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Posted: 10/2/2010 11:45:41 AM EDT
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I am a new AR owner. I have a used DPMS M4 w/A2 upper in 5.56 and having some serious grouping issues. Took it to the range today and was firing American Eagle and Tula 55gr ammo (both brands of ammo had the same results). I have fired different ARs prior with good accuracy results.
From the bench rest, the shots would not group and the impacts would vear all over the place (8-10" up, down, side, etc) at 50 yards and double that at 100. When I would adjust the sights, the shots would vear greatly as compared to what it should do (i.e. 1 click on the front post would cause the shots to rise 5+ inches). I do not know the rate of twist as the barrel does not show it (was painted by previous owner). Rifling looks o.k. and the sight bases appear tight and was firing from a rest with the handgaurds touching the rest and maintained sight picture. Any adivice? |
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I've never had any issues with the 55gr bullets out of my 1/7 twist rifles.
How many rounds does the barrel have through it? Has the bore and chamber been thoroughly cleaned lately ... could have some copper fouling built up somewhere? This is what bad copper fouling build up looks like in a bore. 
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| I do not know how many rounds have been through it as I bought it used...it does look like it has been fired alot. The gun smith said the barrel looked ok, not great, but ok. He noticed some nicks at the crown and recommended it be recrowned or replaced. I do not have a scope to see down the barrel for copper fouling...I did clean the chamber good. How do you know when it is time to replace the barrel? The bore brush did fit a bit loosely when cleaning. |
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I do not know how many rounds have been through it as I bought it used...it does look like it has been fired alot. The gun smith said the barrel looked ok, not great, but ok. He noticed some nicks at the crown and recommended it be recrowned or replaced. I do not have a scope to see down the barrel for copper fouling...I did clean the chamber good. How do you know when it is time to replace the barrel? The bore brush did fit a bit loosely when cleaning. Have someone check the headspace. If there are nicks at the crown that could be the issue right there ... will the gunsmith re-crown it and for how much? if he can't and you want someone good send it to ADCO they do good work and do crowning for like 25.00 but you will need to dis-assemble the upper and send only the barrel otherwise they charge you more. Though being it's a DPMS barrel (they work fine but don't think they have the quality standards of some other companies) and not really knowing the round count or history of the barrel I'm not sure I personally would invest the time and money to try and fix it .. but hey it's your rifle you decide. |
DPMS is OK ... they aren't the worst .. but they aren't the best either. I've definitely had my issues with DPMS stuff but the only major problem was with a barrel that the chamber was WAY to tight on ... once the bolt chambered a round and fired it ... it couldn't extract it. I had to take a cleaning rod and get the case out that way. If you had a Sabre Defense, BCM or Daniel Defense barrel and said the crown was nicked I would say re-crown that puppy and hope that was the problem (which it very likely is) but I don't think I would spend the time, effort and money on the used, unknown round count DPMS barrel.
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Ditto, the crown is only 1/3 of the match, and you have to consider bore condition, and even throat erosion as well.
As for a barrel, what at you trying to go after? If longevity, then something in a chrome plated bore and chamber would the ticket. On the other side of the coin, you have broach cut custom match barrels that will tack drive, but for only about 4K rounds before giving up the ghost. |
| I am looking to get the rifle to give me decent accuracy from iron sights...2-4 MOA with surplus ammo is fine. Will chromed lined barrel help with the extraction of steel cased ammo? What twist rete should I get considering as I will likely use surplus/cheap ammo? |
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I personally would go with a RRA barrel with the "wylde" chamber for using a steady diet of surplus ammo ... it's a little more forgiving in my experience with the cheaper steal and coated ammo's and you can use surplus 5.56 ammo also. Most of the surplus ammo I have used has been 55gr M193 and that is a pretty universal bullet weight in my experience ... I have shot it pretty accurately from both 1/7 and 1/9 twist barrels and I know some people use it in the retro 1/12 twist barrels accurately as well (which is what it was designed for IIRC).
ETA hope that helps. 
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1/7 or 1/9 twist both work. 1/7 can and often does work with lighter stuff, and the 1/9 can and often does work with the heavier stuff, it really just depends on your barrel.
Edit: Chrome lined helps make cleaning easier IMO and you get some insurance from the elements. |
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1/7 or 1/9 twist both work. 1/7 can and often does work with lighter stuff, and the 1/9 can and often does work with the heavier stuff, it really just depends on your barrel. Edit: Chrome lined helps make cleaning easier IMO and you get some insurance from the elements. Complete backwards, and the faster twist is for heaver ammo, not lighter As for chrome plating, has nothing to do with cleaning since it will guild as fast as an un-plated bore, just an unplated bore has a RC hardness of around 40, while a plated bore has a RC of 65 plus, meaning that the rifling will not erode as fast with the plate bore, making the life span of a plated bore much longer than that of one without such. As for the draw back to plated bored, the plated is not as uniform, meaning that a plate bore barrel may not shoot as well as one without plating. |
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1/7 or 1/9 twist both work. 1/7 can and often does work with lighter stuff, and the 1/9 can and often does work with the heavier stuff, it really just depends on your barrel. Edit: Chrome lined helps make cleaning easier IMO and you get some insurance from the elements. Complete backwards, and the faster twist is for heaver ammo, not lighter As for chrome plating, has nothing to do with cleaning since it will guild as fast as an un-plated bore, just an unplated bore has a RC hardness of around 40, while a plated bore has a RC of 65 plus, meaning that the rifling will not erode as fast with the plate bore, making the life span of a plated bore much longer than that of one without such. As for the draw back to plated bored, the plated is not as uniform, meaning that a plate bore barrel may not shoot as well as one without plating. I was stating that a 1/7 will work with light ammo as well and ditto for 1/9 with the heavy stuff. Not 1/7 is for light and 1/9 is for heavy. Guess it didn't come out right. |
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Thanks for the replies. I found a new colt barrel that is cromed for $225 w/sight. It is 1 in 7 but is 14.5 inches. When the muzzle break is added, does it make it legal? I was told, by the seller, chrome helps with extraction of steel cases. As long as the break is 1.5" and it's pinned or welded on it will be legal. I guess the chrome lining probably helps somewhat with extraction ... but chromes main job is for ease of cleaning, corrosion prevention and the general longevity of the barrel. |
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Thanks for the replies. I found a new colt barrel that is cromed for $225 w/sight. It is 1 in 7 but is 14.5 inches. When the muzzle break is added, does it make it legal? I was told, by the seller, chrome helps with extraction of steel cases. As long as the break is 1.5" and it's pinned or welded on it will be legal. I guess the chrome lining probably helps somewhat with extraction ... but chromes main job is for ease of cleaning, corrosion prevention and the general longevity of the barrel. Before buying the barrel, check to see if the barrel is a M-4 unit with extended feed ramps, and your upper receiver also has extended feed ramps cut into it as well. Really, short of adding extended feed ramps into the upper receiver, let the receiver type ramp system (if it has extended ramps or not) dictate the barrel extension type for the replacement barrel. |
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Before buying the barrel, check to see if the barrel is a M-4 unit with extended feed ramps, and your upper receiver also has extended feed ramps cut into it as well.
Really, short of adding extended feed ramps into the upper receiver, let the receiver type ramp system (if it has extended ramps or not) dictate the barrel extension type for the replacement barrel. [/quote] H How can I tell this? I was planning on purchasing the Colt M4 type barrel or any number of M4 barrels from Midway. |
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Follow-up to the accuracy issues...
I spent an hour cleaning the bore with CR10 cleaner. I cleaned it prior using just CLP (and thought it was clean). I took it to the range using the same ammo (55gr American Eagle and Tula) and there was a huge difference. I am now getting 3-4 MOA with the American Eagle and about 5 with the Tula. I am suprised what a good cleaning to the bore can do. Thanks again for all or your inputs. |
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Talk to the guys at adco. I think they can solve your issue. They can put a new barrel on for you. Not that much $$$ considering the alternative. Of course they sell complete Spikes uppers last I checked for <$500.
Edit: Sorry I didn't realize you figured it out. Great
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Quoted:
Follow-up to the accuracy issues... I spent an hour cleaning the bore with CR10 cleaner. I cleaned it prior using just CLP (and thought it was clean). I took it to the range using the same ammo (55gr American Eagle and Tula) and there was a huge difference. I am now getting 3-4 MOA with the American Eagle and about 5 with the Tula. I am suprised what a good cleaning to the bore can do. Thanks again for all or your inputs. That's good to hear  ... people sometimes forget how important it is to REALLY clean the chamber good ... they'll run a bore snake through it and think it's GTG.
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Quoted:
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Follow-up to the accuracy issues... I spent an hour cleaning the bore with CR10 cleaner. I cleaned it prior using just CLP (and thought it was clean). I took it to the range using the same ammo (55gr American Eagle and Tula) and there was a huge difference. I am now getting 3-4 MOA with the American Eagle and about 5 with the Tula. I am suprised what a good cleaning to the bore can do. Thanks again for all or your inputs. That's good to hear ... people sometimes forget how important it is to REALLY clean the chamber good ... they'll run a bore snake through it and think it's GTG.Your right Gator. During that hour of cleaning, the patches kept coming out black and gritty. I thought it would never end (I still need to re-clean as they started to come out green and I just got tired and had to stop). Possible that the previous owner never cleaned it. Beside lead fouling, I did not think a dirty bore could cause that much of an accuracy problem. |
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