Rear bag plate and their importance

[DenisA]

G'day All,

I've just mentioned rear bag plates to Sebastian Lambang on FB. He wasn't too aware of their use and the importance that shooters put on them. I said I'd start a post on here that he can refer back to and get some views from the F class community. I think he'd be really interested to hear from the guys at the pointy end of the game too. I'm pretty sure he's a member here anyway and can chime in if needed.

Current SSR
A plate of board may be used to create a stable platform for the bag to sit on and may include spikes limited to 50mm. in length, unless spikes are prohibited by local conditions.
(d) The plate or board may not have side rails or raised edges and the bag must be free to move horizontally in all directions.
(e) There may be no mechanical means of adjusting the bag, either laterally or vertically

Who uses them?

How important do you feel they are?

What are some features that you think are critical in them?

What diameter is best for the spikes?

How much clearance for spongy grass?

Are tapered bases to counter mound angle better?

etc. Any advice you have on them basically.

Cheers,

[williada]

Denis,

The rear bag in my opinion is the anchor point for the fulcrum of your whole set up. If the fulcrum point changes, so do a range of tunes, from compensation to nodal. The rear bag should be hard, secured and in alignment with your front rest.

I would value Peter S's (edit) input here, and leave it up to others to describe how they go about it. David.

[DenisA]

Thanks David.

I think that rear bag plates are critical in F-class. The biggest issue I had experienced pre-rear bag plate days was on the long range mounds at Belmont mostly. The grass was very spongy and thick and simply having the rear bag sitting on the shooting mat on top of the spongy grass caused additional vertical.

G.Sells mentioned this as a possible cause of his vert in the Nats this weekend.

Ages ago, I made up a simple ply trial plate. It has course sanding belt glued to the top side and 60mm M8 bolts sticking out the bottom with nuts and washers allowing the plate to float 10mm above the dirt leaving 50mm spikes. This stops the board from sitting on the grass. Its extremely crude, but straightaway the difference was such an advantage and it works so well, I've just kept using it. The rear bag is incredibly stable and never moves on recoil, not even with my 300wsm. Rifle tracking and follow through improved instantly. Also any slight movement of the shooting mat due to possible body movements on sloping mounds has zero chance of effecting the rear bag.

A lot of folks have realised the importance of them over the last couple of years. There are lots of different types around now. Some I've seen are wedge shaped, some are really heavy steel plate and some look really well made. There have been threads on the adjustable concepts too.

There are lots around now and it seems like they're becoming standard F-class equipment.

[plumbs7]

Hi Dennis, yep still pinching myself !
However my plate is a cut out off 15-20 mm steel and would cause severe injuries to someone if accidentally dropped . The weight is one of the benefits with 50 mm spikes to tame the Belmont grass. Even then still have to be careful how I put it done as it still can rock.

Another thing I found today and Mark f was a sponsor of this too. Was I took my cheek piece out at the ton ! Well it worked ! Regards Graham Sells.
Ps also had watch the front rest as well for Belmont Bounce too!

[Brad Y]

Ive always used one but recently have gone away from them. Im bringing all my gear into line with international rules to develop my shooting so when the family is a bit older and Im able to travel internationally for shooting events I wont have to alter gear and technique. We have spongy grass mounds here too and so far havent found any issue with a soft stabilising bag under the heavy rear bag- only used it 2 or 3 times so its still a work in progress. The idea is to take out any hollows or lumps in the ground underneath and also prop the rear bag up as level as possible while remaining stable. Also building my stock to have a good stable fit in the rear bag so it rides instead of bounces. Cheekpiece on magnets so easily removable for shooting. Taking time off from shooting has really opened my eyes as to how to set up a rifle consistently each time, rather than plonk it down like I used to- differently each time.

[BATattack]

Should we all just chip in and shout the QRA a decent lawn mower? it'd probably work out cheaper in the long run than people flying extra gear all over the country and then having to lug it to the mound! haha

[DenisA]

Is this only a concern at Belmont? It might sound like a silly question, but I'm not a well travelled shooter..

[Brad Y]

Would be good to hear from other shooters who were at the nationals if they also had problems with the spongy mounds? Maybe different setups handled better than others. Craig, Rod, Shane etc.

[AlanF]

I wasn't there this year but was 12 months ago, and found the 1000yd mound was the worst. The main problem is I think the type of grass on it (kikuyu?) which after some years seems to build itself a thick mat of roots above the hard soil. It is a poor platform for a rear bag, so the idea is to have a platform with spikes that will penetrate through it down to the solid dirt. Sometimes 50mm is barely enough. And you need to have similar long spikes for the front rest. Another way of overcoming the problem is to increase the weight of your bag, or use more than one bag. You can get large "donut" type bags to place under your normal bag. If you do that the weight of the bag itself can be enough to anchor the buttstock. This would be legal under ICFRA rules Brad. I use a very heavy bag AND a spiked plate, but my current plans don't include flying to competitions. If you do want to use an ultra heavy bag, you can tee up heavy sand to be waiting for you at the destination. At Raton for the FCWC, just to be sure I took about 15kg of zircon and paid the excess baggage , but you don't skimp for those once in a lifetime comps.

[Brad Y]

Indeed Alan. I would be flying too, so arranging a 10L bucket of garnet or zircon somewhere would be my best situation. I just thought it would be best to eliminate anything out of the equation that would cause problems come international competition time. It wont happen til the kids are much older, but something I thought hard about when purchasing for getting back into shooting. The next thing is travelling a bit more to get more experience on a variety of range situations.

[plumbs7]

Hi , I just want to clarify what caused the epic vertical into the 4 rings at day 2 900. I failed to put downward pressure on the rear of my stock into the rear of the bag. Just placing in the rear bag leaves a 5 to 10 mm gap between the bottom of the stock and bag ! That's why I think my first 4-5 shots were clean! Process, process ,process hey Jen? ( she is a good coach!).

So before I have the president of Qra chewing my ear off, I will explain more.
The boucne IMO is worth about up to a minute if ur gear isn't set up right! Set up right it's nothing and I think Alan has covered it well above !
Regards Graham.

[ShaneG]

To some extent we may be discussing a moot point?
The projectile exits the barrel before much rifle movement occurs if at all?
I used a relatively light steel plate below my rear bag which was a Doctor filled with sand blasting grit.
Quite heavy! I will increase the weight of the rear plate next time.
Can't fly with such a system though!
I did not use spikes because our rules won't allow them as of next year.

I did have a high and a low 5 at the last Queens 1000 yesterday though?
And #14 in Mace was high 5?
Whether this was shooter error? Hot barrel? No mirage shield? Or mound?
Who knows? I do shoot free recoil as I found that this results in the most consistent vertical for me.
We strive to learn?

[Longranger]

Be mindful that some heavy sands are radioactive especially those containing rutile, zircon and thorium. Probably not that big a deal but something to be aware of. Plenty of info out there about it.

If travelling, you may face some awkward questions if it gets picked up by a gamma detector.

[RAVEN]

http://www.iluka.com/_uploads/documents/Datasheets/Iluka%20Zircon%20MSDS%20Mar%2010%20Aust.pdf

I don't think it would be a problem with the amount we work with
safety data sheet link above

RB

[DenisA]

After the 2015 QRA Queens, how did the Belmont visitors feel about the spongy grass, vertical issues and were you using a rear plate or not?

I see Michael partly attributed the spongy grass to vert dispersion in the 2015 teams thread.