Choking a barrel suggestions

[Taso1000]

Hi All,

So I have been trying to find the best pellet for my fully tuned FD B-26 in .177.  I have not had good luck.  My best groups are around 1/2 inch at 12 yards shooting in my basement with a 24 power scope. 

I have tried to clean the barrel and have run JB bore cleaner with a nylon brush and patches.  Did not make my groups better.  So I ran a pellet through the bore to check for tight or loose spots and for choke. 

I guess bore is ok as there are no tight spots or loose spots.  I do have very little resistance at the muzzle for about 1/64th inch.  It's probably a lip from the crown. 

I am thinking of choking this barrel with my pipe cutter choker.

From what I have researched, a .02 restriction at the muzzle is recommended and it is also recommended that the best way to do this is to choke the muzzle till resistance is felt at the pellets you intend to use.

So here is my question:  I have a .177 PelletGuage.  Which head size should I use to gauge the choking?

I'd like to size for Crosman Premier Lite's in the brown box so that I get the best accuracy from non sorted pellets.  But here is my dilema.  If my rifle's bore is .177" and 4.4958mm What head size do I use to test how much to choke?

If I use a smaller head size to gauge my choking, the bigger pellets will need more resizing in my barrel and should theoretically exit at a lower velocity.  Smaller head size pellets will zip though my barrel at a faster speed since they are not being sized by the choke. 

How do I balance velocity extreme spread and choke size for best accuracy?  If I create a choke small enough to resize all pellets then I will have terrible ES and larger groups. 

If I pick a choke in the middle then what? 

It's a catch 22!   

So I am stuck on how to proceed.

Thank you all in advance for your suggestions and guidance!

Taso

[nervoustrigger]

Unless the bore is grossly oversized, you don't want to apply a choke tighter than 0.002".  Bear in mind that 2 thousandths of an inch is 0.05mm which pretty well spans the range of the smallest and largest sizes of typical pellets.  Also, many barrels shoot great without a choke so if you are getting any engraving on the heads of your preferred pellet, start with a very subtle choke and see if you are happy with the results.  You can always add more.

However, I recommend first dealing with the apparent burr at the crown.

[Mr. Panther]

+1 Jason. I'd take care of the burr first. sounds like it might be the fix to the problem rather than a choking the barrel. JMO

[Taso1000]

Thanks Everyone for the suggestions! 

First I will pull the break off the barrel and inspect the crown.  If there's a ding or lip I'll remove an 1/8" or so of the barrel and recrown.  Then test for accuracy.

Thank you for the clarification of .002 inches!  I remembered wrong.   

So, I was looking at my Pelletgage and the holes increment by .01mm.  I guess I could sort about 100 CPL's and see where the head size distribution looks like and use the most common diameter for testing. 

My thinking is instead of finding the CPL diameter the barrel likes, choke the barrel to like the majority CPL head size. 

I probably wasn't too clear last night when I posted.  And I have yet to choke a barrel so I got excited that I could try it out.

Thank you,

Taso

[nervoustrigger]

No problem!

Regarding the pellet head sizes, I expect you will find them to vary to an extent so as to not be very useful for guiding your choke amount.  Also, know thy measurement limitations. . A go / no go gauge of this sort can only pass the largest chord. Pellets are frequently out of round, Crosman more so than JSB, H&N, and RWS in my experience.  But all is not lost.  Diabolo pellets are more forgiving of dimensions than bullets.  The skirt obturates (expands) to form a seal, and the head need only ride the lands to keep it from tipping as it accelerates through the bore.  So as long as you can push them through and see some engraving, that's all you need. 

[Taso1000]

Thanks Jason!  A couple of the pellets I pushed through had almost no indentation on the head and when they did it was on one side, not all the way around as I could tell. 

I will do more testing today.   

Taso

[WyoMan]

Hi Taso... some thoughts on choked barrels...

I have about 40 barrels of which 30 or so are choked. They're all decent barrels - LW, HW, and TJ's. I recently got a tin of jsb 8.44 that were seriously undersized. There was little to no engraving resistance when being loading. The choked barrels shot them very well (using group size as the metric). The un-choked barrels sprayed them into patterns.

I opened another tin (jsb 8.44) and they were correct in size as I could feel the normal engraving resistance. The un-choked barrels shot them just as well as the choked barrels - no difference. I truly believe that the choke is only needed to 'save the shot' from an undersized pellet... and that happens enough to make a difference. But the barrel has to have a well machined bore or the choke is not going to save the shot.

That being said, I would not attempt to try some home technique to choke a barrel. The LW barrels I slugged and mic'd have a very uniform 'funnel' taper for the choke. It starts at about 1-1/8" from the muzzle and ends with a .002" reduction (o.d and i.d). I've heard it's done on a machine with tapered jaws... don't know for sure.

Jason mentioned the heart of the issue... you need a pellet that fits the bore. It sounds like your barrel has a nice bore (no tight or loose spots), so try some different pellets first. And don't worry (for now) about the lip at the muzzle that causes a slight restriction. I've had many of those and not only did it not affect accuracy, but it went away with enough down the pipe... hth

Wyo

[Rob M]

Wyo , have you see the vigilante hacking thread?? hes getting a good choke on straw barrels using a knurling tool.. radial pressure + time

[Taso1000]

Wyo,

Thank you.  Over 2 days I tried all the different .177 pellets I had.  No pellet gave good accuracy at my basement range of 12 yards.  Yesterday I tried one of those rubber Limbsaver barrel harmonic tuner with brown box CPL's.  Best I could do is 1/2" when moved to 3 different positions about an 1/8" apart. 

Then I thought to give the barrel a good cleaning and also do a quick JB bore treatment.  I then pushed pellets through the barrel and noticed the lip/burr right at the very end of the muzzle.  The breech has resistance and the middle of the barrel has very little to none. 

The next thing I'm going to try is recrowning the barrel.  I also may not be able to choke the barrel with my pipe cutter choker.  I forgot the barrel has the dovetails to mount a front sight.  I don't know if the rollers are going to get stuck in the dovetails.

Oh well.  One thing at a time.   

Thank you All!

Taso