Air Arms Owners Club

Does increasing power improve accuracy?

I have an Air Arms MPR 10m Precision (a version of the S400). It comes out of the factory set at 5.15 ftlb. I'd now like to use it at 25m, so I've increased the power to about 11.5 ftlb. But it seems to be less accurate at the increased power (the grouping, even at 10m, now seems worse).

Could someone enlighten me?
Thanks

could be as simple as pellet choice. what would have seamed good at 10m at 5.5fpe is now not acceptable at 11fpe. the harmonics of the barrel will have changed, plus pellet speed. try cleaning the barrel and test again. if you use a benchrest it will remove yourself from the equation. mpr at 12fpe is very good, there will be a little extra muzzle flip, but at 12fpe i would not worry too much. the pellet batch is also a factor, you can have two different batches, one will shoot wings of flys, the other maybe like a shotgun. you have to accept changing something causes reactions. you need to start again.

Gary

Thanks for the reply.

According to the Air Arms brochure, in the MPR 10m Precision, 'the firing valve is designed to be self-regulating'. But I believe the S400, on which the rifle is based, is non-regulated. So I'm not sure how they achieve this.

It might be reasonable to assume that the 'regulation' is only effective at factory settings, so I'll revert back to 5.15 ftlb and see if accuracy is restored.

I've noted your comments on pellet choice. I'm currently using RWS R 10 Match Rifle pellets (8.2 gn).

Mainliner wrote: ↑

Sun Feb 13, 2022 10:56 pm

Gary

Thanks for the reply.

According to the Air Arms brochure, in the MPR 10m Precision, 'the firing valve is designed to be self-regulating'. But I believe the S400, on which the rifle is based, is non-regulated. So I'm not sure how they achieve this.

It might be reasonable to assume that the 'regulation' is only effective at factory settings, so I'll revert back to 5.15 ftlb and see if accuracy is restored.

I've noted your comments on pellet choice. I'm currently using RWS R 10 Match Rifle pellets (8.2 gn).

Flat headed target pellets don't work well past those shorter ranges. I've tried, I have a huge collection of pellets, if I got to a gun shop and they have anything in 0.177 I don't have I buy em... Case is getting a bit heavy mind..... Anyway... Diabolo are good for 25 to 55, and the best of the are AA Diabolo 8.4 or Express 7. Something grains... They will work in most barrels, the Walther barrels seem to like them a lot.

Thanks for your reply.

You're probably right about flat-headed pellets being used at 25m. The clue's undoubtedly in the name - RWS R 10 Match - clearly designed for 10m!

But that still doesn't explain the poor grouping I now get at 10m, when the power is set to 11.5 ftlb.

harmonic vibrations in the barrel. shooting at a different power setting gives you a different pellet speed. the ideal exit point for the pellet is at a node, either when the barrel vibration has reached tdc or bdc in the harmonic cycle. at these nodes the speed of the barrel in the cycle is zero. a simulation is compare the barrel to a piston in an engine. at bdc the piston speed is zero, it starts to accelarate, at the mid point in the stroke it is at max speed, then as it moves past this it slows down to zero at tdc. if the pellet exits at the mid point or close to it in the cycle ie at max speed the tiniest difference will give a huge difference in poi. at tdc or bdc the barrel speed is slow and gives a less pronounced difference in poi, this is why barrel tuning weights are used to dampen down vibration.

Mainliner wrote: ↑

Sun Feb 13, 2022 10:56 pm

According to the Air Arms brochure, in the MPR 10m Precision, 'the firing valve is designed to be self-regulating'. But I believe the S400, on which the rifle is based, is non-regulated. So I'm not sure how they achieve this.

It might be reasonable to assume that the 'regulation' is only effective at factory settings, so I'll revert back to 5.15 ftlb and see if accuracy is restored.

forgetting pellets, my 2p....

the S3/4/5** (& Mpr) are non regulated as is the sub '6'/lb rifle BUT the valving / hammer setup differs as does the plenium volume @ the valve.

this will have an effect on the valve action and the pellet acceleration...

how did you 'upp' the power? the 'sub6 rifles have a different hammer & hammerspring from the factory and possibly a different valve compared to the sub12 rifles - add this to the plenium volume and possibly decreased accuracy due to 'jetting' from muzzle-blast and even 'recoil' from the hammer impact on the valve (the great ballancing-act )

I could be wrong though

Rich.

more power - more muzzle flip, also flat heads start to loose their accuracy beyond about 20m and don't particularly like it beyond about 650fps. Done a bit of work on this for BR on an HFT500 and that's what i found.