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All Springer/NP/PCP Air Gun Discussion General > PCP/CO2/HPA Air Gun Gates "The Darkside"

Cleaning lead fouling?

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Greg_E:
Since I have a scrap barrel, it would be very interesting to tap a few points for pressure measurement, but no idea how to find those devices or the cost. Even just a single one at the muzzle to grab that last millisecond of pressure before the round exits.

I think your pressure graph highlights the problem I'm having with the Lyman 356637 cast rounds. Since the bullet pushes right up into the rifling, it takes longer to get moving and less air will flow before it gets down the barrel, these are routinely 3/4-4/5 of the speed I would expect. They go down the barrel hard when pushing them through until the rifling is fully embossed. The Griffin boat tails are more pointy and seem to have a lot less effort to get going, even though they are similar size, and similar contact area. I can't test lead hardness past a 6B pencil, and this pencil scratches/digs into both rounds with ease (good lead will do that, should have learned that lesson earlier).

I have not pushed any more of the Nosler rounds through, they are all nominally .357 and I wanted the bigger size to check lands and grooves to see what size I was at. Now I can go back to sizing everything to .357. I'll probably size down to .356, powder coat, and then squeeze them back down to .357, and hopefully do that tonight and maybe get the barrel put back together. My last Friday off is very near and I want to get out to shoot without the normal weekend crowds.

subscriber:
Greg,

I know that you don't plan to lap your new barrel (right away, and only if indicated).  That said, I have reconsidered the method I would recommend to fire lap it:

I think that imbedding grit into bare lead by rolling between steel plates (or glass plates or pellet can lids) will produce more controlled results.  Certainly, compared to placing a somewhat uncontrolled amount of grit paste into the breech ahead of the bullet. 

My concern is the potentially variable dynamics involved when the bullet nose rides over the wave of grit paste.  I am less concerned about this method when using pellets because the narrow head and skirt contact rings would tend to sweep most of the loose grit ahead of the pellet; and ahead of the skirt.   

Any "logjam" with grit paste ahead of the head or skirt and the somewhat fragile head and skirt will simply push out of the way as a sort of safety valve.  I am less confident about such a sweep and relief mechanism working with slugs.   I would be less concerned about a wadcutter with a number of narrow grease grooves, where excess grit paste can be swept along.

Even something like this Benjamin air rifle slug would be preferred, if you bundle a bunch of grit paste into the breech, rather than imbed a smaller quantity in a longer bearing length slug: 



https://www.pyramydair.com/product/benjamin-nosler-ballistic-tip-extreme-air-rifle-bullet-357-cal-145?p=889

https://www.ebay.com/p/1000347641


I would be willing to try the "dust the breech method" with regular slugs, but not in a brand new barrel that looks almost perfect already.  I certainly would not want to lead you astray, into ruining an otherwise good barrel.


Edit, perhaps you were planning to use something like these:  https://www.pyramydair.com/product/air-venturi-356-cal-127-grains-flat-nose-100ct?p=955



I would have less objection to them using the "breech dusted" method due to the short actual contact bands.


If it were not for your shallow breech remark, I would recommend these:  https://www.pyramydair.com/product/air-venturi-358-cal-190-grains-flat-point-50ct?p=1442



I would consider rolling the above slugs in grit paste, assuming that if loaded fast the breech o-ring would not wipe off all the grit from the nose flank and out of the grease grooves.  However, if these slugs are too long already, then starting with the shorter ones makes sense.

Greg_E:
Thanks for the update. I'll probably try to find a different "heavy" round for a while and see how things go before I think about opening up the chamber. Been looking at a Lee 150gr that might fit better, and I think my dad might have that mold so I could borrow it. With the round nose it curves a little more gently and might give that slight amount of jump needed to have a little energy to get past the initial embossing.

When it is time to cut the chamber deeper, I'll probably buy a reamer. Need to send a message to Brownells and see if they can help.

Greg_E:
This barrel made some progress over the previous. Speeds with the Lyman 147gr haven't really changed, I didn't really expect it. The good news is that on the few that weren't mangled in the trap, I can see that the powder coat is not cut down to the lead like the last barrel. So there's and improvement.

Going to have to look back at the poppet to see if I can figure out what it is so different from the previous. I may need to pull the valve and examine it too. Seems like the valve return spring is stronger, and I think I remember the poppet being a different length which might be limiting my first few shots up at the high pressures.

I have about 100 rounds ready to go for the next time I can get out shooting. Only going to put powder coated ammo through this for a while and see what happens. That's 10 more fills worth of air, or probably several hours worth of shooting, then filling.

I'll have to try and get a picture of some of the recovered rounds.

subscriber:
Improvement is great.  Especially as the masses have been brainwashed into celebrating change :)

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