RWS: SUPERDOME question

[robert w]

found a perfect way to taper the barrel opening get the screw off end from a plumb bob put it in a dremel use fine valve grinding compound put a felt cleaning pellet in the bore use light pressure at a moderate speed when getting close to desired clearence clean and use flix then clean swab your barrel out and it does a real nice job

[TCups]

Hmmmm . . .  Well, Superdomes have never performed that well in my springers.  And essentially "crowning" the breech still ends up with a pellet skirt that probably has a suboptimal fit for the rest of the barrel.  Superdomes, I think, are designed to shoot well in CO2 air rifles -- here's why.  Look up the skirt (of the pellet).  Inside the Superdome skirt, you will see a sharp, round hole much less in inside diameter than the inside of the actual skirt. The purpose it so that the "probe" end of the bolt of a CO2 air rifle will center inside the skirt of the pellet and drive it straight into the bore with no cant.  You will find that Superdomes are very accurate in guns like the Crosman 22XX and Hammerli 850 -- any breech loading air rifle with a bolt action.

If you read "The Airgun from Trigger to Target" (now back in print, I think) they describe air rifles of the "blow gun" and "pop gun" type.  Those of us of a certain age remember the pop guns that had a cork on a string.  You squeezed a rubber handle and the cork pops out.  Springers are pop guns.  Optimally, the pellet fits like a cork and only starts moving down the barrel when the piston driven power plant produces enough pressure to pop the pellet loose and send it down the barrel.  The spring-piston power plant also produces, instantaneously, a lot of heat.  The net result is that pellets that have a thinner, open skirt on the underside (unlike the Superdomes) soften and expand against the rifling to an exact fit.  The most accurate results are if you get a very consistent point where the "pop" occurs so that every shot has the same initial velocity at the same pressure.

Blow guns are like our old BB guns.  The BB will literally roll out the barrel in some cases.  And th accuracy depends on supplying the same volume of air at the same pressure. CO2 air rifles, and PCP air rifles are a bit different, but they are more of a blow gun than a pop gun. They don't develop the same, high instantaneous heat and pressure behind the pellet as a springer -- they only develop the PSI that the reservoir is charged to.  And they often perform best with pellets like the Superdome (especially the CO2 guns).

Anyway, if you modify the breech of your springer, it may indeed make the Superdomes easier to load, but it will change the POI of both the Superdomes and any other pellet you load in the breech.  I would suggest, unless there is a burr or some visible roughness  you NOT do it.  Find a pellet that fits your air rifle better.  

For springers, IMO, the JSB Exacts tend to shoot the best. Some might not have that experience, however, and there are probably a couple of simple reasons.  First, the pellet perhaps is not loaded exactly the same way and same depth each time (Solution -- pellet seating tool instead of your finger). Second, the skirts of the JSB pellets, which are thinner and softer lead than, say, Superdomes or Crosman Premiers (look under her skirt, too) get dinged or bent (Solution -- check the skirt and use a pellet seating tool to reshape and flare the skirt before you seat the pellet).

[robert w]

how ever i seen an article in shotgun news that they strongly recomended and cheep also get a bic ink pin 1 of those hex sided clear ones and use it to push the pellet into the chamber it works i tried it and accuracy came up a tad and seemed to help seal to the barrel i got some crosman hps that some are loose fit and some are tight the pin works just fine dont mess up the roundness of the pellet all i can say so far it works for me tried it today in both of my springers hw55 and quest 1000x

[DMikeM]

I have performed this mod on one of my B28's just for the RWS SD pellets. Once the pellet seated flush I gained velocity and accuracy. The pinched skirts were creating flyers and bad grouping. Pushing the pellet in with a tool (pen) made it lose velocity with no accuracy improvement at all. I checked against other pellets after-wards and they shot fine and even better than before. Just don't go deep when you open it up just use a greater angle to just fit the pellet you like the most.