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Air Gun Home Forum Index » Airgun Smithing » Chop Chop    View previous topic :: View next topic  Chop Chop   Posted: Tue Jan 19, 2010 2:30 am kanyon Silver Status Member Joined: 09 Aug 2008 Posts: 1582 Location: New Zealand Spent the last few days choping barrels... Rem Genesis & Kral .177 underlever.. The Genesis was easy..but the kral took a bit more peeing around... Both have 13" barrels now.. Pete   Posted: Tue Jan 19, 2010 2:13 pm Amigo Veteran Member Joined: 18 Sep 2008 Posts: 263 Location: U.S. MidWest Pete: No ifs ands or buts about it, you do VERY NICE work - and Lots Of It. Thanks for the pix, Amigo   Posted: Tue Jan 19, 2010 3:14 pm donec Senior Member Joined: 19 Dec 2009 Posts: 836 Location: central Texas Pflugerville area So what is the reason for chopping the length of the barrel?   Posted: Tue Jan 19, 2010 4:26 pm domer_pyle Senior Member Joined: 17 Sep 2009 Posts: 523 from what i've read the pellet reaches maximum velocity in the first 10 inches of the barrel in a springer, so more velocity and less time in the barrel to affect accuracy.   Posted: Tue Jan 19, 2010 8:21 pm donec Senior Member Joined: 19 Dec 2009 Posts: 836 Location: central Texas Pflugerville area Yes but if your rifle has a choke at the end then you lose that and that may effect your accuracy some and possibly the velocity. If the theories I have heard are correct the choke could cause a last moment seal of the pellet to the barrel and prevent the pressure from blowing past the pellet thus making use of all the pressure. I don't know if any of this is true but to me it is really something to think about. Now that you have cut off the end can you check and see if in fact you do or do not have an increase in velocity and or accuracy?   Posted: Tue Jan 19, 2010 8:40 pm kanyon Silver Status Member Joined: 09 Aug 2008 Posts: 1582 Location: New Zealand donec wrote: Yes but if your rifle has a choke at the end then you lose that and that may effect your accuracy some and possibly the velocity. If the theories I have heard are correct the choke could cause a last moment seal of the pellet to the barrel and prevent the pressure from blowing past the pellet thus making use of all the pressure. I don't know if any of this is true but to me it is really something to think about. Now that you have cut off the end can you check and see if in fact you do or do not have an increase in velocity and or accuracy? I think the USEABLE pressure is long spent by the time the pellet reaches the end of the barrel.... If it has a choke...Thats easy to get around...DON"T CUT IT.... Or cut the breech end... When I cut the Remington...I didn't remove the scope so the settings were untouched...The first thing I noticed its POI was 40mm lower @ 12m that make me think the pellet was not being efected the same by the recoil & barrel rise because of the shorter time the pellet was in the barrel.. Pete   Posted: Tue Jan 19, 2010 8:44 pm kanyon Silver Status Member Joined: 09 Aug 2008 Posts: 1582 Location: New Zealand Amigo wrote: Pete: No ifs ands or buts about it, you do VERY NICE work - and Lots Of It. Thanks for the pix, Amigo Thanks with the Kral I wanted it to look standard.. If you didn't have a uncut one to compaire it to you would never know a grinders been though the barrel & lever.. Pete   Posted: Tue Jan 19, 2010 8:48 pm donec Senior Member Joined: 19 Dec 2009 Posts: 836 Location: central Texas Pflugerville area kanyon wrote: donec wrote: Yes but if your rifle has a choke at the end then you lose that and that may effect your accuracy some and possibly the velocity. If the theories I have heard are correct the choke could cause a last moment seal of the pellet to the barrel and prevent the pressure from blowing past the pellet thus making use of all the pressure. I don't know if any of this is true but to me it is really something to think about. Now that you have cut off the end can you check and see if in fact you do or do not have an increase in velocity and or accuracy? I think the USEABLE pressure is long spent by the time the pellet reaches the end of the barrel.... If it has a choke...Thats easy to get around...DON"T CUT IT.... Or cut the breech end... When I cut the Remington...I didn't remove the scope so the settings were untouched...The first thing I noticed its POI was 40mm lower @ 12m that make me think the pellet was not being efected the same by the recoil & barrel rise because of the shorter time the pellet was in the barrel.. Pete Keep in mind I am very new to airguns. However! Couldn't the drop be caused by loss of energy and rotational spin due to less time in the barrel? With powder guns longer barrels are know to have better accuracy than shorter barrels.   Posted: Tue Jan 19, 2010 9:04 pm kanyon Silver Status Member Joined: 09 Aug 2008 Posts: 1582 Location: New Zealand donec wrote: kanyon wrote: donec wrote: Yes but if your rifle has a choke at the end then you lose that and that may effect your accuracy some and possibly the velocity. If the theories I have heard are correct the choke could cause a last moment seal of the pellet to the barrel and prevent the pressure from blowing past the pellet thus making use of all the pressure. I don't know if any of this is true but to me it is really something to think about. Now that you have cut off the end can you check and see if in fact you do or do not have an increase in velocity and or accuracy? I think the USEABLE pressure is long spent by the time the pellet reaches the end of the barrel.... If it has a choke...Thats easy to get around...DON"T CUT IT.... Or cut the breech end... When I cut the Remington...I didn't remove the scope so the settings were untouched...The first thing I noticed its POI was 40mm lower @ 12m that make me think the pellet was not being efected the same by the recoil & barrel rise because of the shorter time the pellet was in the barrel.. Pete Keep in mind I am very new to airguns. However! Couldn't the drop be caused by loss of energy and rotational spin due to less time in the barrel? With powder guns longer barrels are know to have better accuracy than shorter barrels. Over 12m ?....possable....But a power drop to give a 40mm POI change in only 12m..is a BIG power drop...would be very noticeable... It still puts a pellet though a bit of 12mm 5 ply at 10m as it did before If it has lost power...Hell what was it doing before the chop.. powder burners - airguns / cats - dogs,,,,totaly diffrent animals.. Pete Pete   Posted: Tue Jan 19, 2010 9:18 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2444 Location: New Jersey- outside of Philadelphia Pete, the drop in POI seems odd. Although I would likely attribute it to lock time and recoil. How has the accuracy changed, and how has the velocity changed? Does the rifle itself at least handle better? _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Wed Jan 20, 2010 12:46 am kanyon Silver Status Member Joined: 09 Aug 2008 Posts: 1582 Location: New Zealand fritz wrote: Pete, the drop in POI seems odd. Although I would likely attribute it to lock time and recoil. How has the accuracy changed, and how has the velocity changed? Does the rifle itself at least handle better? The POI change stands to reasion.... EG...If the barrel lifted 10* by the time the pellet reached the muzzle in its unchoped state.. After the chop...being a shorted travel time to the muzzle the barrel has only reached 8* lift by the time the pellet gets to the muzzle...That would account for the lower POI.. It still groups the same with Accupels... Pete   Posted: Wed Jan 20, 2010 3:49 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2444 Location: New Jersey- outside of Philadelphia Then you should be able to compensate for it with an adjustable scope mount. Or just adjust the scope if you have enough left. Maybe re-drill the barrel in the block to compensate for the angle? _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Wed Jan 20, 2010 4:23 pm kanyon Silver Status Member Joined: 09 Aug 2008 Posts: 1582 Location: New Zealand fritz wrote: Then you should be able to compensate for it with an adjustable scope mount. Or just adjust the scope if you have enough left. Maybe re-drill the barrel in the block to compensate for the angle? Adjustment was well with in the adjustment range of the scope... Pete   Posted: Thu Jan 21, 2010 7:04 am fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2444 Location: New Jersey- outside of Philadelphia Problem solved. _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Fri Jan 22, 2010 2:32 am kanyon Silver Status Member Joined: 09 Aug 2008 Posts: 1582 Location: New Zealand fritz wrote: Problem solved. It was never a prob....I was just stateing how much/what the dfffrents iin POI is when you chop the barrel.. I new before I cut that the scope would rwquire readjusting... 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