RAW HM1000x external plenum

Hey guys, how’s it going? I hope you’re all having a great weekend!

I was going to use my Impact M3 for the Precision Marksman at RMAC but couldn’t validate the dope, so I ended up using my Silver MKII that many of you have seen here on AGN over the years. All was going well until three stages from the end of the competition… My set up took a dump on me with three stages to go. Because that was very frustrating, I decided to go a different route for my next Precision amarksman, NRL22 match.

My son Cooper has been shooting a .25 RAW HM1000x for a long time and was super lucky to win a Masterpiece Arms chassis for it at the RMAC banquet. The RAW has been the most simple, reliable, durable, accurate airgun in our lineup and we have some nice airguns. The addirion of the MPA chassis made Cooper, his brother Alex & I all fall in love with his airgun again.

So, I’m sure you can see where this is going… Cooper hasn’t been shooting airguns much since our return from RMAC. School, football, girls & deer season have him busy doing other things. I asked him if I could borrow his RAW for an upcoming NRL22 match in Sept. & he said yes. I got it set up specifically for NRL22 matches. I mounted a new optic on Eaglevision rings, added a Tier One ATAC bipod, an MDT electronic level, a Midwest Elite Airgun high capacity magazine & a carbon fiber Donnyfl Tanto… The new Donnyfl Yokozuna & RYU get here today & they're sick!!! The Ryu will go straight on the RAW! We know which slugs shoot best out of the .25 RAW so I tested those slugs, found the best & tried to validate dope out to 350yds. It was dead on to 160yds but got weird past that. Since I‘m shooting the Varmint Knocker 32.8gr slugs, I called Dale to confirm the BC & talk about using multiple BC’s for different distances… 0-150, 150-250 and 250-350. He agreed the multiple BC idea works but suggested I shoot them even faster. They perform best out of the LW polygonal barrel at 980-1000fps and the BC matches, or is much closer to matching the Kestrel and Strelok.

As many of you know from when I started posting .25 slug data back in 2017/18, I’ve always been a proponent as shooting slugs as fast as possible, not only for stability & accuracy but also the higher BC & retained energy at long range. I was shooting these slugs around 950fps, about all I could get out of the RAW without pushing it too hard. As I mentioned, Dale suggested I shoot the 32.8gr faster, at 980-1000. I adjusted the regulator which increased the velocity a bit, then I tuned the gun with the hammer spring. I’m now close to the velocity Dale suggested but would like the ability to test the higher velocities and also turn down the hammer spring.

Finally, to the point oft this post…😉 I’m trying to find out if any of you have, or know where to get & external plenum for the RAW? Although very cool, I am not interested in Mubhaur’s design. It will not work with the MPA chassis & I don’t like aesthetic. I am looking for the in-line design(I attached a picture). I do know someone who’s brother makes & has them for sale but he is out of town for a while. I was also told that Martin makes them, he too is out of town until Sept. 6th. If anyone knows someone who makes them or has one they’d sell, I would really appreciate it. I’m normally not in a hurry like this but the match is in three weeks. I need time to install, get tuned, validate dope and practice a little bit.

Thank you, have a great rest of your weekend!
Stoti

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Thanks, I can get one from my friend or from Martin in a week or two, I’m just in a crunch for time, so I’m trying to get one asap. If necessary, I can just use my current tune and multiple BC’s for the upcoming NRL22 match and then deal with the plenum when I can. I appreciate the response though.
Have a good one. Stoti
 
Hey Stoti,
Do you have a pic of the in-line plenum Martin makes?

I have made one out of a 16 gram Co2 cartridge holding about 20 ccs of air.
Bob Sterne gave me the idea and specs to make sure it was safe.

My DIY plenum works well, but I would love to have one made by Martin.

Also, mine required me to carve/channel out the stock below the bottom blanking plug.
Its not seen from the outside, which was the main reason I made it For my .25 caliber.

if you have a pic or can direct me to a pic, that would be great😎.
 
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Oops, you have them pictured below.
Because mine in underneath the stock I didn’t see it originally

How many cc’s in Martin making them? Likely whatever you want up to a limit.
You don’t want it hitting the moderator.

IIRC, the additional 20 cc’s allows me to shoot 28 grain Zan slugs about 970 fps, giving me about 70 shots per fill using a SSG, modded regulator and TP reduction.
 
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Haven’t talked to Martin, don’t know anything about the specifics of his plenum. I just know he’s away until Sept. 6th. The other guy I mentioned, the one who has the plenums made… The ones I attached a picture of in the post, he contacted me today. I’ll know more about the specifics tomorrow. I know they’re machined from a solid piece of aluminum, thread into the block on one side, the v-block screws in the other end. If I am able to get one, I’ll let you know the specifics. If you have the ability to thread a co2 cartridge, you could certainly be able to thread a piece of thick walled aluminum. You could make it any length you want.
Have a good one! Stoti
 
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Haven’t talked to Martin, don’t know anything about the specifics of his plenum. I just know he’s away until Sept. 6th. The other guy I mentioned, the one who has the plenums made… The ones I attached a picture of in the post, he contacted me today. I’ll know more about the specifics tomorrow. I know they’re machined from a solid piece of aluminum, thread into the block on one side, the v-block screws in the other end. If I am able to get one, I’ll let you know the specifics. If you have the ability to thread a co2 cartridge, you could certainly be able to thread a piece of thick walled aluminum. You could make it any length you want.
Have a good one! Stoti
Thanks stoti,
I think if I made one it would be out of SS. The walls wouldn’t need to be as thick and it could be made shorter. Unfortunately my Harbor Freight lathe might not be up to the task😒. Will see …..
 
Morning all. You would be surprised that my RAW is actually almost stock, and is shooting Altaros Smooth ATP .22 cal 32.5gr slugs at 915fps. They are incredibly accurate at this speed all the way out to 250 yards so far. See 1 MOA (2”) group at 200yds below.
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I have the regulator set at 145bar and it has a dual hammer spring. The only non-stock part is a small plenum extension that screws into the valve return spring plug hole above the regulator. With this gun setup, I am able to achieve a max of 920 with these 32.5gr slugs, and Altaros says they shoot best at this speed. I tried slower and they weren’t as accurate, but haven’t tried faster yet.
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I plan to start working on some improvements so I can shoot the 32.5gr slugs faster (980fps) and also shoot the Altaros Smooth .22cal 40gr slugs at 910-920fps when it cools off this fall. One upgrade will be a larger plenum.

I am actually very happy with the way the gun shoots now. It doesn’t have much kick, I get about 25 shots per fill, it is super consistent and very accurate, and the Altaros slugs have a very predictable but small wind drift due to their high BC. I am only curious what I can do shooting faster or with a heavier slug, and my goal is to end up shooting 40gr slugs at 1040fps like rimfire rifles do.
 
Thanks for sharing Jeff. I tested the Altaros slugs in .22 a long time ago but never in our .25 RAW. This RAW loves the Varmint Knockers! I’d like to just pick up about 30fps and the plenum will help. Have a great weekend!
Stoti
Altaros makes a plenum like the one in your photos but I don’t know if it would fit.
 
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Thanks stoti,
I think if I made one it would be out of SS. The walls wouldn’t need to be as thick and it could be made shorter. Unfortunately my Harbor Freight lathe might not be up to the task😒. Will see …..
Definitely don’t build it out of aluminum. It will hold the pressure, but I am concerned about bending loads and stress concentrations at the threads where it screws into the action. Remember the old saying “Steel is Real”
 
I make plenums out of solid high grade bar of stainless steel. Safety first.

I would love to offer the inline plenum but I don't have specs of post Airforce models.

I understand that inline plenum is easier to make than my hanging plenums.

Bhaur
Mubhaur,
I asked Corny to give me the specs …. Maybe he can chime in here.
Corny machined my Best Fittings regulator tester to fit my HM1000x regulator.
It’s larger in dia.
 
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