New to AR-10 - NRA XTC shooter

[joey_the_kidd11]

Hi there. I'm seeking advice on my AR-10. I bought a Rock River LAR-8 Varmint A4 for NRA "Across the course" (XTC) shooting in the any rifle / any sight category. I'm a former NRA service rifle shooter, but due to a bad astigmatism in my right eye, I can barely hold the target at 600y with iron sights. This was my solution.

Now that I have background outta the way, here is my question:

Currently, I'm shooting Sierra 175 hpbt's in front of 41.7gr of 8208. These are kicking my butt in the rapid fire courses of fire. But I've read many opposing thoughts on the appropriate billet weight for a .30 cal 1:10t 26" barrel for a gas gun, and wanted to ask the experts here.

As to what use and range I'm looking to implement these loads, it's 200 and 300y I'm most concerned with. Superficially offhand and sitting positions. I'm quite happy with my 600y performance on the 175gr.

 

[lte82]

Tagged for later. I'll reply tonight.

 

[joey_the_kidd11]

Thank you.

This isn't a rush issue. I have until July 24 for load testing and practice. I'll be leaving for Nationals up at Camp Perry by then.

 

[Expert684]

Tried this back in the 90's with a AR 10 myself. The problem is the weight of the bolt carrier. Not the recoil of the bullet. I still shoot and own a few AR10 based weapons. I just ditched the whole XTC thing with the .308 platform, went the same gun in .223. Way better for your shooting cadence in your rapid fire strings. Today they may have different buffers and systems to control the carrier speed. I run adjustable gas systems on mine. Good luck!

 

[joey_the_kidd11]

I can keep my cadence and breathing pretty regularly even with the heavy 175's. I'm just looking to knock down the recoil and pressures a little bit for the shorter yard lines as I would with my service gun. I'm not only reducing bullet weight, but my powder charge as well. 41.7gr of 8208 is stout. And I have noticed some split casings and flattened primers. Recoil will reduce a measurable amount by reducing the weight of the bullet and charge, and at offhand I'll take whatever help I can get. But you are correct, as well. That bcg is MASSIVE. That much mass moving is going to create quite some force no matter what. I'm just looking to reduce it. My goal is to not get as much of a jump on the muzzle. (77's for 200 and 300, and 82's for 600 is what I used in service gun) I'm looking for something similar to that. But as I mentioned, when talking with people this past Sunday at the range, as well as reading, there is a fair amount of discrepancy as to what bullet weight would be appropriate for my particular setup while still achieving accuracy, consistency, and a reduction in noticed muzzle bounce.

 

[Expert684]

Try going with 168 or 155 match bullets on your 200 and 300 strings. Put a gas block with a regulator on it. I shut mine off, then opened it with one round in the mag until it allowed the bolt latch to engage. It slowed the carrier speed down, reduced recoil, and the gun cycles better because it was over-gassed.

 

[joey_the_kidd11]

168's is what I was leaning toward as I know for sure a 1:10t will spin them fine. I just wandered when posting the thread if any other weights lower than 168 would work without causing adverse barrel wear.

As for the gas block, I'm no gunsmith. And wouldn't know the first thing about installing or even utilizing something of that nature. That being said, I do know quite a few people that travel to Camp Butner (my home range) that are very competent in that regard and will get in touch with them.

Thank you for your input. It's greatly appreciated.

 

[Morale_Gear]

168's is what I was leaning toward as I know for sure a 1:10t will spin them fine. I just wandered when posting the thread if any other weights lower than 168 would work without causing adverse barrel wear.

As for the gas block, I'm no gunsmith. And wouldn't know the first thing about installing or even utilizing something of that nature. That being said, I do know quite a few people that travel to Camp Butner (my home range) that are very competent in that regard and will get in touch with them.

Thank you for your input. It's greatly appreciated.

Shoot any weight bullet you want, and don't worry about causing more barrel wear. Not likely at all to happen.

There are plenty of youtube videos on how to swap out gas blocks. Pretty easy process. The LAR's gas block isn't pinned on, which makes it a lot easier.

I had one of the first mid-length LAR-8s, but obviously never used it for Highpower.

 

[Tx_Flyboy]

Joey,

I also shoot a 308AR (DPMS based) across the course.

I use a lighter charge of AR-Comp (40.7gr) with 175s and have no problems with rapids. I bump the load up to 41.4gr for 600yards and 1,000yard prone matches.

I also use the same 41,4gr charge with 175s and 185 Bergers out of the AR-10 & M1A and have recorded my best strings with this combo...98-2X..

If you do not want to reduce the powder charge for the rapids, then you should get an adjustable gas block...that makes a BIG difference in recoil and will help with faster recovery.

Also, another choice is to shoot a ligher bullet. You'll be surprised at the accuracy of the 150gr Hornady soft points...i haven't shot them past 200yards and i am all sorts of impressed with them...the fact that they are cheap is another bonus. Of course, 150SSTs or 155AMAXs r much better choices if you want to reduce bullet weight

 

[joey_the_kidd11]

I don't mind reducing the charge. The 41.7 of 8208 is just the first load I found that worked and grouped well. Admittedly, I'm also still adjusting my positions for offhand and sitting. And fixing those first I'm sure will help. However, as I've stated, I've been advised by many to try lighter bullets to help even more.

I don't have any issue with the adjustable gas block suggestion, but right now my issue is funds. Pesky student loans...

How does the AR-Comp fair? I've heard the AMU is working up service gun loads with it and that the powder is much faster burning at least in .223. Was told that they had to drop nearly a grain and a half off of standard Varget/8208/4895 loads to keep from busting cases in half. I may have to pick up a pound for some added testing. The boss isn't gonna like this...

I'll pick up a box of 168's and 155's come payday, and maybe a pound of AR-Comp for a place to start. I know where I can get both pretty readily.

Thanks guys. Keep the input coming. I'm taking notes.

 

[Tx_Flyboy]

Joey,

Here are my suggestions in order of how i would try them;

1. Work on position...get it as stable as possible. Don't worry about time, get the fundamentals down first, and the time/cadence will take care of the rest.
2. If you have a ton of 175s laying around, i would first reduce my powder charge...0.5 to 1gr makes a BIG difference with the faster burner powders.
3. If you have to spend money, then get some lighter bullets. Even with the same powder charge as the 175s, the recoil will be substantially lower.
4. If items #1 to #3 does not work, then get an adjustable gas block...good ones r spendy ($100 + gunsmithing fees).

AR-Comp is a good powder. Faster burning than Varget or RL-15, but gives great velocity at the cost of being dirty...VERY dirty...builds carbon in places you dint think was possible. I have also shot my best groups with it, and unlike varget or RL-15, its available.

 

[joey_the_kidd11]

Definitely still adapting my position to compensate for the change in rifles. The match rifle sling I purchased was a huge improvement in of itself. But still have to get the finer points figured out. I'm only classified as an Expert, but shoot 748-750 reliably. Nipping at Master's door. So position refinement is always on my list.

I do have a considerable amount of available 175's as my dad uses them for F-Class and we split the cost of a large order some time ago as I planned to pick up F-Class with him. I also have some 168's as we bought 1000 of them and didn't care for then as much as the 175's. I will first reduce my loads on the 8208 for short line before I go spending money. Then work up some seperate 168 loads. That'll make my life easier with the honey.

Thank you very much Tx. You traveling to Perry this year?

 

[lte82]

If I were stuck with a 308, I would go for the lightest bullet possible for the standing and rapids. Maybe even a 135 match king. I would also go with the 155s for 600, as they may actually beat a 175 depending on how fast you can push them. Recoil wise they will also be less, leaving you with more energy to finish out the match focused. When I get fatigued I find it hard to tell what the conditions are doing, and that's when I have the tendancy to start throwing 8's or 9's. I tried the 308 briefly, but found it to recoil a lot more than my 223 no matter what I tried, and it now sits in my safe.

Also, if you ever want to jump up to a purpose built any/any rifle, check out the 6mm cartridges on the AR15 platform. They are extremely low recoil and blow the 308 away. I have a 6mm ar turbo that shoots lights out. I haven't taken it to a match yet, but in practice it feels almost like cheating. I have no doubts if I showed up with it I would jump to high master scores immediately.

Good luck at Perry. I will more than likely be in Canada this year, but I plan on going next year.

 

[Tx_Flyboy]

Joe, yes, i am going to Perry this year. Maybe we can meet up while there.

lte82 is spot on.

I missed the part that your are shooting a 308AR with a 26" barrel, putting you in match rifle category. I actually started out shooting the AR-10 in the service rifle class (20" barrel DPMS based M110 build) while i waited for my AR-15 to arrive...this was the basis of the advise i gave you before.

When your supply of 175s run out, i recommend moving away from the sierra line of bullets. Those bullet designs are old and hold back the 30 caliber chamberings...not bashing them or saying they aren't accurate or don't work, but they are outdated compared to the Bergers and the Hornady 178HPBTs, the 208AMAX and 208HPBT designs.

I am now a big Berger fan. I shot the 185Berger in front of 44.2gr Varget (or 41.4gr Ar-Comp) out of my M1A supermatch for the 1,000yard state match in Houston...while the 175s i shot the week before in practice was just going transonic (per feedback from the pits), the 185s were far more consistent, held better vertical and windage for me than the 175s.

The USAMU's 1,000yard load from a M110 (20" 308 AR) is 45gr Varget with 185bergers. This is the same load/rifle they used to set the 1,000yard record...200(highX count). So, as you can see, the 308 even in a 20" rifle can shoot and clean the 1,000yard target...you just have to be a shooting god to do it hahahahaha.

When you get a chance, run a ballistic program comparing the 185/175s at the same velocity (you can shoot em at same speed because they have the same bearing surface). With your 26" barrel, you should be able to get them up to 2,700-2,800ft/s without operating on ragged edge of pressure. You will be amazed by the difference in windage correction.

For the cost-conscious, the solution may be the 178gr Hornady HPBT. It has the same BC as the 190gr SMK bullet, but can be pushed about 100-120ft/s faster, you should also be able to get this bullet going close to 2,800ft/s if you use the right powders.

I would also check the throat of your rifle. My rifle was chambered with a looooong throat. So long, that i can shoot the 208AMAX at good enough speed to gain maximum wind advantage. If you are able to shoot the 208AMAX or 210Bergers, you won't wanna go back to the SMKs.

The Hornadys are about $10-$20 per box cheaper than the Bergers...you may want to buy a box of each of the 185bergers and 178HPBT (not AMAX).

Ar-Comp will not be the best powder for all this...that distinction belongs to 2000MR & RL-17. Varget is your best bet for temp stability but at the cost of lower velocity.

There are better calibers for shooting XTC, and i too would prefer to shoot a 6mm of some flavor (check out John Scandale's 6mm). It's based on 6.8SPC brass necked down to accept a 6mm bullet. It gets you about 85-90% of 243Win velocities with a better barrel life...still all these calibers will be ultimately more expensive than the .308 due to shorter barrel life.

Since you mentioned cost as being a concern, it does not seem likely you will be buying another rifle or switching calibers. I would work with what you got until its time to re-barrel or buy another rifle. The lowly .223/556 is still a good choice for XTC and will be about 50% cheaper than shooting the 308s.

 

[Greg Langelius *]

You don't need a stratospherically high BC on the bullet you shoot at shorter distances, ala 200/300yd. Seriously consider something much lighter for the rapid fire stages, like a 150/155SMK or even the newer 135SMK. I am shooting a 125SMK at 250yd. What you may lose n wind backing, you could more than regain from an easier/quicker recovery from recoil.

Greg

 

[Tx_Flyboy]

Greg,

My advise on high BC bullets is for the long lines, 600yards and 1,000yards. (I hope that's clear on my post above)

I told the man to look at less powder or lighter bullets (or both) for the short lines...

 

[Tactical]

Try either 155 Scenars or 155.5 Bergers. They will shoot great and cut down recoil. I would go with either N140 or H4895 for powder. Fast for short barrel light bullet gas system weapons.

 

[joey_the_kidd11]

Thanks for all your input, gents.

I will certainly look into those projectiles. You aren't the first to recommend the 155AMAX's. As far as my long line ammo goes, I'm not set on the 175's, they're just what I had. I'm by no means a Sierra Fan Boy, however they are our primary sponsor for the NC junior hp team, which my father is the head coach of, so I order through the team and hence get a small discount. I have no problem with working up some new loads for 600y either, and don't have to stick with Sierra's. From the same guy who suggested this weekend at Butner that I go to 155's for short line, he suggested a 200gr or there abouts for my 600y load.

I believe I might have to pick up some 155's as they seem to be all around recommended. As well as a work up load of the 168's I have. As far as powder, I've got a little over 6lbs of 8208 left, and will be using that.

 

[joey_the_kidd11]

Okey dokey. So, I acquired some Nosler 155gr HPBT's for a mere $32. Figured that was a decent price, and 100 of them should be more than enough for me to be able to determine if I like them as well as try 2 or 3 different powder charges behind them. I figure, I'll load some Sierra 168's at around 40.8, 41.0, and 41.2 of 8208. Based off the fact I'm running 41.7 across the board with 175's, I figure I need to drop down the short line load anyhow. I'll load the 155's at 41.0 and 40.5 with 8208. I figure that'll get my in the 2700fps range easily. Though I wish I had a ballistics program to help me figure that out, or knew someone with a chrono...



That was this past Sunday out at Camp Butner, NC. I don't figure that's too shabby for only my second time with the rifle back at the 6 as well as a new match sling and new jacket. That's also with the 175's at 41.7. As you can tell, I'm not the best at wind reading...



And here is my baby, since I didn't upload a pic to begin with. The bipod is just for show, I can't use it in my class of shooting. Sling hold only. And that's an Osprey International 6-24x50 on top. Nothing special, it's just what I had laying around and I know it can take the abuse of a .30cal.

Anyhow. Anything else I'm missing or more suggestions??

 

[Tx_Flyboy]

Great Shooting Joey!

195-7X is nothing to sneeze at. Guessing you shot that score with your scope?

How did the recoil of the 155s feel?

 

[joey_the_kidd11]

Yessir. Scope stays on, bipod doesn't. I've been working on loading the 155's, haven't gotten them done nor will I have range time until early June.

 

[AMMOWASTER]

Have you looked into a low mass operating system possibly in combination with a adjustable gas block? Pretty common in 3 gun and the recoil reduction is pretty significant according to those I have talked to. JP's match guns with there operating system and muzzle brake allows shooters to sight their own hits out to 300 yards.

I also agree that down the road you might want to play with a new caliber. 260/6.5 Creedmoor or 6XC/6m Creedmoor. The 6mm's will have a noticeable difference in recoil.

 

[sinister]

A 7.62 will abuse the snot out of you, in-line AR stock or not.

For offhand and sitting you can try a light flat-base benchrest bullet. A 135 or 155 (2155) Sierra Match King might not be a bad proposition either. 168s are the standard if you're buying off-the-shelf ammo.

A 175/178, 180/185, or 208 A-Max will take you to 600 at the price of a little more recoil, but in prone and single-feed you won't be beat up.

An XH-308 7.62 buffer can help keep your sights on-target during the rapids and lower the abuse on your 600 slow-fire brass.

 

[joey_the_kidd11]

An XH-308 7.62 buffer

I've not heard of this. Have to give it a look.

600 isn't a big worry for me as of right now. I'm quite happy with the performance thus far, and other than refining my new position and dropping down my charge a bit (41.7 has proved to be a wee bit on the hot side), I don't plan on making any further modifications to that load. Now, in future terms after Nationals, I'll have around 3-4 months of play time to work new loads with the aforementioned 178's and 185's. Not trying to be hard-headed, but the 175's are working pretty good. However, that being said, I will give some 178's, 185's, and possibly 200's a look in the future.

Nor have I heard of recoil reduction systems or of their use in NRA HP stuff. I'll have to do some digging.

As I posted a bit ago, bought some 155's and sequestered some 168's, both for some hand loading. Working up some loads for those now and will be putting them to use in June