Pellet fit in breech

Pellet fit in breech

Postby FPoole » Tue Jan 10, 2017 11:43 pm

I often here that the fit of a pellet, in the breech, needs to be snug. Well, I have this 1992 TX MarkI and the pellets almost fall out of the breech unless a Crosman Premier is used. I think the skirt on the AA/JSB is the only thing keeping the air from just blowing around the pellet. I shot 20 or so out at 55 yards, FT style, and then walked out to refresh some really shot up places on the paper with some 1" orange dots. Using AA Diabolo Fields in 4.51, no it's not a .22, my first 4 shots hit the 1" sticker with the last pushing it through the worn paper backing. I retrieved the dot and all 4 were within a .5" area. This gun must really have a wonderful choke, because the breech is so sloppy. I had tried a JSB 4.52, but they don't group as well. The skirts have a different shape to the hollow area so I think I might try some 4.52 AA. I know common knowledge is that the number means nothing, but the 4.52 JSB definitely fit just a touch tighter. Hoping the AA 4.52 will as well, but I don't see how the accuracy could improve. Did I mention that this gun has a nice little buzz to the firing cycle? Tight guide and loose tophat, but I'll not touch it as long as it's so accurate.
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Re: Pellet fit in breech

Postby Blackbaronfish » Sat Mar 11, 2017 7:14 pm

I had a BSA meteor that loves metric size pellets. I never ever needed to change the breech seal either.

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Re: Pellet fit in breech

Postby TenMetrePeter » Sun Mar 12, 2017 11:40 am

The breech on a thumbed barrel will have a loading taper greater than a probe loader. The initial air blast will expand the skirt to fit whether or not the muzzle has a choke
So long as they dont actually drop out and you get such great accuracy I wouldn't worry.
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Re: Pellet fit in breech

Postby Sake-san » Tue Mar 14, 2017 6:05 am

Thanks for sharing FP, I would not be concerned given the results you achieve.
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Re: Pellet fit in breech

Postby FPoole » Tue Mar 14, 2017 11:20 pm

Decided to chrono the gun since this was first posted. 8.44 AA fields are at 775 and in a very nice sub 10 fps spread. I'm never concerned about the velocity because we have no 12 ft. lb. limit.
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Re: Pellet fit in breech

Postby Timmytree » Wed Mar 15, 2017 6:50 pm

FPoole wrote:Decided to chrono the gun since this was first posted. 8.44 AA fields are at 775 and in a very nice sub 10 fps spread. I'm never concerned about the velocity because we have no 12 ft. lb. limit.


What a coincidence! My PS normally averages 775 fps and is accurate at that level. I put it over the chrono at the weekend after a long period of inactivity and it was up to high 780s but giving the odd flier. I removed one power washer and added a tad more grease and its back down to low 770s with no fliers. The spread is 7fps over 10 shots after a few to settle things down.
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Re: Pellet fit in breech

Postby FPoole » Fri Mar 17, 2017 12:12 am

775 seems to be a very good speed for the 8.44 pellets and the short stroke MarkI and II guns. I have my zero paper out at 25m and, when I practice my FT position, I can pretty much hit a pellet hole. Saves on target paper because I have a bunch of heavy paper that I just pop a shot at and then go for the pellet hole. When I used to shoot the Mark III at fac levels it seemed to like 860-890 and, if I did my part it was good at and just above 900 as well.
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Re: Pellet fit in breech

Postby Sake-san » Mon Apr 17, 2017 5:25 pm

The endless joys of shooting springers.... and perchance pcp's also
I recently discovered (by complete accident) that different batches of pellets group differently (I use 50m for my pellet batch testing) at different muzzle fps.
I have different batches of both AA Field and JSB Express, tweaking by as little as 15fps brings astonishing (at least to me) results.
My benchmark is <2.5 cm at 50m off the knee sitting (aka primary FT position)
I normally batch test pellets at around 775 (8.4g) and 805 (7.9g) it had never occurred to me to test at differing velocities.
Chatting with a true guru (ex advisor to UK 10m squad) he confirmed my discovery.
Long story short, one batch of 8.4 better at 785fps, another better at 770fps, the same equation with 7.9's...
As if it wasn't complicated enough :shock: but, all good fun ;)
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Re: Pellet fit in breech

Postby Sake-san » Mon Apr 17, 2017 5:41 pm

Should have added, I don't mean tweaking the 2.5cm group by a few mm, it is the difference that would for me define "retaining" vs "binning" a batch...
Does it mean that all batches will group well at a batch specific optimum fps... sadly no, it does not (at least for me)
Naturally quality practice time will still pay back far better rewards than testing & tweaking ;) ;) ;)
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Re: Pellet fit in breech

Postby Roj 252 » Sun Sep 03, 2017 7:59 am

Hi Guys

Pellet fit and choice is interesting, as it seems there's a lot of comments here and every time you meet a fellow
Shooter. I've recently done a bit a study on pellets in my .22 Tx200 mk3. My normal pellets are
AA Diablo fields 5.51 16 gr. But I've used Hunters at 5.50 16gr Fields at 5.52 16gr and H&N target trophys at 5.53 14.66 gr !
Unbelievably ( to me at least) they all shoot virtually the same thru my gun. At 50yds I can almost pellet on pellet, which I found quite surprising..... maybe you're not surprised ?

Granted the H&Ns were a bit tight going in but shot fine.

As a bit of further "analysis" ( sorry if this getting a bit anal ) I sunk a 2 gallon bucket into a 3ft deep water butt
And fired 3 of each into butt. When I retrieved the pellets the rifling marks were quite staggering..... my brother who in a previous life was in the paras saw them and said Christ I haven't rifling that deep on anything I've ever shot ..... including a bren gun !!!

Cheers Roj
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