Fire-lapping with/for PP

[303Guy]

There has been a bit of discussion on fire-lapping using papter patched boolits as well as plain cast, jacketed and brass fire-lapping bullets (mine).

Well, here is an example of a rusted bore before and after fire-lapping.



The short bit of muzzle was cut off before commencing fire-lapping and then a bit more was cut off to get to 'good' rifling.

PPCBoo fired in fire-lapped bore with recovered patch.



Boolit fired in mint bore for comparison.



Recovered PPCBoo's. No patch recovered other than a tiny fragment.



The recovered patch fragment is that bit at bottom right.

[matm0702]

Hi 303 Guy

Did you fire lap with paper only or did you apply any sort of polishing compoumd?
I have a No#4 with a sharp bore with some darkness in the grooves I've not been able to eliminate.

Mike

[pdawg_shooter]

My No4 Mk2 still had reamer marks on the top of the lands when I got it. A couple hundred PP bullets, no lapping compound, and the bore looks as good as my Douglass barrels.

[RMulhern]

303 Guy

WHAT.....alloy are you casting?? Your bullets have an awfully strange color to them??

Doesn't even appear to be lead!!

???????

[docone31]

Be gentle with him,
He is a Kiwi.

[303Guy]

Alloy? Nah! We got gold in dem 'ills!

matm0702

For that particular bore and two others with heavy rusting I used a special brass 'fire-lapping bullet' laced with valve grinding paste.

This is the one I used in this bore.


The grinding paste is squeezed into the grooves as the 'bullet' is seated by hand into an unsized neck. No gringing paste is exposed, i.e. it is fully contained in the neck. The bands exposed up front serve to guide the 'bullet' for dead straight entry into the throat and bore. The front bands are sized to just enter the throat on chambering. The undercutting between the nose/bore ride band and the next band is simply for weight reduction so the 'bullet' can accelerate quickly with light charges.

[303Guy]

This will give some idea how poor the rifling is in this gun.


Been testing it with ever increasing loads of AR2205/H4227. The last one left a lead coloration on the lands.


Hollow Point

I'm thinking it's probably not a good idea to be on the recieving end of these boolits!

[lwknight]

That is some of the best shruming that I've seen. Thats better than any high dollar "J" bullets. It gives me an idea that a little tin makes the boolit tougher and hold together better than pure lead.

My water tests with SJHPs showed too much weight loss due to the lead erroding away as it expanded.
Since flat trajectories are the rage and commerce goes where the money is, they trade away terminal ballistic performance for more aero-dynamic pointed bullets that have to be made from pure soft lead in order to expand.

[303Guy]

I didn't think the weight retention would be that good but I just weighed them and I had to sit down! How does 99.99% retention sound!

The first boolit in the line-up turned completely inside out. It left the muzzle weighing 209gr and now weighs 211.5grs! (That's due to adhearing sand).
The second one weighed 246.5gr and now weighs 246grs!
The fourth one was beginning to fail and that still weighs 215grs!

Holy moly, it's better than I thought!

The alloy is mostly lead pipe with some lino in it but very soft.

[Three44s]

It takes talent to produce bullets that gain weight after firing!!

Just kidding ....... very nice!!!

[yondering]

Alloy? Nah! We got gold in dem 'ills!

matm0702

For that particular bore and two others with heavy rusting I used a special brass 'fire-lapping bullet' laced with valve grinding paste.

This is the one I used in this bore.

How many of these did you use for firelapping? Looks like they would be expensive. Why not just lap with lead bullets?

[303Guy]

It takes talent to produce bullets that gain weight after firing!!

Hee hee. Yeah! After cleaning off the sand I was astounded at how little weight was lost! That was a soft alloy too!

How many of these did you use for firelapping? Looks like they would be expensive. Why not just lap with lead bullets?

They would be expensive to buy, yes. But my time is free, so ....

It took two of those - the second was for good measure as the first one seemed to have taken out all the rust including inside some deep pits.

No reason not to use paper patched boolits with a soft core and enough charge to upset the core enough to get into all the corners. I haven't tried patched fire-lapping as a first resort on badly rusted bores (because I didn't have to).

[runfiverun]

i know docone has used lapping compound on p/p to clean out at least one bbl.
airc, he used a final diameter of 313 and added the compound to hit @314 the size of his bbl.
peter, i told you tin had some uses.......
other than mold fill out.

[docone31]

My final dia on the patched casting is .314. I used the lapping compound on .3135. Not only did I get my finished diameter from that, the lapping compound really cleaned the barrel.
I had hammer marks from the chamber to the muzzle. The lapping compound completely eliminated them.
.313 would have been too sloppy.
I had tried my patched loads at .3135. I got perhpas 20 min of berm! Same as with jacketeds.
The only reason I tried this, I had nothing to lose and barrels are not that expensive for my rifle, headspaceing is a snap.
It all came together. Only took less than 20rds. total.