.25 Air Efficiency

[Bob La Londe]

I am wondering what MODS might be really useful on the .25 while I have it taken apart to bottle it. I don't have the cash for a new valve from any of the valve builders so that is out this time, but modifying the valve or opening up the transfer port are within reach.

On the .177 I did one thing at a time. REgulating it bumped me from around 20-21 powerful shots to 27-28 and gave me a more level shot curve. 30 if you fudge a little. Adding a WAR Extension bumped it to about 40. Drilling out the transfer port gave me over 90. (I had to detune the gun to bring power back down.)

That's kind of what I am looking for with the .25. Something that makes a big difference in air usage efficiency.

I am not thinking I'll ever get 90 shots at the power level I am seeking, but 25 plus would sure be nice. Right now I get about 9-10. I put a 10lb spring in it from Discos R Us, but so far have not done anything else with the gun. I am looking at trying to maintain a curve in the 890-920 range with 25.39 JSBs. I've got a 22CI bottle and adaptor for it, so depending on where I cut the tube I am only going to about double the air capacity. With my current tune thats only likely to be 18-20 shots. I guess I could make a reverse adaptor for the bottle, but I don't even like the look of how I visualize that.

I've already shot my play money this month so new valves and new hammers are probably not going to go in it at this time.

[Bob La Londe]

So is it impossible to make any improvements in air efficiency with self done mods or has everybody become enamored only with drop in aftermarket parts.

[daved20319]

I posted a similar question a short time back, and got a similar response, i.e. nothing, or at least, nothing helpful. Not sure just what the problem is, but for a forum that specializes in one rifle model, this isn't a very helpful place. I think the YF is more responsive. Sorry I can't help, I'm in the same boat as you. Later.

Dave

[AlanMcD]

People ARE very helpful here, but even though this forum is dedicated to a single platform it has gotten so huge in terms of posts and topic areas that sometimes it is hard for people to find your thread. The best advice may come form someone that never even sees what you asked because of the different sections - for example, I was just looking in here even though I am not a .25 cal shooter, and here I am about to give you some (hopefully) useful advice days after you asked it . . .

The advantage of the Yellow is that practically every frequent user sees a new post, since they all flow in on top of each other - so if you check it every day you see all the posts on the first page or two and are caught up. But miss for several days and you never know what was posted - and you can pretty much forget about bothering going back to see what was added to a second or later page thread unless you were part of it unless you have some serious time to kill. I have taken the time there to go back and add stuff for "closure" to posts that I made in case somebody finds them through a search, but that is probably a waste of time in most cases as nobody ever ends up there - here that pulls it back up to the top of a section.

Here the recent stuff is always on top, but it can be a nightmare to find people that need do help - even more so because of the people that put the same thread in multiple places and create what amounts to trash and partial/redundant info to wade through. Sometimes we just don't have time for it, and I'll confess to times I can't be bothered to search out things. I do sometimes use the "unanswered posts" link to try to find people that have not been helped, but if any posts are made to that thread it is dropped from that path. And when looking for things I can help with, I often forget where I was in the forum already . . . . none of this is meant as a criticism of the moderators and the site owner - nothing is perfect anywhere, and I do appreciate all I learned here and I do try to give back.

Anyways, I found this, and will try to help. I am a .22 shooter and don't have a .25, but I think I can help. First, several years ago all the modding was being done on our own and we shared what we learned. Then people that were giving out advice decided to make a go of taking what they know and turning a hobby into a small business. So yes, now the easiest and often best path is to buy what you want directly from somebody that can get you there without risk or experimentation. If you go it one your own, you will probably need a spare valve or two from Crosman, but you might get lucky and not mess up on your own.

Much of the knowledge you seek is buried in the past in the Mods section - search is your friend, but it turns up so much now that you do have to wade through a lot to get what you want. If you go back into the past by digging several pages in, you will find things like this:
viewtopic.php?f=14&t=9392
and this:
viewtopic.php?f=24&t=9769

And here is one I posted on the additional mods I made to my already modified .25 cal valve (from Addicted2Airguns - but Dave is no longer selling parts): viewtopic.php?f=29&t=8270

Of course these can lead to other things that you will find too. I will say that all the mods I did to my valve were made with hand tools - I have no easy access to a drill press, lathe, or mill. I did make a simple handy jig for holding the valve that helped a ton: I took a small section of 2x4 and drilled a 1" hole in it, and then cut the wood in half on my table saw right through the centerline of the hole - the allowed me to place my valve (and later my regulator) into it for secure work without damaging it at all.

Hopefully this helps!

[RidgeRunner05]

When I first bottled my .25 using my stock/unmodified valve, stock hammer spring, and t port I was able to get 30-40 shots in the low 900's from a 3000 psi fill. The passages through my adapter block are 7/16" and I have 6-7" from the adapter to the intake face of the valve. I also removed the gauge block from the air tube to allow more unrestricted airflow into the valve.

I just finished de tuning the rifle from experimenting with some heavier slugs. I now have the war valve,12.5# spring and the t port is opened up to .187". My current tune is 50 shots from 875-900-875 from a 2400 psi fill.

With proper porting of the stock valve, I see no reason you shouldn't be able to achieve the shot string you are looking for.

[Bob La Londe]

First off. Thank you for your experience and reply.

When I first bottled my .25 using my stock/unmodified valve, stock hammer spring, and t port I was able to get 30-40 shots in the low 900's from a 3000 psi fill.

That is very good.

The passages through my adapter block are 7/16" and I have 6-7" from the adapter to the intake face of the valve. I also removed the gauge block from the air tube to allow more unrestricted airflow into the valve.

How did you plug the hole? Or did you cut the main air tube back that far when you bottled the gun?

I just finished de tuning the rifle from experimenting with some heavier slugs. I now have the war valve,12.5# spring and the t port is opened up to .187". My current tune is 50 shots from 875-900-875 from a 2400 psi fill.

Also very good. I am actually looking at heavier slugs for my .177. In its current setup it can easily shoot way to fast for the 10.5s and 10.65s I have been shooting. I bought some 16s to experiment with.

With proper porting of the stock valve, I see no reason you shouldn't be able to achieve the shot string you are looking for.

What do you think is necessary? Opening up the port? Increasing the internal volume of the valve by boring it out? Increase flow by turning down the stem? Do you think the actual valve passage from (seat and piston) need to be enlarged? I was thinking I would start with the transfer port and go from there. On the .177 the T-port was smaller than the barrel port or the valve port. It actually still is slightly. Sorry to keep mentioning the .177 (which I am pretty happy with), but it is the only hands on comparison I have.

I have put everything on pause the since my Chrony failed, but a new Pro Chrono Digital should be arriving on Tuesday.

[Bob La Londe]

First and foremost Alan, I want to thank you for your long and well thought out response.

People ARE very helpful here, but even though this forum is dedicated to a single platform it has gotten so huge in terms of posts and topic areas that sometimes it is hard for people to find your thread. The best advice may come form someone that never even sees what you asked because of the different sections - for example, I was just looking in here even though I am not a .25 cal shooter, and here I am about to give you some (hopefully) useful advice days after you asked it . . .

And I appreciate it. LOL.

The advantage of the Yellow is that practically every frequent user sees a new post, since they all flow in on top of each other - so if you check it every day you see all the posts on the first page or two and are caught up. But miss for several days and you never know what was posted - and you can pretty much forget about bothering going back to see what was added to a second or later page thread unless you were part of it unless you have some serious time to kill. I have taken the time there to go back and add stuff for "closure" to posts that I made in case somebody finds them through a search, but that is probably a waste of time in most cases as nobody ever ends up there - here that pulls it back up to the top of a section.

I sometimes read the yellow, and I think I have managed to set up an account there (Maybe its a different forum) with a request and manual approval, but I can't seem to post anything. I'll figure it out eventually.

Here the recent stuff is always on top, but it can be a nightmare to find people that need do help - even more so because of the people that put the same thread in multiple places and create what amounts to trash and partial/redundant info to wade through. Sometimes we just don't have time for it, and I'll confess to times I can't be bothered to search out things. I do sometimes use the "unanswered posts" link to try to find people that have not been helped, but if any posts are made to that thread it is dropped from that path.

I don't know enough about airguns to help others much, but I do the same on some of the machining forums I read. I started getting serious about machine work as a hobby about six (6) years ago, and now I have a small but profitable side business in making lure molds for lead and soft plastics. I would not have gotten there without the help of others. When I had such a successful last go around with the .177 S-Rod I did post a detailed run down of what I did and how it got there.

And when looking for things I can help with, I often forget where I was in the forum already . . . . none of this is meant as a criticism of the moderators and the site owner - nothing is perfect anywhere, and I do appreciate all I learned here and I do try to give back.

I actually find this site to be very good in that regard with little meddling of the moderators in honest comments and opinions. Unlike atleast one where an unpopular opinion or negative critique can get you chastised or even banned. Maybe as a primarily brand-centric forum those types of opinions just don't get posted as often. Regardless, this is a good forum for Marauder owners.

Anyways, I found this, and will try to help. I am a .22 shooter and don't have a .25, but I think I can help. First, several years ago all the modding was being done on our own and we shared what we learned. Then people that were giving out advice decided to make a go of taking what they know and turning a hobby into a small business. So yes, now the easiest and often best path is to buy what you want directly from somebody that can get you there without risk or experimentation. If you go it one your own, you will probably need a spare valve or two from Crosman, but you might get lucky and not mess up on your own.

Well, a spare valve or two down the road may be an option. Even drop in parts might be in the future, but right now I am being careful.

Much of the knowledge you seek is buried in the past in the Mods section - search is your friend, but it turns up so much now that you do have to wade through a lot to get what you want.

Very much so. I think I can tune for power modestly well. In fact I think from my minimal experiments so far that tuning for efficiency give you more range to tune for power. I did do a bit of searching and like you said found a morass of information. Distilling it down to the basics is the hard part. I was hoping some more experienced users like yourself and Alan would have pity on me and point me towards some of the gems within the (also valuable) pile of coal.

If you go back into the past by digging several pages in, you will find things like this:
viewtopic.php?f=14&t=9392
and this:
viewtopic.php?f=24&t=9769

I will read those next.

And here is one I posted on the additional mods I made to my already modified .25 cal valve (from Addicted2Airguns - but Dave is no longer selling parts): viewtopic.php?f=29&t=8270

I can understand. There is only so much time in a life.

Of course these can lead to other things that you will find too. I will say that all the mods I did to my valve were made with hand tools - I have no easy access to a drill press, lathe, or mill.

Fortunately I do have a couple small lathes, a couple small mills, a couple drill presses, a small CNC mill, and a couple larger CNC mills, but I can tell you that you can do any amazing amount of work with hand tools. I've made machine parts to fix things in the past with a grinder, file, and hand drill.

I did make a simple handy jig for holding the valve that helped a ton: I took a small section of 2x4 and drilled a 1" hole in it, and then cut the wood in half on my table saw right through the centerline of the hole - the allowed me to place my valve (and later my regulator) into it for secure work without damaging it at all.

And you illustrate my point beautifully. That is a nice bit of basic engineering. You know I make jigs and clamps using similar methods for use on my CNC mills (and manual mills) all the time out of suitable materoals for the current project. On one machine I replaced the steel jaws on the vises with aluminum jaws just so I could easily and deliberately machine them to hold special parts.

Hopefully this helps!

It does. Thank you.

[FuzzyGrub]

Search for posts from RDSAIL. He did a number of valve mods, mainly for power, and then detuned latter for shot count. While he has posted some here, there will be more data on GTA. You would have to review his data to see if he had any strings at the power range you are seeking, and then extrapolate to what your new air volume will be. If you want to be cautious, just open the valve exhaust and TP a little larger than stock.

[Bob La Londe]

Search for posts from RDSAIL. He did a number of valve mods, mainly for power, and then detuned latter for shot count. While he has posted some here, there will be more data on GTA. You would have to review his data to see if he had any strings at the power range you are seeking, and then extrapolate to what your new air volume will be. If you want to be cautious, just open the valve exhaust and TP a little larger than stock.

Thanks.

[Nickdizonc]

I've modded both of my rifles .22 and .25 cal for raw power and never thought much about shot count. That said, I recently decided to go back to making one of my rifles (the .25) fully stock once again and after doIng so, I realized with all the drilling and modding of this port or that inlet, the gains are respectable but not tremendous. I'd keep your rifle stock if you are looking for reliability, shot string consistency, and a reasonable amount of power. The stock .25 is plenty powerful and can be tuned for shot count and excellent consistency without ever having to drill a thing. I was previously obsessed with making the most powerful mrod I could so I def understand the obsession. RAYk actually has an excellent tune for shot count. he made a lengthy post in it as well but it's not for a regulated in its just for a plain Jane stock .25. I've modded all my Mrod's before I even took the first shot on some. Little didnI realize the stock gun is pretty awesome as is...just my 2 cents:)