Will heavy pellets hurt my new 397S

[Ron B]

Hi
This is my first post. I have been lurking for a few days, learning lots from other posts. I am new to air rifles. 63 and still learnin. I just bought a 397S. Haven't shot it too much yet due to the weather and I am waiting on a set of Williams sights as the open sights don't work that well for me. I really like Ghost Rings in all of my other rifles. Anyhow the other day I noticed some heavy JSB Beast pellets online and ordered them. They still haven't been delivered and I am worried they might be too heavy for my 397S? Will shooting very heavy pellets like this hurt my new rifle? Maybe I should leave them in the tin?
Thanks in advance!
Ron

[Hoosier Daddy]

Nope, won't hurt that Pumper one bit.
 You will probably need to give it 8-10 pumps, to get out there in distance, but they should hit with "authority" 

[Insanity]

It wont hurt at all.

[Robert 5mm]

The pnuematic style pellet pusher actually uses the mass of the heavier pellet better than the piston spring guns.
My 397s produces more FPE with a heavier pellet at the same 10 pump level.

[RBQChicken]

As Timmy Mac once said (he was talking about a 392P) "heavy and slow is the way to go".  I've always thought the ideal for a pumper would be heavy AND hollow point or wadcutter style.  Man, would that pack a wallop.

Shouldn't Benjamins be limited to 8 pumps, same as the Sheridans?

[Ron B]

Thank you all for the info! The new Benjamin's are supposedly rated for 10 pumps. Not sure why that's changed?

[Robert 5mm]

The new 397s has a maximum pumps of 10 on the box.
I know the internal valve is the same as the wood stock 397 ( I opened mine up and increased the valve volume )
Maybe, Crosman upped the pumps because the new stock pump arm is longer ?

[Hoosier Daddy]

The old TRUE Benjamins were 8... but I think when Crosman bought the name, and redesigned it to the cartridge valve version we know today, they have been 10.

[Robert 5mm]

Looking at my chrono data for the 392 versus 397s - really shows the knock down power of the .22
Both have slightly modified enlarged volume valves.
10 pumps - 392 with Crosman 14.3g - 735 FPS - 17.16 FPE
12 pumps - 397s with Crosman 10.5g -  742 FPS -  12.84 FPE

I think the 397s .177 is trying to push too much down a thin pipe - is why the FPS is not comparable.

[Habanero69er]

Multi-pumps as well as PCPs produce better power with heavy ammo. Bottom line, no heavy ammo will not hurt your 397. "Heavy & slow". I shoot 28g pellets all the time out of my 342s.

[Techie]

Yeah, the 397 does not make much sense compared to the 392.  I bought a brand-new/damaged-box wood-stocked 397 for 50 bucks a few weeks ago, and now I'm wondering why?  Answer: because it was 50 bucks!  A 392 makes much more sense.  The 397 is just as hard to pump as the 392, and you get a whole lot less power for the same effort.  If you think a .177 pellet has a flatter trajectory, spend some time with a ballistics program.  There is no advantage to the .177 other than slightly cheaper pellets.

Let me know how fast those JSB Beasts shoot out of your 397.  The heavier the better if you get accuracy out of them, in an attempt to turn the 397 into a 392.  I doubt the 397 will approach the power of the 392 even with the same weight pellets though, because the smaller bore will not be as efficient.

Oops, I just realized I assumed you have a chronograph, and you said you are new to air rifles.  A chronograph is something every serious airgunner should have.  You can now buy a cheap one on ebay for 30 bucks, such as this one: https://www.ebay.com/itm/Fixable-Chargeable-Premium-Precision-Ballistic-Chronograph-Bullet-Arrow-Velocity/283675713381

[Ron B]

Hi!
I do in fact have a chrony. I used it for developing 45-70 loads a few years back. I will post the results when I get them. It might be a while though. Busy time of year and I read on this sight that pumpers don't like the cold too much.
I got the pellet rifle mostly for plinking. I hope to plink away at the back of a campsite without alarming anyone. I love the idea of only having to use 3 pumps to shoot paper targets. I have been filling cereal boxes with rags and taping targets on both sides. I catch the pellets that way and don't pollute my property with lead. It may be interesting to see how much the lead adds up after a few years!
The best thing about the .177 is the cost of pellets.
Ron

[Airwoods]

Well a 392 with a 14 grain pellet averages around 450-60 FPS  with 3 pumps and a 397 with a 7.9 gr pellet around 540-50 FPS at 3 pumps but with a 10gr pellet around 475 FPS with 3 pumps.

So if 3 pump plinking and paper shooting will be most of what you’ll be doing the 397 will be good for that and will be a little flatter shooting with at 3 pumps compared to the 392 and you can stretch your target out a bit further out.Thats with the average 7.4-8gr pellet.

The heavier pellet 10 grn not much different than the 14grn .22 pellet. Just doesn’t have that volume needed on that little .177 barrel for the air to push that pellet out. But the important thing is not the weight pellet but the pellet your gun likes for accuracy.

[Techie]

Like I said, if you think the .177 is flatter shooting than the .22, spend some time with a ballistics program.  My point is there is no significant trajectory difference between the two, especially in the same power plant and at the distances we shoot these guns at.

[Airwoods]

Ya but in this graph both projectiles are roughly shooting out the same speed.What would it look like if the the other projectile was starting out 100 FPS faster at the muzzle? Which is what the 397 compared to 392 is. Probably even more faster than 100 FPS if both were at 10 pumps.

[Techie]

I just used the velocities and pellet weights you said the 397 & 392 shot them out at.

[Airwoods]

Show me the graph of a 7.9gr pellet moving out  the muzzle at around 800 FPS compared to a 14.3 gr pellet at 700 FPS.Im curious to see the difference.

[Techie]

Show me the graph of a 7.9gr pellet moving out  the muzzle at around 800 FPS compared to a 14.3 gr pellet at 700 FPS.Im curious to see the difference.

Sure Delmar; here you go.  Click on the image to make it bigger.  I even put the correct ballistics coefficient in for both of those pellets, although that does not matter much at these short ranges.  This assumes sighting in for 25 yards, which makes the most sense to me.  I wouldn't trust the accuracy of my Benji 392 or 397 to hit a 1-inch kill-zone target beyond 30 yards.

I wrote this Windows ballistics program myself.  It's totally free to everyone if you want a copy.  You can download the setup file from my server at sanesoftware.com/bbsetup.exe

[Airwoods]

So from 20-40 yards is roughly a 1 inch drop more for the .22 cal and keeps dropping after that. Not bad but can make a break that shot needed if you dont know your hold over.That being said my max to be able to hit a 1 inch kill zone consistently would be around 25 yards.So if i were hunting the .22 would be great for me for that extra oomph.I did really well in the early 80's as a kid with my peep sighted benji 342 .22 cal.

[moorepower]

The new 397s has a maximum pumps of 10 on the box.
I know the internal valve is the same as the wood stock 397 ( I opened mine up and increased the valve volume )
Maybe, Crosman upped the pumps because the new stock pump arm is longer ?

From what I have read the new 397/392 valve uses a Mrod style valve with a smaller stem o.d. and a smaller valve o.d. that will allow it to open under higher pressure, allowing more pumps without valve lock.