brown dog

Just brainstorming...  silicon sheet...  cut for 1mm thick fore-end shims...

9 minutes ago, Popsbengo said:

Excellent - what make of rubber bands should I use and have you considered differing rubber compounds?   😂

 

😂  Royal Mail .. nothing else will do

I also wonder if 5 of these would be a cheap and less obtrusive limbsaver

9 minutes ago, brown dog said:

😂 k.i.s.s

My instinct is that a liquid silicone gasket at the same point, but between barrel and stock, will be a game changer..... just a feeling 😂😊

2 minutes ago, Ronin said:

You need to patent that and sell it

 

 

😂 k.i.s.s

Well, I realise this is statistically valid as a feeling in my water,  and I'm afraid I stopped just after I started due to it starting to snow....

I wanted to see what, if anything a 'tight rubber band' deresonator might do. 

Group on the right is 'without bands'... then did one on left 'with bands' ( and then, annoyingly, I packed in) ..... the left group is typical of the better groups (25%) I get with the rifle.. it was just felt odd that it happened straight after I put the bands on, and despite the weather deterioration...I know, chance... but interesting if it turns out to be repeatable 

45m/49yds   bipod, back bag 

9 hours ago, ds1 said:

Lapua,  CCW (Carrying a Concealed Weapon).....short version....concealed carry. It’s legal in CZ ( I think even protected under our 2A - Second Amendment type rights). Cz -11m population.......about 370,000 FACS of which 250,000 have CCW.

Do you have to have 'good reason' type justification, or is it just a 'right'?

I've never bought a pistol, so I'm not price-calibrated - but £4k and higher- blimey! That's some serious retail therapy! 😊 

16 minutes ago, terryh said:

😂😂 Actually as an engineer I thought the barrel length should be ‘horizontal’ as that’s how I shoot and also how I’d hacksaw it down in size 😉

Yeah, horizontal, but left to right, not right to left!😂  .

Not seem that 6 x 5 thread before... that's some serious reality!   

("All under a thumbnail at 80m" - bolloqs!)

5 hours ago, terryh said:

Allan,

I'm seeing locally more interest in 22rf for a few reasons, personally it is a bit of a challenge (couple of other shooting buddies also jave this view). As to the smaller groups at longer ranges. I hate to point to the US but here is a listing of 6 x 5 shot groups  https://www.snipershide.com/shooting/threads/6x5-thread-v5-0-new-1-1-21.6253073/ 

Also here's some of BD's linked data graphically:

You an Arab? Interesting choice on the direction of the x axis! 😂

Interesting that SK is flattest

Aware of the change, but not really had a chance to understand the what and why, which don't seem obvious at a quick look. The colour change may be a clever anticipatory move, given the change of US leadership?

https://forum.accurateshooter.com/threads/latest-test-on-1-cut-on-barrel-length.3946283/

1 hour ago, 1066 said:

Rimfire benchrest rifle makers set great store in taper lapping their barrels - I believe the method that Anschutz use at one time to simulate that effect in a mass production environment was to heat shrink a sleeve on the last 2-3 inches of the barrel and constrict the bore.

How interesting.... one the things I was going to suggest as a solution to 'the resonant doughnut'  (or 'vibrating ring'?! 🤔😂)

I'd hazard a guess that these target-grade mfrs have known for a long time that a cure for a vibrating ring... sorry, unstable muzzle, is a choked bore. 

Pre-compressing the muzzle outer surface is almost a reverse-autofrettage. Makes total sense.

2 minutes ago, Popsbengo said:

Damn! who'd have thunk it?  Bloody ballistics expert got it right,  😂🤣

😂 yup;  but we've also shown it  ain't 5.56NATO rimfire either 😂😊

Right, I need to do some work ...

42 minutes ago, Popsbengo said:

Quite a bit different to your original guesstimate of 2.5mS for 16".

I've drawn a more representative curve and recalculated = 1.57mS ± some beans

We need 1066 to chop the barrel at 1.5 " 😂

😂 yup. 

We now have your Kolbe of 1.75mS

Your drawn answer of 1.79

Your redrawn answer (to fit your preconception?😂😊) 1.57

And my calculated  of 1.88

.... three data points 'group' with one outlier.

Squad avg without outlier : 1.8mS

Squad avg with outlier: 1.74mS

....which is the Kolbe value, give or take🤔

To my mind, we've just idiot-checked the Kolby figure and validated it.

Answer: 1.88mS

Damn. Was it 16.25, not 16... standby

Right, well, here's a 4-step calculation for 16" using one of the step MVs Allan gave earlier.

Spoiler: The answer is 1.84mS

1 hour ago, Popsbengo said:

 

BD, I think your assumption of linear acceleration does not stand up,  therefor taking 50% of MV as an average velocity is also not correct.  The bulk of the acceleration is clearly in the first inch or so.

 

I said interpolated to linear in first 16... not the whole way ..😉😊

As regards a baseline commonsense check; I mentioned earlier, even if there was no acceleration, and the bullet did the whole barrel at 324m/s  ...it would take 1.28mS to transit a 16" barrel.... so, we know any value below or near 1.28mS is patently nonsense. 😊 ...so I don't think QL looks to be producing anything 'likely to be right' for us in rimfire

Allan's cut barrel data will allow a 3-step iteration calculation... I'll do it in a mo (for a break! 😂)  I also note the barrel times shown on the X axis of the Varmint Al graph - which chime with my calculation

I'm a bit horse-not-zebras.... if any of those things definitely always had and effect, that's how all guns would now be made.... most of them are voodoo and feelings in people's water rather than supported by hard repeatable data.

Have to say, the resonant-doughnut idea chimes with me, as I've often wondered why big guns - 105mm+ are so very much more accurate than small arms.... and it could go some way to explaining that... too much to type!

8 hours ago, 1066 said:

These are velocities shot through  3.27", 7",10" and 16" barrels

Remington Subsonic Hollowpoint, part # SUB22HP
Barrel length Average
3.27 766
7 934
10 972
16.25 1016

That's bloomin useful data  - I've got a mad day, but later, that can be used to calculate a slightly finer-grain representative acceleration/ barrel time to 16"

Just now, Popsbengo said:

Not at all,  as I said, there's no .22LR data I can find so I've just made a imaginary cartridge that has fast powder, achieves something similar to .22LR in a 16" barrel at the muzzle.  I can't plot anything else as Kolbe's program just gave me that output. 

My two earlier eg graphs compare plotting against time vs plotting against distance.

Against time, acceleration is an S Shape that interpolates to show linear acceleration

... I'm pretty comfy that linear acceleration to 16" followed by constant vel is 'about right' for a .22match round

 I think you're being distracted by the shape of the 'against distance' graphs?

Im still struck that your barrel times so far haven't been significantly different to rounds giving mvs 3 times higher...., and the latest, I can't follow, but it still doesn't seem intuitively right... 

We're into tale chasing without an 'actual' number.   My ancient pirate copy of QL is long gone with the laptop it was on; so I can't play with approximation tuning, I'm afraid.

3 minutes ago, Popsbengo said:

looking at these graphs from Geoffrey Kolbe's P-Max program, I've used finger in the air to get similar to .22LR ballistics:

75% of the acceleration is all in the first 4 inches.  The pressure curve shows pressure to 1.75mS, so I've taken that as barrel time.

Am I missing something here?  I read this to show a Mv of 1061 fps achieved in 1.75mS in a 16" barrel

?

Plot one showing velocity against time, not distance.

I've got a pretty strong audit trail to my calculation; you seem to be plucking numbers🤔😊

Thinking on.... even if a 22lr instantaneously accelerated from 0m/s to 324m/s in the first 0.0001mm of barrel;

and did all 16 inches at 324m/s...which, clearly it doesn't..

.... it'd take 1.28mS  to do 16"

...so 1.5mS fails a commonsense check to my mind.

(PS edit:   

Note in the 6br graph how S-shaped the acceleration curve is - interpolating to a broadly linear acceleration... this is because the X axis on the graph is 'time'.     

Similar QL graphs, appearing to show faster initial acceleration have the X axis as distance (rather than time) which shows 'where' the acceleration happens, not 'when' it happens - which gives a subtly, but significantly different visual:

)