AR with 1 in 7 twist with cast

[deepwaterco]

Hello all! I just picked up an AR with a custom Chanlynn match barrel with 1 in 7 twist. I am looking to use some cast boolits in this and I am in need of some reccomendations from you all ! I am getting 3/8 inch groups with 60 gn Sierra's and benchmark! So I know it shoots well with jacket stuff but I am a lover of the cast boolits! I am thinking about an LBT in 75 to 80 gn. Any input will be most helpful.

[Larry Gibson]

That LBT bullet along with medium and slower powders like 4895, Varget, AA4350, H4831SC, RL19, or perhaps RL22, etc. Don't expect accuracy at too high a velocity.

Larry Gibson

[deepwaterco]

Thanks Larry!

[Larry Gibson]

Your welcome. In my 7" twist AR I went for functional reliability with AA4350 and H4831SC under 60 gr cast bullets and just accepted the accuracy. Shoots about the same as M193 which isn't all that bad. Just isn't fast is all.

Larry Gibson

[Moonie]

Now my AR is a little different than yours, I have 1-9" and you didn't mention your gas port length, mine is mid-length.

I found my action functions at 18gr of H4895 with 55gr Bator. This is about as low as Hodgden recommends (60% of max) for this weight.

[madsenshooter]

I've been trying to get the Eagan MX2-243 to shoot out of my AR, but I too have a fast twist barrel, looks to be a 1/8 or tighter. I started up on the high end as I knew the alloy was good for 2450fps out of my 30 calibers. I'm now down around 2200fps and the best I'm getting is 2.5"-3" or so at 100yds. The slower I go, the smaller the groups are getting. I want to use this rig for coyote hunting where the max shots will be around 200yd, so just living with the accuracy I have isn't an option. It just isn't worth putting all the time in if I can't hit what I'm aiming at consistently. In shooting j-words, I can see it isn't the rifle, 1" groups with about any jacketed load I throw together, and that's with loads that show a lot of runout! It doesn't appear that I'm going to be able to get things going as fast as I'd like and I'm don't know if it's the twist rate, the 5R rifling, or maybe a bit of both.

[Larry Gibson]

madsenshooter

If you are expecting the same 1" accuracy with your cast you will have to drop the velocity quite a bit further. Given quality cast bullets, the right alloy, the right fit and good loads it all has to do with RPM and where you begin to exceed around 140,000 RPM. With n 8" twist that will be down around 1550 fps. Functional reliability can be a problem at that low of a velocity. I've done quite a bit of testing with my 7, 9 and 12" twist ARs. I've also done a lot of cast bullet testing with 8" twists and 14" twists. Above 140,000 RPM such 1 moa accuracy is very alusive.

Like moonie, I also use 18 gr H4895 with a 1/2 gr dacron filler under a 225462 (58 gr fully dressed) and just accept the 2 moa accuracy out of my Colt 9" twist AR. Velocity is not such that I would make a habit out of hunting Coyotes behond close range calling distances with it. However, out of my 12" twist AR I push the 225415 at 2200 fps with the same 2 moa accuracy and am confident of it's ability on coyotes out to 150 yards. However, with the limited number of coyotes shot the cost of quality jacketed bullets is prohibitive by any stretch.

Larry Gibson

[45 2.1]

Ho hum............. sounds like alloy and technique failure. You should note that your loads fail at a certain pressure level. Strange that the 22-250 guys have went well above the levels mentioned here with cast and MOA accuracy (several published articles on it)... now isn't it.

[outdoorfan]

I am thinking about an LBT in 75 to 80 gn. Any input will be most helpful.

That 75-80 grain LBT has a lot of bearing surface. Will the throat in your rifle be able to handle it?

[madsenshooter]

45 2.1, I can see that it happens at a certain pressure level. The pressure level delivered by 23.3gr of 4895 or 26.3gr of either DP85 or W760 all at about 2420fps. Up one grain and they're all over the target. I guess I'll just have to keep loading and shooting until I find the right spot, I've not gone much lower with either, but, I know the slow burners are out, I've already gone down far enough in charge that I've lost function with them, so I'll keep going down with the 4895 and see where I wind up. If it winds up being a 1500fps load, I guess that I'll have to just get used to a high powered squirrel rifle and use j-words, or one of my Krags on the coyotes.

[Larry Gibson]

Ho hum............. sounds like alloy and technique failure. You should note that your loads fail at a certain pressure level. Strange that the 22-250 guys have went well above the levels mentioned here with cast and MOA accuracy (several published articles on it)... now isn't it.

Nothing "strange" about it. The 22-250s have 14" twists which means they don't hit 140,000 RPM until 2700+ fps. A 7" twist hits that RPM at 1450+ fps, an 8" twist at 1550 fps or so, a 9" twist at 1750 fps or so and the 12" twist at 2330 fps or so. Driving a cast bullet with accuracy out of the 22-250 isn't difficult at all, it is difficult with a 7 - 9" twist AR though.

I'm shooting 1.5 moa 10 shot groups at 2600+ fps all day long out of my 14" twist .308W. Can't do that with a 10" twist or even a 12" twist. I can shoot those groups all day long at 1900 fps out of the 10" twist and at 2200 fps out of the 12" twist though. Guess what they all have in common? Yup, they're all about the same RPM. Strange now that some don't seem to understand why....now isn't it?

Larry Gibson

[45 2.1]

I'm shooting 1.5 moa 10 shot groups at 2600+ fps all day long out of my 14" twist .308W.
Larry Gibson

Lets see.... in another thread you quote......6" at 200 yards (2 moa). http://castboolits.gunloads.com/showthread.php?t=98191&page=5 post #83. Lets see, that would equate to 3" per MOA at 200 yds or 1.5" at 100 yds. From that I guess you meant you shoot 2.25" groups at a 100 yds at 2600+fps........... at least it looks like that by your math in what you posted........
don't it. Hee hee hee............I would try that again and get it right this time............

You really need to prove the all day long thing............ 4 sequential targets like you want out of everybody else would do as a minimum, but wouldn't qualify as all day long either. Otherwise its just so much of what comes out of the south end of a north bound bovine male.

[Larry Gibson]

45 2.1

If you're going to follow me around this forum and criticise you should really pay closer attention. I've posted this series of targets several times with a complete explanation of the load etc. The details have all been posted before but briefly I fired 40 shots total with 37 of them into 3 groups at 100 yards and one group at 200 yards. The first 3 shots were fired on a different target to confirm zero.

As everyone, including you, can plainly see the average group size for the three 100 yard groups of 8, 10 and 10 shots and the 9 shot 200 yard group is 1.52 moa. All day simply means I can shoot this load all day long without cleaning and it maintains the same accuracy. I have subsequently shot over 100 shots of this load through this rifle without cleaning and it still shoots as accurately. At 300 yards I can regularly put 10 shots into 6" or less.

I'm not sure how you do your math but what I said refering to this rifle and load in the post you cite is; "I do have 3 cartridges that I will used to 300 yards (they are the .308W with a 160 gr cast bullet at 2600+ fps, a .375 H&H with a cast bullet at 2350 and a 45-70 with a cast bullet at 2050 fps. The 1st has the velocity for 300 yards and the other two have the bullet weight and caliber to remain effective out to 300 yards. All 3 cartrdges out of the rifles I use are 2- moa accurate. Now 2 moa at 300 yards is 6", at least based on my math, and since I can shoot this load into 6" or less at 300 yards that equates to 2 moa or less, just exactly as I stated. Judging from the targets, with 37 consecutive shots in 4 different groups at 100 and 200 yards, it is obvious that the rifle and load I am talking about is indeed 2 moa capable. I don't have any idea what you are talking about.

Larry Gibson

[45 2.1]

Now 2 moa at 300 yards is 6", at least based on my math, and since I can shoot this load into 6" or less at 300 yards that equates to 2 moa or less, just exactly as I stated. Larry Gibson

You stated this before you edited it last night:

6" at 200 yards (2 moa). http://castboolits.gunloads.com/show...t=98191&page=5 (http://castboolits.gunloads.com/showthread.php?t=98191&page=5) posts #83 and 92.

Somehow, somewhere you left your eyesight or something else laying on the floor because those two statements didn't match. At least you can correct your mistake after a couple of notices, but that was a very basic thing to mess up. BTW............a 2 MOA rifle doesn't shoot 1.5 MOA all day long as your targets show. Wishfull thinking on your part......

[Larry Gibson]

45 2.1

Yes I did edit that mistake. I have no problem admitting to making a mistake like some do. However, if you read that post you will note that the 6" group at 200 yards was in reference to "hunting accuracy" which was the topic of that thread and my post. The 6" at 200 yards had absolutely nothing to do with the .308W loads I mention later in the post. You're interpretation that it did has you confused.

Would you care to comment on the target posted? You made the challenge to me to "prove it" by posting such. I did so where is your comment? I do what you claim to do but I simply and easily do it by controlling the RPM. We know you disagree with that but the proof is rather obvious. You and I are taking this thread off on a tangent so let us get back to discussing cast bullets in 7" twist ARs, eh?

Larry Gibson

[Pat I.]

Larry you should try out the "Ignore" button it works wonders.

[swheeler]

"I'm shooting 1.5 moa 10 shot groups at 2600+ fps all day long out of my 14" twist .308W"

Now your talkin' Larry, I need a 308 with 14' twist, BUT instead I've got 2 with 10" twists, damn! Good shootin' with the gas gun too!

[45 2.1]

Would you care to comment on the target posted? Larry Gibson

You have a PM.

[Larry Gibson]

swheeler

Yes I've found that the easiest way to shoot cast bullets at higher velocity is to use a slower twist. If one is rebarreling or buying a .308W or an '06 the 12" twist is better than the 10" twist but the 14" twist is really the best choice of all. The same applies to .223s in ARs. However, like you and most everyone else you have what you have for a barrel twist and want to make it work (me too...I have numerous 10" twist '06s and other like twists in other cartridges). 45 2.1s technique does work with some cartridges that have sufficient capacity but a former member who is good with that technique says it doesn't work with the .308W. May or may not work with the .223, I don't know as I've not tried it.

I was very successful with 45 2.1s technique in the 6.5 Swede even though I did not have the correct bullet and did not quite get the same accuracy or velocity that was said possible with the correct "Kurtz" bullet. However, I was very satisfied with the accuracy I got at 2100 fps or so out of 3 of my Swede barrels with the 2 bullets I used. I probably could do better if I got the correct "Kuurtz" bullet mould from BaBore but, frankly, my point was to determine if 45 2.1s technique worked. It worked so that is good enough for me as 2100 fps with 2 moa accuracy is fine with the 3rd GB bullets or the Lyman 266455 I am using. It shows there is more than one way to skin the cat.

However, back to the AR, most ask about using cast bullets of 55 or so gr. That's where my experience is with the .223 in the AR with the 7, 9 and 12" twists using cast bullets of 55 to 60 gr. I've also shot some in 8" twist ARs and a couple older 10" twist Mini14s with predictable results. If one is using a 7 or 9" twist AR and doesn't already have a mould then the heavier 70 gr NEI or the LBTs the OP asked about are probably the better choice. Not sure I'd go above 70 gr if the twist was 9" though. With the AR my experience is that a medium powder such as 4895 works best for reliable functioning and accuracy when that reliable functioning is reached. With the heavier bullet a bit slower powder might be better. I would look at AA4350 as I’ve hound it to be a very good cast bullet powder for heavier bullets at higher velocity. It is small kernelled, throws accurately and goes into smaller case mouths without “bridging”. It might be worth a try in the ARs with a heavier 70+ gr cast bullet. One of these days I might have to revisit the .223 in ARs with a heavier bullet also.

Larry Gibson

[swheeler]

I kick myself for not buying one or two of the 308 14" twist barrels offered by Sarco a few years back, BSA manufacture I believe. Coulda-shoulda-woulda

Parker Hale, that's whos they were

[Larry Gibson]

I kick myself for not buying one or two of the 308 14" twist barrels offered by Sarco a few years back, BSA manufacture I believe. Coulda-shoulda-woulda

Yeah, I passed on that deal also much to my chagrin also....

I was looking to build an AR upper with a 14" twist in .223 as it would handle the Speer 52 gr HP (it's a FB'd bullet and shoots just fine out of 14" twists in colder weather) and of course cast bullets but primarily for the M261 .22LR conversion device I have. Most all .22LR has not done well in the 7" twist AR except the 60 gr stuff. Most of the standard velocity .22LR does ok in the 9" twist if I swage them to .225. Most all .22LR does very well in a 12" twist AR but I tried some in a 14" twist 24" varmint barreled AR and they did extremely well at 50 yards. However, I came across the M16 upper with a 12" twist for a decent price in Hattisburg, Missippi last year and took a chance on it. Turns out it was a very good deal as it not only shoots the cast 225462s very well but also most .22LRs including the high velocity HPs. I've 30+ of the 10 round magazine adapters which I've put in 20 round AR mags. Makes for some interesting jack rabbit "gunning":bigsmyl2: The 225415s at 2150 fps are also very deadly on jacks but I don't have to chase brass with the .22LRs:bigsmyl2:

A 14" twist competition upper with the gas port farther out like they do on them would be my idea of a perfect cast bullet AR in .223, better yet in .222 Rem for the longer neck to keep all the lube grooves and GC in the case neck. Should be able to push the 225462 or the 225646 upwards of 25-2600 fps with very good accuracy. Just my thoughts but maybe someday I'll do it.....

Larry Gibson