Air Gun Home :: View topic - Weighting a stock to improve accuracy- using pellets

SMP · Silver Status Member

I have an AR2078 which is essentially a QB target rifle based on an older Anschutz, something around the Anschutz 250

As target rifles go the AR2078 is a super featherweight at 7lb 12oz. Most 10m rifles start at about 9 1/2 pds and can be as heavy as 12pd 2 oz. The original anschutz has slots cut under the barrel channel and in the buttstock so that the user can tune the weight and the balance of the rifle to their own shooting preference.

I have to give the chinese credit because when they decide to copy something it's an exact copy regardless of whether the feature they are copying has any use in their application. I had noticed that there is a slot running under the barrel which oddly matches the size of the original cast weights. The only remaining question was what about the butt. A quick removal of the adjustable butt pad and voila there it is

The only issue is it's probably been 20 years since Anschutz produced the weights for a model 250. But there is always a good supply of shot pellets at my place.
Smile

First I checked the original balance of the gun. typically the balance point should sit at or just forward of your rest hand. I shoot off my knuckles and the AR's balance is perfect for this

I decided that I would use the ventilation slots in the forearm instead to the weight channel because I need to add 2 pds of weight and they were big and readily accessible.

The slots measure 1/2x2" and the butt stock relief was all 5/8. I made two casting forms by screwing together two pieces of maple block and drilling with a forstner bit right down the seam between the two halves. The forms were then sprayed with dry graphite spray so they would release easily

Next came the task of converting shot pellets into lead weights. There is no need to have clean pellets. Throw the pellets, bits of target paper and duct seal into the melting pot and blast it with the heat. I just put the can in the woodstove but a stack of bricks and a torch works just as well if you do it outside.

Once the pellets are melted pour the molten lead onto a clean steel surface in blobs. The slag and crude will stay in the melting pot. I used the surface of the table saw. Don't worry the lead does not stick and will not harm the steel. Once all the clean lead is poured knock the slag out onto a concrete surface.

A minute later gather up your now pure clean lead and put them back in the melting pot and back on the fire. Once the lead is melted you can pour the molds.

A minute or two later the lead will go dull and sink a little in the middle. This is when you can open the mold.

Your castings will usually require a quick clean up to remove the flash and shape to fit. Only use a knife and a coarse file for this. There is no need to break out the power tools and fill the air with lead dust.

To be continued when the image server stops misbehaving....

SMP · Silver Status Member

In the end all my cleaned up and smoothed weights added up to 2lbs 3 oz....perfect. That will put the gun at 9lb 15oz.

All of the forestock weights were installed and the the butt stock weights were added to bring the balance back to original. I ended up leaving one weight or 3 oz out. So the finished gun now weighs in at 9lb 12oz. This is just about the right starting point point to start tuning the barrel weight and the overall balance.

I plan on finishing the job by painting the ends of the weights with some black epoxy paint.

Now I need to figure out a way to replace the barrel weight with something that weighs about three times as much. The barrel weight is the enlarged section just behind the front sight.

Any suggestions?

MSEO · Member

You could cast a piece of lead "pipe" and slide it on, but that might not take an attractive finish.

SMP · Silver Status Member

I was considering it. I'm just trying to figure out what I could use for a 15mm core plug.

MSEO · Member

Know anyone with a metal lathe?

SMP · Silver Status Member

lol...ya me. But it's about 5 hours away at my home away from home.

And I don't have a boring bar that would reach 5 or 6" in. My bars are limited to about 4"

http://www.busybeetools.com/products/BORING-BAR-SET-3%7B47%7D4IN..html

rsterne · Moderator

Drilling it should be accurate enough.... on a lathe you could probably drill it good enough for a weight from both ends and then secure it with setscrews.... Moving it along the barrel might tune the harmonics, too....

Make the OD as large as you can without being above the bottom of the hole in the globe sight.... Steel is pretty heavy, brass even heavier....

Bob

MSEO · Member

I was thinking you could turn down a piece of pipe to 15 mm and use that as a core. Pipe would let you run cold water through to shrink it to allow the lead to slide off.

SMP · Silver Status Member

Alright that settles it. I'll have to wait until the 23rd of Jan though. I'll cast the core(s) and turn them when I reunite with the lathe.

If I add a fair bit of tin it should give a decent surface finish. I think the manufactured are tin/antimony. I'll hit them with black epoxy for looks and surface toughness

Here are the rules on the subject.

7.4.2.3 Exterior Weights
7.4.2.3.1 Only barrel weights within a radius of 30 mm from the center of the
barrel are permitted. Barrel weights may be moved along the
barrel.
7.4.2.3.2 Any other weights must be within the dimensions of the stock.

Shocked

30mm radius Shocked

I thought it was 30 mm diameter