Canadian Airgun Forum

The #1 Community for Airguns in Canada!
It is currently Mon Jul 22, 2019 1:53 pm

All times are UTC - 5 hours


The Canadian Airgun Forums are a place for people to discuss and learn about airguns and the airgunning sport in Canada. There are lots of discussions about airguns, airgun accessories, reviews, modification and repair information, airgun events, field target and free classifieds!

 

You need to register before you can post: click the register link to proceed. Before you register, please read the forum rules. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload your own pictures, and access many other special features. Registration is fast, simple, and absolutely free! To start viewing messages, select the forum that you want to visit from the selection below.






Post new topic Reply to topic  [ 5 posts ] 
Author Message
PostPosted: Sat Mar 31, 2018 6:41 pm 
Offline

Joined: Fri Jun 08, 2007 8:45 pm
Posts: 758
Location: Toronto
I bought two at the same time 1 1/2 years ago and used the first one regularly since then until recently when it developed problems.
In all that time, I used it with 3 pumps at 18 - 22 feet with same card stock target and same JSB pellet.Very good accuracy -5 shot groups at 1/2 inch.
The second one- not so great. At same distances, target and pellet ,it is a little erratic.Grouping not as tight and all shots produce an elongated / larger opening on impact compared to the first rifle which produced neat uniformed and small dome pellet holes.
I don't have a chrony but suspect the amount of air pressure is not the same as on the first rifle at 3 pumps. As with the first one ,more than 3 pumps opens up the grouping. So in direct comparison, the two rifles are not equal. I do consider, that for this low budget item, it is entirely possible to have variances as described. I guess the same can be said for many other identical model air guns. Am I right?


Top
 Profile  
 
PostPosted: Sat Mar 31, 2018 6:48 pm 
Offline
User avatar

Joined: Mon Feb 11, 2013 12:46 am
Posts: 4052
yes you are right...
id first suggest you ad one more pump making it 4 pumps and see if anything changes
then id suggest you try a different type of pellet....some airguns are finicky like that...
also just for curiosity sake check the barrel crown see if it looks normal..even run a Q-tip
around it and see if it snags a peace off the Q-tip if so that could be your problem

_________________
"A candle loses nothing by lighting another candle"

Image


Top
 Profile  
 
PostPosted: Sat Mar 31, 2018 7:26 pm 
Offline

Joined: Fri Jun 08, 2007 8:45 pm
Posts: 758
Location: Toronto
Hi Ace, the Qtip test was negative. Four pumps opens the group up as was the case with the first one. I had tested the first 760 with Exact RS and Exact Express but the heavier Exact 8.44 was slightly better. I will try the lighter pellets in this new one after most replies are in.
The hole size non -uniform shape is most curious for me.


Top
 Profile  
 
PostPosted: Mon Apr 02, 2018 2:43 pm 
Offline

Joined: Fri Jun 08, 2007 8:45 pm
Posts: 758
Location: Toronto
Just finished another session with new 760. Comparisons with the first 760:

1. Not grouping at all with Exact JSB Exact Express and Exact RS. Best is the heavier Exact 8:44 Gr.
2. Some shots rebounding several feet back perhaps by hitting previous pellets in the duct seal or uneven FPS?
3. Same issue with opened up holes on target as previously noted.
Prior to this session , I added more pellgun oil to pump cup to get the same pumping feel as with the first 760 at 3 pumps.
In summary: Had I not had another 760 to compare. I would accept the second one as being reasonable. Perhaps it was built on a Friday/ Monday :(. If I rated the first one at 95%, the second is 80%. I can only conclude that the air intake and FPS is not as consistent with the second 760. I don't know what other factors may be in play. It is what it is for a sub $100 pumper.


Top
 Profile  
 
PostPosted: Sat Apr 07, 2018 8:27 am 
Offline

Joined: Fri Jun 08, 2007 8:45 pm
Posts: 758
Location: Toronto
" In a smoothbore barrel, the skirt will still flare to provide a tight seal, but since there is no rifling, the pellet will not spin, and is less accurate. In most cases of this type, the solid head in the front and hollow skirt in back will work to prevent the pellet from tumbling. However, this is not always the case, and some ammo types of this nature will tumble in flight, and hit the target sideways. When this happens the pellet will not leave a clean, round hole in the paper, but will instead, leave behind a keyhole-shaped silhouette. This phenomenon is known as keyholing."

I found the above quote in Wikipedia after much digging on the internet about why my second 760 was not performing as good as the first one. This finding at least answers my question on the ragged holes and wider groups. Elsewhere, I read that if a barrel is slightly larger in diameter, some air will pass around sides of the pellet in motion rather than the full force pushing it and reduce its possibility for accuracy.

So, I assume my first 760 was the best, having good impact on target. Needless to say , shooting pellets in a smoothbore is not the best option for ultimate accuracy. Just wondering if a "jumbo" type pellet filling the barrel better would be an option?

The second 760 is for sale with these limitations.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
News News Site map Site map SitemapIndex SitemapIndex RSS Feed RSS Feed Channel list Channel list

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group

phpBB SEO