AR Sponsor
Posted: 11/3/2009 5:40:17 PM EDT
|
I recently built my first rifle of the following components:
Mohawk lower RRA LPK and A2 buttstock kit RRA A2 National Match upper half Assembly of the lower went off without a hitch, everything fit easily. Tested the magazine catch using a GI 20 round mag, it worked fine. After fitting the RRA NM upper half everything seemed to fit and work properly except for the magazine insertion. The mag would not insert fully into the receiver even with a good, solid smack. Close examination revealed that the bottom of the upper RRA receiver protruded slightly into the magazine area and stopped the magazine from inserting fully. Marks on the mag and upper receiver indicated they were hitting each other. It appears the upper protrudes into the magazine area just enough to snag the front lip of the magazine and stop it from going any further up into the receiver. Searching here found a couple of posts mentioning this issue (upper receiver protruding into magazine area preventing full insertion of the magazine) but nothing about how to remedy the issue. Do I have an out of spec lower? Out of spec upper? Any assistance appreciated! |
|
Take a look at the front inside edges of the lower receiver mag well to the upper receiver mag well portion. The two should be on the same plain, and if the upper receiver front mag well edge is protruding over the lower receiver top edge (into the mag well void opening), one of the two is out of spec.
RRA has a batch of uppers that had this problem (milled incorrectly), so best guess would be that it's the upper receiver out of spec. |
|
Accu-wedge causing the problem?
Well, this morning I dug out my digital caliper, scrounged up what blueprints I could find online, and decided to measure everything to be sure I was sending back the defective or out of spec part rather than a good part. I wasn't able to find blueprints for the upper but the lower blueprints here on this site seemed to match everything I measured on my lower (Mohawk Armory). The measurements from the verticle centerline of the pivot pin holes to the front face of the magazine well and the face of the upper that was protruding into the magazine area were within .000" to .003" of each other each time I measured. Keep in mind these measurements were taken by hand and eye with an inexpensive digital caliper. When taking the upper and lower apart I removed the Accu-wedge I had used in the original assembly to remove a very small amount of slop between the upper and lower when assembled. After measureing and finding the measurements so close I reassembled the upper and lower without the Accu-wedge and tried a magazine. It popped right in with a light smack on the bottom. When I pressed the magazine release the magazine didn't fall out on its own but as soon as I touched it to remove it the magazine did fall out without me having to pull on it. The magazine was a brand new NHMTG 20 round mag. I repeated the magazine insert and release 30 times. After that the magazine would drop out when the magazine release was pressed without any assistance other than gravity. Examination of the top front of the magazine revealed the parkerizing worn off at the top front corners of the mag down the front of the mag for a distance of approx. 1/8 of an inch with very, very faint wear visible in the annodizing of the rear face of the upper receiver. I had to use a powerful magnifying glass to see the wear in the annodizing. A second magazine, also a new NHMTG 20 rounder produced the same results. A bit tight at first but after several insertions and removals it also would insert, lock in place, then fall out of its own weight when the magazine release was pressed. The wear on the second magazine was similar to the first. Wear was visible on the front face of the magazine at the top outer corners down approx. 1/8" with very little wear between those two areas. I measured the two "worn" magazines from front to back and compared those measurements with two untried new NHMTG mags. The measurements varied from 2.380" to 2.385" with the smaller measurement being the "worn" mags and the larger the new mags that have not been inserted into the receiver. So, my question at this point is if the removal of the accu-wedge and the bit of wear on the magazines lets everything fit am I within acceptable tolerances on everything such that the weapon is safe to fire? All help and opinions appreciated! |
|
Quoted:
I recently built my first rifle of the following components: Mohawk lower RRA LPK and A2 buttstock kit RRA A2 National Match upper half Assembly of the lower went off without a hitch, everything fit easily. Tested the magazine catch using a GI 20 round mag, it worked fine. After fitting the RRA NM upper half everything seemed to fit and work properly except for the magazine insertion. The mag would not insert fully into the receiver even with a good, solid smack. Close examination revealed that the bottom of the upper RRA receiver protruded slightly into the magazine area and stopped the magazine from inserting fully. Marks on the mag and upper receiver indicated they were hitting each other. It appears the upper protrudes into the magazine area just enough to snag the front lip of the magazine and stop it from going any further up into the receiver. Searching here found a couple of posts mentioning this issue (upper receiver protruding into magazine area preventing full insertion of the magazine) but nothing about how to remedy the issue. Do I have an out of spec lower? Out of spec upper? Any assistance appreciated! Do you or a friend have another rifle that you can swap parts with to narrow this down ? God bless Wyr |
|
Quoted:
Do you or a friend have another rifle that you can swap parts with to narrow this down ? God bless Wyr Yes, I do, but after talking to the guy at RRA I'm getting the feeling it's the upper. He didn't seem at all surprised and immediately told me to ship it back on their dime so they could check it. I got the feeling he's seen this before. Either way he was quite helpful and immediately said to send it back so they could check it. If it turns out that isn't the problem I'll try the lower on someone else's upper but all the measurements on the blueprint for the lower on this site checked out when I measured the lower from Mohawk. |
|
Well, I got the upper half back a few days ago from RRA. The enclosed letter said they replaced the bolt carrier group, no explanation as to why. I didn't think the BCG would make any difference in the problem I'm having and after reassembling the rifle found that it didn't. I still had the exact same problem. A call to RRA was no help either, all they could tell me was the same thing that was on the letter, bolt carrier group replaced, no idea if the tech even looked at the area that was at issue. The marks are still faintly visible on the inside of the upper receiver where the front of the magazine is snagging. I tried the upper on two different Colt lowers and had the same problem.
I think I'll just take a file to it and remove those few thousandths that are causing the problem. I understand that any company will produce a product now and then that has a problem but it really pisses me off when they can't fix it. I didn't buy this rifle so I could spend weeks shipping it back and forth. I want to shoot the damn thng. |
AR Sponsor