Canadian Airgun Forum

The #1 Community for Airguns in Canada!
It is currently Wed Nov 20, 2019 3:26 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  [ 152 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7 ... 11  Next
Author Message
 Post subject: Re: .30 cal Disco Double
PostPosted: Sat May 11, 2013 6:28 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
My prototype breech is 6061-T6 and I'll be leaving it natural.... Sean will be making the kits from steel and they will be blued....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Fri May 17, 2013 5:17 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
While waiting for our new barrels to arrive, I thought I'd do a practice run using a .308 cal PB barrel I had.... I cut off the .300 Win. Mag. chamber, ending up with a 21" usable section, and then I turned down the breech end to 1/2" OD to fit into the breech, and machined in a chamber and leade and a transfer port and O-ring groove.... Here's how it turned out....

Image

I assembled it into the breech to check the functioning of the bolt, and the nose pushes a pellet just past the transfer port and then withdraws into the "J" slot so that it is just clear of the port and completely out of the airflow, just as designed.... I also machined out the groove in a .25 cal MRod single shot tray to take the .30 cal pellet.... It clips onto the end of the barrel which protrudes 0.060" into the magazine bay, the same way the magazine mounts....

Image

By adjusting the diameter of the O-ring groove inside the barrel, you can customize how tight the O-ring grips the nose of the bolt.... I have set it up for a noticable drag, but the pellet slides through fine.... I'm sure it will seal perfectly as I've done this type of breech seal in the past with great results.... While outside the original design parameters of the gun, this barrel and loading tray will allow me to test cast .308" bullets up to 120 gr. in single shot mode (providing I cut the chamber deeper), just to satisfy my curiousity....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Fri May 17, 2013 5:23 pm 
Offline
User avatar

Joined: Sun Jul 15, 2012 10:49 am
Posts: 6029
Location: Victoria, BC and Clarkston, WA
Nicely done!

_________________
-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Sat May 18, 2013 8:23 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
Just a couple of pics of the finished stock.... I'm very pleased with the results....

Image

It's a Boyd's Blaster in Forest Camo (green, brown, black).... Inletting done by Norm at Discos-R-Us....

Image

I finished it with 7 coats of Watco Danish Oil, wet sanded (2 x 220, 2 x 400, 2 x 600) and then a final coat of Minwax....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Sat May 18, 2013 11:45 pm 
Offline
User avatar

Joined: Thu Feb 02, 2006 11:35 pm
Posts: 3099
Location: Alberta Canada
Bob have to Say That is One Good lookin piece of timber there.

Congrats

_________________
May the cry of the pack be with you upon your hunt

Whitewolf


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Sun May 19, 2013 12:34 am 
Offline
User avatar

Joined: Sun Aug 19, 2007 3:12 am
Posts: 769
Location: Oshawa, Ontario
Whitewolf wrote:
Bob have to Say That is One Good lookin piece of timber there.

Congrats


x2 what he said!!!!

I am looking forward to the finished rifle!!

GT

_________________
QB.30 PCP w/ Leapers Bug Buster 4x32AO Mil-Dot
QB78D .22 w/ Leapers 3-9x40AO Mil-Dot
QB78 .22 Custom HFT Stock w/ Leapers 3-9x40AO Mil-Dot
Crosman 1100
Crosman 2240
Custom 2050
Brass M2250
Tanfoglio 1911


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Sun May 19, 2013 2:20 am 
Offline
User avatar

Joined: Sun Jul 15, 2012 10:49 am
Posts: 6029
Location: Victoria, BC and Clarkston, WA
How much are one of the stocks Bob?

_________________
-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Sun May 19, 2013 10:34 am 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
I bought mine already inletted from Norm at http://discosrus.net/ .... On his website, mouse over the "Stocks" menu, then up to the "Thumbhole", then up again to "Marauder" for the Blaster design.... If you want a Thumbhole Featherweight model, select "Discovery".... All the prices are there, finished and unfinished.... Mine was $155 plus shippping.... You can also purchase them uninletted directly from Boyd's.... but Norm does a superb job of inletting, I couldn't duplicate it, he's set up for it.... There are severl laminate colours available....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Mon May 20, 2013 8:11 am 
Offline

Joined: Sun Oct 26, 2008 6:14 pm
Posts: 1343
Location: quebec
very nice woods even its laminated ,
you sand like a fool ,(2 x 220, 2 x 400, 2 x 600) :lol: :lol:
passionate carver sand like that ,,you may feel arthritis after that :lol:

the stock is surly nicer in real than the pics show us,

_________________
9 mm cal,discovery pumper
.25 cal,crosman pumper


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Tue May 21, 2013 12:44 am 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
I got the gun assembled with the short .308 PB barrel and fired a few test shots tonight.... First the photo.... I know, it's ugly with the barrel shorter than the tubes.... and parts still needing bluing.... but you can see the potential there....

Image

The gun was pretty hard to cock, I'll have to take a look to see if there is anything binding.... However, I was still able to cock it at coil bind, and the good news is that is way too much preload, even at 3000 psi.... The first shot was the fastest, the gun was very loud, and the 46 gr. JSB pellet screamed through the Chrony at 971 fps which is 96.3 FPE.... Four shots later it was down to 920 and those 4 shots used 700 psi.... I backed the adjuster out 2 turns, and got 6 shots starting at 953 and ending at 918, using 750 psi.... Out 2 more turns, and I was starting to get a string.... Starting at 2900 psi (my tank needs filling) I got 10 shots starting at 914, peaking at 929, and ending at 886, and it used 800 psi.... Backed out 2 more turns, starting at 2900, I got 13 shots starting at 861, peaking at 906, and ending at 860 fps at 2000 psi.... That string averaged 880 fps (79 FPE) at an efficiency of nearly 1.1 FPE/CI.... At 8 turns out the usuable pressure range is from about 2600 down to 1600, returning 14-16 shots in the mid 800s.... and at 10 turns, the string starts in the high 700s, peaks in the low 800s, and returns, but this is with running stock Disco pressures starting at 2000 psi and ending at about 1300.... and the gun is still shooting 65 FPE, three times what a stock Disco does....

These are just preliminary tests, using upsized JSB 46 gr. pellets in a 21" barrel.... I just couldn't stand the suspense of waiting until the new barrels get here.... The additional barrel length should add roughly 5 FPE.... but I have already surpassed my goal of 88 FPE in .30 cal.... so tonight's testing was a resounding success.... BTW, I was running a 3/16" transfer port, I can go to 7/32" if I want to....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Tue May 21, 2013 12:54 am 
Offline
User avatar

Joined: Sun Jul 15, 2012 10:49 am
Posts: 6029
Location: Victoria, BC and Clarkston, WA
Thank YOU Bob for the update!
Ugly is in the eye of the Beholder!

Did you have to do some inletting of the stock to get your breech to fit properly?
Do airgunners glass bed actions in rifles? Is that something you can do bedding the main/air tube?
I know barrel bands are the norm for airguns, but with the thin whippy barrels I can see why the manufactures do it. Maybe a barrel that thin is better off supported by a band or two?

Sort of irrelevant questions but thought you might have the insight?

_________________
-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Tue May 21, 2013 10:13 am 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
The breech doesn't touch the stock, it mounts on top of the main tube, and the stock I purchased was inletted for a Disco tube, MRod trigger and guard, and the lower Disco Double tube conversion.... The only inletting I had to do was to miss the front breech mounting band, which is 1/4" wide x 1/8" thick and goes completely around the tube, I just did it with a Dremel....

Glass bedding isn't usually done on airguns, as for the most part it's the tube that fits into the stock, not the barrel.... No reason you couldn't, but the tube bears over such a long distance maybe no advantage?.... If I was going to be leaving the barrel as is, I would use a single barrel band where the existing one is, but the upper portion would have an oversized hole carrying an O-ring to support the barrel.... I call that "semi-floating" as it prevents any damage or POI change but allows the barrel and air tube to move lengthwise relative to each other as sometimes you get a POI change from the tube moving as the pressure changes....

This gun will be getting a 7/8" OD Carbon Fibre shroud, and THAT may end up with a band around it....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Tue May 21, 2013 4:54 pm 
Offline
User avatar

Joined: Tue Apr 03, 2012 12:08 am
Posts: 821
A very interesting project BOB. And a good read.
Thanks for sharing.

_________________
I'm O.C.D. and A.D.D. so everything has to be perfect, but not for long.


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Wed May 22, 2013 6:01 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
I changed the gun over to a rear cocker last night, and also enlarged the transfer port to 7/32".... Here is the hammer, which now weighs 82 gr. with the cocking knob....

Image

The gun is now very easy to cock.... I put a small O-ring on the shaft which can be used to directly measure the valve lift.... You simply slide the O-ring up against the back of the RVA screw, cock the gun, fire it, and the O-ring slides back exactly the amount the valve opens and you can measure the space with calipers.... I did that for all RVA settings from coil bound to 12T out, for the first shot, and the last shot before the velocity fell more than 4% below the peak.... The smallest lift measured was just under 0.06", and the largest was 0.13".... In virtually every case where there was a proper bell-curve, the lift at the first shot was about 1/16".... and at the last shot was less than 1/8".... This is a very valuable piece of information, and while it won't be the same for every gun, for this gun it indicates that limiting the valve lift to 0.15" (eg. by having the hammer hit the back of the valve at that point) would not have any affect.... That means I can lengthen the hammer stroke on this gun to a full 3/4" by grinding a bit more off the valve stem or counterboring the front of the hammer a bit more.... The fact that the valve lift was virtually the same regardless of pressure and preload.... once the gun was adjusted for a proper bell-curve.... was a bit of a revelation to me.... though in retrospect it makes perfect sense....

The larger transfer port increased the power a bit, made the shot strings more curved (and hence shortened them), and required about 3 turns less preload on the RVA for the same FPE level.... Possibly 1 turn of that is likely due to the slight increase in hammer weight with the longer guide and the cocking knob.... Here are the results of the testing, from coil bind to 12 turns out, by which time the fill pressure required was less than 2000 psi....

Image

You can see that with a 3000 psi fill, anything within 6 turns of coil bound, while producing a bit more power, drastically shortens the shot string, and of course wastes a lot of air.... I saw 1000 fps (102 FPE) with everything maxed out at 3000 psi, however.... but the gun ws using nearly 200 psi per shot, and was down 4% in just 3 shots.... The best setting I could find was 7 turns out, starting from 2900 psi and ending at 1900.... It peaked at 929 fps (88 FPE), and averaged 913 fps (85 FPE) over 11 shots.... but the efficiency was only 0.88 FPE/CI.... This is the first gun I have tried where the area of the transfer and barrel ports (0.219"D) were larger than the area of the throat, which is the equvalent of a 0.203" hole.... I'm pretty sure that is why I couldn't get over 1.0 FPE/CI like I did with the 3/16" transfer port in the initial trials yesterday.... This leaves me with two choices, either drill the throat out to 1/4" (it is currently 15/64").... or refit the 3/16" transfer port.... The former should increase the power even further, and may increase the efficiency slightly.... The latter will drop the power a bit, but increase the shot count and efficiency.... I will wait until I get the new longer barrel to make the final decision.... but since I'm already pushing these pellets into the mid 900s more power may not be the answer.... so I'm leaning towards going back to the 3/16" transfer port with the 25" barrel....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
 Post subject: Re: .30 cal Disco Double
PostPosted: Thu May 23, 2013 10:40 am 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
This gun will have a shroud, but not one that will affect the noise level of the gun, they are prohibited in Canada, unfortunately.... I will be using a 7/8" OD x 3/4" ID Carbon Fibre tube located on two 3/4" bosses, one on the front of the breech, and the other on the back of this modified Hatsan air stripper.... These strippers are available in .177, .22 and .25 cal (shown), having different inserts for the different bores.... The brass insert is adjustable fore-and-aft to adjust the air gap between it and the muzzle, which can have a dramatic effect on accuracy.... I will be making a .30 cal insert for the stripper on this gun....

Image

The rear portion of the stripper was tapered, but I turned a parallel section with a 3/4" diameter up to where the stripper was 7/8" OD (where the shoulder is).... It will thread onto the end of the barrel on standard 1/2"-20 NF threads.... The shroud will mount between the bosses on the breech and stripper, and when the stripper is tightened up, the shouders will put the shroud in compression and the barrel under tension.... which should stiffen the barrel and raise it's resonant frequency.... In theory, this should reduce or eliminate the effect of barrel harmonics.... which can be quite a problem on long, thin barrels.... In addition, the woven finish of the CF tube should look pretty KEWL.... Once in place, all three tubes will be the same diameter, and also the same width as the breech....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 152 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7 ... 11  Next

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 0 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