Tanfo aftermarket barrels ...

[johnbu]

On 4/10/2019 at 4:34 PM, emjei said:

Updates ??? Chrono Data ??? Accuracy ?

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Sorry for the delay.  "stuff" got in the way.

Prep and overview of the gun. Standard prep and a vortex venom 6MOA dot.

 

 

 

The shooting area from a rest on a bench.  distance lasered to 31 yards. Note the white stuff on the ground... we got 12+" in the last 36 hours!    Temps were right around freezing.

 

 

[johnbu]

I used two different bullets, Acme 124grain "new profile" and DG Bullets  124 grain. The Acme is a narrow ogive and the DG is a wide profile.

 

First... i like to "sneak up" on a barrel fitment.  it's not something I've done much and as they say, "removing metal is easier than replacing it".   So, as can be seen a "tweak" maybe needed,  but probably just self machining by shooting may work out.

 

Chrono results:

PD -Acme 1101fps, StDev 16  six rounds

PD - DG 1112fps, StDev 12 six rounds

T Acme 1075fps StDev 5 six rounds

T DG 1087fps StDev 19 six rounds

PD Acme 1096 StDev 13  - 94 rounds

 

Difference:

Acme PD - T  1096-1075 =21 fps faster

DG PD - T 1122-1087 = 25 fps faster

 

Consistently 20+ fps faster.

PF 2.6 to 3.1 points  higher.

 

The variability in StDev is approximately the same between the barrels.

[johnbu]

Initial Accuracy.

 

Using the PD barrel,  shot 6 rounds of Acme and pasted with BROWN.   Then switched to the Tanfo barrel and shot 6 rounds of Acme and pasted with WHITE.  Then shot 6 rounds of DG 124 bullets. 

 

 

Then switched back to the PD barrel and shot six rounds of  DG bullets. Those holes are unpasted.

 

You can see the average point of impact is shifting more towards the center and tightening.

 

At this point, I decided to shoot a bunch and see how the point of impact might change.

This is after about 30 more rounds with the PD barrel and Acme bullets. Sadly, after 45 minutes of 31F temps my ability to

shoot tight groups was diminishing and those "fliers" were on me.  Not the gun or barrel.

Here is the target after 94 rounds of Acme thru the PD barrel .   You can see the point of impact has shifted both up and left from the initial 6 rounds.  The target eventually was shot out just to the right of the center.  And yeah, there are some fliers.  But remember that I'm using a 6moa dot and that is about the size of the shot out spot.  And it was 31F, windy and after the 90 minutes this took I was COLD. 

 

This does tell a story.  That there is about a 0.001" to 0.002" somewhere that is holding it out of perfect lock.  But the shift in POI is telling me that it is self machining and getting better on it's own.   So... the plan right now is to shoot it a bunch and see how it improves.  Yeah,  that's a bit slower but I think it will result in the tightest long term fit.

 

This is the last picture from today.  you can see the hole in the snow on the berm from all the rounds.  The distance to the back berm is just under 40 yards. A pretty small zone for 40 yards. 

 

Summary:

I'm not 100% satisfied with the fitment of the barrel to the gun.  I chalk that up to my inexperience, but it should be close enough to "break in" or self machine and tighten up as the last bit is worn off.  To be honest,  It's at the point where I'm afraid I may take off too much from the wrong spot.  A good cleaning,  an inspection, probably sharpie mark it up and then shoot it another couple hundred rounds and see where things are rubbing will be the next steps.

 

The difficulty of fitting the barrel wasn't too bad.   The hardest part is being patient and avoid trying to remove too much all at once. BUT !  it isn't a "15 minute job" for the average person with common tools and a roll of sand paper.  So, don't even THINK it's that fast. 

 

 

 

Edited April 13, 2019 by johnbu

[je85]

37 minutes ago, johnbu said:

Initial Accuracy.

 

Using the PD barrel,  shot 6 rounds of Acme and pasted with BROWN.   Then switched to the Tanfo barrel and shot 6 rounds of Acme and pasted with WHITE.  Then shot 6 rounds of DG 124 bullets. 

 

 

Then switched back to the PD barrel and shot six rounds of  DG bullets. Those holes are unpasted.

 

You can see the average point of impact is shifting more towards the center and tightening.

 

At this point, I decided to shoot a bunch and see how the point of impact might change.

This is after about 30 more rounds with the PD barrel and Acme bullets. Sadly, after 45 minutes of 31F temps my ability to

shoot tight groups was diminishing and those "fliers" were on me.  Not the gun or barrel.

Here is the target after 94 rounds of Acme thru the PD barrel .   You can see the point of impact has shifted both up and left from the initial 6 rounds.  The target eventually was shot out just to the right of the center.  And yeah, there are some fliers.  But remember that I'm using a 6moa dot and that is about the size of the shot out spot.  And it was 31F, windy and after the 90 minutes this took I was COLD. 

 

This does tell a story.  That there is about a 0.001" to 0.002" somewhere that is holding it out of perfect lock.  But the shift in POI is telling me that it is self machining and getting better on it's own.   So... the plan right now is to shoot it a bunch and see how it improves.  Yeah,  that's a bit slower but I think it will result in the tightest long term fit.

 

This is the last picture from today.  you can see the hole in the snow on the berm from all the rounds.  The distance to the back berm is just under 40 yards. A pretty small zone for 40 yards. 

 

Summary:

I'm not 100% satisfied with the fitment of the barrel to the gun.  I chalk that up to my inexperience, but it should be close enough to "break in" or self machine and tighten up as the last bit is worn off.  To be honest,  It's at the point where I'm afraid I may take off too much from the wrong spot.  A good cleaning,  an inspection, probably sharpie mark it up and then shoot it another couple hundred rounds and see where things are rubbing will be the next steps.

 

The difficulty of fitting the barrel wasn't too bad.   The hardest part is being patient and avoid trying to remove too much all at once. BUT !  it isn't a "15 minute job" for the average person with common tools and a roll of sand paper.  So, don't even THINK it's that fast. 

 

 

 

Great job John!!

I look forward in hearing how things work out in a couple thousand rounds of testing.

[johnbu]

Ok, i was dry firing and when my elbow started up to hurting, i switched to playing with the tanfo stuff.

 

Sharpie marked up the cone end and the chamber side. Racked it a bunch and inspected.

 

.pre rack here

The post rack cone pick didn't turn out (sorry) but it looked "normal". However i thought a bit heavy on the rub.  so i hit the cone with 600, 1200 and 3000 grit, then polished.

Post rack. You can see the left side is rubbing more. I think that would push the nose of the barrel right.

 

Naturally, it's even colder today, cloudy and in fact it started to sleet.

Next step will be more rounds.

[johnbu]

Ran 230 rounds.  same target as before, but i used the upper zone and moved to 15 yards for ease of aiming.

[emjei]

So.....the best solution is to buy the barrel and let it fit itself by shooting a bunch ???

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