pumpmaster 66 vs 760

[waterman]

I have 3 cros 760,s that don't shoot very accurate like 2" at 10 yards, one with a rifled barrel. Now I have 2 pumpmaster 66's that are very accurate. I'm not sure why. Then you try bb's and you're lucky to hit a paper plate. Why?       thanks  den

[birdmove]

   The 66's have a rifled barrel. Good for pellets, but bad for bb's. I have a 66 in the form of a 664, and it's rifled and shoots pellets well. I won't shoot bb's it it, as it may damage the rifling.

[N.E.Dan]

I don't understand why the 760 with a rifled barrel is inaccurate?
Do you have any theories or reasons you know of for this.

I've been switching back and forth from the 760 pdf to the M4 parts explosion But can't understand why it wouldn't work just fine?

[bantam5s]

I don't understand why the 760 with a rifled barrel is inaccurate?
Do you have any theories or reasons you know of for this.

I've been switching back and forth from the 760 pdf to the M4 parts explosion But can't understand why it wouldn't work just fine?

Maybe the rifling's been damaged from bb's or has a bad crown. If your gun is a recent one ( '99 or newer ) you can replace the barrel with One from an m417 or m4177 ( they were called the m417 for the first few months ) I did it to mine when my m417 broke and it's plenty accurate with pellets ( never bb's ) i

[N.E.Dan]

I ordered the Rifled barrel and barrel support from the MK177 today.
There is some confusion at Crosman The M4 exploded parts barrel and support is not available.
A little research from Crosman support and myself turned up that the MK177 Barrel (MK177-010) and support (MK177-012) Should fit.
I'll know in 5-7 working days

[one_shot]

I experimented with m417 barrel on my 760 10 yard groups open sights were quarter sized. Put a scope on it groups were the same.
My issue with the plastic 760 was too much body flex while pumping,i did careful micrometer measurments with 760 in a vice.
Simply pump,load ,use mic and dial indicator on barrel then shoot.
Every pump deflected the barrels tip location from 28-49 ths of an inch and after 8 pumps the barrel never settled back to the same zero location.
Upto 18 ths off .
18 ths at muzzle adds up to almost 1/2of an inch at 10 yards.
Being scope was mounted to flexy plastic body and poa of barrel kept shifting every shot.....ive come to accept my 1 in groups from a $20 760.
Just my thoughts.
An old metal body 760 would be sweet.
When i was a kid we had metal 760's with wood stocks and pump arms......many years taking down game with her open sites.....9 out of 10 shots found its intended target.
Same could be said about the old 2100

[bantam5s]

I experimented with m417 barrel on my 760 10 yard groups open sights were quarter sized. Put a scope on it groups were the same.
My issue with the plastic 760 was too much body flex while pumping,i did careful micrometer measurments with 760 in a vice.
Simply pump,load ,use mic and dial indicator on barrel then shoot.
Every pump deflected the barrels tip location from 28-49 ths of an inch and after 8 pumps the barrel never settled back to the same zero location.
Upto 18 ths off .
18 ths at muzzle adds up to almost 1/2of an inch at 10 yards.
Being scope was mounted to flexy plastic body and poa of barrel kept shifting every shot.....ive come to accept my 1 in groups from a $20 760.
Just my thoughts.
An old metal body 760 would be sweet.
When i was a kid we had metal 760's with wood stocks and pump arms......many years taking down game with her open sites.....9 out of 10 shots found its intended target.
Same could be said about the old 2100

my 2nd variant powermaster 760 from the early 70's is not all that accurate and as far as I know there's no drop in rifled barrel to be bought for it. So I have to settle for 1" at 5-10yds in my hallway.

[N.E.Dan]

The mk177 rifled barrel and support came today just after I winter camo wrapped it !
Now to take it apart
BTW the support does not work for this gun but if careful you can remove and re-use the old one. I would have rather bought a replacement for the 760.
 Not shown is a bantam 3x scope that is very small and light so hopefully I won't have variation shot to shot   because of a scopes weight.
I will look into making secure the plastic breach area and barrel as much as possible when in there. Can't hurt.
Thanks for sharing your results one_shot. I wish I had a 66 to compare.
If unsuccessful I too will have to be happy with one inch groups at 10 yards for whats now a $40.00 gun because of the barrel.
More important is I'm having fun from the process.

[JMJ in NC]

I had a PM66 that I used for pesting. After pumping I always gave the foregrip a good twist ccw and accuracy improved dramatically. This puts the barrel/receiver closer to the same position every time. Used a laser boresighter to match the cheap scope to this position.

In the end, I used the PM66 compression tube on a 1377-based carbine build, & sold all the other parts off.

JMJ

[N.E.Dan]

Thanks John. I just shot her and she seems to give real tight 10yd groups. less than an inch without any fliers so far. The plastic 760 seems pretty stiff. I didn't really see where to improve it when it was apart this morning But I'm still thinking about it because I'm real close to clover leafing.
Looks like I lost the choice of open sights or scope since the new barrel didn't have provisions for them which I'm fine with.
I have to and want to scope everything.

[bantam5s]

Thanks John. I just shot her and she seems to give real tight 10yd groups. less than an inch without any fliers so far. The plastic 760 seems pretty stiff. I didn't really see where to improve it when it was apart this morning But I'm still thinking about it because I'm real close to clover leafing.
Looks like I lost the choice of open sights or scope since the new barrel didn't have provisions for the which I'm fine with.
I have to scope everything.

you can actually still get the rear and front sights on, but the front just won't go as far on as it would with that flat filed in.