quote:

Originally posted by maladat:
The example I've personally seen where method of support has the largest impact on POI the fairly common hunting technique of shooting standing and supporting the rifle by bracing the stock, or worse, the barrel, against a tree trunk or vertical or angled tree branch. When fired, the rifle will jump sideways away from the support, sometimes surprisingly hard.

I guess you could still call this "induced by the shooter" in the sense that the shooter made a poor choice about support method that resulted in an increased tendency for POI shift.

You can pretty much eliminate the problem by using the tree for support but not actually making contact between the tree and the rifle - basically, you use the tree to support your hand and your hand to support the rifle.

Matches sometimes include stages where some part of the rifle must touch a tree branch or trunk. To wit, this spring's 2-gun match at Raton, NM. The stage rules required wearing the pack, with precision rifle slung, shooting the carbine from a standing position. Carbine targets were shot from 5 different positions -- the first 4 were tree trunks. Each position had 2 steel plates, one 5" and the other 6", hung from a t-post. IIRC target distances were roughly 100, 110, 130, and 140 yards -- with target distances increasing with each successive position.

The first target was pretty easy. The tree trunk leaned to the right some 20-30 degrees, and we shot from the top of the trunk. I suspect almost every right-hander placed the handguard directly on the trunk, using the left hand on the lower left of the handguard to stabilize the position. Hit percentages were very high.

Second position was a big more challenging. Vertical trunk, gun must touch the trunk's left side, tall shooters had to crouch down a bit so that branches on another tree didn't obscure line of sight. Most of us pinned the handguard against the trunk as best as possible with left-to-right pressure. Hit percentages dropped a bit.

Third position was OK. Slightly right-leaning trunk, by maybe 10 degrees. We could support the carbine from a branch on the right side of the trunk, and we had to shoot from the right side of the trunk. Many people placed their scope against the trunk. Some grabbed the handguard around the front of the trunk, others grabbed the scope for stability. Hit percentages were generally pretty good, as long as the shooter had a good stance -- i.e. feet, hips, and shoulders square to the target. Guys who bladed their bodies to their shooting hand (i.e. facing 1-2 o'clock for a right hander) struggled here.

Fourth position sucked canal water. We all hated it, and hits were difficult. The tree leaned some 20 degrees left, had no branches, and we had to shoot from the left side of the trunk. It was hard to support the rifle and keep it stable. Most of us canted our rifles a bit to the left, then did our best to have handguard and scope touch the trunk. Hit percentages were low, even for the best shooters.

Shooting fundamentals were really important in all 4 of these positions -- square stance, cheek weld & eyebox position, breathing, trigger control, recoil management, follow through. Fortunately we were allowed multiple shots per target. But the guys who struggled in barrier-type shooting positions just absolutely collapsed here. I got all my carbine hits, but used up a lot of the clock. Fortunately I transitioned quickly to the prone position for the bolt gun targets, and did pretty well on this stage.

quote:

Originally posted by maladat:
I will also say that I've also seen more of a tendency for POI shifts in rifles with non-free floated barrels. I assume this is because different positions apply different forces to the forearm, and different forces on the forearm result in different forces at the contact points between the forearm and the stock. But if you're doing precision shooting, it's generally assumed you have a free-floated barrel.

All my match rifles are free floated, which helps in wonky shooting positions. I was in a match where one stage required a shot with the barrel resting on a horizontal fence wire. Got to practice that the day before. Found out that my heavy-barrel bolt actions have their POI shift up about 1 MOA if the wire is just forward of the forearm. If the barrel is resting near the muzzle, the upward POI shift is a touch over 2 MOA.

In Competition Dynamics matches -- Steel Safari, Team Safari, Team Challenge -- there is generally at least one stage where the bolt action shooter must support the rifle from from a tree trunk or branch. This means only one shot per target for the bolt guy, unlike the multiple shots per target for the a carbine shooter.

Sometimes we can finagle a tripod for rear support. Sometimes we must support the rear of the stock with a bag. Sometimes they put the position in the middle of a dense Juniper tree that offers nothing but a wonky standing position with only our shoulder for rear support.

In such stages, one finds out rather quickly which shooters can get into wonky positions and not have their POI shift because of the position.

Thanks for all that, fritz, but what is the justification (if any—other than the course designers being dicks because they can) of requiring part of the rifle itself to contact the support? If I can use two hands when shooting, I cannot think of a situation in which I could not put my support hand between the gun and the support.

Great info fritz, thanks!

I've never used a rear shooting bag, is that only to support the rifle vertically?

quote:

Originally posted by matai:
I've never used a rear shooting bag, is that only to support the rifle vertically?

Depending upon the bag and the shooter’s technique, it also helps control and suppress lateral movement of the buttstock. That’s why many bags intended for rear support have large “ears” that the stock fits into.

quote:

Originally posted by Jimbo54:
Here is a chart showing the trajectory of a 55gr 5.56 or .223 bullet. ...

Well, now, that's very eye-opening.

quote:

Originally posted by sigfreund:
Thanks for all that, fritz, but what is the justification (if any—other than the course designers being dicks because they can) of requiring part of the rifle itself to contact the support? If I can use two hands when shooting, I cannot think of a situation in which I could not put my support hand between the gun and the support.

Competitions are games in which the course designers set the rules. Sometimes the rules make sense in how we must think outside the box. Sometime the rules on a stage make no frickin' sense. I like Alpine's descriptions of the latter -- he calls them Special Olympics Stages.

We can pretty much always find a way to place our support hand between the rifle's forend and the resting device. But it doesn't always make sense:
- The rough tree bark on those stages would not have felt good during recoil. Or any direct pressure, for that matter.

- The best barrier resting point may be with the very front end of the forend. Putting a hand there often compromises our ability to get square with the rifle -- which compromises recoil management. For a right handed shooter this means our bodies are probably bladed to the right, maybe at 1 or 2 o'clock.

- Many barriers are often best shot with a bag on top of the barrier, with the rifle resting on the bag. Bags often stabilize the gun better than a hard barrier surface. A bag can smooth out the top of a barrier surface, making the gun level. Properly used the "Game Changer" and similar bags can be amazing at stabilizing shooting positions.

One place you will definitely not place you hand between the supporting surface and the rifle -- barbed wire. In the Nebraska match this past spring, we had one stage where two shots each were required from each of 5 wires from a somewhat wobbly fence. Like almost everyone else I saw shoot this stage, I draped my game changer bag over each barbed wire, then rested the forend on the bag. Of course, the bag became tied up in a @#&@ barb at each wire height. I'm somewhat surprised I don't have holes in the bag from the barbs.

quote:

Originally posted by egregore:

quote:

Originally posted by Jimbo54:
Here is a chart showing the trajectory of a 55gr 5.56 or .223 bullet. ...

Well, now, that's very eye-opening.

The relative flight curves of this trajectory chart are pretty common to most center-fire rifle cartridges. Do you have any questions on how it might apply to your rifle and a specific use?

quote:

The relative flight curves of this trajectory chart are pretty common to most center-fire rifle cartridges.

It's eye-opening when I didn't know any of it before.

Is JJ still the one putting those matches together? Because he loves to make people shoot off branches.

quote:

Originally posted by Stlhead:
Is JJ still the one putting those matches together? Because he loves to make people shoot off branches.

Yep, he's still doing the 2-rifle matches -- carbine & precision rifle. This year there were 2 events, in spring and summer. Carbine and rifle positions included support from trees, fence posts, barricades, logs on the ground, and a old-man's aluminum walker -- a stage which I really sucked on.

JJ announced that there will only be one match next year. Event sponsorships are getting to be challenging. Nightforce backed off a lot this year, as did the other major gun companies. They are still kick-ass matches, even if the prize tables are very modest.