.217/.218 Slug investigation

[Dave]

I have been testing slugs in a Lothar-walther barreled airgun and noticed for the same tune that a slug of .217 Dia. is slightly slower than a slug of .218 Dia. However at their best velocity for accuracy, the .217 Dia. wins every time. I believe this is due to the reduced ID of the choke liking the .217 Dia. better as it exits the barrel.

I wanted to see how the .218 interacted with the lands and grooves of the rifleling, so chambered a Slug and removed my barrel from the action to prevent accidental discharge. A gap between the slug and groove can clearly be seen, but is slightly smaller than the gap of the .217 slug by .0005. This tighter fit would be the reason for the more efficient use of air, which allows the velocity to be slightly higher.

This leads to my question and experiment.

https://www.airgunnation.com/topic/big-bore-airgun-deer-hunting-ammo-pro-tip-how-to-make-45-death-star-slugs/



I saw the video that copper slugs were coated to size them up for the Airforce Texan, and wonder if these lead slugs can be done in simular fashion. Something to help make the seal in the bore better, allowing a tune that reduces air consumption. while generating little drag on the projectile. In the video it seamed that the coating didn't interfere with anything and didn't leave debris inside the barrel, but may require more frequent cleaning of my baffles.

I just purchased a can of the coating and will do some testing with the .217 and see if this works. This might require use of a single shot tray to prevent the coating from being peeled of by a magazine before entering the barrel. 

Any way I have 23 gr NSA's in .217 coming tomorrow, which I will do initial setup and testing on to get baseline data. Then when the graphite coating comes in I will see what if any benefits might be had.

https://www.greenpartstore.com/John-Deere-Graphite-Lubricant-TY25797.html

 

[JimNM]

Subscribed! Waiting not patiently for more info

 

[bubblerboy64]

I have been testing slugs in a Lothar-walther barreled airgun and noticed for the same tune that a slug of .217 Dia. is slightly slower than a slug of .218 Dia. However at their best velocity for accuracy, the .217 Dia. wins every time. I believe this is due to the reduced ID of the choke liking the .217 Dia. better as it exits the barrel.

I wanted to see how the .218 interacted with the lands and grooves of the rifleling, so chambered a Slug and removed my barrel from the action to prevent accidental discharge. A gap between the slug and groove can clearly be seen, but is slightly smaller than the gap of the .217 slug by .0005. This tighter fit would be the reason for the more efficient use of air, which allows the velocity to be slightly higher.

This leads to my question and experiment.

https://www.airgunnation.com/topic/big-bore-airgun-deer-hunting-ammo-pro-tip-how-to-make-45-death-star-slugs/



I saw the video that copper slugs were coated to size them up for the Airforce Texan, and wonder if these lead slugs can be done in simular fashion. Something to help make the seal in the bore better, allowing a tune that reduces air consumption. while generating little drag on the projectile. In the video it seamed that the coating didn't interfere with anything and didn't leave debris inside the barrel, but may require more frequent cleaning of my baffles.

I just purchased a can on the coating and will do some testing with the .217 and see if this works. This might require use of a single shot tray to prevent the coating from being peeled of by a magazine before entering the barrel. 

Any way I have 23 gr NSA's in .217 coming tomorrow, which I will do initial setup and testing on to get baseline data. Then when the graphite coating comes in I will see what if any benefits might be had.

https://www.greenpartstore.com/John-Deere-Graphite-Lubricant-TY25797.html

 

[Dave]

Updated to reflect the correct slug weight of 21gr.



After discussing with a few coworkers my idea, I remembered that we have a John Deere store just outside of town. I called them and they had the TY25797 graphite coating in stock, so I was able to get some to test with today. 

Luckily, I still had just enough .217 21gr slugs left to verify my hypothesis about the increased velocity. The uncoated slug can be seen setting in the rifleling, which was protected by my flashlight onto the paper.

The first thing I did was to verify the .217 Dia., then washed the slugs to ensure all mold release and lubrication had been removed. I then sprayed them with a few coats of the TY lube, to ensure that they were coated well. 

I measured them after coating to check final Dia., which varied from around .219 - .220. The goal was to prove a better seal with higher velocities, so consistent coating thickness was not really looked at. 

They definitely look Tacticool in black.

Setup conditions:

Airgun is the Lothar-walther barreled .22 cal Mrod. set to approx. 2800 psi before each string.

Chronograph is the Competition Electronics Pro Chrono. set 6" from muzzle for both strings.

Slug is NSA .217 21gr .22 (Not 19gr)

Here are the results:

I think the greater ES and SD comes from the variation in coating thickness, which I will have to find a way to get a more consistent thickness. But with no change in anything except the thickness of the projectile and a little graphite lube help, There was a 20 FPS increase in Avg speed. 

When the new slugs arrive tomorrow, I will have to see if there is any difference in just an extremely thin coating, which might suggest that the velocity comes from the graphite lube or if a thicker coating is required.



I tried coating the last 7 21gr slugs I had very lightly to see how much the thickness mattered. That's when I discovered that I was actually using the 21gr .217 instead of the 19gr .217 slugs( which I have already used up the supply of), Which makes more sense in relationship to the velocities I recorded during the string. After coating the thickness was around .2175 - .218, which yielded an average FPS of 838 FPS which is 9 more than uncoated.This would suggest that it is more due to tighter seal in the bore.

 

[AirSupply]

Really interesting. You could try just lightly lubing some pellets with Ballistol and see if that gives the same increase in velocity. I have a metric sizing die that is .2172 in. I have had good results using it on .218 slugs in my fx slug liner. I personally think if you shoot slugs and can find the right sizer for your barrel it’ can be very useful.
I’ve also had slugs that weren’t exactly the size I ordered. If you have the sizer that’s just right for your barrel you can run them through to check them. You can often notice some inconsistencies in the pressure required to push them through. 
Would be nice to be able to get hold of sizers in smaller fractional steps to experiment with. 

 

[Dave]

 I go the 23gr slugs today, and unfortunately, they are a bust for me.

I had them moving at about 840 FPS and making over 35ft-lbs, but they couldn't hold a group out of my barrel. 

One thing I noticed was that there is significant more slug engagement with the rifleling.

I could tell the difference as I chambered each slug as compaired to the 21 gr slugs. 

Here is what I got at 12 yards

Velocity was withing 10 FPS on all slugs.

 

[mercado]

Slugs are harder than pellet skirts..NSA slugs I have measure mine depending on weight between 5.50...5.51..5.52..my lothar Walter condor barrel in 24"..and..18"..will only shoot perfect 5.49 sized slugs hole in hole..any other size simply don't work for me..

 

[mercado]

I have even sized pile drivers to 5.49 and now they shoot great...the sizer is the one from Europe in Ebay I buy the 5.50 to be sure.. still to tight then I ask if they could machine me one in 5.49..and they do..it work awesome for slugs..don't buy it to size pellets.i don't se any advantage. 

 

[AZ_Shooter]

I have even sized pile drivers to 5.49 and now they shoot great...the sizer is the one from Europe in Ebay I buy the 5.50 to be sure.. still to tight then I ask if they could machine me one in 5.49..and they do..it work awesome for slugs..don't buy it to size pellets.i don't se any advantage.

Can you PM me a link to the sizer on eBay?