AR-15 300 fireball build

[pug]

I am sure a lot of people have found all sorts of little things out when building one of these uppers but I really can't say I saw a lot of it posted when I started to build mine so I thought I would share.

Went with a pistol gas port because of the cycling problems but still had to open it up just a hair to get it to lock back on the subsonic 147s and found the pp gas port to definitely run a little dirtier but that was expected.

M4 feed ramps a definite must especially if shooting round nose bullets and mine needed the ramps rounded up on the edges to keep from cutting the bullet jacket. It now feeds everything tried so far including broad nose hollow points.

I never realized how many different kinds of mil spec magazines there were until building this. Those little ears that stick out and guide the round out of the magazine seem to be long or short and/or wide or narrow. For mine the short narrow ears seem to feed the 308s the best. Also the magazine catch notch seems to be where ever they like to place it. Mine feeds best with the notch low which makes the mag set up higher. Also like someone mentioned the newer anti tilt followers work really nice.

The dies and brass took a little time to figure out. Since mine was a 300 fireball I decided to use reformed 223 mil brass using redding dies. Forgot to read you have to cut down the die and/or shellholder in order for the crimper to work since it won't engage a 1.355" long case. After cutting down expander, die and shell holder it all works great now :). The Lee M1 crimper will also crimp them but the crimp band is right wide. I prefer the roll crimper built into the die to do cannelured bullets.

Don't take this for complaining as it was a blast to build and now runs like a champ. I really appreciate the info that different ones posted here and I am now checking out all the load data. I think some of you have said you have an adjustable gas block in the pistol position. Is it a low profile one (brand?) and do you adjust it to shoot from subsonic to supersonic or just leave it alone?

Thanks.

I edited this post to remove the part about modifying the expander because Redding didn't like the idea as well as some I got negative feedback from. Actually I can only speak for my dies anyway. Redding stated on the phone you must first use their form die to reform the .223 case then their trim die and then turn the necks so you have a .221 case. Then you can resize with smaller expander then larger one and final trim. Then you will have a 300/221 case to use. Personally I liked my way of just reforming, trimming then loading but what do I know :). Always use every safety precaution when reloading of course.

[320pf]

Pug,

I have an adjustable low profile gas block (JP Enterprise) in the pistol position on my AR. The barrel is an Olympic Arms stainless steel barrel. The gas port is about 0.071" in diameter if I am remembering it correctly. I am able to shoot both subsonic and full power loads without having to adjust the gas block. For 125 gr full power loads I could close down the gas block and bit but the gun runs find as is.

Here is all of my load data that I have worked up so far. They are listed under "Not yet verified user loads" The only ones that are not mine are the two that use AD2205 powder. They were worked up by spmorgan on this site. (I may have sent you here once already... but I like to share my work :))



http://www.reloadersnest.com/frontpage.asp?CaliberID=135

What is the load data for your 147gr subsonic load. I think I might be interested in that load

Thanks

320pf

[Quarterbore]

Thanks for shaing your experience.

I just purchased a 16-inch A3 J&T "300 Whisper" upper and I have not decided what I want to do with it yet. I really need to strip the barrle down and check the profile to see what would be involved with adding one of the JP Enteprizes gas blocks back in the pistol location.

I have a SWS Float tube (http://www.superiorweaponssystems.com/ar15rifle.htm) that would give the carbine a Dissipator look and when I add a can it would look more balanced.

I plan to initially just purchase and install the JP Adjustable Gas block and perhaps add a PIG-Tail gas tube to see if that works at all. I figure if it doesn't work I can always use the pigtail on my AR-15 pistol (that has a 11.5-inch barrel) and then move the gas block back to pistol.

I have not started any major projects in quite some time but with those darned liberals in Washington they are making me think about some new builds!

[pug]

320pf I have used your work all ready :). My setup is OA also but even having counter sunk the gas port to reduce any misalignment with the gas block and centering and locking the block down it still would not lock the bolt back with the 147-150s as it was. 8 gr of H110 is the load I was using but don't quite like the small charge I get so going to a bulkier powder to try to fill up the case more. After seeing you said you had a low profile jp which I hadn't seen (just the railed one) I went to their site and sure enough they did offer one so that is probably what I will use if the supersonic loads seem to hard on the setup. Right now everything seems to be running ok with what I have tried so far.

[kugle]

[QUOTE=pug]I forgot to read somewhere that you had to grind the expander down in order to size the inside of the neck because of the thicker brass.QUOTE

Where can I find out more information on this. I have not come across this before?

Right now I am just collecting parts and reloading supplies for my build.

[pug]

kugle unfortunately I didn't get to read it either and found out the hard way so to speak. Actually it all made sense after I couldn't run the expander through the newly reformed and trimmed 223 brass and I set down and checked the dies out. 221 fireball brass gets thinner as it is necked up to 308 and thats what the dies are for. 223 brass gets squeezed down to form 300 brass and the mil brass is already thicker to begin with. You can remove the expander completely and just size the brass down, trim it and load and shoot and I imagine a lot of people do this. However after firing the brass you may find it is a little out of shape and needs the inside of the neck shaped up to reload it again but without an expander it would be tough. I put my expander and stem in the lathe and clamped a dressing stone in the tool holder and ground it down to .304". I would have preferred .306" for .002 neck tension but the mil brass I have on hand needed it to be .304. As far as the crimper it would also have been correct for true 221 formed 300 brass but again people are leaning to 1.355" case length for the 300 fireball and that makes the case to short to touch the crimper in the dies. Since the crimper can't be changed the only thing to do is shorten the bullet seating die or shorten the case holder so the case gets inserted far enough to engage the crimper. After machining all the bevel off the top of the case holder I still wanted a little more leeway so I took about .020" off the bottom of the seating die also.
If you are going to shoot match bullets then it doesn't matter since your bullet needs a crimp ring in order to use a roll crimper because that is what its for. If you wish to crimp the match bullets then the Lee M1 carbine factory crimper is the right length for 1.355 cases but it puts a fairly wide crimp band on them.

As a side note for 308 size bullets I start paying attention to whether they need crimping or not. Anything over a 100 grains will have enough mass if slammed into a chamber fast to start to unseat itself. How much depends on how heavy the bullet is and how fast it is moving when chambered. The .308 125s unseat themselves a couple of thousandths of an inch when chambered in a semi and the really heavy ones will move tens of thousandths. Remember an automatic action is performing the exact same operation as one of those kinetic bullet pullers. One of the problems with shooting subsonic bullets at high rates of fire is if the bullet unseats in the throat the powder will still ignite but pressure will be a lot lower and the bullet sticks in the barrel. The second round may not unseat and fires just fine and well you know...another bad day.

[Foxfire]

Pug,

I didn't like the wide crimp left by my M1 carbine crimp die. But a good crimp was a must for me.
I took my micrometer to Lowes and picked out a verity of 3/8 fender washers. By slipping one around the cartridge before ramming it into the crimp die, I am able to adjust the crimp were I want it. Works for me.

[pug]

Yep with the Lee factory crimper the sooner you trigger the crimper collet without turning the die down the higher the crimp will be. Sounds like you have got a good method worked out there.