Do pumpers loose velocity as they age

[JDR]

I have a Crossman 761XL that I recently had resealed. Came back with just a 347 fps with 10.8 grain pellets rating. I oiled up the chamber and shot over chronograph and got the following.

JSB Exact Heavy - 10.34 grain 418 fps 4.01 fpe
H&N Final Match 7.78 grain 483 fps 4.08 fpe
Crossman Fast Flight Lead Free 5.4 grain 555 fps 3.69 fpe

Thinking with a 8 grain pellet, I should be getting 550 fps. Plan to use a 20 yard or less gun for pests. The 7.78 H&N look like the best for that but wish I had another 75 fps. Forgot to check BBs Is their dimishing return in velocity as you continue to reseal the gun. Anything that might need to be replaced or altered that is normally not done on a reseal gun. I always thought the transfer hole between the compression chamber and the barrel looked like it was inefficient and leaked too much. Tried an o ring but could not get barrel to fit. I did notice a lot of air blowing out by the bolt but did not seem to be as bad after I oiled the gun. Thanks in advance for any replies.

 

[Struckat]

New seals should freshen it up like new. There may be something else wrong?
How fast did it shoot in the past?

 

[marflow 777]

the 761xl is a fancy 760 so this might help for numbers
https://www.pyramydair.com/blog/2019/12/crosman-760-pumpmaster-classic-part-2/

 

[JDR]

New seals should freshen it up like new. There may be something else wrong?
How fast did it shoot in the past?

Do not know. When I bought it, it leaked.

 

[JDR]

the 761xl is a fancy 760 so this might help for numbers
https://www.pyramydair.com/blog/2019/12/crosman-760-pumpmaster-classic-part-2/

They are so cheap, may just buy one. Wondering if the new 760s are more powerful than the old 760s. I remember the 760s being rated for 550 fps with lead pellets in the old days but have no proof.

 

[Struckat]

That sounds about right, I had one in the 70’s and my buddies 880 was much more powerful.

 

[JDR]

the 761xl is a fancy 760 so this might help for numbers
https://www.pyramydair.com/blog/2019/12/crosman-760-pumpmaster-classic-part-2/

Thanks for the Tom Gaylord review. Forgotten about him. Great 5 part view. Seems Pyramid Air and him got about 600 fps with pellets with the new model 760. However what was interesting is the lead BBs (which are oversized slightly) gave the best accuracy. However, seems like the H&N Excite Smart Shot is no longer made. Cannot find in stock. Also accuracy did not improve with a red dot over open sights. Seems getting a Daisy 880 is a better choice but I gave mine away and I do not need any more reasons to fill stupid on all the good stuff I got rid of over the years. Just saw a video where a late model 760 outshot a 880 although both groups were poor in my opinion.

 

[JDR]

New seals should freshen it up like new. There may be something else wrong?
How fast did it shoot in the past?

You know I see wide velocity ranges on some airguns that Baker Airguns reseal. Some even go below 400 fps. Something must be going on. Why would 2 exact airguns differ so much in velocity. Some may be due to different pellets used to chronograph but think something like compression tubes not up to specs or something like that which was with the gun when it was new.

 

[Treefrog]

This is certainly interesting. The old smooth-bore Revelation 760 does 540-fps with 7.1g pointed Crosmans and a little more with BBs at ten pumps. It's all original. I'll have to find the data for the 760XL that I have, but I think it's close to that.

The XL isn't any more accurate than the smooth-bores are.

Cheers

J~

 

[JDR]

Ok, I got 601 fps with Avanti match BBs. I then switched to a target at 20 yards with iron sights, 6 shot group (had a flier so I shot a 6th shot) with the H&N Final Match 7.87 gr off a sand bag. I also used this eye patch. (https://www.amazon.com/dp/B01D1AJZ06?psc=1&ref=ppx_yo2ov_dt_b_product_details). I put the patch on the very upper left hand corner of my progressive lens. In the old days, I could see the iron sights clear but target was fuzzy without my glasses and the opposite with my glasses. 2" but closer to 3" groups was the norm. With the patch on my glasses the iron sights were very clear and the target pretty clear. Anyway although the gun is not as powerful as specs, accuracy exceeds everything that I expected. This gun is a keeper. I agree with Tom Gaylord on not to scope it. I don't see how you could pump it. Funny thing is on the Youtube reviews and even Tom Gaylords review, the accuracy of the Crossman 760 does seem impressive. Must be the button rifled barrel vs smoothbore on the newer 760s. Trigger must be 15 lbs, horrible but still good accuracy. I will get around to measuring it sometime as I want to have a vintage pumper shootout and compare accuracy , velocity, energy and triggle pull of my pumpers. Need a Benjamin 342, 314 0r 347 plus a S&W pellet gun to complete my collection but that will take some time. Should be fun with what I got.