Gunsmithing Big bullet jump - throat damage?

[palma]

I'm fireforming some loads for a new ackley improved. The rounds are loaded very short, and the throat is very long. Jump will be at least 0.1". Is there a greater risk of damaging the lands from a bigger jump? I could care less about accuracy from these loads and doubt that I'll even set out a target. Most likely the rounds will be fired directly into a berm.

 

[Criver600]

Re: Big bullet jump - throat damage?

No damage from jumping 0.1". What have you done to ensure positive head-space? False shoulder? All of my Ackley Improved cartridges shot extremely well during fire-forming.

 

[palma]

Re: Big bullet jump - throat damage?

Length of brass is long so bolt closure is tight (i.e., crush fit). Head space is fine. This is a new gun.

 

[tfsron]

Re: Big bullet jump - throat damage?



If you don't want the wear on the barrel from fire forming, use cream of wheat.

Good shooting
Ron

 

[Red_SC]

Re: Big bullet jump - throat damage?

I have a factory barrel or two that require a jump that far or more in order to fit the round in the magazine- and they still shoot well. Don't worry about it, it's fine.

 

[donovan]

Re: Big bullet jump - throat damage?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ron Morrison</div><div class="ubbcode-body">

If you don't want the wear on the barrel from fire forming, use cream of wheat.

Good shooting
Ron

</div></div>

+1 all my AI cases where formed this way.

 

[Austan]

Re: Big bullet jump - throat damage?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: donovan</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ron Morrison</div><div class="ubbcode-body">

If you don't want the wear on the barrel from fire forming, use cream of wheat.

Good shooting
Ron

</div></div>

+1 all my AI cases where formed this way.</div></div>

Either of you guys want to write up exactly how that's done. It would be helpful for those of us who don't know the technique.

 

[tfsron]

Re: Big bullet jump - throat damage?




The "Cream of Wheat" method is a light charge of a pistol powder, a small wad of toilet paper, Cream of Wheat ™ or other similar inert filler (fine filler will pack too tight when firing), and a wax plug, but NO bullet.

To determine how much powder to use (I use bullseye, others would also work), fill a unformed case 10 percent full of your pistol powder. Should be about 10 Gr. for 223 type cases, 15 Gr. for 308 & 3006 type cases, 20 Gr. for bigger cases. As long as you do not overload the case, this is not critical.

Drop in 1/4 sheet of of toilet paper into the case and pack it down. Next, fill the case to the neck with your cream of wheat, pack it down. Finally, plug the case with paraffin wax, pack it down. I force the case neck into the wax. The wax is there to keep everything together until you fire it. The case is now ready to fire.

If it doesn't form well when you fire it, use more powder. Just don't get too carried away, the shoulders don't need to be sharp, you are looking for the basic form.

Good shooting
Ron

 

[Austan]

Re: Big bullet jump - throat damage?

Thanks for the write up Ron.

 

[Cheyenne19]

Re: Big bullet jump - throat damage?

My fireforming loads shoot very well. I wouldn't waste my time with COW.
What AI case are you working on palma?

 

[BLAWTON]

Re: Big bullet jump - throat damage?

A false shoulder is the best way to form cases. The COW is a messy PIA and i will never do that again. It doesnt always form the case all the way like a real bullet and charge does.

No a jump of even .25" isnt going to harm your throat in the gun. Pushing bullets into the lands will cause more erosion the jumping them.

 

[E.Shell]

Re: Big bullet jump - throat damage?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: NotAGuru ⊕</div><div class="ubbcode-body">A false shoulder is the best way to form cases. The COW is a messy PIA and i will never do that again. It doesnt always form the case all the way like a real bullet and charge does.....</div></div>
Absolutely. I always set up a secondary shoulder in my AIs and when I used to make .35 Whelens from .30-06s. I also had to do that with a .35 Remington Contender or suffer head separation in just a couple loadings.

Fireforming loads have always delivered excellent accuracy for me and I use them to practice marksmanship.

 

[sobrbiker883]

Re: Big bullet jump - throat damage?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: NotAGuru ⊕</div><div class="ubbcode-body">A false shoulder is the best way to form cases. The COW is a messy PIA and i will never do that again. It doesnt always form the case all the way like a real bullet and charge does.

No a jump of even .25" isnt going to harm your throat in the gun. Pushing bullets into the lands will cause more erosion the jumping them. </div></div>

Nice to hear someone "in the know" with barrels finally say that!! I gave up chasing lands when I was thinking about how FGMM can shoot so well in so many tubes...I figure chasing lands is a longshot bet that the erosion will remain perfectly concentric as it progresses.