Position dependant point of impact shift with Swiss Arms PE90?

Is there a POI shift from bipod shots to mag supported shots?

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scottm

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-5 rounds fired at 100 yards using the included bipod (position A).
-5 rounds fired supported off the magazine (position B).

Question: Is there a shift in the point of bullet impact from position A to position B?

I would appreciate feedback from owners or users with extensive rounds fired from these 2 positions. An off topic discussion in another post found three users saying there is a shift of up to 3 MOA and one user saying there was no shift.

Shift comments:
1. The PE90 - Yes bipod pressure will affect bullet impact, when using its bipod care must be taken not to load the bipod. I'm getting better at this the more I use my Swiss, but I prefer to shoot off the mag in the prone and hold just in front of the mag when sitting, kneeling, standing. This way there is no pressure on the barrel and it hits consistently.

2. The same thing with the Swiss arms. As much as 3MOA change if it is shot on the bipod, and the changes depend on the different amount of pressure being applied on the barrel.

3. Agreed with the bi-pod part about the SA. I don't even use my bi-pod, and have removed it from the rifle. I use a magazine rest or hold it right in front of the magazine.

No shift comment:
1. There is no difference when firing off the the bi-pod, the magazine, or resting on a sandbag

Poll follows which will be open form October 5 to October 10. Written comments also appreciated.
Thanks in advance from a potential Swiss Arms purchaser who has never fired one.
 
As the originator of comment 1, allow me to clarify:

This is simple physics guys.

If you pull or push the rifle down when using the bipod, it will put upward pressure on the barrel and shoot slightly higher. Same with putting a sandbag further up on the forend.

If you grip high up on the hanguard like a monkey during your CQB kung-fu stance, it can put directional force on the barrel.

If you are aware of this and don't put a load on it when using the bipod, all is well.

the SA barrel is quite thick at the receiver and tapers down evenly towards the front. If you want to support the rifle, do it close to the receiver and you will have no problems.

Do I personally have a POI shift problem when holding the handguard? No I dont, because I hold at the rear of the handguard.
How about when using the Bipod? Nothing signifficant because I dont pull the rifle down or load the bipod by pushing/pulling backwards or forwards.

My prefered method to shoot is off the magazine without anything touching the forend and holding just ahead of the magwell. This comes from shooting the C7 in the CF and I like to do it that way. It works great with most rifles of this type.

In the photo below the soldier can be seen shooting off the mag and adjusting movement/lightly steadying the rifle with his support hand close to the receiver. Makes sense to me.
Note that the bipod has been removed from his rifle.

As long as you dont reef on the front of the rifle when shooting, all is well.
Same goes for an A2 AR15 with govt profile barrel. Incidently the Swiss Arms barrel is thicker and more ridgid.

To answer your question: No, as long as you do not create excessive forend pressure.

dmr.jpg
 
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As the originator of the No shift comment I feel I must clarify:

As explained above, physics clearly tells us the affects of pushing too hard on the front end of a rifle will shift the POI up.
What I believe is that the entire issue is blown completely out of proportion, mostly by people who don't even own a Swiss Arms Rifle. You would have to be pushing down with a hell of a lot of pressure. And I know some guys do that, but to each there own I guess.

I have personally fired over 3000 rounds through one of my Swiss rifles and have never experienced this. Perhaps it's because I don't push down too hard when using the Bi-Pod or when resting the hand guard on a sand bag or something. But in complete honesty, I have never paid attention to this, I just go out and shoot, and I am sure that the pressure I put on the front end of the rifle varies from day to day and from position to position, but again NO POI SHIFT. I also hold my hand guard firmly and softly and in many different positions sometimes and none of this affects my POI. This doesn't mean it doesn't happen to other people, I just think people on this forum will take a something small and completely misunderstood, and turn it into a serious issue. Look at the XCR for example, everyone claims there garbage, and there personnel experience may suggest that, but I shoot with another guy who uses an XCR and over the course of 2000 rounds it has been relatively flawless and surprisingly accurate as well. But this is just my experience with it right?

Again, I am not saying this POI shift doesn't happen. I am just saying it has never happened to me! Use some common sense (Not too common on this forum unfortunately) and like the guy above sais, as long as you don't REEF on the front end of the rifle, all is well!

Edit: June/2012, On closer observation, POI does occur, no where near the amount some have suggested, but on the two different Swiss Arms I own, they both shifted up when using the bi-pod, I still feel it's blown way out of proportion, but does happen
 
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I don't own a Swiss Arms, but in general there is a noticeable POI shift every time you change how you support or hold the gun. The benchrest shooters try not to touch anything more than the trigger to minimize this effect and target shooters of all stripes and disciplines know that having a comfortable natural point of aim and consistency in holding/supporting the rifle are crucial to good groups.


Mark
 
Yup, I've seen a major shift from bipod to prone sling supported position. Not just with this rifle, but many others as well.

If you really want to do well in a match, be aware of these shifts and compensate for them between positions.
 
mmattockx

Most benchrest shooters I have seen with one of these have the forend sitting on a rest about halfway down the handguard and are leaning into the rifle, which on a non-freefloated barrel creates upward pressure and rounds will impact higher and inconsistently.
Please describe how the rifles you saw being used were supported.

Zupermann

I do alot of shooting with sling and since the SA's sling mounting point is at the 9 O'clock position it is clear to me that the barrel will be pulled to the left when slung up.

I decided not to attempt sling use with mine for that reason. If I did I would try aiming off to the right until I walked the rounds into target.
As it sits this rifle is not well suited for sling use.

Was the sling mounting point relocated to the underside of the rifle in line with the bore? If not, I can well imagine that there was a major POI shift.
 
I use a harris Bi-pod on my SAN. Quite honestly I have never thought about it, but there maybe a POI shift depending on my hand position. Guess I have an excuse to go and tinker.
 
Steve Janes said:
f:P:
Click to expand...

If you would like to buy me a $4K rifle, I'm all for it. Not owning the gun in question doesn't mean I haven't seen POI shifts in other rifles the same as OP is asking about.


J996 said:
mmattockx

Most benchrest shooters I have seen with one of these have the forend sitting on a rest about halfway down the handguard and are leaning into the rifle, which on a non-freefloated barrel creates upward pressure and rounds will impact higher and inconsistently.
Please describe how the rifles you saw being used were supported.
Click to expand...

I was not talking about Swiss Arms, I was referring to competition benchrest shooters. The ones I have seen use bags and line the rifle up while barely touching the stock with their cheek and shoulder on the butt. The shot is taken from the same position with the trigger hand not on the rifle at all or very lightly gripping the stock, just a gentle touch of the trigger and allowing the gun to recoil pretty freely into the shoulder as it slides on the bags.

The stocks looked like this, without any real pistol grip to grab onto:

BordenBr-KwithNeonYellow.jpg


Mark
 
Well, next time I head to the range with my Swiss Arms, I guess I'll have to shoot with different rest setups and hopefully answer this question once and for all.

I'm expecting around 1-2" high at 100 yards when firing off the bi-pod in comparison to a magazine rest.

And I'll clarify that I have tested this before, I just didn't record and post the results. ;)
 
Pretty common with hunting rifles to see this kind of ####. Always taught never to rest the barrel on a hard surface. The barrel vibrations will cause the barrel to move (bounce) away from a solid object. Similar thing here with a bi-pod mounted on a hand guard that is not free floating. Pressure on the hand guard transfers to the barrel.

I proved the point to myself with a hunting rifle last year. Zeroed the rifle holding the forend and resting the back of my hand on a bag. Then later during a match I adopted a tight sling hold and my POI dropped 4-6 inches at 100 yards. I forgot the fact that this particular rifle attaches the sling directly to a barrel band, not the stock. I was effectively pulling the barrel down and altering its harmonics. Opps. Good thing it was a paper target an not a deer.
 
My experience with the Bipod.

When I first got my SA, I gave up on the bipod rather quickly and just went to the mag because that's what I know works.
I now know it was because I was loading the bipod too much and shot high as a result of that.
After trying it again recently I find if I set it straight on the ground wihout loading it and support myself on my elbows and don't lean against the rifle, the group shift is not worth talking about (hits roughly in the same area).
I will add that it is rather flimsy as bipods go. I don't like using it much but it can get the job done.

Hand pressure on handguard affecting POI.

I have not found any POI shifting going on between shooting off the magazine and holding the lower portion of the handguard (When I rest the rearmost portion of the handguard in the palm of my hand).

This Fig 11 was shot at 300m. I fired 70 rounds at this target, they are all there.

Shooting positions used:

- Prone off the mag nothing contacting the forend of the rifle - 30 rounds.
- Sitting holding lower handguard- 20 rounds.
- Rice paddy squat holding lower handguard - 10 rounds.
- Kneeling holding lower handguard - 10 rounds (not taped up).

I dug it out of the garage today and measured it.
Prone and sitting is the center area, that 50 round cluster measures 14.5" high X 8" wide. All but 1 round are within the vertical lines of the 8" box.
I did not detect any POI shift from prone shooting off the mag, to sitting holding base of handguard. They all went into the same area.

I can however pick out the 10 rounds I shot in rice paddy squat on the targets lower right arm, but I know I shoot slightly left in that position, I'm sure its me not the rifle. That group measures 7" high X 3.5" wide. The last 10 rounds (not taped) are from the kneeling position and are nothing spectacular (umm lets just ignore that shotgun blast hehe).

DSCN0618.jpg
 
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J996 said:
My experience with the Bipod.
I find if I set it straight on the ground without loading it and support myself on my elbows and don't lean against the rifle, the group shift is not worth talking about (hits roughly in the same area).
Click to expand...

I couldn't agree more. That's what I always do, but I always did this naturally, as pushing down on or leaning into your pi-pod just always seemed retarded to me....
 
Steve Janes said:
I couldn't agree more. That's what I always do, but I always did this naturally, as pushing down on or leaning into your pi-pod just always seemed retarded to me....
Click to expand...

Why thank you Steve:p When you have been trained using the Harris bipod, you are supposed to lean into it;) Old habits die hard.
 
I'd question the validity of anyone's comments who have indicated they have trigger time on this gun and have claimed they have not seen a poi change....either that or all their shooting is done inside 50m.....:jerkit:
 
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