Thank you to our advertisers!







Author Topic: crosman 1720T tuning  (Read 1403 times))

Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
crosman 1720T tuning
« on: April 09, 2021, 06:33:11 PM »
Hi can anyone recommend hammer spring , hammer throw settings and TP size needed for a reasonable shot count at around 10.5ftlb with a 7.87?
Many thanks

Offline johnbrown

  • Sharp Shooter
  • ****
  • Posts: 615
  • yes
  • Real Name: Nick
Re: crosman 1720T tuning
« Reply #1 on: April 09, 2021, 07:30:42 PM »
For a good shot count at a consistent pellet velocity you need a regulated air gun which the Crosman 1720T is not.
Whatever settings you may find it will never get as good as a regulated air gun.

Crosman has been complacent with their dominant market position in USA for way too long.
Now there are many Chinese PCP air guns (pistols and rifles) that are better or much better.

Crosman compete not on how good the air gun is, but on warranty and availability of parts.
I agree that at this time (and for many years before) Crosman had the best warranty and best part availability and prices.

I am not Chinese, I simply say what I think, which is a trait that has unfortunately been lost in this country.

Crosman's latest PCPs (Akela, Cayden, Kratos) have been designed and made in Turkey.
Apparently it's too expensive to do most things in this country, except for customer support, and obviously the management.
I have never seen a manager who wants to outsource their job :)
« Last Edit: April 09, 2021, 07:35:29 PM by pinguinu01 »
  • Redmond, WA, USA

Offline moorepower

  • Expert
  • *****
  • Posts: 1707
  • yes
Re: crosman 1720T tuning
« Reply #2 on: April 09, 2021, 08:14:28 PM »
For a good shot count at a consistent pellet velocity you need a regulated air gun which the Crosman 1720T is not.
Whatever settings you may find it will never get as good as a regulated air gun.

Crosman has been complacent with their dominant market position in USA for way too long.
Now there are many Chinese PCP air guns (pistols and rifles) that are better or much better.

Crosman compete not on how good the air gun is, but on warranty and availability of parts.
I agree that at this time (and for many years before) Crosman had the best warranty and best part availability and prices.

I am not Chinese, I simply say what I think, which is a trait that has unfortunately been lost in this country.

Crosman's latest PCPs (Akela, Cayden, Kratos) have been designed and made in Turkey.
Apparently it's too expensive to do most things in this country, except for customer support, and obviously the management.
I have never seen a manager who wants to outsource their job :)

Obviously you have never owned/shot a 1720P.
  • Nebraska eastern

Offline Rick67

  • GTA Senior Contributor
  • ******
  • Posts: 4505
  • yes
  • Real Name: Richard
Re: crosman 1720T tuning
« Reply #3 on: April 09, 2021, 11:34:51 PM »
For a good shot count at a consistent pellet velocity you need a regulated air gun which the Crosman 1720T is not.
Whatever settings you may find it will never get as good as a regulated air gun.

Crosman has been complacent with their dominant market position in USA for way too long.
Now there are many Chinese PCP air guns (pistols and rifles) that are better or much better.

Crosman compete not on how good the air gun is, but on warranty and availability of parts.
I agree that at this time (and for many years before) Crosman had the best warranty and best part availability and prices.

I am not Chinese, I simply say what I think, which is a trait that has unfortunately been lost in this country.

Crosman's latest PCPs (Akela, Cayden, Kratos) have been designed and made in Turkey.
Apparently it's too expensive to do most things in this country, except for customer support, and obviously the management.
I have never seen a manager who wants to outsource their job :)

Obviously you have never owned/shot a 1720P.


I am actually in the process of building one, but mine will have a 1701P barrel.

Oh, it will also be a low power build, so don't mind me  ;D
  • Abq., NM, USA

Offline RDB

  • Sharp Shooter
  • ****
  • Posts: 973
  • yes
  • Real Name: Rod
Re: crosman 1720T tuning
« Reply #4 on: April 10, 2021, 12:11:24 AM »
Do you have a chronograph?

Search here for bstaley mod. This will get you started. With the correct tune, you should be able  to get a good 30+ shot string at that power level.

https://www.airgunnation.com/topic/1720t-mod-question-4-o-ring-bstaley-mod-is/
  • Michigan Lapeer

Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
Re: crosman 1720T tuning
« Reply #5 on: April 10, 2021, 04:58:08 AM »
Do you have a chronograph?

Search here for bstaley mod. This will get you started. With the correct tune, you should be able  to get a good 30+ shot string at that power level.


Thanks for that.

Yes I have a Skan chrono.

Looks like I'll try opening the TP out to 3/32 and start playing there.
I have some bs113 o rings on the way to do the Bstaley mod, which should be with me in a day or so.

I reckon at some point, I will reg it, but I do want to try it unregged first.
My BP2220 is unregged and good enough for me.

Offline WildCJ5

  • Sharp Shooter
  • ****
  • Posts: 823
  • yes
Re: crosman 1720T tuning
« Reply #6 on: April 10, 2021, 10:27:56 AM »
I had two of these pistols at one time and regret selling them. They are incredibly accurate.

Both of mine I did drill the tp, sorry I forget the size. I did the oring mod and added a DonnyFL to the end.

For the tune I liked starting with both hammer and spring backed off and the gun around 2k. Then start turning the hammer adjustment in until I start getting a pop on the valve. This seems to get me a good starting point with the orings doing their job.

Next start turning up the hammer spring looking for the velocity to rise.

On both of mine I did remove the crosman baffles because I was using the DonnyFL and this was more accurate and almost no noise.
  • Corona CA

Offline nervoustrigger

  • GTA Senior Contributor
  • ******
  • Posts: 8244
  • The Grin Reaper
    • My youtube channel
  • Real Name: Jason
Re: crosman 1720T tuning
« Reply #7 on: April 10, 2021, 10:56:01 AM »
I set up my buddy's 1720T for a similar state of tune
https://www.gatewaytoairguns.org/GTA/index.php?topic=86564



The hammer spring tension and O-ring stack will vary from gun to gun.  The best you can hope for is some semblance of a useful starting point. 

edit: Oops, I just realized Rod linked to a thread that references the same information.
« Last Edit: April 10, 2021, 11:06:12 AM by nervoustrigger »
  • MS
Conduct yourself so that when a man accuses you of something dishonorable, no one will believe him.
Barrel accurizing guide
My youtube channel
QB79 HPA conversion
2240 HPA conversion
Intro to PCP airguns

Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
Re: crosman 1720T tuning
« Reply #8 on: April 10, 2021, 04:35:07 PM »
I set up my buddy's 1720T for a similar state of tune
https://www.gatewaytoairguns.org/GTA/index.php?topic=86564



The hammer spring tension and O-ring stack will vary from gun to gun.  The best you can hope for is some semblance of a useful starting point. 

edit: Oops, I just realized Rod linked to a thread that references the same information.
Thanks very much

Offline RDB

  • Sharp Shooter
  • ****
  • Posts: 973
  • yes
  • Real Name: Rod
Re: crosman 1720T tuning
« Reply #9 on: April 10, 2021, 06:11:54 PM »
Rob, a little silicone grease on the orings helps keep the stack stay together and in place. Just make sure the top oring, hammer face and tube are grease free.  That will keep the top oring from trying to stick to the hammer. A stack of 4 worked well for me. Very small adjustments to the striker make a big difference. Very close to maximum spring and just barely tapping the valve with the striker is a good starting point.
  • Michigan Lapeer

Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
Re: crosman 1720T tuning
« Reply #10 on: April 10, 2021, 07:22:52 PM »
I set up my buddy's 1720T for a similar state of tune
https://www.gatewaytoairguns.org/GTA/index.php?topic=86564



The hammer spring tension and O-ring stack will vary from gun to gun.  The best you can hope for is some semblance of a useful starting point. 

edit: Oops, I just realized Rod linked to a thread that references the same information.
Where would you suggest I start with TP ID ?
I was thinking 3/32 but have seen a post that suggests going over .080 (around 2mm) is not productive.

Offline WildCJ5

  • Sharp Shooter
  • ****
  • Posts: 823
  • yes
Re: crosman 1720T tuning
« Reply #11 on: April 10, 2021, 09:21:15 PM »
I think the stock prod is .08. I would start there or just under. Worst case scenario you can fill the tp with jbweld and start over.

I remember on one of mine the plastic piece that goes on the end of the barrel caused me accuracy issues and I ended up removing it.

  • Corona CA

Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
Re: crosman 1720T tuning
« Reply #12 on: April 11, 2021, 05:35:37 AM »
I think the stock prod is .08. I would start there or just under. Worst case scenario you can fill the tp with jbweld and start over.

I remember on one of mine the plastic piece that goes on the end of the barrel caused me accuracy issues and I ended up removing it.
The info I have from the parts supplier here is that the PRod TP is 1.86mm, where .08 would be around 2mm.
Guess I'll start at 2mm thanks. I can always go bigger easily.

When you say "plastic bit" do you mean the shroud support ? Or the baffles forward of that?
My PRod has the standard shroud support and baffle arrangement, but I have replaced the end cap with a 1/2" UNF adaptor so I can run a moderator.
Accuracy is stunning.

Planning to use the same adaptor and mod on my 1720T.
Thanks for the info on the number of O rings .

Here's my 2220 and 1720T
The adjustable cheek pieces are printed by a guy over here and transform the shoulder stock into a really effective stock


Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
Re: crosman 1720T tuning
« Reply #13 on: April 11, 2021, 06:17:34 AM »
I think the stock prod is .08. I would start there or just under. Worst case scenario you can fill the tp with jbweld and start over.

I remember on one of mine the plastic piece that goes on the end of the barrel caused me accuracy issues and I ended up removing it.
Just realised the barrel support / baffle arrangements in the 2220 / 1720t are very different. I know the part you mean, now.
Though mine still has it in situ.
I've found that not over tightening the shroud and end cap help on the 2220

Offline WildCJ5

  • Sharp Shooter
  • ****
  • Posts: 823
  • yes
Re: crosman 1720T tuning
« Reply #14 on: April 11, 2021, 10:28:16 AM »
It was part 012. It was only on the on pistol hat it caused issues.
  • Corona CA

Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
Re: crosman 1720T tuning
« Reply #15 on: April 11, 2021, 11:02:38 AM »
It was part 012. It was only on the on pistol hat it caused issues.
Ah thanks

Have you had any issues running without it?

Offline Rick67

  • GTA Senior Contributor
  • ******
  • Posts: 4505
  • yes
  • Real Name: Richard
Re: crosman 1720T tuning
« Reply #16 on: April 11, 2021, 11:30:16 AM »
I think the stock prod is .08. I would start there or just under. Worst case scenario you can fill the tp with jbweld and start over.

I remember on one of mine the plastic piece that goes on the end of the barrel caused me accuracy issues and I ended up removing it.
Just realised the barrel support / baffle arrangements in the 2220 / 1720t are very different. I know the part you mean, now.
Though mine still has it in situ.
I've found that not over tightening the shroud and end cap help on the 2220


Yes, they are quite different; the 1720T having 2 baffles and a spring.

I am using this particular foam (cut to length) grip, and it does an excellent job muffling the sound even more:


https://www.exercise-equipment-parts.com/mini-sponge-grips.html


It is a tight fit on the PROD/1720T shroud, but it can be semi-forcibly coaxed in.

The hole is about 9.5mm and will get compressed once it is inside.

I am actually modifying a pen tube with perforated holes  ;D

It should work very well on my not-done-yet-due-to-still-incoming-parts 1720T with a 1701P barrel build because the latter is shorter by 2".
  • Abq., NM, USA

Offline WildCJ5

  • Sharp Shooter
  • ****
  • Posts: 823
  • yes
Re: crosman 1720T tuning
« Reply #17 on: April 11, 2021, 02:39:10 PM »
It was part 012. It was only on the on pistol hat it caused issues.
Ah thanks

Have you had any issues running without it?

I didnít and I was using a DonnyFL adapter and one of his small ldc. In this pistol it fixed a flier issue I was chasing.
  • Corona CA

Offline Michael Loar

  • GTA Senior Contributor
  • ******
  • Posts: 4110
  • yes
  • Real Name: Mike
Re: crosman 1720T tuning
« Reply #18 on: April 11, 2021, 04:39:53 PM »
When using the bstasley mod you want just enough hammer spring tension to open the valve at max 3000 psi pressure so as to keep cocking as easy and light as possible. Then use the hammer stroke adjustment to get to desired velocity in the 2500 to 2000 psi range which should be the middle of the shot curve.

When I have it apart to install the o rings I degass the gun so I can roughly measure the amount of valve lift I get with turning the stroke adjuster in while holding hammer against the o rings. I shoot for about .080" of valve lift from point the adjuster contacts the valve stem to when the hammer contacts the o rings using a vernier caliper and find that is a good starting point for tuning.

I would start with the TP drilled out to 2mm or .089" and go from there since you can always go bigger but not smaller without buying new TP.

BD. 
  • Oxford, Alabama
Benjamin Marauder 177 in Boyds blaster stock 
Benjamin Marauder25 Wicked Air rifles bottled
Hatsan 22 AT 44S10 long
FWB 124 177 Tuned
FWB 300s Match L 177 Tuned
FWB 300s Match Junior 177 Tuned
Diana 48 177 Vortek Tuned
Xisisco 60C PCP Tuned 22
Xisisco 60C PCP 177 tuned LW barrel
Benjamin Titan NP 22 Tuned GRT trigger
Crosman Titan GP 22 Tuned GRT trigger
Crosman Venom 177 Tuned GRT trigger
Taipan Mutant Standard 22, BSA FFP 4x14x44 scope
TX200 , TL 22mm kit 177
B-40, TL 22mm kit 177
B50 in 51 stock Tuned .177
CH2009 challenger 177
1720T carbine regulated 177
Prod carbine with AR butt stock 22
CZ200 regulated 177
C9 silver streak 20 rocker safety
Crosman 1400 X 2 177 and 22
B28 Mike Melick tuned 25
Hatsan flash 25
Daisy 853 X 5 177
B3-2 177
Benji Maximus 177 Mrod trigger
QB 78/79 177 and 22 HPA bottled
HW Blue Laminate 97 .22cal tuned
1966 Diana model 60 Tyro resealed and tuned




Bikes, Guns and Family is all I need for a good day

Offline robs5230

  • Shooter
  • *
  • Posts: 62
  • yes
  • Real Name: Rob
Re: crosman 1720T tuning
« Reply #19 on: April 11, 2021, 05:21:21 PM »
Thanks very much for the info chaps.
I should be making a start on it as soon as the o rings arrive.
I've ordered N90.