Pellet seating depth vs. accuracy ?

[Richieg]

Another shooter and I were discussing the differences in the JSB 25.39 pellets. You can see the different depth of the lead when looking into the skirt of the pellets.COULD the difference make the pellets seat to shallow and may be covering part of the transfer port and cause accuracy issues when seated with the pellet probe? Or the irregular seating depth between batches ? Any thouughts?

 

[beerthief]

your saying the depth of the inside base of the skirt is shallower ?

 

[nervoustrig]

Definitely want the skirt seated past the barrel port under all circumstances. Worst case, the pressure pulse deforms the skirt. Best case, there is merely some blow-by around the head before the pellet advances fully past the barrel port.

Whether it is a concern for the particular pellets you describe will depend not just on the pellets themselves but the nature of the specific rifle. In most cases the gun will be designed to accommodate pellets with both deep and shallow skirts. Of course we're talking about pin probes only...a flow-through bolt always seats to the same depth since it pushes on the skirt.

 

[Richieg]

your saying the depth of the inside base of the skirt is shallower ?

Yes, you can see the difference with the naked eye. The other shooter I was talking to is a national cast bullet champion, he was saying bullet depth was a big deal for accuracy in that discipline and MAYBE pellets seated at different depths because of the design COULD maybe affect accuracy. ????

 

[beerthief]

this would require some careful testing ,with a way to measure and accurately seat the pellets the same every time .
the onlt way i could do this is making longer or shorter bolts .

 

[nomojo65]

I experimented with this theory a couple yrs. Ago with my BM and 13.4s trying to eliminate flyers and get more consistency, I made a pellet seating tool for trying to seat each pellet the same regardless of the inner skirt pocket depths. Didn’t really improve groups or scores! But I don’t want to discourage you from trying it, hopefully you might have better luck?
I have tried most theories and concept’s presented on this forum and some of my own. I believe some barrels shoot many variations of the same pellets very good and others are very particular in what they like.
The best barrel I ever had was a LW 12groove that came on my first RAW TM1000! It shot everything, and some of my best scores are with that combo.

 

[BackStop]

Definitely want the skirt seated past the barrel port under all circumstances. Worst case, the pressure pulse deforms the skirt. Best case, there is merely some blow-by around the head before the pellet advances fully past the barrel port.

Whether it is a concern for the particular pellets you describe will depend not just on the pellets themselves but the nature of the specific rifle. In most cases the gun will be designed to accommodate pellets with both deep and shallow skirts. Of course we're talking about pin probes only...a flow-through bolt always seats to the same depth since it pushes on the skirt.

Just curious, what airguns actually do use a flow-through bolt?

I am totally ignorant since I haven't owned a lot of airguns, PCP or otherwise. (smile)

p.s.

I do like the O-ring on the probe better than the O-ring in the breech. Maybe because the Nova Vista Freedoms were so accurate (for me) and I haven't had anything that accurate since. Not to mention it is a LOT harder to blow an O-ring off of the probe than out of the breech, or at least it seems so for me. Oh well... (chuckle)

 

[nomojo65]

I wanted to elaborate the theory for seating depth, I was having very good performance with a given lot of pellets that had a shallow pocket depth and checking the depth of other lots that weren’t working well I noticed a much deeper pocket depth, so I theorized with the pin probe style of the RAWS that the deeper pocket would require a tool to get these to be seated at the same depth as the best performing shallow pocket pellets.
That was my Theory anyway! haha!

 

[nervoustrig]

Just curious, what airguns actually do use a flow-through bolt?

Understandable that you may not have run across a flow-through bolt. They aren't nearly as common as pin probes but they can be found at both ends of the price spectrum.

From a $100 QB78:

To a $2000 FX Impact:

 

[BackStop]

Understandable that you may not have run across a flow-through bolt. They aren't nearly as common as pin probes but they can be found at both ends of the price spectrum.

From a $100 QB78:
View attachment 281979

To a $2000 FX Impact:
View attachment 281980

Thanks! And WOW!!!

Oops... I thought you were saying the price of the probe for the Impact... (silly grin)

Doesn't matter for me anyway... I can't justify $2000 for an airgun for pesting in my backyard.

If money was not an object... well... But money IS an object and getting to be more and more of an object lately and looks like it will be even worse soon.

 

[Airgunmann]

I use the mk2 34 gr jsb pellets in my raw 25 cal I was told they vary in depth but my pre air force raw loves them out to 100 yards

 

[Airgunmann]

I think seating depth would make a difference depending on how far the free bore is or how far the pellet has to jump till it gets to the rifling

 

[Airgunmann]

My raw is rifled all the way back past the transfer point

 

[dizzums]

my thoughts are it ideally should have its nose stuck in the actual bore and the throat sized accordingly so when its fired it doesnt get thrown into the rifling sideways .. so to speak ..

 

[nervoustrig]

To lend some perspective, consider the original Smooth Twist barrel. The freebore is most of the barrel's length.

These barrels are known to shoot spendidly, which challenges any notion that pellets are particularly sensitive to seating depth.