NSA .25 Slug testing LW barrel

JamesD 

I started out just putting the slugs in like I did the JSB's and didn't notice at first that they were not flush with the back of barrel. See picture Below



I now press them flush, but I wouldn't say it makes my fingers sore. I don't typically do long sessions as I normally just do pest control, however I will be putting in my time as I find the best slug and tune for what I am trying to do. I did order some 43.5 and 55.5 gr slugs to test with the 18" LW that I have coming. I will test out the 12" barrel first before I swap, as I want to change the ring lock cap as I was suggested to and test this first. I want to keep it one thing at a time so I can see how everything is affected.

I got the batteries replaced in my measurement devices today and measured the expansion of the hollowpoint.

length: 0.327

Diameter: 0.250

Hollowpoint Depth: 0.2055





The slugs shot into duct seal at 12 yards had the following Dimensions: Length 0.1965 and Diameter 0.3865



What I found interesting was slugs that I fired at 33 yards and 50 yards into duct seal at a -5° angle to target. With the slug not hitting perpendicular to the target the hollow point started to open up unevenly. This created a oblong shape and larger maximum Diameter. 33 yards yielded 0.4245 Max and 50 yards yielded 0.3925 the 33yard shot was at a steeper angle than the 50 yard one. it was also interesting that penetration at these further distances were almost identical to that of 12 yards. I am not sure if that has to do with fresh seal vs seal that has been shaped a few times after retrieving pellets.The shot a 50 yards dragged a little grass into the block and can be seen in the bottom picture in the cavity or the slug.





I also made a slug case from a piece of high density foam cut in half and a plano waterproof tackle case. If holds 196 slugs total.

Today I cut the choke out of a LW 18" heavy barrel and re-crowned it after work with the help of one of the machinists. I talked to an Airforce airgun rep. and found out that the choke is only the last 1". We started my cutting off 1.25 Inch and facing is off in the lathe. We then recessed the crown and finished the bore off on the center lap to chamfer it. I already had blueing liquid at home from another PB project to finish it off. Here is the finished product. 



Tested on my 12 yard basement range the 33.5 and 31.7 grain NSA's with much better results then when the choke was there. Also, set at 10/8 proved that I had lost no power over the section I removed. Now I am going to play around with power till I find the sweet spot for the slugs in the balance between accuracy, power, and shot count. Currently I can shoot the 33.5 pretty accurate at 927fps for about 63ft-lbs. Once I get her set, I will get her out and test at 50 yards, and maybe try the shooting tree at 100.

Hobbyman

The 33.5 and 34gr slugs seat much better in this barrel than the 12" that came with it. It only takes slight pressure. I will look at doing this after I try the JB bore paste method on the barrel. 

I did get a little time to do some testing outside today, but had to cut it short due to weather. I didn't move the power wheel from the 10/8 setting, but sighted her in at 27 yards based on data from chronograph and chairgun. The 927fps avg gives me a +/- .5 " window from zero from about 21 yards out to about 61 yards, which means a quick no holdover shot for anything in that range. 

After that, I then moved back to 100 yards since the weather was going to be limiting my outing. I don't have a steady bench to use, so I went prone with shooting bags. This was not very comfortable and didn't give the most stable setup since the rear stock is just a minimalistic one and hard to get a perfect position on the rear bag, but it worked ok. I shot a couple of groups to watch how the impact changed over the shot curve, and then set up to take some shots that are in the current sweet spot for my 927 avg. With the weather coming in I shot three to see how it was shooting in this tune and then shot the duct seal target to see expansion. The wind was coming in somewhere between 10 and 11 o'clock, but I just held directly on target.



I think that part of the size of the group may be due to the trigger on the gun, which is kind of heavy and nowhere as nice as FX guns. I think practicing will definitely help.

As for the recovered hollowpoint from the duct seal, I wasn't particularly impressed with penetration depth, which was around 1/2" or maybe a little less. It did however go completely through the 1x6 board my target was taped to at that distance. It expanded pretty well, so a body shot would still prove fatal, but a head shot could potentially bounce off a thicker skull like on a raccoon or groundhog. 

 

I will have my adapter for the Ronin this coming week, so I will be able to start fiddling with power and testing in basement. I haven't done too much with new barrel yet because it is pretty loud as is, and my basement walks out to the back yard allowing any loud noise to be heard by neighbors. 

I finally got the adapter for my Ronin installed and come to the conclusion that even though the 33.5gr group pretty well, the 34gr dimple nose group better. I tuned it to shoot the 34gr @ 880fps. At 12 yards in basement range put all shots through a hole only slightly larger that .25 at I shot it down to empty tank and replace pressure gauge with a better one that has 200 lbs increments, which will make every 100lbs easier to read. I was impressed with the ability to keep the group even though I was way under what I would use while shooting. 

Today, I got the last piece installed, which is the anti-slap hammer, and then made a few adjustments to bring it close to the 880 mark again. I shot a 2x4 with the 34gr dimple nose just to see how far is would go through, and It pierced completely through and still had the energy to flatten out. This is what it looked like afterwards.