Trail Boss and Paper Patch in the 303 Brit

[303Guy]

Been thinking about this for a while and having trouble with shotgun powder generating strange pressures in the case neck region actually locking up the case in rust pits in the chamber. Then posters have been talking of lighter pp loads so I decided it was time to take the plunge.

Well, test tube results are encouraging.

http://i388.photobucket.com/albums/oo327/303Guy/003.jpg

303 Brit Lee Enfield Pig Gun
14.8gr Trail Boss which completely fills the case up to the base of neck
205gr PPCB

On the second test there were no recoverable paper bits. They must have gone somewhere but they must be pretty small to 'disappear' like that in a test tube. That would indicate proper patch disintegration at the muzzle.

This is a short barrelled gun fitted with an over barrel suppressor so it should be pretty quiet. That's the idea anyway.

Trail Boss is so low density that it is sold in large 1/4 kilo containers. It is the same price as any other powder in my parts which would shock you Americans. eg, 1lb W748 at NZ$67! :groner: Even so, at 14.8gr per load it's still quite reasonable.

[303Guy]

Here's a boolit that stopped in the catch rags (as opposed to penetrating into the sand beneath). It flipped sideways leaving one side essentially intact.

http://i388.photobucket.com/albums/oo327/303Guy/TrailBosstrials007.jpg

The 'intact' side. Rifling impressions are deep but the absence of knurl marks and striations on the boolit indicate patch failure. Either that or passage through the rags have created the striations. I'm not convinced of that.

http://i388.photobucket.com/albums/oo327/303Guy/TrailBosstrials005_2.jpg

Notice the case mouth impression on the previous photo as well as this one? Curious! Makes me wonder what is going on.

This time I found tiny patch fragments on top of the catch rags. Two bits are visible in the photo's above.

A cotton ball through the barrel picked up flakes of lead. Strange that a full power load of W748 produced a shiny clean barrel with the same boolit and patch! (Not the actual same one but .... you know what I mean :roll: ).

So why would the patch be failing with low pressure loads and not with high pressure loads with long pressure duration? Insufficient lateral obturation pressure to hold the patch between boolit surface and bore?

Is the above photo revealing something that takes place before the boolit gets moving? One can see the throat entry expansion on the boolit. But how could it be preserved? Did that portion of boolit expand into the throat entry and get swaged back down but because swaging actually softens lead alloy, did it expand in that same spot on impact with the catch medium?

Is Trail Boss actually a suitable propellant for patched boolits? I'll just have to load some up and go test them.

[Nobade]

A case full of Trailboss in the 303 isn't a low pressure load. It doesn't go very fast, but it's likely over 30KPSI. Trailboss is extremely fast to rise, and drops off just as fast. A big, hard kick in the butt instead of a nice long push.

When I first tried Trailboss, I found that most bottlenecked rifle cases would lead the bore with a full load. I tried what Hornady said and started at 70% fill and it still didn't work. Then I got the new update to Quickload that had Trailboss and saw the pressure curves. Wow, no wonder it didn't work! Most rounds like 30-06 only needed 55% to 60% fill to be at full pressure for naked cast bullets. I tried that and it works great! The funny thing is, the velocity difference between 50% and 100% fill is quite small, but the pressure difference is huge!

I don't know if you will get any joy from Trailboss or not, but I suspect not. A big fast pressure spike will allow gas to blow past the bullet before it moves, at least that's my guess. (and why 748 works so well)

[longbow]

303guy:

I have found similar case mouth impressions on some of my .44 boolits from my smooth sided push out moulds. Not all just some loads.

My thoughts are that it may be caused by fast pressure rise and/or soft alloy resulting in obturation before the boolit leaves the brass.

I have not seen it reported before and thought it was just an anomaly as I have only found obvious impressions on a few recovered boolits.

However, the fast pressure rise would be in line with what Nobade says about Trailboss.

I am normally loading the .44 with IMR4227 and occasionally Blue Dot. I also had some Lyman 429421 boolits collapse at the lube groove and if I recall correctly, those were Blue Dot loads shot into wet end grain birch. I am thinking the smooth sided boolits with case mouth marks may have been same alloy and load. Unfortunately, I did not record the load used with the recovered boolits.

I should bag and tag all recovered boolits for future reference!

I posted a couple of photos in one of your other threads and if you look at the .44 boolits there is a slight mark from the case mouth on some. Since I do not crimp and I do flare the case mouth, this is must be formed by the boolit bumping up.

Photos in the link here (post #14):

http://castboolits.gunloads.com/showthread.php?t=130530

3rd from the bottom in the first photo has a faint mark.

3rd and 4th from the bottom in the second photos also show marks. Note that the "lip" is more obvious and is facing backwards on the 4th from the bottom and that the boolit is actually larger diameter where it was inside the brass and smaller diameter outside the case mouth. Curious because this is a parallel sided boolit.

The marks are not large here but I have a couple where they are more obvious. Also, it is pretty obvious that a smooth sided boolit will show this mark where one with lube groove and especially with crimp groove would not. However, it does not appear on all my recovered smooth sided boolits so... ?

I am thinking it is the result of a swift kick in the butt.

Longbow

[geargnasher]

I agree 100% with Nobade, the TB load is probably much higher pressure than the 748, but you have to realize that TB is one of the fastest-burning smokeless powders in existence, making peak pressures almost instantly. That is probably why your patch failed.

I detest TB for most applications using cast boolits, it's the exact opposite of what we want in a powder as far as pressure curves go. Now, if IMR would focus their research on creating a powder with the burn rate of 2400, but the bulk of TB, THAT would be a good powder.

Gear

[303Guy]

Yup. My thinking too. Plus one on the TB bulk and 2400 burn rate!

I'm not sure the pressure spike is all that high in my load. I say that because shotgun powder produces a pressure in the neck area that expands the neck into chamber defects (rust depressions). The TB load doesn't. Primer flattening is much less with TB too.

What suspect might be happening with TB is the pressure rises rapidly initially as stated which stresses the patch then falls off rapidly leaving no lateral pressure to hold the patch fragments between boolit and bore. What makes me think that is the fact that the bulge in the boolit is still visible. Had the patch been lost early, the boolit might obturate and wipe out that impression. I don't know - it's just a thought. To test the idea I might reduce the powder charge some and use wheat bran filler and see what happens.

I've had a boolit before that must have expanded into the throat entry leade then been swaged back. This appears to have softened the alloy as the boolit twisted in this zone. The rifling had 'skidded' forward of the zone and not behind it.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-524F-1.jpghttp://i388.photobucket.com/albums/oo327/303Guy/MVC-521F-1.jpg

[dnepr]

I wish I had read this before I bought a can of trailboss , I was thinking of trying something very similar

[303Guy]

I don't think it's all lost. I'm suspecting that the bore needs to be polished up a bit. The patch is being rolled off in the grooves, not in the lands. This boolit is a bit tighter fitting than previously. Lighter charges of Trail Boss do not damage the boolit. So while I was hoping for a quite but near supersonic load with the 205gr boolit, I may achieve that with a lighter boolit and since the idea is for the great nephew to shoot rabbits with it (and me) that's not a problem. (205gr boolits might be just a little bit of overkill! ;) But it would extend the capabilities of a subsonic boolit).

The most important aspect of TB is the inability to accidently overload and damage something.

Addendum:
I just fired a 185gr boolit over 10gr TB in my cavalry carbine which has a worn but clean bore and there was no sign of patch failure or boolit damage. This one could work.[smilie=w:

http://i388.photobucket.com/albums/oo327/303Guy/BSAMTrailBoss002.jpg

So, I like Trail Boss after all. It's fun stuff to experiment with.:mrgreen:

[barrabruce]

The most important aspect of TB is the inability to accidently overload and damage something.

:

Don't know about that.

I think I heard that with even a slight compression that Trailboss with spike the pressures way up there somewhere.

Iv'e had people at the range who have tried it says that is a Slow powder [smilie=b:[smilie=b:

Co's yer can fill the case up and get low velocity loads

Another said its good if you stuff more in and he was getting like 2100+fps with it. :shock::shock:
I don't wanna even know his pressures with that load in a 308-35 200 grners even in a modern Mauser type action.


Barra

[windrider919]

TB did NOT work in my 458 with PP loads and I tried loading densities of 60% to 100% and accuracy was terrible, 5" groups at 100 yds being the standard. Plus, at around the 3/4 load mark, I started getting paper rings in the chamber and leading showing ...in the last inches of the muzzle.

Tried some test loads with 50% fill and PE granuals for filler to finish fill to 100% = no rings and no leading but accuracy was still sub-standard for this rifle.

Gave the remaining TB powder to a Cowboy Action shooter who swears by it in his .45LC revolver and 1894 carbine.