AR-15 in .204

[bowsniper]

Hello,

I'm new to the forum. I'll be building my first 204 on an AR15. I'll be shooting mostly 40 grain bullets.

I'm looking for barrel manufacturer and barrel twist suggestions.

Thanks,

Mark

[Rick in Oregon]

First of all, welcome to the 204um! There are many AR shooters here that will chime in, but if you want to cruise even deeper into the AR world, go here:

http://www.ar-15.com/index.php?r=1440

Those guys over there are all over the AR platform, full of advice for guys starting out with the brass chuckers. For shooting the heavier weight bullets like the 40's, you'll probably want to go with a 12 or 11 twist in the 204. An 11 twist would be a better bet, as many 12 twist guns won't shoot the 40gr V-Max well. Give the Sierra 39gr BK a try too. Good luck with the new rig.

[joghotrod]

Predatormasters also has alot of info on AR's for varmint shooting.

http://www.predatormastersforums.com/ub ... hreads.php

Jimmy

[Over-the-Hill]

joghotrod,
I know this is jumping the post but I see you have a Ruger Mod. 77 MK II also. I'm interrested on what you came up with for load data. You can post here or e-mail me @ tmdukes@msn.com.
Thanks,
OtH

[joghotrod]

joghotrod,
I know this is jumping the post but I see you have a Ruger Mod. 77 MK II also. I'm interrested on what you came up with for load data. You can post here or e-mail me @ tmdukes@msn.com.
Thanks,
OtH

I bought this rifle used from a member here and he worked up the load. It is 27.7 grains of H 4895 behind the 39 SBK's. It is the only load I use with this rifle because it is accurate even with me shooting it. I use a load real close to this in my 12 twist .204 Dtech. AR also.

Jimmy

[Over-the-Hill]

joghotrod,
What primer are you using? I finally found some 39 gr. Blitzkings on-line. Hopefully I'll have them next week.
Thanks again,
OtH

[joghotrod]

joghotrod,
What primer are you using? I finally found some 39 gr. Bilitzkings on-line. Hopefully I'll have them next week.
Thanks again,
OtH

I am using CCI BR4's. Good luck.

Jimmy

[stevecrea]

The advice above from Rick in Oregon is good. I have noted many forum posters conveying that their rifles tended to not shoot 40 grain bullets as well as lighter ones.

Further, I believe that DPMS, who makes an AR in .204, which I believe, has a 1 in 12 twist, specifically states that bullets heavier than 36 grains or so should not be expected to shoot well. However, I do not know if the warning has as much to do with the cycling of the action properly, or with the stabilization of the bullet, or both.

Further, I have a story for you:

My friend and I were shooting our 204s at long range rockchucks several seasons ago. His rifle is a Cooper Varminter, 26 inch barrel, 1 in 12 twist. Mine was a Savage 12 VLP, 26 inch barrel, 1 in 12 twist. I was shooting 40 grain bullets. I recall that he was shooting 32s. We were shooting at rockchucks in an alfalfa field at ranges varying from about 500 yards to 550 yards, determined by a Leica rangefinder. The result: It appeared that no matter how much elevation we gave our 204s, we could not reach the chucks. The bullets all fell short, as we could see the puffs in the dirt as they fell.

Our simplistic conclusion: After the velocity of the bullet drops to 2000 fps or so, the bullets become unstable, and quickly begin tumbling. Well, I do not know for sure. Has anyone else experienced this? Further, would a faster twist, as Rick suggests, ameliorate or cure this apparent problem? Further, why do not some mfrs go to a faster twist, if 1 in 12 is borderline for the heavier bullets?

Comments?

[stevecrea]

According to my Hornady's ballistics calculator, the 204 bullet may drop to 2200 fps or so after 450 or 500 yards, depending on assumptions used for ballistic coefficient, beginning velocity, etc. If bullet stabilization is marginal when it is being launched at 4000 fps, perhaps a simplistic conclusion is that as velocity drops rapidly to below 2500 due to the low BC of the bullets, then stabilization may suffer.

[joghotrod]

The advice above from Rick in Oregon is good. I have noted many forum posters conveying that their rifles tended to not shoot 40 grain bullets as well as lighter ones.

Further, I believe that DPMS, who makes an AR in .204, which I believe, has a 1 in 12 twist, specifically states that bullets heavier than 36 grains or so should not be expected to shoot well. However, I do not know if the warning has as much to do with the cycling of the action properly, or with the stabilization of the bullet, or both.

Further, I have a story for you:

My friend and I were shooting our 204s at long range rockchucks several seasons ago. His rifle is a Cooper Varminter, 26 inch barrel, 1 in 12 twist. Mine was a Savage 12 VLP, 26 inch barrel, 1 in 12 twist. I was shooting 40 grain bullets. I recall that he was shooting 32s. We were shooting at rockchucks in an alfalfa field at ranges varying from about 500 yards to 550 yards, determined by a Leica rangefinder. The result: It appeared that no matter how much elevation we gave our 204s, we could not reach the chucks. The bullets all fell short, as we could see the puffs in the dirt as they fell.

Our simplistic conclusion: After the velocity of the bullet drops to 2000 fps or so, the bullets become unstable, and quickly begin tumbling. Well, I do not know for sure. Has anyone else experienced this? Further, would a faster twist, as Rick suggests, ameliorate or cure this apparent problem? Further, why do not some mfrs go to a faster twist, if 1 in 12 is borderline for the heavier bullets?

Comments?

I don't know if what you say is true or not, but when I first bought my Ruger 1/12 twist .204, I went to the rifle and pistol club that I belong to and shot it at the 600 yd. targets. I had to change the elevation about 13 MOA. using 39 SBK's. All but one or two made it to the target without a problem. One or two didn't make it to the target, but I think it was because they flew apart down range, not because they started tumbling. But I don't know for sure. I have also shot some 39 sbk's out of a 9 twist and I have seen some of them come apart down range. I could see several puffs of dust in front and to the right and left of target (pd's). I think this was from spinning them too fast out of the 9 twist barrel. I later switched to 50 grain Bergers for this rifle so that would not happen.

I even called the bullet maker and they could not explain why or if the bullets were coming apart or not. So if anybody knows for sure, let us know.

Jimmy

[jwc41]

I built a 204 AR upper before last varmint season and spent a bit of time working out the kinks. I bought a DPMS stainless, fluted 24" 1-12" barrel from Brownells and mounted it on a DPMS Hi-ride upper. That upper was out of spec, so I bought a Model 1 flattop upper which has worked great. I've added a Timney trigger to the lower, along with a MagPul precision stock.

Initially, I had issues with severe copper fouling from 32 grain bullets at 3900fps after normal barrel break in. The gun shot the 32 Nosler BT's pretty well, but scrubbing the barrel for an hour after 10 shots wasn't fun. I bought a box of David Tubb's fire lap bullets from his website (Midway and Brownells didn't carry them) and shot half of them as directed (5 rds per # grit instead of all 10) to smooth the barrel. As I was finishing that process I saw on this forum that the 39 Sierra BK's were highly regarded and upon shooting with W748 (used because of it's lower flame temperature) and IMR4895 I discovered they shot quite well too (all groups of 5 shots went under .75", some as low as .3").

For long range PD's I now have no reason to shoot the 32's except for shortages of the 39 BK. I had 39 BK's loaded up as my buddy and I pulled into one of our P-dog towns and got a snap shot at a distant coyote. It ran 20 yards and went down. I later lasered the distance to be 561 yards. It was the luckiest shot of my life--probably because I didn't have time to think (analysis paralysis). The 39 BK left a quarter-sized exit wound on the off side, so it obviously didn't have enough steam left to expand violently but had enough to penetrate. I haven't tried the 40's yet--maybe after the season.

If you reload, be sure to size new brass. Case neck tension is critical for AR use. You may also need to gently crimp the bullets after seating; be careful, as it's very easy to collapse the shoulder on 204 cases. 20 round mags are best for bench work. I found my barrel likes the 39's loaded out as far as possible, so P-Mags are out since they have the shortest front-to-back interior dimensions. Old GI 20 rounders allow a little more room, but the most spacious mag is the HK 20 rounder as COL of nearly 2.27 is possible. This season I'll be using H4895 so I don't have to rezero from cool spring W748 loads to summer IMR4895 loads. Another issue with relaoding for any AR is primer pockets. While you can get away with mildly loose pockets in a bolt gun, the violent feed cycle with an AR can pop the primer out of a loose pocket pretty easily. That's why the military has crimped pockets on all it's ammo.

I like the AR platform for bench shooting at varmints. The lack of the 204's recoil (a 12 lb. gun helps) allows you to see bullet impact, and if you miss an immediate follow up is at your fingertip. Plus, when the barrel is cooling or needs cleaning, I can pop off the upper, replace it with an accurate 24" bull barreled 223 1-9" upper (with the same scope as the 204 upper) and keep shooting with minimal disruption. However, I have shot with others who have the Jim Zumbo attitude towards AR's as varmint guns and have made disparaging remarks. I ignored them and they moved on. I think they were just a bit jealous that fast follow-up firepower can be just as accurate.

[OldTurtle]

Bowsniper, As to your original question, when I had my AR upper built (before DPMS and others), I went to Randall Rausch at AR15Barrels.com and he was very knowledgeable about the .204.....

Due to his advice and my cost constraints, I wound up with a Douglas XX Stainless Match barrel with a 1/12 twist. He suggested that I keep the minimum length to 22" and he custom cut the chamber to allow a .030" jump to the lands using a 40gr Hornaday V-Max and this allows about a .035" jump with the 39gr SBKs.

This chamber restricts me from using the 50gr Bergers, as they are too long.

This combination allows me to shoot some really great groupings, so far.

This is a typical 100yd group with my load: