AEA HP SS Max 357 Project
- Thread starter caliusoptimus
- Start date
I suppose. I got the barrel back today and I think I'm happy with it as-is. Lotta effort to flute one barrel.
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Barrel came back from a local gunsmith today. Apparently they really enjoy machining projects so they knocked it out quick.
As expected the barrel weighs in at 1.7lbs which makes it about 0.7lbs heavier than stock.
I ordered a variety of different slugs to try out. The barrel still really likes the NSA 125s the best. I tried the NSA 142s which weren't as accurate as the 125s and velocity was lower than I prefer. I also tried some seneca slugs in the 115-127 grain range and they weren't great. Quality on the senecas was not worth the price either. Still have a few others on the way to try.
Here's the NSA 125s at 50yds. Upper left and upper right were 8 shots tethered and regulated at 250 bar, about 200lbf. Center was 8 shots no tether starting at 4500psi. 3 regulated shots then the rest tapered off on velocity. Quite sufficient for hunting. I wonder if I can get it even better with a little tuning... maybe sorting ammo too...
As expected the barrel weighs in at 1.7lbs which makes it about 0.7lbs heavier than stock.
I ordered a variety of different slugs to try out. The barrel still really likes the NSA 125s the best. I tried the NSA 142s which weren't as accurate as the 125s and velocity was lower than I prefer. I also tried some seneca slugs in the 115-127 grain range and they weren't great. Quality on the senecas was not worth the price either. Still have a few others on the way to try.
Here's the NSA 125s at 50yds. Upper left and upper right were 8 shots tethered and regulated at 250 bar, about 200lbf. Center was 8 shots no tether starting at 4500psi. 3 regulated shots then the rest tapered off on velocity. Quite sufficient for hunting. I wonder if I can get it even better with a little tuning... maybe sorting ammo too...
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Nearing final form...
I bead blasted and cold blued the barrel. Came out pretty decent for a few minutes of work. I also shaved off some weight by getting rid of all the picatinny adapter nonsense I had on there before. These rings are almost perfect, but they won't let me tilt the scope much without binding. A few minutes in the mill might solve that.
Feeling a little dissatisfied with the AEA regulator so it's gone for now. Doesn't work consistently above 200 bar and I think I know why... the belleville washer springs in there just aren't enough force for more pressure.
I have one more super custom mod in mind: fixed stock/hammer spring adjuster. I've been getting by without this but it sure would be nice to just turn a knob rather than fiddle with loosening and tightening the stock with castle and spanner wrenches. Tbd... not in a big rush to do this.
I bead blasted and cold blued the barrel. Came out pretty decent for a few minutes of work. I also shaved off some weight by getting rid of all the picatinny adapter nonsense I had on there before. These rings are almost perfect, but they won't let me tilt the scope much without binding. A few minutes in the mill might solve that.
Feeling a little dissatisfied with the AEA regulator so it's gone for now. Doesn't work consistently above 200 bar and I think I know why... the belleville washer springs in there just aren't enough force for more pressure.
I have one more super custom mod in mind: fixed stock/hammer spring adjuster. I've been getting by without this but it sure would be nice to just turn a knob rather than fiddle with loosening and tightening the stock with castle and spanner wrenches. Tbd... not in a big rush to do this.
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I've been experimenting a lot with this rifle to find the best combination of power and accuracy. Still not satisfied as I think it can do better, but I've learned a lot so far.
Overall, the accuracy has been better with the new barrel versus the stock barrel. The stock barrel shot about the same no matter what ammo I put through it. Roughly 2-3" groups at 50yds tethered. The new barrel is a bit worse with pellets and smaller slugs like 80gr. It seems as the slug size goes up, so does the accuracy. The best so far is still NSA 125s, which were hitting 3" groups at 100yds (with an external regulator) last weekend with some wind.
I'm wondering how much the twist ratio has to do with these results. At 1:20" it seems, based on various calculators, that the twist is too fast for typical airgun ammo. Maybe explains why longer and heavier ammo shoots better? The bore size on this barrel is also quite a bit smaller than the AEA barrel. Stock barrel was .3585 grooves and .3525 bore. New barrel is .357 grooves and .347 bore.
I've been shooting 200-250 bar which gets at least a full mag. With the hammer spring near balanced, 125gr slugs are in the 190-220ftlb range. Up to 240ftlb with the hammer spring turned up. Side question... what is the correct abbreviation for "foot pound" of energy?
I picked up an MP mold recently... seems to be shooting pretty well out of this barrel. I tried pure lead first, about to try a harder alloy. This slug is one of the longest so far and it might be just what the barrel wants. Tbc
Overall, the accuracy has been better with the new barrel versus the stock barrel. The stock barrel shot about the same no matter what ammo I put through it. Roughly 2-3" groups at 50yds tethered. The new barrel is a bit worse with pellets and smaller slugs like 80gr. It seems as the slug size goes up, so does the accuracy. The best so far is still NSA 125s, which were hitting 3" groups at 100yds (with an external regulator) last weekend with some wind.
I'm wondering how much the twist ratio has to do with these results. At 1:20" it seems, based on various calculators, that the twist is too fast for typical airgun ammo. Maybe explains why longer and heavier ammo shoots better? The bore size on this barrel is also quite a bit smaller than the AEA barrel. Stock barrel was .3585 grooves and .3525 bore. New barrel is .357 grooves and .347 bore.
I've been shooting 200-250 bar which gets at least a full mag. With the hammer spring near balanced, 125gr slugs are in the 190-220ftlb range. Up to 240ftlb with the hammer spring turned up. Side question... what is the correct abbreviation for "foot pound" of energy?
I picked up an MP mold recently... seems to be shooting pretty well out of this barrel. I tried pure lead first, about to try a harder alloy. This slug is one of the longest so far and it might be just what the barrel wants. Tbc
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@caliusoptimus Nice thread. Thanks for taking us along for the ride. I have a question for you. It’s difficult to see in the video, but when the bolt is cocked and out of the loading slot that you milled (bolt handle up), is the probe protruding slightly into the breech preventing you from inserting a magazine?
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Yes, the probe is protruding a bit unless the handle is pulled back farther and locked into the second notch.
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I've got some more experiments planned for this bad boy.
First one is enlarging the ports in the barrel. I'm not sure if this is going to make a difference at all, but it was easy so no big deal if it doesn't help.
Second is messing with the belleville washers in the AEA regulator. The AEA regs seem to get weird above 200 bar... for example slow refill of the plenum, inconsistent pressure setting, ultra sensitive to the adjustment screw, and trying to go up to 250 bar usually leaks the full tank pressure into the plenum. I think this is all because the springs (belleville washers) are maxed out and not able to provide enough force for higher pressures. By rearranging the stack I think I can get more force and make it work... TBD. Here's a pic of the stock config.
Another modification I'm working on is a new barrel and a few changes to the machining. First concern is the twist rate. I think 1:20" might be too much twist for the 80-125gr I'd like to use. I'm trying to get my hands on a TJ 1:26" liner. If that happens I'll use a carbon fiber tube to tension the barrel. Also trying to get a .25 TJ liner for my SF. For the same reasons... more power from a longer barrel and better accuracy.
Second concern is the design of the chamber/leade/-that area before the rifling starts-. On the stock barrel and on the barrel I have currently, the slug seems to have a lot of wiggle room before it is fired. I don't know if this is contributing to poor accuracy but my gut says yes. I imagine the slug hitting the rifling at a slightly different angle every shot. In any case, if/when the TJ liner comes in I'm going to try something different.
Here is the stock design that I followed. My design has a slightly tighter fit on the probe and the slug than the stock barrel, but not by much. The area where the slug is resting is 0.368" diameter. This is a pretty loose fit.
Here's my idea for the next barrel. I'll tighten up that area to 0.3585" ish. The goal is to go as tight as possible without making it hard to chamber the slug. I think 0.3585" is a good starting point, as it will still allow .358 slugs, though the may require a little shove.
First one is enlarging the ports in the barrel. I'm not sure if this is going to make a difference at all, but it was easy so no big deal if it doesn't help.
Second is messing with the belleville washers in the AEA regulator. The AEA regs seem to get weird above 200 bar... for example slow refill of the plenum, inconsistent pressure setting, ultra sensitive to the adjustment screw, and trying to go up to 250 bar usually leaks the full tank pressure into the plenum. I think this is all because the springs (belleville washers) are maxed out and not able to provide enough force for higher pressures. By rearranging the stack I think I can get more force and make it work... TBD. Here's a pic of the stock config.
Another modification I'm working on is a new barrel and a few changes to the machining. First concern is the twist rate. I think 1:20" might be too much twist for the 80-125gr I'd like to use. I'm trying to get my hands on a TJ 1:26" liner. If that happens I'll use a carbon fiber tube to tension the barrel. Also trying to get a .25 TJ liner for my SF. For the same reasons... more power from a longer barrel and better accuracy.
Second concern is the design of the chamber/leade/-that area before the rifling starts-. On the stock barrel and on the barrel I have currently, the slug seems to have a lot of wiggle room before it is fired. I don't know if this is contributing to poor accuracy but my gut says yes. I imagine the slug hitting the rifling at a slightly different angle every shot. In any case, if/when the TJ liner comes in I'm going to try something different.
Here is the stock design that I followed. My design has a slightly tighter fit on the probe and the slug than the stock barrel, but not by much. The area where the slug is resting is 0.368" diameter. This is a pretty loose fit.
Here's my idea for the next barrel. I'll tighten up that area to 0.3585" ish. The goal is to go as tight as possible without making it hard to chamber the slug. I think 0.3585" is a good starting point, as it will still allow .358 slugs, though the may require a little shove.
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@caliusoptimus 0.368 down to .3585 is a significant difference on your leade. What’s the groove diameter on your incoming TJ’s barrel?
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A couple weeks ago I picked up a bigger CNC lathe. Good deal through FB marketplace, old toolroom lathe converted to linuxCNC. Will be helpful for work, and also super handy for my hobbies 
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I used it to finish up a green mountain blank. 27" .357 1 in 20" twist. I went with the leade design from my previous post. Results TBD, but it sure looks nice.
.I used it to finish up a green mountain blank. 27" .357 1 in 20" twist. I went with the leade design from my previous post. Results TBD, but it sure looks nice.
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Finally got around to making an external hammer spring adjuster!
It works beautifully. Easy to adjust, 8 detents, and a screw that can lock it down.
Also made another barrel to try... this one is almost exactly the same as the last but I left it full diameter. Just want to see the difference between a bull barrel and one that has been turned down.
It works beautifully. Easy to adjust, 8 detents, and a screw that can lock it down.
Also made another barrel to try... this one is almost exactly the same as the last but I left it full diameter. Just want to see the difference between a bull barrel and one that has been turned down.
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@caliusoptimus Those are a lot of bellvilles!! Over 30, damn!! Do you have to remove the buffer tube or buffer tube adapter to adjust the hammer spring? How do you turn the adjuster?
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Unfortunately never figured out a configuration for the bellevilles that gave decent consistency over 200bar. I may try again... but I've been getting better consistency with an external reg anyway.
Here's the adjuster.
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@caliusoptimus Nicely done. Will you anodize it later or do you intend to leave it bare metal colored? Did you laser engrave the numbers?
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Meh... I might send it in for ano on my next batch of ano parts. This rifle is my "Frankenstein's monster" so looks aren't a concern. And yes, I did the lasering.
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