Reply To: FWB 124D Has PCP like accuracy.

Forums Springers, Pumpers, C02, & Vintage FWB 124D Has PCP like accuracy. Reply To: FWB 124D Has PCP like accuracy.

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10x
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I'm just copying and pasting this here…enjoy from another forum from the past.

Hi All,

We often see comparisons of similar types of airguns, so I thought it would be interesting to take a look at two very different air rifles. Both are classics, manufactured by Feinwerkbau, but one is a sporter and the other a 10m match rifle. I bought my FWB 124 Standard new in the mid 1980’s and made a target-style stock for it a few years later. I’ve been doing Beeman-style tune-ups on it since then and recently put in a Maccari tune kit. The Maccari spring made the rifle’s shots snappier. The original spring, which broke last year, was very long and had a lot more preload, which kept the spring force more constant and a bit lower than the fully-cocked spring force with the Maccari. Although the muzzle velocity went down a bit (especially if the pellet was seated with a Beeman Pellseat, which reduced the MV by 50 fps compared to finger-seated pellets), the rifle shoots great with the Maccari kit. The cocking is super easy and smooth. The rifle gives a short jolt on firing, but there’s no vibration. 

Last year, I finally got a FWB 300S, after dreaming of owning one since I was a kid. The rifle was manufactured in 1975. What a beautiful piece of engineering and machining! The trigger and firing behavior are amazing. The barreled action slides back a few mm after each shot, leaving the sight picture virtually unchanged. The cocking handle anti-bear-trap clicks like a Swiss watch. When I carved the target-style stock for my FWB 124, I used photos of the 300S as a guide. It’s fun to compare my homemade FWB 124 stock now to a real 300S. 

Slide 1 shows the rifles side-by-side, along with a homemade hamster for the 124. I’m going to try field target shooting with the FWB 124 this spring. I also took a picture of the accessory hand rail that I inletted in the 124 stock. On both rifles’ accessory rails, I made rulings with distances marked in cm from the front of the pistol gripped so that I can consistently place the handstop when I switch from my air, to smallbore, to high power target rifles. Both rifles wear a Nikon Prostaff EFR 3-9x40m. This is a fantastic scope, but I wish they made it with higher magnifications (and had ¼ MOA clicks instead of ½ MOA).

Slide 2 shows the 124 on a collapsible bench that I recently made along with my home-made chronograph http://www.network54.com/Forum/79537/message/1452739305). Although I’ve read a lot about sporter springers not being very accurate off sandbags, my 124 does pretty well, especially if a wool knit cap is placed under the forend to dampen motion during the shot release. I think the beefier and heavier match stock may be helping here as well. 

Slides 3-5 show groups at 10m. Note that although some wadcutters (like the RWS R10) do very well at 10m, they don’t do as well at 20 yards. The round headed pellets definitely do better than the wadcutters at longer ranges. In the FWB 300S, the QYS Training pellets are the best deal and almost as good as the RWS R10, but the RWS Meisterkugeln were a real disappointment. I thought the RWS MK and R10 would be closer in performance.

Both rifles did well at 20 yards and it was surprising to see how close their accuracy was at this range. I agree with many people that a 5-shot group doesn’t mean much, so I shot six 5-shot groups with both rifles. After testing dozens of brands/types of pellets, I found that the 124 does best with Air Arms Diabolo Field 4.52mm domed pellets (average muzzle velocity 828 fps, and typical standard deviation of 4 fps for 30 shots) and the 300S likes JSB Match Diabolo Exact RS domed pellets (average muzzle velocity 626 fps, and typical standard deviation of 4 fps for 30 shots). Unfortunately these pellets don’t cut very clean holes in paper, and the groups may therefore appear a bit smaller since pellets could be bending the edges of the hole rather than cutting them bigger. The 20-yard groups are shown in Slide 6. At the bottom, I traced out the groups and overlayed them to show how the 30 shots line up. Thanks to the chronograph, I found that lower velocity shots tended to impact higher than higher velocity shots!? This is opposite of what one would expect from pellets falling during their travel and needs to be checked more systematically. Anyway, small differences in velocity cannot account for such a vertical spread due to differences in time of flight. A 10 fps decrease from 830 fps would result in roughly a 1 millisecond longer flight time to 20 yards and an additional drop of around 0.5mm. Could it be that the lower velocity pellets stay in the barrel longer and therefore leave the barrel when it’s risen more after the shot is initiated? Have you seen this in your springer?

The 300S doesn’t have this problem and is really consistent. The 124 is also more hold sensitive. When I shoot it in the sitting position with the hamster on my knee, it shoots about 1” low compared to bench-rested at 20 yards. Are other people getting similar results with their springers? Is it just a difference in muzzle jump upon firing or is the barrel/receiver moving/vibrating? Here's a nice high-speed video showing how much the barrel moves in a springer:

 

I also tested the rifles at an indoor range using the same bench. This allowed me to test the accuracy and trajectories out to 50 yards. I never shot these rifles out to such distances and was very pleasantly surprised. One major factor limiting accuracy was that the targets were dimly lit and with my Nikon at 9x it was very hard to see the aiming marks (they were faint and slightly fuzzy). Slide 7 shows 5-shot groups at 10yds, 20yds, 30yds, 40yds and 50yds, with the scopes' elevation unchanged. You can see that the FWB124 shoots much flatter than the FWB 300S, but the 4” drop for the 300S at 50 yards is still pretty good. 

Slide 8 compares the trajectories calculated by Chairgun with the measured drops from Slide 7. Either the ballistic coefficients that I used in Chairgun or my measured velocities were too low, as both rifles shot flatter than Chairgun predicted. Still, I think Chairgun is a great program and really enjoyed comparing predicted and actual trajectories. I wish there was a way to export the trajectories calculated in Chairgun. I had to digitize the Chairgun trajectories by hand using Grafula.

Slide 9 shows three 5-shot groups at 50 yards for the FWB 300S and FWB 124. If we throw out the second FWB 300S group and the first FWB 124 group, we get 10-shot groupings well inside 0.75 inches. Of course, I cannot justify throwing out any groups, but I wouldn’t be surprised if much of the spread was due to operator error, especially since the aiming marks were pretty faint/fuzzy at 50 yards. In fact, I sent the target back to 50 yards after my first two groups with the 300S, after noticing how much better the first group was. I ended up shooting a pretty nice third group. The FWB 124 groups just got better, so that could just be me settling down.

I’m curious to hear what experiences other folks have had with these rifles. I hope that you enjoyed reading this post as much as I enjoyed putting it together!

 

 

  • This reply was modified 4 months ago by 10x.