Slug anomalies

[spoon]

Shooting slugs from a smooth bore barrel I noticed a strange thing. We are talking about Federal Tru-Ball Rilled Slugs in a smooth 18 inch and 14 inch barrel. This is a Remington 870. When using a 14 inch barrel the slugs will rise 12 to 14 inches above point of aim at 50 yards compared to the 18 inch barrel. The only difference being barrel length. I haven’t tried any other brand of slug and several other people think this may be unique to the Federal. Any comments and insights would be welcome. Both barrel lengths give 6 to 8 inch groups , 50 yards kneeling position.

[Peregrine]

Easiest thing first, it may just be your hold. If you have a bead sight on both, and you're elevating the bead to a certain elevation to get your sight picture, the 14" barrel will will be pointed higher.

Now beyond that this gets messy theoretically.
Do you have a reference to people who claim this is unique to the federal slug?

There's a lot of different things going on that could potentially be causing the POI shift, and all of them are somewhat hard to definitively prove/disprove as the cause. Assuming it's not user induced (not being condescending here, having done a lot of it myself shooting short shoguns at significant range with slugs is a real art), it could be the extra barrel weight towards the front on the 18" is simply keeping the muzzle from rising as much from recoil as the slug is still traveling down the barrel. That's just a theory, although the idea that recoil starts to affect POA and therefore POI before the bullet has exited the barrel is something i've talked through with people a lot smarter and more experience than myself.

Why it would only be apparent with federal though...you're going to have to test out a couple more brands of slugs back to back and see if that's really the case for you in your shotgun.

[Winger Ed.]

Except for flinching- it shouldn't do that.

Is there a chance the mounting ring that goes around the magazine tube on the 14" is higher than the other?
That might have the effect of raising the front sight's point of aim in relation to the other.

[cas]

Choked different?

[bmortell]

I don't think a completely different barrel hitting a different spot is weird at all. what would be weird is if you try different brand of slugs and they both hit the same spot while federal dont

[bikerbeans]

You need a taller bead or front sight to lower POI. I have chopped a few slug barrels and all needed a taller front sight. It is not an ammo problem. Chopping a barrel changes the sight plain between the front and rear sights.

BB

[a danl]

recoil and the time the slug is in the bbl has a lot to do with point of impact. think about it. 14 inch bbl the slug is out quicker than the 18 inch. recoil rise of the shotgun will be quicker therefore point of impact will change.

[longbow]

What bmortell said.

Before losing any sleep over it or drawing any conclusions you should do a comparison with another slug brand in both barrels (or preferrably more than one other brand). If you get the same results then likely it is the barrel length/sights thing going on.

If the other brand of slugs doesn't give the same results then I'd start wondering.

Generally I would expect more barrel time in the 18" barrel to result in more movement during recoil so raising the barrel giving higher POI but that is reverse effect you are seeing.

It is certainly possible (and likely) that between sights and just being a different barrel the 14" barrel shoots higher than the 18" barrel. Also, I'd expect tighter groups than 6" to 8" at 50 yards from Federal Tru-Ball slugs. If you are using just a bead that may explain it. I had Federal Sluggers shooting into 6" at 100 yards from my Browning BPS with slug and buck barrel with rifle sights.

Maybe next time shoot off a bench with the gun on a rest. I made bench cross sticks so I can sit upright and absorb recoil better. Being low over a bench and shooting off sand bags with 12 ga. slugs gets old real fast! I've been beat silly by 12 ga. slug recoil doing that. My cross sticks almost make slug shooting pleasant... almost.

Just my thoughts.

Longbow

[longbow]

Yikes! Two more slipped in there while I was typing!

[bikerbeans]

Yikes! Two more slipped in there while I was typing!

Kent,

You type in metric units, much slower than english units.;)

BB

[243winxb]

The barrel locks into the receiver differently every time.

[spoon]

I typed this out and it didn't show so again.
At 25 yards 18 and 14 inch barrels POA and POI are the same. I should have made it clear that we are talking about multiple 14 inch and 18 inch 870's. Barrels are not switched. Rifle sights, factory Remington barrels. Talking to other folks familier with this Remington Tactical slugs don't show the rise at 50 yards.

[longbow]

I knew it wasn't due to fat uncoordinated fingers and wrinkled slow old brain!

Thanks for giving me a better excuse BB!

[243winxb]

Guns have adjustable rifle sights. Adj sights to where the slug impacts. There is no point of aim thats the same between different guns.

The sight radius difference between barrel lengths ,when zero is at 25 yds, then going to 50 yds is going to make a difference. The higher the sight is above the center of the bore, the more the slug will climb.

The shorter sight radius , makes the most difference. edit. More sighting error.

If talking about the same gun, same ammo, shooting 2 different groups , 14" apart, its a ammo problem. :confused:

[spoon]

But why so much rise between a 14 and 18 inch barrel?

[243winxb]

Both barrel lengths give 6 to 8 inch groups , 50 yards kneeling position. When your shooting groups this big, i would not bother trying to make a comparason. To much sighting error from a kneeling position.

At 25 yards, when the slug hits below the point of aim, the impack at 50 yds will not be higher. The distance from line of sight to middle of bore may be as much as 1 1/2"

At 25 yards when bullet impack is at or above the line of sight, the slug will rise on its way to 50 yards. The higher the line of sight is above the bore, the higher the slug will impack at 50 yards.

[243winxb]

Using a line of sight 6 oclock hold @ 25 yard on a 6" bullseye target , with slug impact in center of target, as zero.
At 50 yards impact should be higher at 50 yards? Now i am confused, when using the calculator. [smilie=b:

https://www.federalpremium.com/shotshell/premium-slug-buckshot/vital-shok-truball-rifled-slug/11-PB127+LRS.html

[megasupermagnum]

I typed this out and it didn't show so again.
At 25 yards 18 and 14 inch barrels POA and POI are the same. I should have made it clear that we are talking about multiple 14 inch and 18 inch 870's. Barrels are not switched. Rifle sights, factory Remington barrels. Talking to other folks familier with this Remington Tactical slugs don't show the rise at 50 yards.

So what you are saying is that both barrels are hitting dead on at 25 yards, and the 14 inch barrel hits 12"-14" higher than the 18 inch barrel at 50 yards? That simply isn't possible, and with 8" groups, something else is going on.

If you are zeroed at 25 yards, you should be roughly 1/2" LOW at 50 yards with most rifled slugs.

[243winxb]

3" The higher the sight is above the center of the bore, the more the slug will climb, when sighted in at 25 yards.