Tuning .25 Impact w/PP slug build

[Centercut]

Decided I’d like to reach out past 200 yards (250?, 300?) for ground squirrel hunting. I recently bought a used Impact with PP in .30 that I want to turn into a .25 dedicated slug gun. I’d like to shoot heavier (36 to 40 grain) NSA slugs at 950 to 1000 FPS accurately enough for long range schwackin’

I have the 700mm Slug A liner, Ernest dual transfer port, pin probe from FX power set along with HST washers and lighter valve spring, liner lock, high power hammer spring, barrel attachment, and barrel house (tube that liner goes into). Anything else needed?

I’d appreciate any advice from those that have already been down this path as far as Reg pressure, most accurate speeds, etc... I could have gone .22 but wanted .25 since my .22 Eddy R3 long already shoots NSA 20.2 accurately out to 175+ yards. Thanks!

Mike

 

[Powerage]

I have a similar setup . PP. with the slug power kit . 700 mm barrel. With the Slug A the nsa 36.2 and the 38 had the best accuracy around 880 - 910FPS. With the superior heavy the accuracy is better at higher speeds . 36.2 at 1020fps is my current setting. Reg at 155.

 

[Centercut]

Thanks. I intend to try a Superior and a Superior Heavy once FX finally starts importing them again. They are not available in the USA...

Do you remember how far in you set the pin probe?

Mike

 

[Mrshosted]

You got a Impact, nice! Congratulations. Try and set the prope so it pushing the slug all the way into the riflings. Some of the early liners have 3/8 of a inch smooth area before the riflings start. This is one one of the reasons why the new barrels are shooting slugs better. The new liner's have the rifling starting at the opening, there is no smooth lead in. The depth can be tricky, requiring some trial and error. I'm finding my Impact like the larger diameter slugs, that are very tight pushing into the riflings. 

Mont

 

[Powerage]

At first the new pin probe made the magazine to index to much. Result 2-3 slugs in the barrel. I just had to back it out to line up with the magazine. Haven’t tried adjusting more. I can see the probe pushes the slug past the transferport holes. With the original probe that was not always the case. Specially with smaller slugs.
I live almost in the arctic and one of the biggest issues is the difference in temperature inside where you storage the rifle and outside . The slug is stable at a exact speed . Specially the 25 seems to be very picky when it comes to changes in temperature . 1020 FPS is very accurate. 1010 FPS and the group opens up. 

 

[Centercut]

Put the gun together today, shifted from .30 caliber to .25 caliber, 700mm Slug A liner with FX Power Plenum upgrade to Impact X. Installed Ernest dual transfer port, FX Slug Power pin probe set to push slug in as far as possible. Increased reg pressure to 120 bar. Took up all tension when power wheel on MAX. Valve adjust on 3rd line.

Shooting NSA 36.2 grain slugs at 960 FPS with power wheel on "MAX". Shooting JSB Heavy 34 grain pellets at 905 FPS with power wheel on "3". Looks like I can easily go much higher than the current 75 FPE setting, but gun isn't stressed at all and is still easy to shoot, feels like its just coasting... Will take out this weekend to tune for accuracy and try other weight NSA slugs. I have the 38.5 and 43.5 to try yet. More to follow...

My goal is to basically have an air powered .22 LR that I can reach out and “touch” the ground squirrels east of San Diego at up to 250, maybe 300 yards...

PS., thanks to @biohazardman and @justweld and everyone above for their tuning recommendations

PPS. If you look at the photo right side you can see the slug magazine inserts that @orion makes and sells here on AGN and on his own web site. Mine are yellow and red, and they work great. 
https://www.airgunnation.com/topic/wts-fx-impact-magazine-replacement-feeder-to-fix-slug-issue/

 

[triggertreat]

Very nice setup with good power!

I am doing a similar thing with my MKII .30 cal. with focusing on .25 cal slugs, but I'm working with a 600mm Superior liner instead. I am getting good consistency with 33.5gr NSAs. The best accuracy so far has been with the AVS slugs off eBay. They are .254 cup base HPs that can be ordered in weights between 28 - 48 gr. in 120 Ct. The Superior liner really likes the .30gr at 970 FPS.

 

[golfer70]

My 700mm Impact does very well with the 33.5g NSA’s at 1025fps. Regulator at 145 bar and the VA out just past the 4th line with the Superior liner. I hope this helps. 

 

[Smok3y]

PPS. If you look at the photo right side you can see the slug magazine inserts that @orion makes and sells here on AGN and on his own web site. Mine are yellow and red, and they work great. 
https://www.airgunnation.com/topic/wts-fx-impact-magazine-replacement-feeder-to-fix-slug-issue/

I was wondering what those were. Thanks for confirming.

 

[Powerage]

Looks like you have a promising tune there. The ability to switch between jsb King heavy and NSA with the power wheel is what makes the impact so versatile. And those king heavy mk1 are accurate ! On a calm they it’s one hole at my garden range (88 yards).

 

[Centercut]

Not the best of news. Shot at 50 yards Saturday. All NSA with 700mm Slug A liner. 33.5 at 1000, 36.2 at 960, 38.5 at 920 and 43.5 at 855 FPS. These speeds were with power wheel on Max and Valve adjust about 2 1/2 lines. The only slug that was under an inch 5 shot group was the 43.5. And that wasn’t stellar, about 3/4 inch.
So do I keep trying with the 36.2, which seems to be the most recommended for the Slug A liner, or raise the power some and see if the 43.5 tighten up at closer to 900 FPS? 
Or, do I find a Superior liner and try lighter slugs like the 29 or 33.5 NSA, 34 JSB KO or similar?

The negative part about the 43.5 is the length. They don’t fit in the magazines, and I had to use the single shot loader from CARM. Also, even if they are accurate at 900 FPS after I bump up the power, the drop past 200 yards becomes very steep compared to a lighter slug like the 36.2 at 1000 FPS

The surprising thing was Mk2 Heavy pellets at 900 FPS couldn’t group under an inch either, at 50 yards, contrary to Ted’s latest video.

 

[Powerage]

Maybe I’m wrong but didn’t ted shoot the Jsb mk1? For me they are magic. MK2 is not that good. I can’t tell the difference but my liner can . 

A good group for me is 5 shots sub inch at 100 yards. If I doesn’t group that well it’s not for hunting. 
The slugs are picky to group in 25. I don’t know how many thousand slugs I wasted to get a decent tune. I don’t know if I’m more happy with the superior heavy. But if your goal is nsa I think the superior heavy is a bit better . after all it still takes a lot lead to get a decent tune with both liners. For me a nice tune with jsb mk1 is a good starting point for the 33.5 nsa. They tend to act similar. In that way you save some costs . 

 

[Centercut]

@powerage Thanks! I think I was spoiled how easy it was to get slugs accurate on my Bleu .22 Red Wolf HP. Turned power from 8 to 9, loaded .217 JSB KO slugs, shoot at 990 FPS. Simple as that and as accurate as the RD Monster pellets at 980 FPS. Total tune one 10 shot magazine and 5 minutes time. Hopefully my .25 Delta Wolf is that easy when I finally get it...

 

[Guest]

Hi Mike, please forgive me if I am going off your subject a little bit but thought maybe I could steer you in a different direction... 

Shooting the heaviest projectile possible is always preferable because it will be less affected by the wind, etc. So if I was trying to help you accomplish your goal I would suggest that you put your .30 cal. barrel back on your rifle with one of the original slug liners, and set up your rifle to shoot the NSA 61.5 grain slugs. I set up an Impact for my friend Angel that on MAX is shooting the NSA 61.5 grainers at an average velocity of 951 ft./s which is about 124 ft. lbs. energy. At that same setting it shoots the NSA 49.5 grain slugs at an average velocity of 1045 ft./s which is about 120 ft. lbs. energy.

My point is that rather than try to set up your rifle to shoot .25 caliber slugs, why not just set it up to shoot the NSA .30 caliber slugs? In all my slug testing in .30 cal. out of a plain slug liner from a year ago, the hands down most accurate of all was the NSA 61.5 grainers. (Second place went to the 49.5 grainers) Now there are those that would argue the merits of a flatter trajectory...but I always counter with the proven fact that heavier projectiles are not only less affected by the wind, but also retain much more of their energy downrange than a lighter one does. Lighter projectiles may fly somewhat faster and flatter but bleed off that speed much faster than the heavier ones do. 

I tested everything out there from Nick Nielsen, and my friends Dale Riggert, and Bob Vogel in .25 and .30 caliber, at all different velocity, and could never get anything to shoot as accurately as the NSA 61.5 grainers, with the one exception being the 34 grain HP from Dale Riggert in .25 caliber. Dale's 62 grainers in .30 caliber were extremely accurate also but were just a hair too long to fit in the FX magazines. 

By the way, on the parts you listed in your opening comments you didn't mention anything about a hammer weight...I would recommend a minimum hammer weight of 6 grams, and no more than 8 grams. I personally prefer to use the 8 gram hammer weights when setting up Impacts for shooting slugs. I may still have a few in my parts box...

Best regards, Chuck

 

[Glem.Chally]

.22 and .30 is more accurate with a variety of slugs from my experience also. The .30s are ridiculous, the best I've gotten with the .25 slugs is pretty good. But right off the hop better results with .22 and. 30.

Some have gotten great results with .25 I just havent had anything jaw dropping.

 

[Guest]

I agree with you 100% Nathan! That's why I thought to try and steer Mike towards .30 cal. because I could just never find anything in .25 cal. to get very excited about...that's why when all my testing was done I sold my .25 barrel and kept the .30. If you guys haven't tried the NSA 61.5 grainers or Dale's 62 grainers I strongly urge you to do so. I can remember calling up my friend Angel last year on the phone and just screaming with glee and uncontainable joy at the accuracy I was getting out of those NSA 61.5 grainers!  I was just beside myself with excitement! If I remember correctly those are the ones our forum friend from South America shoots most accurately also...and at distances that are hard to believe! 

 

[Centercut]

Thanks guys. I’ll see where I can go with the .25 before I give up on it. I’m settling on about 75 to 80 FPE for a couple of reasons.

First is guns are easier to shoot accurately in competition at lower less stressed powers. I won’t be shooting this off a bench. It’ll be from bucket and sticks, prone, barricades, and more. 

Second NRL-22 is limited to a max of .25 caliber with slugs.

Third, the new Extreme American Field Target is limited to 100 FPE.

So numerous reasons for .25 (or .22). I didn’t go .22 since I already have a laser beam shooting .22 slugs in my Bleu Daystate Red Wolf HP shooting JSB .217 KO slugs at 990 FPS, easily as accurate at 100 yards as the RD Monster pellets. I have the hammer weights from the FX slug power kit but haven’t installed them since I’m at about 78 FPE where I want to be without them. Shooting the 43.5 NSA at approx 900 FPS looks very good performance wise... Very high BC and they just barely fit in the magazines

So there you go, make sense?

PS., our South African friends shoot .22 caliber, not .30. 

 

[Guest]

Make perfect sense to me!

 

[zx10wall]

Good job C’Cut. Yes, they are limited to .22 in South Africa. That is unless they go though hell & high water to get the impossible to get permits for larger calibers. Of course, they are plenty happy with .22 as they are destroying game with precision accuracy & delivering plenty for power.

 

[Guest]

I understand that our airgun friends in South Africa are limited to 22 caliber... if you re-read my post above you will see that I specifically said our Forum friend from South America! So there you go... make sense?