Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 71 users online :: 4 registered, 1 hidden and 66 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

accuracy and muzzle treatments

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

accuracy and muzzle treatments

Unread postAuthor: Anatine Duo » Wed Mar 15, 2017 9:25 pm

Planning to do some informal accuracy testing tomorrow...

For some time I have considered muzzle porting to release barrel pressure so that uneven forces on the base of the projectile at the muzzle can be minimized. I have an extensive firearms background and this is not a strategy pursued by mainstream firearms manufacturers. I think this is because mainstream manufacturers use rifling to provide a lot of gyroscopic stability and also high density projectiles (lead core) of high precision combined with precision crowning (balanced forces as the projectile exits)

For us, shooting usually lower density, lower precision projectiles, out of smoothbores with lower precision crowns, dropping barrel pressure just before the muzzle might help our projectiles exit our barrels pointing the way we want, whether that means more range because a spud slug isn't tumbling wildly, or more accuracy because the slug isn't tumbling wildly.

I'll be shooting patched round ball tomorrow, my hope being a patch better obturates the compressed air in the barrel (for power) as well as reducing random spins (for accuracy)

In future I would like to shoot longer heavier slugs (cylindrical) to improve efficiency at launch as well as sectional density, but I feel these would be more vulnerable than roundball to muzzle blast effects. Also arrows are a strong possibility but I think these are even more vulnerable to muzzle blast effects as the light base is easily pushed around.

I am considering a rifled-choke-style addition to my Bullshark launcher... this could be compared to a ported barrel extension...

Please speculate... :)
  • 0

User avatar
Anatine Duo
Sergeant
Sergeant
 
Posts: 84
Joined: Sat Feb 01, 2014 11:16 am
Country: Canada (ca)
Reputation: 5

Re: accuracy and muzzle treatments

Unread postAuthor: jackssmirkingrevenge » Wed Mar 15, 2017 9:52 pm

I would say that any kind of choke or porting isn't going to have a visible effect on accuracy once you're still shooting through a smoothbore barrel.

The first step would be to concentrate on a stable projectile that can be fabricated in a consistent fashion. If you step up to a 0.75" from 0.64" cartridges for example, 12 gram CO2 capsules are an exact fit and when cut in half and weighted on one end, you have a relatively easy and effective slug that will not tumble:

  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24593
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 87

Re: accuracy and muzzle treatments

Unread postAuthor: Anatine Duo » Wed Mar 15, 2017 10:20 pm

Stable in flight yes, but maybe you have heard of Taofledermaus ;)

High frame rate often shows wild oscillations at muzzle but point-first impacts at 25 yards

Since I am used to moa accuracy (oh man I love my 17 HMR when there is no wind) ... and design challenges... I am curious what we can do.

Of course I keep my used 12gram co2 cartridges for exactly this purpose but I find they are not consistent wall thickness (non concentric)
  • 0

User avatar
Anatine Duo
Sergeant
Sergeant
 
Posts: 84
Joined: Sat Feb 01, 2014 11:16 am
Country: Canada (ca)
Reputation: 5

Re: accuracy and muzzle treatments

Unread postAuthor: jackssmirkingrevenge » Wed Mar 15, 2017 10:31 pm

Anatine Duo wrote:maybe you have heard of Taofledermaus ;)


Who? :D
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24593
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 87

Re: accuracy and muzzle treatments

Unread postAuthor: Sear » Thu Mar 16, 2017 10:12 am

Why not to use fin-stabilized projectiles instead of "simple" slugs?
  • 0


Sear
Private First Class
Private First Class
 
Posts: 30
Joined: Thu Apr 21, 2016 6:17 pm
Country: Austria (at)
Reputation: 11

Re: accuracy and muzzle treatments

Unread postAuthor: jackssmirkingrevenge » Thu Mar 16, 2017 10:40 am

I'll go one further, why not try and source a rifled shotgun barrel?
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24593
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 87

Re: accuracy and muzzle treatments

Unread postAuthor: Anatine Duo » Thu Mar 16, 2017 1:52 pm

Rifled barrel is too expensive for me! I would certainly consider a rifled "choke" tube... wish I'd bought one years ago. Also I am leaning toward larger bores than 12ga.

Accuracy has been crap so far with cloth patched marbles. Will keep trying.

Sedak I plan to use some fin/otherwise drag stabilized projectiles but I remain concerned about muzzle blast hitting the fins and losing accuracy that way.
  • 0

User avatar
Anatine Duo
Sergeant
Sergeant
 
Posts: 84
Joined: Sat Feb 01, 2014 11:16 am
Country: Canada (ca)
Reputation: 5

Re: accuracy and muzzle treatments

Sponsored

Sponsor
 


Re: accuracy and muzzle treatments

Unread postAuthor: Sear » Thu Mar 16, 2017 2:51 pm

And what is the pressure and slug material you are using?
  • 0


Sear
Private First Class
Private First Class
 
Posts: 30
Joined: Thu Apr 21, 2016 6:17 pm
Country: Austria (at)
Reputation: 11

Re: accuracy and muzzle treatments

Unread postAuthor: WizardNoodle » Thu Mar 16, 2017 5:22 pm

And just an idea, maybe you can also test the effects of a simple muzzle brake and how it compares to barrel porting.
  • 0

Penetration is key

WizardNoodle
Specialist
Specialist
 
Posts: 56
Joined: Fri Feb 24, 2017 10:13 pm
Country: United States (us)
Reputation: 0

Re: accuracy and muzzle treatments

Unread postAuthor: Anatine Duo » Thu Mar 16, 2017 9:12 pm

150 to 240 psi roundball, 90gn

So I recovered some patches and noticed the majority had a hole torn through in the middle. I think they are being blown past the marble? Going back to paper patches next. They were all intact during function testing.

Paper patches were surprisingly consistent... as in the paper patches all landed in the same spot! I got some decent groups (nothing as good as my initial 3 shot sight-in) but occasional flyers. Tight marbles grouped with loose ones, not sure why the fliers (I guess those marbles were not as round) Got a few exploded marbles from near dead-on hits.

Tried foam gas checks and overshot wads, same thing, half decent group with flier.

Tomorrow is a gas check with cloth patch. I guess I'm trying to get a launch similar to a clean slingshot launch i.e. no spin.

Still need to source material for heavy drag stabilized slugs... 5/8" by 1" steel cylinder on top of 5/8 by 2 wood dowel, paper wrapped to fit bore.

My porting question really is like the airstripper question... I read at least 2 references here to porting improving accuracy/range. The airstrippers are debated on the airgun forums.

Anyway the foam gas checks under cloth patched marbles was a fail... 6" groups at 7yards. Paper-patched-only gave a 3 shot cloverleaf at 7yd, no fliers but 3 shots is a small sample. Started shooting at 90psi due to noise issues.
  • 0

User avatar
Anatine Duo
Sergeant
Sergeant
 
Posts: 84
Joined: Sat Feb 01, 2014 11:16 am
Country: Canada (ca)
Reputation: 5

Re: accuracy and muzzle treatments

Unread postAuthor: BertieKerter1 » Tue May 23, 2017 8:22 pm

You can make it.
  • 0


BertieKerter1
Private
Private
 
Posts: 2
Joined: Tue May 23, 2017 2:11 am
Country: United States (us)
Reputation: 0

Return to General Spud Cannon Related

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Yahoo [Bot]

Reputation System ©'