Benjamin Got my first PCP

[Ischgl99]

I have had an HW95 for several years that I use for pesting and target shooting, but being slow to reload, too many birds got away. I decided to take the plunge into the PCP world and got a used gen 1 Marauder along with a GX CS2 compressor. The previous owner seems to have tuned it well, initial testing seems to be pretty good for shot count. I was considering the Marauder and Akela, and decided to go with the Marauder because of the tuning capability would be a good learning experience for me. I know I already want to make a depinger, that gets annoying!

I have been testing different pellets to see what works best, I have an old box of Crosman Premiers 7.9gr that didn’t work well with the HW95, that shoot great at 25m, but at 35m the group opens up a lot. I have some CPUM from Walmart that do the same thing, great group at 25m, then much worse at 35. I have a JSB sample pack, the Exact 8.3 looked like a shotgun at all ranges, but the Exact 10.3 did really well out to 45m. The RWS Superdomes are my go to pellets in the HW95, but are horrible in the Marauder. Of course the expensive pellets work the best.

Does the issue with the Crosman pellets shooting great at 25m and then much worse by 35m sound like it could be improved by optimizing the velocity? The boxed Premiers in 7.9gr are shooting at about 950 fps. I plan on doing some more testing at different velocities, but it would be helpful knowing if there is a typical optimum velocity for these pellets, I couldn’t find that in my searching, so it looks like it depends on the gun.

 

[EmptyTin_Tim]

Typically the average speed for diabolo pellets to fly stable is about 880 fps. 950 is fast for that light weight pellet thats like slug speeds and I'd guess it groups well initially because the velocity is so high it just lasers to the target but then it bleeds off FPS so fast and the spin on the pellet doesn't match the forward fps and it might spiral then? Someone else with more knowledge can comment on that...
But that brings up this: if you are in an area where the speed of sound is closer to 950 than where I am you may be getting into the trans sonic speeds where it is about to break the sound barrier and that's gonna kill your accuracy too since the pellet is experiencing so much turbulence at that speed.

The twist rate of the barrel is a fixed item in the equation and certain pellet weights like the faster spin vs other weights like slower spin. It can be affected by velocity like the light pellets may get too much spin or the heavy ones not enough to stabilize. Again someone else can comment here.

But sounds like your twist rate is matching up for heavier pellets and that makes sense because typically PCP like heavier stuff, or at least they're capable of sending it accurately unlike some springers that can't get enough FPS (twisting fast enough) to stabilize the heavy ones. And the heavier pellets have higher BC and cut through the wind better.

JSB is some high quality stuff with good tolerance and softer lead that uses the initial blast of the air to expand the skirt into the rifling and that's why they are accurate pellets in lots of guns. The Crosman alloys used are harder so they don't form to the rifling as tightly however because they're hard you may not find as many crushed/deformed ones in a tin as you'd think for their cost so they can also be accurate.

If you want to try heavier Crosman try these they are sorted by manufacturering die so all are from the same place unlike the 500 tin:

Amazon.com

Or if you want to stick to JSB I have had great luck ordering from here it is always so well packaged, lots of bubble wrap etc:

JSB Exact Heavy .177 cal. Pellets, 10.34 Grains, Domed | Trenier Airguns

JSB Exact Heavy .177 cal, 4.52 Head., 10.34 Grains, Domed, 500ct, precision airgun ammunition for your shooting needs.Whether you shoot from an air rifle or pistol, 4.5mm, 5.0mm, 5.5mm caliber or larger, outdoors or indoors, from paper to knock down targets, from 10 to 100 meters, JSB offers you...

www.trenierairguns.com

FX is just rebranded JSB you can save a couple bucks:

FX Airguns .177 Cal 10.3 Gr 500 Ct Pellets | Trenier Airguns

FX Airguns .177 Caliber, 10.3 Grain 500 Count Lead Pellets. High performance domed (round tip) air rifle pellets. 4.52mm Head Size. Made by leading pellet manufacturer JSB to FX Airguns specifications. High quality ammunition for your airgun.

www.trenierairguns.com

 

[rcarlisle]

I would suggest leaving it as-is and see how it does with a heavier pellet. My .177 Gen 1 Marauder liked JSB Monsters (but not the re-designed) from its Crosman barrel at about 880-890 fps. You might be real close to those numbers by switching to heavier ammo without making any adjustments. I put a Lothar Walther barrel on mine and things changes a little, but the Monsters still kick butt on anything else I've tried in mine.

 

[beerthief]

Typically the average speed for diabolo pellets to fly stable is about 880 fps. 950 is fast for that light weight pellet thats like slug speeds and I'd guess it groups well initially because the velocity is so high it just lasers to the target but then it bleeds off FPS so fast and the spin on the pellet doesn't match the forward fps and it might spiral then? Someone else with more knowledge can comment on that...
But that brings up this: if you are in an area where the speed of sound is closer to 950 than where I am you may be getting into the trans sonic speeds where it is about to break the sound barrier and that's gonna kill your accuracy too since the pellet is experiencing so much turbulence at that speed.

The twist rate of the barrel is a fixed item in the equation and certain pellet weights like the faster spin vs other weights like slower spin. It can be affected by velocity like the light pellets may get too much spin or the heavy ones not enough to stabilize. Again someone else can comment here.

But sounds like your twist rate is matching up for heavier pellets and that makes sense because typically PCP like heavier stuff, or at least they're capable of sending it accurately unlike some springers that can't get enough FPS (twisting fast enough) to stabilize the heavy ones. And the heavier pellets have higher BC and cut through the wind better.

JSB is some high quality stuff with good tolerance and softer lead that uses the initial blast of the air to expand the skirt into the rifling and that's why they are accurate pellets in lots of guns. The Crosman alloys used are harder so they don't form to the rifling as tightly however because they're hard you may not find as many crushed/deformed ones in a tin as you'd think for their cost so they can also be accurate.

If you want to try heavier Crosman try these they are sorted by manufacturering die so all are from the same place unlike the 500 tin:

Amazon.com

Or if you want to stick to JSB I have had great luck ordering from here it is always so well packaged, lots of bubble wrap etc:

JSB Exact Heavy .177 cal. Pellets, 10.34 Grains, Domed | Trenier Airguns

JSB Exact Heavy .177 cal, 4.52 Head., 10.34 Grains, Domed, 500ct, precision airgun ammunition for your shooting needs.Whether you shoot from an air rifle or pistol, 4.5mm, 5.0mm, 5.5mm caliber or larger, outdoors or indoors, from paper to knock down targets, from 10 to 100 meters, JSB offers you...

www.trenierairguns.com

FX is just rebranded JSB you can save a couple bucks:

FX Airguns .177 Cal 10.3 Gr 500 Ct Pellets | Trenier Airguns

FX Airguns .177 Caliber, 10.3 Grain 500 Count Lead Pellets. High performance domed (round tip) air rifle pellets. 4.52mm Head Size. Made by leading pellet manufacturer JSB to FX Airguns specifications. High quality ammunition for your airgun.

www.trenierairguns.com

never heard of the speed of sound changing with location ???

 

[Ischgl99]

Thank you for the detailed reply, I’m at 1,000 feet, I’ll have to check on the speed of sound for my elevation and see how much it changes from sea level. Last night was cooler with lower humidity, earlier in the week was hotter and the pellets were more accurate in some informal testing, so that may be causing it, or partially responsible.

I plan on getting some of the brown box heavy premiers and see how they perform, Midway has them for about $26, so I might get a box, or two to offset the shipping. I try to avoid Amazon due to the number of issues I have had with buying from them in the past. I didn’t realize FX were rebranded JSBs, I was planning on ordering a tin of the JSB heavies since I only have a small amount in the sample kit, but I’ll try the FX ones first and see what happens. Thanks for the link to Trenier, they look like good prices.

I measured the pellet diameter of the different brands and was surprised to find the RWS pellets were 4.45mm, that is a lot smaller than the others and might be the reason they grouped so bad. I’ll have to push a pellet through the bore and see if the dome is even touching the bore, or if it is just the skirt.

I would suggest leaving it as-is and see how it does with a heavier pellet. My .177 Gen 1 Marauder liked JSB Monsters (but not the re-designed) from its Crosman barrel at about 880-890 fps. You might be real close to those numbers by switching to heavier ammo without making any adjustments. I put a Lothar Walther barrel on mine and things changes a little, but the Monsters still kick butt on anything else I've tried in mine.

The nice thing about the Marauder is how easy it is to experiment with tuning, so I will probably try some adjustments and see what happens, I can always put it back to where it was. I never considered the monsters, thank you, when I place my next pellet order, I’ll get a tin of those and see how they work.

 

[EmptyTin_Tim]

never heard of the speed of sound changing with location ???

Location as in elevation above sea level. Air is more dense or less dense depending how close you are to sea level and that affects the trans sonic speeds / speed of sound.

 

[Long_Gun_Dallas]

Already stated but I was going to recommend slowing down the 8gr Crosmans to about 880fps as well. Might even try some of the lighter Neilson slugs and see how they do. Seems your gun is tuned well for 10-11gr projectiles

 

[starlingassn]

ill offer this.

if you want good groups,use good ammo.

jsbs have been the gold standard for years,
but the jts dead center pellets are another great option.

get those speeds down if you want to see real accuracy potential,
pellets are not designed to go fast,
and don't like to fly much faster than 920 or so,
and are much happier around 850-880.


for example,
my .25 impact m3 compact shoots 34gn jsb king heavies at 870fps,
and will headshot starlings out past 75yds without missing a beat.

 

[Ischgl99]

It’s too windy today to try any groups, but I played around with the adjustments and have it at 900 fps. If it calms down tonight, I’ll shoot some groups again and see what I get and then drop it some more and do another set of groupings.

I ran some tests at various hammer spring, striker and velocity port settings to see how the speed changes, and was able to hear what it sounds like when it burps from hammer bounce, so it was an educational afternoon. My chrony kept giving me errors, so I’ll try some more settings another time.

Thank you for the feedback, I think I am going to blow through a lot more pellets with this one than my springer, so effortless to keep shooting!

if you want good groups,use good ammo.

I plan on getting the good stuff too, but I already had the Crosmans on hand, so was hoping one of them would work well for now. The prices at Trenier bring them close to the price of the Crosman boxed Premiers, so at those prices it doesn’t make sense to use the Crosmans.

 

[Pea-shooter O.G.]

I have a .177 Marauder. It has a factory Lothar Walther barrel I installed. Alot of good info has been given above. I'll also add, to get the ultimate in accuracy, use a single shot tray instead of the magazine. I use the JSB original monsters at 780 fps as I shoot Field Target. Mine also likes the Crosman 10.5g domes real well at 850 fps, especially at lower power(750fps). I don't know why, but it'll also shoot the Crosman 7.9 hollow point awesome at well over 950 fps. Will get a flyer from them though. Same with JSB 10.34. I got some 16g Beasts and it really likes them too! I crank power up to 22fpe for them.

 

[Ischgl99]

I am assuming my barrel is a Crosman, but next time I take the shroud off, I’ll take a closer look. Is there something on the barrel that indicates which one it is? I don’t have a single shot tray, but I do have a well outfitted machine shop in my basement, so could probably make one. The rifle didn’t come with a degassing tool, so I need to make one of those too. I like having the magazines for convenience, but I can see the benefit of single feeding. That would help a lot too to see if the magazines are damaging the pellets enough to affect accuracy.

I will be placing an order for pellets soon, so I will make sure to get several of the different weights recommended here and experiment. I spent many years during my engineering career doing pilot testing of process equipment, so this will be right up my alley. The hard part is I don’t know what I don’t know yet, but at least it’s fun learning . Thanks for the tips, this is giving me a lot of good info to work with as I dial in how I want to shoot.

 

[Pea-shooter O.G.]

The Crosman LW barrel didn't have any distinguishing markings. It is a 12 land/groove barrel. The Crosman standard barrel may be 10? I got the single shot tray off ebay from seller rsdproe. Its less than 13 bucks shipped. I get good accuracy from my magazines but there is a difference with using single shot tray.
I also installed a Huma regulator, Tim Hill light weight hammer, peek striker, hammer spring and valve spring. I can get 90 shots at 18fpe or turn my hammer spring adjuster to lower the power and get 140 at 10 fpe for safer pest shooting in the backyard. And its REALLY quiet.
I got the barrel from Tim Hill Airguns as well. If you find yourself feeling the need for these items, Tim is super helpful!

 

[Ischgl99]

Holy cow, 140 shots per fill!? I thought I was doing good with 40 lol. I’ll take a look at those parts and keep them in the back of my mind as I decide on what to upgrade. I’ve seen other positive comments about Tim Hill, it’s nice having someone dependable you can rely on. Some of those upgrades look like opportunities to buy new tooling for my shop, one of my other mistresses

 

[Ischgl99]

My order of FX pellets arrived, so I spent some time testing them against the Crosman Premier heavies I ordered as well. Before I get into that, @rcolletti messaged me to come shoot with him, we live in the same town. I got to try his rifle, and OMG was it nice to actually experience a one hole group that so many of you have talked about! I had a great time with him and got some good pointers for field target that I would like to try, and look forward to shooting with him again soon. I now have the N+1 rifle/scope in the back of my mind after the wife gets over the shock of the Marauder and compressor on the current credit card bill…

So, today I compared the light, medium and heavy FX pellets against the Crosman 10.5 gr domes. The 13.4 pellets worked best at just about any speed, so I settled on about 850 for now. The Crosmans are closer in accuracy than I expected, so those might be good plinking pellets, as well as taking out the starlings. At 45m, I have about 1/2” groups with the FX pellets, so very happy with that.