It will depend some on the upper reciver you choose.
I have a Seekins. I went that way because they offer a rail with a 2" wide flat bottom. I thought it would ride a bag well.
That particular forend will ride the bags well. Watch for abrasions to the material however. I have a Randolph with the adjustable top and it has played hell with the nylon tubing he used for the sand. That stated, I still like the forend for my "accuracy" AR's. I will qualify the "Accuracy AR" with my honest opinion that they are all high priced prostitutes. No matter how much money you throw at them, they are still gonna break your heart..... Sorry if the last sentence offended anyone, but I said it was my honest opinion.
As far as weight is concerned, when you get a typical sewer pipe bolt action size barrel on an AR, it is gonna be very muzzle heavy and not balance well. The last is just my opinion after putting more than a few typical sever pipe bolt action size barrels on AR's.
I have thought about the abrasion. I most likely will put some stock tape on the rail to eliminate the problem. This is a gun for tinkering I plan on loading it with match grade bullets and Lapua brass. It will see 10-20 rounds at a time. I will use something cheaper for plinking.
I'm going to use a Lilja blank that is .936" from the gas block forward. For the barrel extension I'm getting a oversize one made by Bat. I will then hone the receiver to have a zero clearance fit. What are the thoughts on a 22 inch barrel? It will be scoped.
22 Cal? What would be maximum distance?
26" barrells are standard on space guns used in Highpower using standatd uppers, even with them slotted out for a side handle. John Hollinger uses a +2" extended gas sysetm on those though. THe gas block is .936 and the barrel is .925 or so to the muzzle. Under the handguard the diameter depends on the clearance of the barrel nut you use, but its usually less than 1", IIRC about .950 or so.
As far as your fit of your barrel extension to your upper, I feel that more important is that the face of the upper be square to the bore. You can check this with red layout blue and by turning up a mandrel/lapping bar to ensure this, so that the barrel nut tightens the extension against a square surface. THe only upper I ever had that would not shoot had a small burr, about .002 or so, and a small dip about the same opposed from each other. Lapping that square turned a 2-3" upper into a .75" upper.
I have shimmed them in the past, but have never used a custom ground one. There may be something to it, but I have never seen the results.
Just cut out a little strip of .001 shim/foil and wrap it around the extension, you don't even have to wrap it all the way around if its too tight of a fit, you can just wrap half the extension. I would be leery of heating the upper, It is heat treated. plus if you ever need to pull the barrel, you will have a hell of a time and probably ruin something for very little return in the accuracy dept.The standard Barrel extension is .999". I found a mil spec print for an upper that listed the hole at 1.00" +/- .002". Bat machine makes a over size barrel extension at 1.00" and they said they could make specials larger. My upper measures 1.001" so my thought was to get a over sized extension and hone the hole to a zero clearance fit. I plan to put the receiver in the oven and heat it enough to expand about a thousands and slip it together. It will take about 80 degrees over room temp to expand it a thousands. At room temperature of 70 degrees that would put the upper at 150 degrees, not hot enough to do any damage.
Maybe I'm going overboard but it's fun
Just cut out a little strip of .001 shim/foil and wrap it around the extension, you don't even have to wrap it all the way around if its too tight of a fit, you can just wrap half the extension. I would be leery of heating the upper, It is heat treated. plus if you ever need to pull the barrel, you will have a hell of a time and probably ruin something for very little return in the accuracy dept.
I use the blue loctite method. Makes sense to me, since I don't have the equipment to fit a barrel extension.I've seen others 'bed' the two with blue loctite or other compound. I like the shim method, but I gave the front of receiver to keep parallelism and haven't seen an issue since. (Or plane normalized to bore...)
-Mac
I use the blue loctite method. Makes sense to me, since I don't have the equipment to fit a barrel extension.
