My new .22 BMK12 (seems pic heavy, only 491 Kb)

[Brutuz]

My new .22 BMK12 (seems pic heavy, only 491 Kb)

Received both a BMK 12 and a BMK 27 last week.

The BMK 27 (Rebadged Remington Summit) same action as B19/Quest etc. Not a challenge to tune so am leaving it as a future project for now and started with the BMK12.

Started the wrong way, instead of breaking it in first, without recording out of the box performance, I started doing that right away.

Since the rifle was smoking after each shot this must have caused a relative positive performance.

After about 100 shots trying several brands and types of pellets decided to continue using H&N Hollow Points, in the US sold as "Beeman Silver Bear Hi-impact .22 Cal, 12.65 Grains, Hollowpoint".

Stripped the rifle, opened up the breech, cleaned the internals, flattened and polished the spring ends, inserted one slip washer into the piston, re-assembled took a few unrecorded shots and soon the rifle wasn't smoking anymore and started recording to find 0.3 less fpe.
OKthis could have been caused by no longer smoking.

Next tried to up the power a bit by inserting another slip washer into the piston gainging 0.08 fpe. Weird.

Next took out one slip washer from the piston and added a 5mm powerband onto the spring guide, that should up performance a bit. Not. Fpe dropped 0.34 fpe, very confusing.

Next flipped the spring, performance up 0.09 fpe.

Next inserted a delrin slip washer into the piston, performance down 0.22 fpe, even more confusing.

Next removed the powerband from the spring guide and the delrin slip washer, performance up 0.59 fpe.

Out of the box (smoking) 7.59 fpe / 6.9 fps spread, current setup 7.49 fpe / 6.6 fps spread.

Doesn't feel as if the spring has shrunk, so am a bit puzzled why adding a bit of preload isn't effective.

Do think the spring guide needs replacement, not sure if I should invest in delrin parts and a better spring since this isn't my "main rifle" and it does cock and shoot smooth as is. Am aware a custom made tuning kit would improve it.

Haven't tested accuracy yet, but short distance in the workshop it looks promising.

Since there isn't much preload I stopped using my spring compressor after the first disassembly and closed it pushing the end of the rifle to my work bench carefully preventing it from slipping off. Cannot reccomend working this way though, to be 100% safe always use a spring compressor!

First undo the bolt onto which the triggerguard screw goes half a turn, next tap the rear pin out using a phillips screwdriver about same od as the pin, leaving it in place, if using a spring compressor pull back the phillips screwdriver and slowly release tension, in my case push it on the edge of the work bench, pull it out and release tension.

Pull the triggerunit out, keeping one finger on the safety.

How to remove the barrel so the piston can be removed has been written quite a few times before.

When done cleaning, tweaking, re-lubing etc, it's important when the trigger unit is inserted the sear is in the wright position to allow the phillips crewdriver to pass through, and to keep the safety in position is important too. When closing it "by hand" like I did it's important to keep pressure under an angle to the phillips screwdriver so the holes and internals are alligned correctly while tapping the rear pin back in. Don't forget to put the bolt onto which the triggerguard screw goes back in and tighten it and reverse half a turn to allow movement.

Easy rifle to work on, due to the small piston / volume of air hard to tune for more power. Had read that before and have experienced it myself the last few days *grin*

Here's a LINK pointing to the pic showing the Chrony recordings, it's a long one...

A few snapshots:

















A few pictures:



















Overall a sweet lovely rifle that has a more adult feel compared to the old B1 I own and doesn't feel like a kids rifle compared to regular rifles like the 19.

Finish looks good, stock looks good, value for money and easy to work on.