Crosman 1377 Modding

[Adam77K]

I have an FTP in mine. Had to cut the hammer spring right down to keep it from over.

[Biker_Bob]

Right, I'll be giving that one a miss then.
With the extended pump handle it's so easy to pump anyway.

[Adam77K]

Right, I'll be giving that one a miss then.
With the extended pump handle it's so easy to pump anyway.

I agree it's not necessary if the rest is optimised. I got it as I was having trouble getting mine over 3 ft.lbs with 10 pumps. Turned out the 2 main issues were the hole in the back of the valve plus the restricted port.

[Biker_Bob]

I agree it's not necessary if the rest is optimised. I got it as I was having trouble getting mine over 3 ft.lbs with 10 pumps. Turned out the 2 main issues were the hole in the back of the valve plus the restricted port.

Did you see that old thread I did about that bleed hole in the valve?

[Adam77K]

Did you see that old thread I did about that bleed hole in the valve?

It sounded familiar so searched and yes, I did, and made several posts on it years ago!

[--ped--]

on a pistol i generally don't fit a flat top i have one in my favourite one which is 5.2 with 5 pumps and won't go over with extra pumps as i changed a few bits
i do a pressure releif valve for the older crosman 140 that had a FTV and i'm in the process of looking if i can make it small enough to fit a 13xx but primaraly it will be for a 362 i hope to be getting

[Biker_Bob]

I spent a bit of time on a 140, trying to make it legal.
I got close by reducing the valve volume by fitting inserts inside it, but the only way I could ensure it stayed below 12ftlbs was to have it so that it needed 14 pumps to get up to power - a relief valve would do the trick.
It's the same with these pistols, although it's generally accepted that you are supposed to put no more than 10 pumps in, if putting more pumps takes it over power then it's illegal. Whatever mods you do you have to test by just pumping and pumping to find the point where the pressure in the pump does not exceed the pressure in the valve and therefore no more power will be made by continuing to pump. I'm very concerned with those flat top piston conversions on the 1377, if it makes full power at 7 pumps what does it do with 10 pumps, 12 pumps. 20 pumps?

[evert]

I spent a bit of time on a 140, trying to make it legal.
I got close by reducing the valve volume by fitting inserts inside it, but the only way I could ensure it stayed below 12ftlbs was to have it so that it needed 14 pumps to get up to power - a relief valve would do the trick.
It's the same with these pistols, although it's generally accepted that you are supposed to put no more than 10 pumps in, if putting more pumps takes it over power then it's illegal. Whatever mods you do you have to test by just pumping and pumping to find the point where the pressure in the pump does not exceed the pressure in the valve and therefore no more power will be made by continuing to pump. I'm very concerned with those flat top piston conversions on the 1377, if it makes full power at 7 pumps what does it do with 10 pumps, 12 pumps. 20 pumps?

A weaker striker spring would probably solve the legality issue, if the gun starts to get valve lock when pressures go too high,
there cant be any chance of going over power?

[Biker_Bob]

A weaker striker spring would probably solve the legality issue, if the gun starts to get valve lock when pressures go too high,
there cant be any chance of going over power?

Yes, I've been down that road too with an old Benjamin pumper. You never knew where you were from one shot to the next. In the end I settled on taking the shot I wanted to take then dry firing to clear the valve and pumping again. Too much like hard work.

[Adam77K]

Yes, I've been down that road too with an old Benjamin pumper. You never knew where you were from one shot to the next. In the end I settled on taking the shot I wanted to take then dry firing to clear the valve and pumping again. Too much like hard work.

That's what I had to do in the end. I was going to experiment with valve inserts but never got round to it.

[--ped--]

A weaker striker spring would probably solve the legality issue, if the gun starts to get valve lock when pressures go too high,
there cant be any chance of going over power?

the 140 has a dump valve so reducing volume and leaving head space atr the other ways power can be increased

[TonyL]

What pellets do most use for the 1377 for accuracy?

I see Bob had tested with JSB 8.44.

My "mini-carbine" one, a Mk III with shoulder stock, Crosman steel breech and 4x32 scope is lazer-accurate (at garden ranges, at least) with the RWS Hobby.

My totally standard later one (later valve, lower power) had been delivering poor results with some RWS Geco that I was given when I bought my .177 HW45 last Autumn. A little bit of a session yesterday revealed the Hobby as better but the Superdome as better still. Very pleasing 10 shot group at about nine yards apart from one errant one which will have been pilot error!

I'll give it a go with some JSB 8.44 and 7.87 when I get the chance. Plus some H&N FTT and Baracuda FT to see if any of these fare even better than the 'Domes. Satisfactory performance with more cost-effective pellets would please me and would be more in keeping with the nature of the pistol. Shame it doesn't seem to like the Geco!

[Biker_Bob]

The JSBs work well for me, although they are getting very expensive.
Maybe I'll investigate some others and report back, I've always started with Superdomes when I get a new gun as more often than not they work just fine but on this occasion I had some JSBs so I've stuck with them.
The new Wasps look OK.

Maybe time to try lead free, get ahead of the curve?

[Adam77K]

The barrels are variable. Mine is really good with JSBs, Hobbies, R10s, but the one I bought initially that I returned due to low power (before realising they were all like that) wasn't as good. Also had a 2250 that was shockingly bad - shotgun at 10m bad.

[TonyL]

Yes, I understand that to be the case, Adam, and seeing some of that here. Thank you.