???.Am i not using a warm enough F/F charge?They shoot fine.Then I neck size only and they shoot likewise.What,s the collective thinking?If it aint broke,dont fix it,eh? Thanks,Mike

Perfectly normal and expected..... You're forcing the headspace with the shoulder when you do the "light crush fit" to fireform (slight resistance going into battery.) Then when you fire it, the case fills out to the chamber and springs back a little, leaving you with a case that mirrors the chamber (not just "kinda resembles it" like when it went in.....) Sounds like you're just about right with the F/F charge, unless you're getting sooting on the outside of the case.....



Dan

[curator]

Check to see if the case heads on your fireformed brass are still square with the body. Stand them up in line on a flat surface to see it they tilt one way or another. I have had this problem where the bolt face was not perpendicular to the chamber axis resulting in off-square case heads. Orienting cases the same way each firing eliminated the problem. So too did squaring the bolt face.

[hardy]

Gotcha! Thanks for all the info.I,ll check out all the suggestions and report back.Be safe,Mike.

[hardy]

Hi All, Glad to report no sooting,bolt face is square and no noticeable case stretch and all rounds chambering OK so thanks again for your input.Mike

[canyon-ghost]

Isn't broke, don't fix it. Lol, sounds like the right way.