Author Topic: increased barrel length vs speed, linear graph? (Read 5215 times))

Rob M · « **Reply #20 on:** February 20, 2020, 07:04:11 PM »

it can be done easily , but you need to bypass the regulator , and you will likely only get 5 shots per fill

Long_Gun_Dallas · « **Reply #21 on:** February 20, 2020, 07:08:37 PM »

Another member has done that. (shorten the pp700) Vetmx I believe?

subscriber · « **Reply #22 on:** February 20, 2020, 07:42:19 PM »

Matthias,

I can see adding a stock to the PP700 to improve its handling. Have never had one in hand, but think it would be muzzle heavy, if fired offhand, or unsupported without the stock. So, I think the reason to cut it shorter would be to improve its balance. If you have a scope on it, then the weight reduction can't be significant, just the center of gravity shift. Also, scoped you are not carrying it in a holster.

Perhaps total length with a moderator on is your goal? Anyway, technically speaking:

A 5.5" barrel in .22 has slightly more expansion volume than an 8.25" long .177. So, if an 8 FPE tune in the stock 8.25" barrel .177 PP700 is reasonable (rated at 9 FPE out of the box), then a .22 with a 5.5" long barrel is just as reasonable. That is, assuming you don't mind the loopy trajectory. Assuming a 14 grain pellet, that works out to just over 500 FPS. Fine for short range targets and vermin.

Shortening the air tube will cause a proportionate reduction in shot count, even with the standard barrel. The air tube is a large diameter, so the loss of volume is significant (but proportionate). Reducing the barrel length will also reduce shot count, if you boost the hammer strike to restore (and especially,exceed) 9 FPE.

I 2" length reduction will change (improve?) the feel of the pistol. A 1" reduction seems like a lot of work for no reason. More than a 2.75" reduction will start to cause the .22 version to become less efficient than a stock .177. This is because the stock .22 should have the potential to be 50% more powerful, or 50% more efficient than the stock .177. Cutting the .22 shorter (within reason) would just make the expansion ratios equal between calibers. This making their FPE per CC of air used the same.

If you are able to do the work without destroying your PP700, and can live with the reduced shot count, go for it. Playing the role of heckler heckler here

.

How long is the air tube? Are there components inside that take up volume? If not, then a 20% length reduction should equate to a 20% useful shot count reduction.

JungleShooter · « **Reply #23 on:** February 21, 2020, 04:48:53 PM »

Long_Gun_Dallas,

Thanks for the pic of Frank's shortened PP700! 😊

subscriber,
Thanks for the encouragement! 😊

This is a project I have been thinking of for a while now, and it's a bit out of reach yet, as it'll require funds..... 😄

I'm looking for a smaller pesting pistol that can actually be carried in a pocket or holster instead of a plano case...! 😄

And once the moderator is on it's so long I might as well shoot a compact bullpup rather than a li'l pistol....

It would be for very short range pesting, with a laser sight.

What I take away in length of barrel and airtube, I'd like to add in volume to the moderator — a 1.5" or 2" tube, asymetrical — yeah, a man is entitled to dream, right?! 😄

Anyhow, too bad that Artemis did such a whimpy job on the shroud, it looks good, but is basically not functional....

All this modding is really new to me and I still need to find some kind of machine shop here in Lima that can modify and make me parts.....
FUN!! 👍🏼😊

Matthias

subscriber · « **Reply #24 on:** February 21, 2020, 06:03:40 PM »

Matthias,

With some work, you might be able to hollow out the shroud and add an air stripper that blows back into the shroud.

subscriber · « **Reply #25 on:** February 21, 2020, 06:24:03 PM »

Based on the Krale link and image below, it looks like the PP700 already has an air stripper, so perhaps just the shroud volume could be opened up by some clever machining?

Perhaps you could core out the shroud from the sides, as shown in one of my crude attached images? Then add curved hollow covers to increase shroud volume?

You may be better off making a new shroud without conflicting features...

https://www.krale.shop/en/silencer-adaptor-artemis-pp700s-a/

Long_Gun_Dallas · « **Reply #26 on:** February 21, 2020, 06:55:29 PM »

Thought I'd share this as well. I chopped down a spare fx liner I had to get some FPS figures off my Crown in 22. Ran 16gr pellets thru at highest hammer and port setting and the lowest on a tune intended for the same pellets and a 15" barrel.

The gun I got the data for which I think I mentioned earlier is shooting 16gr at a max speed of 820fps thru a 7.6" barrel. There is no regulator, though, not yet anyhow. I'm not sure if I will add one. The plenum is essentially 160cc (the whole air tube)

subscriber · « **Reply #27 on:** February 21, 2020, 09:16:12 PM »

Thanks Dallas,

It seem your "low" setting is pertinent to the OP's 8 FPE goal. It reinforces my opinion that cutting 2.75" off the stock 8.25" barrel will not be a problem, at that power level. Your results suggest more can be cut off, but perhaps not, if the same efficiency as an 8.25" long .177 barrel needs to be maintained.

Long_Gun_Dallas · « **Reply #28 on:** February 21, 2020, 09:50:08 PM »

Well, the .177 is a bit harder to squeeze power from. The low tune on the crown is very close to the max output of my 14.5" hot rodded pump 1322. Being a 15" barrel, I figured it would give me data that would be somewhat relatable... I just didn't know the valve setup I would get would flow so much.

JungleShooter · « **Reply #29 on:** February 22, 2020, 01:09:23 AM »

This is exciting! 😄
Thanks for sharing!

Interesting design idea for the shroud, subscriber. Thank you for taking the time to draw and post.

I had been thinking about simply taking the OEM shroud off, and replacing it with a huge pipe, diameter 1.5" or 2.0".

Then making asymmetric baffles (3D-printed) (asymmetric because the airtube would interfere with such a big shroud).

I have no problem with a pistol being bulky, even bulgy — but long is just too complicated for carrying. 😄

Matthias

subscriber · « **Reply #30 on:** February 22, 2020, 01:18:32 AM »

Hi Matthias,

I like your idea even better. A bit like the EDgun Leshiy; except a repeater, with an under barrel air tank:

JungleShooter · « **Reply #31 on:** February 22, 2020, 01:38:55 AM »

Yupp, that's the gun I saw this on!
And when I thought about silencing the shortened PP700, I knew a Ronin or Emperor wouldn't work — they are too long.

So, the only other way to go more quiet is to give the air/"sound" more space to expand and "dissipate" without making everybody's ears ring.
So, a bigger shroud tube. But since is so ridiculously short, it would need to have a ridiculously big diameter.... 😄

There is a series of articles by a guy who did semi-scientific comparative tests on a bunch of silencers, and who designed and tested replacement baffles for the Leshiy — better than EDgun made them.
He did some radical designs, too. Thinking outside the box, fascinating. 👍🏼😊

Matthias

Matthias

Long_Gun_Dallas · « **Reply #32 on:** February 22, 2020, 08:27:16 AM »

If you take a look at the 1322 above, it has an Integrated air stripper, and several cnc cone baffles. I also added some felt dampening in the tip. It is actually very quiet. Much more so that I would have expected. It is about 5 or 5.5" long. The shroud is rather small

I have found cone baffles to be most evbective. More volume helps of course. And I always try to add a retaining cage + felt in the end of the unit.

Of course the shorter the barrel, the more wasted air (noise) you will have at higher power levels. Also, hammer bounce, if at all present, contributes heavily to increased report volume

KnifeMaker · « **Reply #33 on:** February 22, 2020, 09:04:44 AM »

I beg to differ as to whether the shroud oin the PP 700 is effective or not. It may not do what you wish it did, but it is Very Effective for what its design purpos is.

It is designed to add tension to the barrel, and does it well. It is not a sound deadening device, nor is it intended to be.

However, Rocker 1 makes an adapter for very low cost to fit a mod if wanted. I have two Rocker 1 mods, and jor grins installed the Tatsu from DonnyFl that came with the Mini Raptor. All work well.

Rocker's are much lighter and do not interfere with the Reflex sight.

The same air pistol is avaliable for lesser money with a typical tube shroud that is more effective as a silencing device.

Knife

JungleShooter · « **Reply #34 on:** February 22, 2020, 09:49:54 AM »

Quote from: KnifeMaker on February 22, 2020, 09:04:44 AM

The same air pistol is avaliable for lesser money with a typical tube shroud that is more effective as a silencing device.

Knife,
do you mean the green gripped PP700-W? 😊

subscriber · « **Reply #35 on:** February 22, 2020, 05:31:53 PM »

Quote from: JungleShooter on February 22, 2020, 09:49:54 AM

Knife, do you mean the green gripped PP700-W? 😊

The round shroud version appears to be discontinued, in favor of the barrel stiffening "square" shroud version. Milling away too much of that may make the barrel whippy and less accurate, so Knife has a good point. Of course, a larger custom semi round shroud could restore that rigidity.

This adapter for the OEM shroud seems cheap enough: https://www.krale.shop/en/silencer-adaptor-artemis-pp700s-a/ The question is, what is available in Peru; or can be shipped to Peru?

JungleShooter · « **Reply #36 on:** February 22, 2020, 08:24:04 PM »

Quote from: subscriber on February 22, 2020, 05:31:53 PM

This adapter for the OEM shroud seems cheap enough: https://www.krale.shop/en/silencer-adaptor-artemis-pp700s-a/
The question is, what is available in Peru; or can be shipped to Peru?

No, it is not available in Peru. 😟

Yes, it can be shipped to Peru. 😊

Yes, it seems cheap enough!! 😄
It seems....

Only $12.50 for the adaptor, and a little bit of shipping to Peru, just $54.18!!! 🤣

➔ That's why I buy most of my airgunning stuff in the US or Germany, and have friends or colleagues bring them to me when the come to Peru....

Makes sometimes for 6-month waits.... But hey, at least I get the stuff, so I'm thankful...! 😊

Matthias

Long_Gun_Dallas · « **Reply #37 on:** February 22, 2020, 10:19:29 PM »

😮 Wow, what's up with that? Definitely makes me appreciate low shipping cost in the US

subscriber · « **Reply #38 on:** February 23, 2020, 05:34:16 AM »

Quote from: JungleShooter on February 22, 2020, 01:38:55 AM

since is so ridiculously short, it would need to have a ridiculously big diameter.... 😄

Offset and fat, like this?

Long_Gun_Dallas · « **Reply #39 on:** February 23, 2020, 10:40:40 AM »

I'd be real curious to see how effective that design is. Looks like it'd work fantastic

Thank you to our advertisers!

increased barrel length vs speed, linear graph?

Author Topic: increased barrel length vs speed, linear graph? (Read 5215 times))