BAM5 50 : Stage 2 accuracy test

[Ribbonstone]

STAGE 2 ACCURACY TESTS:

Nearly prefect day for pellet testing, 52-53F and light winds locally (and mostly shielded by fence and shrubs).


Last time out, tested 6 potential .177 pellets at 20 yards. Only the best 3 of those 6 moved on to 40 yards.






Considering I was driving them too fast (+20 foot pounds) for the lightweights to make the cut, were not that many pellets to test.

The “winners” of round 1 (and I’d not have predicted this as I’ve had less than great luck with Crosmans):




So these 3 moved on to 40 yards.  When I get a chance, the top 2 of these three will move on to 60yards. 


Things I did NOT CHANGE:

1. Did not change the windage/elevation of the scope. Did refocus the parallax, but left the adjustments alone from the 20 yard test.

2. Did not change the pellets, both the 20 and 40 yard groups were from the same tins.

THINGS I DID CHANGE:

1. Cleaned the barrel and shot a dozen fouling shots before starting these tests.

2. ONLY shot in the “sweetest of the sweet spot” range for each pellet.  So just took 15 shots between fills and kept the fills in the area where previous shot counts showed the best of the best variation.

3. Fired one shot into the dirt as I walked from the fill area to the bench area.  Haven’t tested this rifle for a problem, but SOME rifles seem to do odd things with the first shot after a refill.

4. Probably a little harder visual inspection of each pellet than normal.  If in doubt about anything, set that pellet aside.

5.. Piles of sand bags rather than my more typical lighter bench rest system.  Looked a little like WWII Japanese machinegun nest, but it was stable.


40 Yard results:



#1. I need a bit of right windage, but didn’t want to add fumbling around with the scope as a variable, so lived with it.

#2. Do NOT take too much meaning in the drop at 40 yards as they were not perfectly sighted in at 20.

#3. I have no clue why the Crosmans did so well.  Considering my record with Crosman pellets, it’s not unheard of, but pretty rare.  Did notice they chambered with that nice feeling of snugness, so it’s probably a diameter difference.

Draw what conclusions you see, but until I get some 50 or 60 yard shooting, will let the guns that prefer the JSB’S enjoy them and just sight this one in dead on at 40 with the cheaper Crosmans.

[rsterne]

Some barrels just plain like the CPHs.... I know a few FT guys that use them, simply because of that fact....

Bob

[Ribbonstone]

Didn’t expect to become so enamored with the .177 this late in the game.

1. Will retest some of the other .177’s with these particular Crosman pellets to see if these pellets just shoot better than expected.

2. Old .177 Pneuma (single shot) going to go though a re-revision and get powered back up as well. (although I think I’ll just test it with the AT44 .25’s air tube as a start).
3. Modded issue BAM brake is at least usefully quiet with the heavy weights….rat phart if not mouse phart.

[moorepower]

Wow, I bought one of Mike's 24" .22 match barrels to put on my B-50, but perhaps I should shoot the .177 first.

[Ribbonstone]

Won't hurt to try it.

Got the .22 some years back and it had a problem grouping real well.  Crown was good (still is the factory crown) but the chamber had a burr at the transfer port.

This .177 has no burr at the transfer port, but it seems Mike did a little crown polishing.  All Iv'e done to it is clean it.

Hard to judge by eyeball if a crown is oiir, it is even hard to judge unless you have some good crowns to compare it to.  It's not about "pretty" but about a smooth even transition at the muzzle (meaning ugly can work just as well as pretty).

[SpiralGroove]

Hey Ribbonstone,
Use a small piece of masking tape and 1/8" or 3/16" dowel w/500 grit paper wrapping.  Run through bolt passage to beginning of chamber.  With a little (back-forth/twisting) movement you should be able to remove the burr.  Also, I have used a patch/jag/400 grit clover to really scour a few of my BAM's.  Just a few back-forth pulls and all the rough edges are gone.

You may want to try..........

[Ribbonstone]

Only the .22 showed the need.

Here's my cure (a lot like yours)

1. Barreled action off the gun.
2. Remove bolt
3. Bamboo BBQ skewer
4. Small (like 1/2" long) pad of fine abrasive paper rubber cemented to just the BOTOM 1/2 of the skewer.
5. Reach in though the empty action and just polish the burr.
6. Can peel the little pad you cut and replace it if need be (which is why the rubber cement).
7. Peel off the pad, slot the tip of the skewer for about 1/2"
8. Slide a tuft of OOOO steel wool (and OOOOO would work if you can find it) into the slot.
9. gently polish the transfer port area.
10. Clean everything (twice).
11. lube bolt
12 reassemble

[RayK]

This .177 has no burr at the transfer port, ... All I've done to it is clean it.

I've been playing with my "brand new" 177 B50 and I've seen the same thing.  Barrel looks pretty good and I could not feel/see any burr on the transfer port in the inleede.

I pushed a variety of pellets through then examined them with my 10X jouler's loop and they looked pretty good - especially the CP Domes.  Rifling was clear and even.  I did not feel any choke at the muzzle.

I took the B50 to the range and shot 43 yards and nothing grouped well (although CPD were most promising), but it was clear the inleede needs a funnel-taper polishing to allow a smooth transition into the chamber.  Each time I loaded a pellet, it felt rough and I'm sure some of the pellets (especially the very soft JSB & H&N) were getting deformed.  The probe was hitting the rear of the pellet off  center (a bit high) which further tended to cock the pellet as it was going into the chamber and the head grabbed on the rough inleede.  I was shooting tethered from a solid benchrest, but if I lifted the gun and pointed muzzle down, the pellets loaded much more smoothly.

It may not be backyard friendly, but it isn't that loud even shooting the 10.5 grain pellets at almost 1000 fps so that cosmetic muzzle break most help a little.

I got it all apart again (and am stuck with getting the valve out)  Pin and screws are out, but it won't budge, so I assume the long screwdriver is required.  I'll try to get over to HarborFreight today to get one.

I'm going to use Bob Sterne's upgrade of tapering the poppet to 5/16" after I get the valve out.

Ray

[GarthThomas]

"I'm going to use Bob Sterne's upgrade of tapering the poppet to 5/16" after I get the valve out."
Ray may I suggest you also replace the washer like Rsterne did as well to help reduce the chance of the spring binding, also you may find that changing to a weaker hammer spring and lightening up the spring guide will be necessary because the power will go up for sure.

[RayK]

Thanks!  Yes, I will look into all those things after I get the valve out. 

I will definitely ensure there is no poppet spring binding.  Without seeing the parts I can't yet tell, but I'm leaning towards removing spacers and installing longer stiff poppet spring (as I did with my XS60CPCP and it worked awesome - far better than Bstaley o-rings).  I will probably try a better quality hammer spring from one of those I've used in my Marauders since they are the same size as the B50 hammer spring.

My hammer is not a two piece like I've seen in some of the threads.  The hammer spring guide at the rear is part of the one-piece hammer.

Ray