Did it - extended the polygonal barrel with smooth bore extension

[mubhaur]

I do no find a logic in changing the twist rithm of the pellet at the middle of the travel trough the barrel.

In my mind is like the pellet was hiting something inside the barrel.

Do not find a logic.

I understand that as I am going to put the smooth bore section on the breach side, there is no twist in that area and hence there is not change in twist rhythm. Rather the twist will start when the pellet will enter the grooved part.

I understand it will not be much different than FX smooth twist concept.

Regards,

Bhaur. 

 

[Emu]

I do no find a logic in changing the twist rithm of the pellet at the middle of the travel trough the barrel.

In my mind is like the pellet was hiting something inside the barrel.

Do not find a logic.

I understand that as I am going to put the smooth bore section on the breach side, there is no twist in that area and hence there is not change in twist rhythm. Rather the twist will start when the pellet will enter the grooved part.

I understand it will not be much different than FX smooth twist concept.

Regards,

Bhaur.

What I did on the poligonal barrel is my Bantam is to make a bigger entrance to the barrel with a wider drill, and then, with a small drill (but using my hand not the driller) very slowly, erased the first two centimeters of the twist of the barrel in order that the pellet do not get damage in the travel from the magazine to the breach.

The insertion of the pellet to the breach is now very smooth.... The accuracy of my Bantam at very long range is perfect.

I am of the idea that I achieved what you want, but without merging two kinds of barrels.

 

[mubhaur]

I do no find a logic in changing the twist rithm of the pellet at the middle of the travel trough the barrel.

In my mind is like the pellet was hiting something inside the barrel.

Do not find a logic.

I understand that as I am going to put the smooth bore section on the breach side, there is no twist in that area and hence there is not change in twist rhythm. Rather the twist will start when the pellet will enter the grooved part.

I understand it will not be much different than FX smooth twist concept.

Regards,

Bhaur.

What I did on the poligonal barrel is my Bantam is to make a bigger entrance to the barrel with a wider drill, and then, with a small drill (but using my hand not the driller) very slowly, erased the first two centimeters of the twist of the barrel in order that the pellet do not get damage in the travel from the magazine to the breach.

The insertion of the pellet to the breach is now very smooth.... The accuracy of my Bantam at very long range is perfect.

I am of the idea that I achieved what you want, but without merging two kinds of barrels.

Agreed

I also enlarge the lead of the barrel a bit. It helps pellet enter the barrel without getting deformed.

I am going to use the same principle during pellet transition from smooth bore to grooved bore.



Bhaur 

 

[Motorhead]

just make SURE !!! the short section of barrel you add if at breech "DOES NOT" have a tighter bore than barrel it must also seal within and have head support before it hits rifling.



Being a POLY creates a NON ROUND profile out of a Round pellet .... forcing it again to shape shift back to ROUND i have my doubts on being successful ?

Dear Motorhead,



Thank you for guiding me. 

I just need a bit of elaboration. I understand that the smooth bore at breach should support the pellet but it should be a bit loose than the rest of grooved barrel otherwise the smooth bore will reduce the dia of the pellet and then it will enter the grooves.



I understand that I should give a bit of a taper angle at the joining parts. I shall keep the smooth bore a bit loose than the rest of the rifling while supporting the head of the pellet. 

If executed properly,do you still have doubts of success?

I shall choke the muzzle as well. 

Please advise further.



Regards,



Bhaur

Thoughts off the top of my head .....

Pellet stability being held head to tail YAW free is paramount the entire trip breech to muzzle !

Any shifts in a pellets shape or size can upset staying YAW FREE

Altering a pellets shape absorbs energy and when this shape shift happens early and at low speed, the pellet can continue to accelerate and gain RPM proportional to the velocity obtained while contacted to rifling. Only getting a slow down if a Choke is present. 

In my testing / cobbled together barrel, the Smooth bore was slightly smaller than the rifled section therefor NO Yaw could happen so long as pellet was a correct fit within the rifled section.

Compression seal was un-compromised being the rifling marks were eliminated as it passed into the smooth bore. 





ADDING MORE BARREL LENGTH for the sake of gaining velocity from an otherwise TOO SHORT a barrel ..... get a NEW longer barrel !!!



Scott S

 

[mubhaur]

just make SURE !!! the short section of barrel you add if at breech "DOES NOT" have a tighter bore than barrel it must also seal within and have head support before it hits rifling.



Being a POLY creates a NON ROUND profile out of a Round pellet .... forcing it again to shape shift back to ROUND i have my doubts on being successful ?

Dear Motorhead,



Thank you for guiding me. 

I just need a bit of elaboration. I understand that the smooth bore at breach should support the pellet but it should be a bit loose than the rest of grooved barrel otherwise the smooth bore will reduce the dia of the pellet and then it will enter the grooves.



I understand that I should give a bit of a taper angle at the joining parts. I shall keep the smooth bore a bit loose than the rest of the rifling while supporting the head of the pellet. 

If executed properly,do you still have doubts of success?

I shall choke the muzzle as well. 

Please advise further.



Regards,



Bhaur

Thoughts off the top of my head .....

Pellet stability being held head to tail YAW free is paramount the entire trip breech to muzzle !

Any shifts in a pellets shape or size can upset staying YAW FREE

Altering a pellets shape absorbs energy and when this shape shift happens early and at low speed, the pellet can continue to accelerate and gain RPM proportional to the velocity obtained while contacted to rifling. Only getting a slow down if a Choke is present. 

In my testing / cobbled together barrel, the Smooth bore was slightly smaller than the rifled section therefor NO Yaw could happen so long as pellet was a correct fit within the rifled section.

Compression seal was un-compromised being the rifling marks were eliminated as it passed into the smooth bore. 





ADDING MORE BARREL LENGTH for the sake of gaining velocity from an otherwise TOO SHORT a barrel ..... get a NEW longer barrel !!!



Scott S

Dear Scott,

Thank you for your opinion. I still think that it may be hit or miss. Let's see but in either case I shall learn I hope.

If I go to New barrel route then in my experience old stock BSA barrels are most accurate. I may be wrong but at least to my limited experience BSA legendary old stock barrels are unique for accuracy. 

I shall find a BSA barrel and install it.

Regards, 

Umair Bhaur 

 

[mubhaur]

An experiment on lengthening the barrel by joining a barrel to a smooth bore. 

Final touches are yet not completed but good accuracy has been successfully achieved. 

Around 3" smooth bore has been attached to the breach side.

Proper sealing of joints and good crowning is yet to be done.

I am achieving 1.5" groups of 5 shots with 34 grain .25 mk1 and similar results with 25 grain jsb. 95 yards.

Off course at different power levels.

I understand that results will improve once the comple barrel breaks in and some refinements are incorporated. 

Regards, 

Umair Bhaur 

 

[mubhaur]

Finally I have achieved the goal with good success. 

Now I have to refine a few areas in the barrel etc. Muzzle shall be threaded and crowned properly. 

I shall update in due course.

Regards, 

Umair 

 

[mtnGhost]

Congrats!

 

[knifemaker]

Once again, Air Gunners not knowing what has come before in shooting. What you have created is called Free Bore. It was one of the aspects that made
Weatherby world famous for there unusual fps and power. The Wheel has be re-created. 

Knife

 

[mubhaur]

Dear members, 

Here I share a failure in the experiment.

I polished down the smooth bore extension a bit as there were tool marke in it. But after removing tool marks now the barrel is not accurate at all. 

Looks like a bit tighter smooth bore is needed for this purpose. 

I might develop one out of brass for better cutting and machining characteristics with ordinary machines that I have access to.

Regards, 

Umair Bhaur 

 

[Emu]

Dear members, 

Here I share a failure in the experiment.

I polished down the smooth bore extension a bit as there were tool marke in it. But after removing tool marks now the barrel is not accurate at all. 

Looks like a bit tighter smooth bore is needed for this purpose. 

I might develop one out of brass for better cutting and machining characteristics with ordinary machines that I have access to.

Regards, 

Umair Bhaur

Try different pellets. Not all have the exact same diameter.