.177 13,4gr Monster REDESIGNED stability

[skorec]

I theoretically assume that Monster has standard bullet shaping ( weight=13,4gr, length=6,3mm , caliber=.177 - made from  some lighter lead ) the stability calculator let me ( for TR:17,7” and velocity 920FPS ) stability value only  1.28 ( the same but shorter bullet are  much more stable ).
If the skirt drag increase the stability it should be OK but my accuracy  1,5-2 MOA ( CF stiffened choked LW barrel 605x15mm ) not persuade me at all.

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Here you may see my today horrible  3 targets (24 shots 3000-2500PSI/970-900FPS) at 35 yards only.
Groping  was a little bit closer 1,2-1,8 MOA  at higher velocity and longer distance 77 yd . Se the next target from the same gun/barrel . 
 

[Ribbonstone]

Shame...it makes me NOT want to try the "redisigned" versions as I've hot so much good luck with the orginals.
 Think it's just that that barrel doesn't "like" that pellet more than it's stability.  It'snot that long, and it shoots well in many barrels of the same twist (at least the original verion has for me).


So it may not be choke/barrel smoothness, vibration, or twist...may just be that that barrel just doesn;t like that pellet.

Have had some .177's that just "hated" the 8.4 JSB's...which is is close to a "universal" pellet as curret airgunning gets.   No logical reason I could detect...just didn't suit the barrel's needs (and the barrel always has the last work on accuracy).

What I have noticed in the 3 .177 PCP's that can shoot them that fast, is that they seem to resent (at least the MKI versions) being shot faster than about 925-940fps. 

Why...I do not know...I just accept it (after all, I don't have EVERY .177, just the ones I got, and the ones I got agree about that speed as the "going-to-ship- speed".

[skorec]

Ribbon,
Have you ever tried shot old style ( Monster or Beast )   at 50+ yd . ?
Peter

[skorec]

Because also .177 JSB Exact Heavy 10,34 gr  was grouping not good at all I have changed/swapped  the riflescope.
Today grouping with new riflescope  at 77 yd was close to 1*MOA.

[Ribbonstone]

Rare...but it is one of the pellets I did try out to 75 yards.I don't normally shoot so far, but was trying heavier weights and as the 13.4's do so well in this particular rifle,included them in the long range tests (21gr.Piledrivers totally failed in this rifle).  These would be the older version, not the "redesigned"version.

Not a great/clear picture...but I did take them out to 50 and then to 75 yards for a short head-to-head test with two heavier weights is an old BAM 50.





Idea here was to shoot the 50 yard target as near dead on as I could adjust the scope,then shoot the 75 yard target...then start over at 50 yards with the next pellet.  Those 3 happened to be the best at 25 yard grouping,so they moved on to farther range.

(It's the BAm on the bottm...top on is a BAM 51 in .22):



Nothing really specal about the rifle,same Chinese barrel ia alwarys had (a little polishing of the crown) andit'stuned to what I call a "soft tune"for this rifle (meaning it's running about about 3/4speed).
Soft tune:

These pellets didn'tmake the accuracy cut...but pretty representitive of the "soft tune". From13.4 to 16.3gr. would ahve beeen something between 24 and 25 foot poundsper shot.

[skorec]

Thanks Ribbon,
I now remembered that I saw your targets at 75 yd. Seriously nice shooting at 75 yd mainly by using old style Beast .177 it is absolutely unbelievable grouping .

I have found out excellent document about BAM 50/51 but unfortunately the are no some details  about barrel bore.
https://www.airrifle.co.za/library/Adjusting_the_Bam_B50_B51.pdf 

[Ribbonstone]

Doesn't seem to be any odder than any other factory barrel.  No choke I can detect, doesn't seem excessively loos or tight compared to others (by slugging and measuring the slugs).

Not the easiest barrel to get a full look at as they glued the barrels into the breech and most folks just don't want to unglue them. Can remove the bolt, and deal with the barrel from the back of the breech, but it's hard to get a real good visual on the "chamber"  from that distance.