AR Sponsor
Posted: 4/14/2010 7:18:54 PM EDT
Hey guys, I was trying out the function of a new mag by just cycling a few rounds and I noticed that the bullets (55 gr. fmj) were very scratched and one with a fairly deep scratch. I was wondering if this could be bad for accuracy and if a possible fix would be to enlarge and smooth the feed ramps 
|
| odds are that its not happening when the round is being chambered, its happening when its being extracted / ejected. normally it would just be the case without the bullet present during extraction and ejection. also, cycling by hand is alot different than when the gun cycles normally during fire. |
|
Quoted:
odds are that its not happening when the round is being chambered, its happening when its being extracted / ejected. normally it would just be the case without the bullet present during extraction and ejection. also, cycling by hand is alot different than when the gun cycles normally during fire. I didn't think of it the way you explain it which is logical, so I tried 2 clean rounds with a magpul, that would kind of eliminate any scratch from the magazine, that said I checked the bullets with an 8 to 1 magnifying glass, out of 17 total scratches most of them very light there were 6 fairly deep, I was able to determine the direction of these scratches due to the way the ripples (for lack of a better term) pointed back towards the brass casing, meaning they were done in the feeding direction, if caused by extraction they would point towards the tip, I'm not too worried about hard military rounds, I've shot about 75 rnds. with this upper and accuracy has been 2––2 1/2 groups at 100 yrds, I worry about using soft points in the higher weights they may really get damaged, I still wonder if widening the feed ramps slightly and polishing them would make any difference atleast to minimize any possible damage to the softer heads.
|
|
I have this same problem with a new DD non-HF barrel build. I was having trouble feeding with jams on first charge. Found that the feed ramp led to a very sharp bolt lug slot on the barrel extension leaving scratches on bullets (sometimes actually wedging themselves into that cut, requiring BFH tactics to extract.) Tried different mags and checked lower lock up placement of mag catch. Scratches look like two vertical lines running lengthwise on bullet. They match the slots for the lugs above the feed ramps. It is my belief that these need chamfer / radiused.
I replaced with a new Spikes spring and buffer. Slams home with authority now, but this was the first time in 22 years that I had that problem with feeding. In the future I will remove barrel and smooth out feed ramp lug edges on extension, and do so with every barrel I assemble from now on. And yes, gouging up a bullet will not help with its accuracy, but accuracy is a relative term. |
|
Quoted:
I have this same problem with a new DD non-HF barrel build. I was having trouble feeding with jams on first charge. Found that the feed ramp led to a very sharp bolt lug slot on the barrel extension leaving scratches on bullets (sometimes actually wedging themselves into that cut, requiring BFH tactics to extract.) Tried different mags and checked lower lock up placement of mag catch. Scratches look like two vertical lines running lengthwise on bullet. They match the slots for the lugs above the feed ramps. It is my belief that these need chamfer / radiused. I replaced with a new Spikes spring and buffer. Slams home with authority now, but this was the first time in 22 years that I had that problem with feeding. In the future I will remove barrel and smooth out feed ramp lug edges on extension, and do so with every barrel I assemble from now on. And yes, gouging up a bullet will not help with its accuracy, but accuracy is a relative term. Well I can understand your problem, I haven't actually had feeding problems once I have the first round in battery but if I don't let off quickly on first charge I too have experienced jamming, I don't feel my spring is light but your experience is further evidence of feed ramp problem, as far as I can see my barrel extension has plenty of meat that can be safely removed and smoothed and can be carefully done with a dremmel without having to remove the barrel, but that would depend on how comfortable a person would feel with a grinding tool. |
|
you can try it, but if you aren't having any real feeding problems to speak of and this isn't, i'm assuming, a competition/match grade rifle and you're not seeing any issues with accuracy, i would say leave it be.
ps we've all seen jams due to "riding" the bolt home, ever so slight as it may be, it can happen. |
|
Quoted:
you can try it, but if you aren't having any real feeding problems to speak of and this isn't, i'm assuming, a competition/match grade rifle and you're not seeing any issues with accuracy, i would say leave it be. ps we've all seen jams due to "riding" the bolt home, ever so slight as it may be, it can happen. You make a very valid point, but to me it's more than accuracy now, personally I 'm from the school of "if it ain't broke don't fix it", yet for the first time I have an upper which I don't trust to function reliably, I fully agree with your "riding" the bolt statement but this one has proven to be toooo sensitive on a few occasions, 75 rounds of one type of ammo is not a whole lot inspiring confidence, I want to achieve the same reliability as my old trusty carbine, regardless of what I feed it, it's always hungry for more, the only hiccups ever experienced have been with bad primers, this sucker just shoots and if you cycle live rounds it doesn't gouge any of them. |
RF, I understand. Reliability is everything to me. If the freakin' thing doesn't want to work 99% of the time why bother. The 1% should be when it his overused and dirty .
By the way, being a HP and CMP shooter I never use the charging handle to load a first round. I always lock back bolt to show chamber empty, and then release bolt on mag to charge. I don't "Ride the Bolt," which was the surprise to a first round not charging for me. (However HP rules have since changed, but I don't use this rifle for that.) Another thing about modern day mindset is to not polish feed ramps, which I have been doing since Bonzo was president. I don't see a reason not to, as you are just wearing in a contact surface now, rather than 1000 rounds later. Good luck with making it right. |
|
Quoted:
RF, I understand. Reliability is everything to me. If the freakin' thing doesn't want to work 99% of the time why bother. The 1% should be when it his overused and dirty .
By the way, being a HP and CMP shooter I never use the charging handle to load a first round. I always lock back bolt to show chamber empty, and then release bolt on mag to charge. I don't "Ride the Bolt," which was the surprise to a first round not charging for me. (However HP rules have since changed, but I don't use this rifle for that.) Another thing about modern day mindset is to not polish feed ramps, which I have been doing since Bonzo was president. I don't see a reason not to, as you are just wearing in a contact surface now, rather than 1000 rounds later. Good luck with making it right. Agreed 100%, as you state the idea is for the darn thing to work, I will personally polish all of my ramps from now on even if brand spanking new, no exception. 
|
AR Sponsor