1377 Barrel into a 760?

[Icemanxxxv]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

[bantam5s]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

It has been done and will work.
Imo the 760 is what it is for a reason and a longer barrel seems weird.
I shortened mine and it shoots great with it's shortened m417 barrel in it.
If you really want a long barrel then I guess you could use the barrel you already have, and you could also thread it for any sort of muzzle attachment you may want to add / make.

[Icemanxxxv]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

This might be a moot point! I cleaned the barrel after an over night soak in Kroil. Ran two dozen patches down the bore and gendered down it with a bore light. There is lands and grooves in there! Looks like I have my rifled barrel already. Now l hope she ain't all shot out. Another plus is the crown looks good. Parts on order hope to have it shooting soon!
The gun is old school only three plastic parts flat top chamber and pump.

[bantam5s]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

This might be a moot point! I cleaned the barrel after an over night soak in Kroil. Ran two dozen patches down the bore and gendered down it with a bore light. There is lands and grooves in there! Looks like I have my rifled barrel already. Now l hope she ain't all shot out. Another plus is the crown looks good. Parts on order hope to have it shooting soon!
The gun is old school only three plastic parts flat top chamber and pump.

Awesome, rifled barrel 760's are out there but not exactly seen everyday.


Btw the receiver is zamak ( a zink alloy which hot wheels are made of ) not steel.

[Icemanxxxv]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

This might be a moot point! I cleaned the barrel after an over night soak in Kroil. Ran two dozen patches down the bore and gendered down it with a bore light. There is lands and grooves in there! Looks like I have my rifled barrel already. Now l hope she ain't all shot out. Another plus is the crown looks good. Parts on order hope to have it shooting soon!
The gun is old school only three plastic parts flat top chamber and pump.

So what kind of stocks does it have ?
Is it solid styrene with the checkering, or is it the hollow abs stock with the faux butt plate ?
Also is it self cocking or do you actually have to cock it ?


Btw the receiver is zamak ( a zink alloy which hot wheels are made of ) not steel.

Solid styrene  wood forestock. I believe it cocks with bolt. Steel is a Generic term. Didn't know what alloy it was I know it ain't plastic. lol!

[bantam5s]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

This might be a moot point! I cleaned the barrel after an over night soak in Kroil. Ran two dozen patches down the bore and gendered down it with a bore light. There is lands and grooves in there! Looks like I have my rifled barrel already. Now l hope she ain't all shot out. Another plus is the crown looks good. Parts on order hope to have it shooting soon!
The gun is old school only three plastic parts flat top chamber and pump.

So what kind of stocks does it have ?
Is it solid styrene with the checkering, or is it the hollow abs stock with the faux butt plate ?
Also is it self cocking or do you actually have to cock it ?


Btw the receiver is zamak ( a zink alloy which hot wheels are made of ) not steel.

Solid styrene  wood forestock. I believe it cocks with bolt. Steel is a Generic term. Didn't know what alloy it was I know it ain't plastic. lol!

According to crosman If the forearm is wood and the stock is solid styrene this would make it a 3rd variant made  from 1974 to 1975 and will be self cocking. This means that the valve cocks itself when you pump and the brass bolt is just there for loading.
They started the date code system in July if 1975.

[Icemanxxxv]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

This might be a moot point! I cleaned the barrel after an over night soak in Kroil. Ran two dozen patches down the bore and gendered down it with a bore light. There is lands and grooves in there! Looks like I have my rifled barrel already. Now l hope she ain't all shot out. Another plus is the crown looks good. Parts on order hope to have it shooting soon!
The gun is old school only three plastic parts flat top chamber and pump.

So what kind of stocks does it have ?
Is it solid styrene with the checkering, or is it the hollow abs stock with the faux butt plate ?
Also is it self cocking or do you actually have to cock it ?


Btw the receiver is zamak ( a zink alloy which hot wheels are made of ) not steel.

Solid styrene  wood forestock. I believe it cocks with bolt. Steel is a Generic term. Didn't know what alloy it was I know it ain't plastic. lol!

According to crosman If the forearm is wood and the stock is solid styrene this would make it a 3rd variant made  from 1974 to 1975 and will be self cocking. This means that the valve cocks itself when you pump and the brass bolt is just there for loading.
They started the date code system in July if 1975.

Thanks I'm a bit on the uphill side of this power curve

[Icemanxxxv]

Now I'm bummed! Upon further review of the play the barrel is indeed not rifled. Just scored up from BB's. On the better side I grabbed a .177 24 inch barrel for for a 2240, 2250, or 2300 off the eBay. I figure after cutting the breach off just forward of the transfer port it should be just an inch or two longer then the original. Thankfully I have a friend with a lathe and a mill. I'm also planning to fabricate a new bolt to seat the pellet past the transfer port and incorporate and o-ring seal. Should be an interesting project. Might just start a real build thread for it.

[mav72]

I know the M4 barrel is a direct fit into the plastic fantastic 760, but what about modding a 1377 barrel? I have access to a lathe and mill I was just wondering if the 1377 20" barrel would be a candidate for the swap into a steel receiver 760? Anyone know the optimum barrel length for a .177 rifle?

I've done it with the original 1377 short barrel when there was no direct drop in. You need to find your measurements depending on the type of transfer port/barrel holder that you have. Dont forget to make a "lead in" so the pellet doesnt get damaged when loading. From what I've read, the optimum barrel lenght for a .177 is around 17-18".

[Icemanxxxv]

I've done it with the original 1377 short barrel when there was no direct drop in. You need to find your measurements depending on the type of transfer port/barrel holder that you have. Dont forget to make a "lead in" so the pellet doesnt get damaged when loading. From what I've read, the optimum barrel lenght for a .177 is around 17-18".
[/quote]


I've taken all my measurements and rendered a drawing to follow when my end mills and other raw material arrive. Getting close to getting this project off the ground. I allready have the 20" barrel. Minus the bolt and lead in it should leave about 17" of rifled tube out the front. The gun sports a factory flat top valve and piston. I already have a shortened check valve and lighter spring. Going to add a heavier hammer spring and increase the volume of the valve and smoothe out the airflow to the transfer port. Seems that increasing the t/p size may be detrimental to velocity, I can't say that is confirmed or not. I have read conflicting posts on that subject.  A new extended bolt will be fabricated with an o-ring seal or close enough tolerance to the raceway so one won't be needed. I also intend on chambering it a shade longer for a bit of head space maybe 2-5 thousandth.I will start at 2 and work up from there.

[Big Bore Bart]

  That is a self-cocker you have, do not change the "hammer spring",  it's not a hammer.    Also, increasing the valve internal volume won't do much for these guns, without a whole lot of pumping.   The best velocity increase comes from very slightly opening the exhaust nipple on the valve, do not overdo this .145-.150" is about max.

[mav72]

Going to add a heavier hammer spring and increase the volume of the valve and smoothe out the airflow to the transfer port. Seems that increasing the t/p size may be detrimental to velocity, I can't say that is confirmed or not. I have read conflicting posts on that subject.  A new extended bolt will be fabricated with an o-ring seal or close enough tolerance to the raceway so one won't be needed. I also intend on chambering it a shade longer for a bit of head space maybe 2-5 thousandth.I will start at 2 and work up from there.

Sounds good. I'm not familiar on the sysetm the self cockers use to release air from the valve. I've read that the transfer port shouldint be opened too much on a .177 pumper or spring/gas spring gun because you loose velocity due to the finite amount of air in the valve or air chamber. I would think you woud need to find that perfect balance where you would have minimum restriction and not lose velocity. As for valve space, you just have to find that perfect median to where you are not pumping too much OR the gun is too hard to pump. Old trends were to open up the valve and you had people pumping 20 some times before a shot. The newer trends have people stuffing valves which makes the gun VERY hard to pump but with fewer pumps. As for the extended bolt tolerances, you might be able to get it to seal with just oil but, then again, it might bind. I always say, "Bart really knows his stuff" so I'd take his suggestions in account. Try and take pics and post. I like to see the product of hard work.

[unionrdr]

I and one other member found 2 N.O.S. 761xl barrels to fit our 760 v1 Powermasters. Nice rifled barrels I measured @ 20 3/4 inches. Identical to the original barrels they came with...save for being rifled rather than smoothbore. Here's a pic of it polished up for bluing...before B/C Super Blue ruined it a 2nd time;

[Icemanxxxv]

I and one other member found 2 N.O.S. 761xl barrels to fit our 760 v1 Powermasters. Nice rifled barrels I measured @ 20 3/4 inches. Identical to the original barrels they came with...save for being rifled rather than smoothbore. Here's a pic of it polished up for bluing...before B/C Super Blue ruined it a 2nd time;

Nice score on the barrels! Me not so lucky! Good luck on the Bluing hope it turns out this time!

[unionrdr]

Me too, man. My fingers are still sore from all that polishing. Worked on it a lil more today. Got the front and rear sight parts polished. Just need to find someplace that has B/C Perma-Blue, rather than Super Bleck.

[HunterWhite]

I'm happy to see a 760 thread. I tried to order a M4 barrel, 417-005 and 760E-125 support block, but Crossman told me that was an obsolete part number. What barrel would you guys suggest? My 760 is a new plastic 50th anniversary version. It seems to hit pretty hard but it's not accurate.
T. I.A.

[Matchstickshooter]

Ask Crosman for barrel for MK 177-010. That's a drop in RIFLED barrel.  Length is just under 17 inches. Takes the same barrel support, 760E-125,
which you can also find on ebay.

HTH

[unionrdr]

I'm still working on the video where I'll finish work on all the parts of my 760 variant 1. Then assemble it with the NOS 761xl barrel and mac1 seal/piston upgrade kit. Plus the 1892 Winchester saddle gun-style butt plate I'm making for it.

[HunterWhite]

I have the barrel and support on order from Benjamin.
The little guy is not much, but out in the country I can sit on the back porch drinking Ice tea for hours pumping this thing as I go.
Thanks again.
Hunter Whitebeard.

[HunterWhite]

Crosman sent me a letter dated Mar 7 stating that the items will ship as soon as they can be gathered up. They will send email when it ships.
Barrel     $9.97
Support  $1.00
Handling $4.00
Tax         $1,2
Total      $ 16.17
If it can shoot 1/2 at twenty yards I'll be very happy.