Re-doing bottled Prod build

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UCChris

UCChris

Member
Mar 12, 2017
1,191
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Chicago, IL, United States
Back in 2019, I built this cool little bottle gun

Czk5N9f.jpg


It was a Prod converted to .177 by having a Mrod barrel machined and the factory .22 bolt probe turned down. It then got a 9ci bottle and 1300 psi reg by way of a Gauntlet tank block and custom Cothran tube. It was shooting around 11fpe and getting a decent number of shots. I ended up gutting the build to make my wife a Prod bullpup that she adores. However, I now have the parts to build it again. I'm trying to figure out where to go with this one though.

All of my air rifles are .177 and all shoot great with the JSB 10.34, so all I have to do is buy one pellet. However, I kinda want to stick with .22 on this gun, but the one odd caliber out is bothering my OCD. Regardless, I want to go with a longer barrel to fill out the shroud and put an LDC adapter on, just like my previous build.

So then I get thinking, if I'm gonna have a new barrel done up, I might as well just do .177 and stick with congruency in my collection. Decisions, decisions... The big issue is that the plenum on this gun is tiny. I had Cothran make the tube such that the tank block damn near butts up to the valve, in order to make the gun as balanced and compact as possible. So .177 might be best.

Any thoughts would be appreciated!
 
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I've got a couple of those smaller regulated bottles as well as an adapter and then another adapter that allows for the stock tube to be used. I got all in hopes of doing a similar project as you have, but currently, one bottle is stashed in my gun room and the other with the funky adapter is sitting on my desk as I type this. Maybe one day I'll get on it.

No thoughts other than maybe this will get me off my tail to do my own build or I'll realize that I'll just have this stuff sit and sell it one day. Will be looking forward to what you build out of it!
 
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Well, little update. I got the factory Prod guts into the Cothran tube. This is with minimum HS preload, full hammer travel. Stock HS and TP. Regulator on bottle set at 1450 psi. I was expecting way under this power level with the tiny plenum.

Screenshot_20221229-122613.png


I think I will put in a poly tube TP next to see if the gun increases in power or if it is already dumping the entire plenum each shot.
 
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Well, definitely wasn't dumping the entire plenum. Going to the poly tube TP netted another couple fpe! I'm downright shocked I'm getting the power I'm getting, considering the plenum is nearing .5 cc/ftlb at this point.

Screenshot_20221230-084938.png


I installed the following spring from McMaster, based on some posts from FuzzyGrub on GTA. Can't tell anything different from the sound of a dry fire, but the report sounds a bit snappier due to the shorter, heavier spring. I'll shoot a string shortly.

PXL_20221230_144631495.jpg
 
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Well, velocity didn't change going to the heavier, shorter spring. So I installed another spring identical to the above spring, except .045" wire. Again, no velocity change. I was noticing a bit of hammer bounce so I shortened the .045" spring a bit and shot this 4 shot string.

Screenshot_20221230-121842.png


No velocity drop still but the bounce was completely gone. Since I'm still running above the knee, I'm going to bump the reg to 1700 psi and see where that lands us. I'd really like to hit 15 fpe in this carbine.
 
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Major update - got a carbon bottle and regulator set to 1800-ish psi. First shots were 9 fpe, so it seemed my hammer spring was too soft. Put in a full length 9434K162 spring from McMaster. That netted this shot string, starting at about 2500 psi. My chrony failed to read about 10 shots throughout this string, so it's not perfect.

Screenshot_20230114-205614.png


Screenshot_20230114-205719.png


Shot count: 45
Low: 636
Hi: 698
Avg: 679
STD Dev: 17.1
Spread: 62.0

1/14/23 8:42:36 PM,675
1/14/23 8:42:41 PM,696
1/14/23 8:42:44 PM,691
1/14/23 8:42:49 PM,694
1/14/23 8:42:53 PM,677
1/14/23 8:42:57 PM,680
1/14/23 8:44:02 PM,698
1/14/23 8:44:06 PM,684
1/14/23 8:44:10 PM,696
1/14/23 8:44:44 PM,677
1/14/23 8:44:48 PM,694
1/14/23 8:44:53 PM,689
1/14/23 8:44:57 PM,687
1/14/23 8:45:49 PM,696
1/14/23 8:45:54 PM,691
1/14/23 8:45:58 PM,680
1/14/23 8:46:02 PM,698
1/14/23 8:46:07 PM,689
1/14/23 8:46:11 PM,696
1/14/23 8:46:14 PM,696
1/14/23 8:46:17 PM,696
1/14/23 8:47:15 PM,694
1/14/23 8:47:19 PM,698
1/14/23 8:47:22 PM,680
1/14/23 8:47:25 PM,694
1/14/23 8:47:29 PM,675
1/14/23 8:47:32 PM,691
1/14/23 8:47:36 PM,684
1/14/23 8:47:39 PM,682
1/14/23 8:48:36 PM,687
1/14/23 8:48:40 PM,684
1/14/23 8:48:44 PM,670
1/14/23 8:48:47 PM,673
1/14/23 8:48:50 PM,666
1/14/23 8:48:53 PM,670
1/14/23 8:48:57 PM,670
1/14/23 8:49:00 PM,659
1/14/23 8:49:47 PM,656
1/14/23 8:49:51 PM,659
1/14/23 8:49:54 PM,656
1/14/23 8:49:57 PM,645
1/14/23 8:50:00 PM,649
1/14/23 8:50:04 PM,647
1/14/23 8:50:06 PM,643
1/14/23 8:50:09 PM,636

Trimming the string to 5% ES from peak velocity, we get:

Screenshot_20230114-210046.png


Screenshot_20230114-210031.png


Shot count: 32
Low: 673
Hi: 698
Avg: 688
STD Dev: 7.8
Spread: 25.0

1/14/23 8:42:36 PM,675
1/14/23 8:42:41 PM,696
1/14/23 8:42:44 PM,691
1/14/23 8:42:49 PM,694
1/14/23 8:42:53 PM,677
1/14/23 8:42:57 PM,680
1/14/23 8:44:02 PM,698
1/14/23 8:44:06 PM,684
1/14/23 8:44:10 PM,696
1/14/23 8:44:44 PM,677
1/14/23 8:44:48 PM,694
1/14/23 8:44:53 PM,689
1/14/23 8:44:57 PM,687
1/14/23 8:45:49 PM,696
1/14/23 8:45:54 PM,691
1/14/23 8:45:58 PM,680
1/14/23 8:46:02 PM,698
1/14/23 8:46:07 PM,689
1/14/23 8:46:11 PM,696
1/14/23 8:46:14 PM,696
1/14/23 8:46:17 PM,696
1/14/23 8:47:15 PM,694
1/14/23 8:47:19 PM,698
1/14/23 8:47:22 PM,680
1/14/23 8:47:25 PM,694
1/14/23 8:47:29 PM,675
1/14/23 8:47:32 PM,691
1/14/23 8:47:36 PM,684
1/14/23 8:47:39 PM,682
1/14/23 8:48:36 PM,687
1/14/23 8:48:40 PM,684
1/14/23 8:48:47 PM,673

Overall, I think I'm running above the knee as it drops 15-20 fps right off the regulator and descends pretty rapidly, considering I have a 15ci bottle on this gun. I'm very happy though, as I'm running a plenum somewhere around 5-7cc. Here's a pic of the gun as it stands now. I may convert to .177 as IL classifies .22 as a firearm and so having an LDC is a bit questionable. Bonus pictured is my wife's .177 converted Prod in bullpup stock with 20" Mrod barrel. It does the same 14 fpe, but much more efficiently. I'm expecting 100+ shots on the bottle for her.

PXL_20230115_054206522~2.jpg
 
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UCChris said:
Major update - got a carbon bottle and regulator set to 1800-ish psi. First shots were 9 fpe, so it seemed my hammer spring was too soft. Put in a full length 9434K162 spring from McMaster. That netted this shot string, starting at about 2500 psi. My chrony failed to read about 10 shots throughout this string, so it's not perfect.

View attachment 323249

View attachment 323250

Shot count: 45
Low: 636
Hi: 698
Avg: 679
STD Dev: 17.1
Spread: 62.0

1/14/23 8:42:36 PM,675
1/14/23 8:42:41 PM,696
1/14/23 8:42:44 PM,691
1/14/23 8:42:49 PM,694
1/14/23 8:42:53 PM,677
1/14/23 8:42:57 PM,680
1/14/23 8:44:02 PM,698
1/14/23 8:44:06 PM,684
1/14/23 8:44:10 PM,696
1/14/23 8:44:44 PM,677
1/14/23 8:44:48 PM,694
1/14/23 8:44:53 PM,689
1/14/23 8:44:57 PM,687
1/14/23 8:45:49 PM,696
1/14/23 8:45:54 PM,691
1/14/23 8:45:58 PM,680
1/14/23 8:46:02 PM,698
1/14/23 8:46:07 PM,689
1/14/23 8:46:11 PM,696
1/14/23 8:46:14 PM,696
1/14/23 8:46:17 PM,696
1/14/23 8:47:15 PM,694
1/14/23 8:47:19 PM,698
1/14/23 8:47:22 PM,680
1/14/23 8:47:25 PM,694
1/14/23 8:47:29 PM,675
1/14/23 8:47:32 PM,691
1/14/23 8:47:36 PM,684
1/14/23 8:47:39 PM,682
1/14/23 8:48:36 PM,687
1/14/23 8:48:40 PM,684
1/14/23 8:48:44 PM,670
1/14/23 8:48:47 PM,673
1/14/23 8:48:50 PM,666
1/14/23 8:48:53 PM,670
1/14/23 8:48:57 PM,670
1/14/23 8:49:00 PM,659
1/14/23 8:49:47 PM,656
1/14/23 8:49:51 PM,659
1/14/23 8:49:54 PM,656
1/14/23 8:49:57 PM,645
1/14/23 8:50:00 PM,649
1/14/23 8:50:04 PM,647
1/14/23 8:50:06 PM,643
1/14/23 8:50:09 PM,636

Trimming the string to 5% ES from peak velocity, we get:

View attachment 323251

View attachment 323252

Shot count: 32
Low: 673
Hi: 698
Avg: 688
STD Dev: 7.8
Spread: 25.0

1/14/23 8:42:36 PM,675
1/14/23 8:42:41 PM,696
1/14/23 8:42:44 PM,691
1/14/23 8:42:49 PM,694
1/14/23 8:42:53 PM,677
1/14/23 8:42:57 PM,680
1/14/23 8:44:02 PM,698
1/14/23 8:44:06 PM,684
1/14/23 8:44:10 PM,696
1/14/23 8:44:44 PM,677
1/14/23 8:44:48 PM,694
1/14/23 8:44:53 PM,689
1/14/23 8:44:57 PM,687
1/14/23 8:45:49 PM,696
1/14/23 8:45:54 PM,691
1/14/23 8:45:58 PM,680
1/14/23 8:46:02 PM,698
1/14/23 8:46:07 PM,689
1/14/23 8:46:11 PM,696
1/14/23 8:46:14 PM,696
1/14/23 8:46:17 PM,696
1/14/23 8:47:15 PM,694
1/14/23 8:47:19 PM,698
1/14/23 8:47:22 PM,680
1/14/23 8:47:25 PM,694
1/14/23 8:47:29 PM,675
1/14/23 8:47:32 PM,691
1/14/23 8:47:36 PM,684
1/14/23 8:47:39 PM,682
1/14/23 8:48:36 PM,687
1/14/23 8:48:40 PM,684
1/14/23 8:48:47 PM,673

Overall, I think I'm running above the knee as it drops 15-20 fps right off the regulator and descends pretty rapidly, considering I have a 15ci bottle on this gun. I'm very happy though, as I'm running a plenum somewhere around 5-7cc. Here's a pic of the gun as it stands now. I may convert to .177 as IL classifies .22 as a firearm and so having an LDC is a bit questionable. Bonus pictured is my wife's .177 converted Prod in bullpup stock with 20" Mrod barrel. It does the same 14 fpe, but much more efficiently. I'm expecting 100+ shots on the bottle for her.

View attachment 323253
Click to expand...
Chris, that a Rapid bullpup stock? Wish he made them in wood still. Looks good regardless, and the hook stock on your Prod is strikingly familiar to the one on my 556 lol. Mission first tactical I believe.
 
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Boostcreep said:
Chris, that a Rapid bullpup stock? Wish he made them in wood still. Looks good regardless, and the hook stock on your Prod is strikingly familiar to the one on my 556 lol. Mission first tactical I believe.
Click to expand...

That is indeed a Rapid pup. Cool stock, if a bit too futuristic looking for my preferences. Also correct on the MFT stock!
 
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Okay, update with where I'm at. I took the 1800 psi bottle off and put it on my wife's bullpup that has a 20" barrel to try and make it an 18 fpe shooter. That's still a work in progress. For now, I've swapped the lower psi bottle onto my .22 Prod in hopes of creating a sub 12 fpe setup that would work great for taking pest birds out of farm enclosures. To recap where I'm at:

.22 Prod - factory length barrel
Bottled - regulator at 1100-ish psi
Plenum around 1.8cc - not counting valve/tank block volume
McMaster HS - shorter/stiffer than factory

Okay, so I previously had this bottled at 1800-ish psi and was getting just over 14 fpe (13.43 @ 688). With nothing else changed, the swap to the 1100 psi bottle put me at just under 11 fpe (13.43 @ 598). It's shooting extremely consistent with a spread of 11 fps over a shot string. Pretty much exactly what I was looking for - low power, acceptable trajectory out to 30 yards with a high mounted red dot. Except there are a couple issues.

1) I have to test this further, but it appears that the velocity drops really bad on the first couple shots if I let the gun sit. I was shooting a string, let the gun sit halfway through the string, and the fps of the first shot after sitting was almost 100 fps slower than the average of the good shots. Now, it only happened once so maybe it was a chrony glitch, but I have to check further.

2) It's pretty freaking loud for only putting out 10 fpe. I understand there are a couple things working against me here. The 1.8cc plenum being the biggest problem; one can only do so much with the limited amount of air. Second, I know the report from a lower pressure shot cycle is lower pitched and longer in duration than a higher pressure shot cycle.

As an aside, I was getting some leaking from the poly tube TP (.18") and decided I had enough of dealing with those. I put in a drilled out the factory TP (.125") and saw zero velocity change. So it would appear that I'm dumping the plenum shot to shot and the only way to increase velocity at this point is higher regulator pressure. I don't necessarily want more velocity, but I'm running at the peak of HS, whereas I could probably increase pressure a few hundred PSI and tune for the plateau. That would likely net me similar power but increase efficiency and quiet the shot report.
 
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