BSA Sportsman HV all of a sudden shooting low velocities

Jump to latest Follow Reply
NNMV

NNMV

Member
Mar 5, 2022
22
6
Ellesnburg WA, United States
I have a BSA sportsman‘s HV. I’ve had it for a long while now. It has performed well for years. Over the years I have replaced some of the O-rings on it and always got it back to working condition.

All of a sudden the other day I noticed the rifle appeared loose. Wobbling around. I thought at first it was a stock screw. But it was not. After further investigation it was the screw that holds the barrel and receiver to the valve and tube assembly.

I ended up removing that screw and discovered it was a little buggered up. I got a new screw and it tightened things up. I also decided to replace all the O-rings in the whole rifle. But now I am getting extremely low velocity‘s 😕. Mid 500s. The interesting part is the extreme spread and standard deviations are very low. And at those velocities it is still very accurate. But before all this I was getting low 800 ft./s velocities(with great accuracy). The research I have done this rifle does not have any ability to make adjustments as far as feet per second go. I’m not sure what’s going on. But I want it back to the 800 ft./s in velocities.

Can anybody help me with this?
 
The only adjustment you have on that rifle for velocity is via the hammer spring at the rear of the gun. It's hidden under a cover that just slips off.

Did you actually separate the breech (upper part) from the hammer tube (lower part) of the action? If so, there is a transfer port that sandwiches between the two, with an oring on top and bottom of it. It's very easy for the oring to slip out or get smashed while trying to fiddle the breech back onto the action.

If that transfer port got obstructed, it would reduce power greatly.

Also make sure that the MMC cocking lever that pushes back on the hammer, moves freely and isn't keeping the hammer from coming forward upon firing. The rod can get bent and bind slightly and cause this. It has a spring to push it back forward when you cock it, so if it feels funny start there.

Lastly, and the last thing I'd check, is make sure the spring behind the firing valve isnt jammed up and deformed. Firing it with no air or getting it misaligned when assembling could cause this.

Judging by the consistent but low velocities, my guess is the transfer port orings are messed up. But who knows.

Those are excellent guns, I wish I would have kept mine
 
  • Like
Reactions: NNMV
Upvote 0
You obvious, know this rifle in and out 😉. And yes I really like the rifle. The gateway to my PCP world. 💰
I know it well too now. I have disassembled and reassembled it many times lately. 🤨.

Yes, I separated the upper and lower parts. Correct there is that transfer port with two O-rings. I actually discovered one of the O-rings was partially cut but still intact. So, I got excited because I thought this was the problem. Put two new O-rings on the transfer port and still had the same problem 😖.

After reading your post it made me start thinking of what I had disassembled and reassembled. It was working correctly with good velocities before I took it apart, right?

The comment that you made about the hammer being slow made me think. I know the gun has correct air pressure, I’ve replaced all the O-rings and checked everything else. Why, am I still getting such low velocities? Thank goodness I still have the manual which has the schematic for the rifle. A hard to read schematic but it works.

Anyway, after looking at the schematic closely I realized I had put the Hammer spring and the Main spring guide back together incorrectly. Even though the way I reassembled it worked and seamed logical. So, when I put the Hammer spring and Main spring guide rod back together correctly, voilà! Velocities back up! (you have no idea how elated I was about this 😀 ).
With all the new O-rings and the rifle reassembled correctly it is shooting like a house of fire. I even gained over 50 ft./s from the last time I had Chronographed it. It is still incredibly accurate and whacking targets at 25 and 50 yards. Thank you very much for your input on this. It helped me tremendously! There was a point I was about to completely give up on this rifle.

I have to give a shout out to XTX air! He’s got some great YouTube videos that helped me very much with the disassembly and reassembly of this rifle.
 
  • Like
Reactions: bf1956
Upvote 0
Right now I’m shooting the JSB Hades 15.89 grain. They’re going 914 ft./s.
It also shoots the JSB 18.13 grain pellets really well. They are going 883 ft./s.
Attached is my group with 30 shots at 25 yards. The target dot is 1 inch.
93FD9764-A665-45C3-9908-40A40E4A3795.jpeg
 
Last edited:
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu