So I screwed up (bought upper w/o M4 feed ramps)

As I understand, M4 feed ramps are only necessary with the high rate of fire of fully automatic M4s. Its nice to have, but I don't think I've ever heard of someone having problems because they didn't have them (especially in a varmint rifle).

NM, didn't realize you didn't have a barrel yet and mistakenly thought you had A2 style feed ramps on the non-existent barrel & M4 cuts on the upper.

Got this from another site, explains it well. I think you are OK.

Just get an A2 barrel. Larue purposefully omitted the M4 ramps on the OBR to maximize accuracy and because they weren't needed for reliability.

Check out Lilja barrels at www.riflebarrels.com. According to their site they are now threading their bull barrels. Their barrels are amazing!!! Have a 24" bull on a custom build of mine and it holds 1/4 moa with no problem. if you would like some pics as evidence PM me with your email and will send you some.

Eddie

Getting a raw barrel threaded is not a big deal. OTOH something like an AK with a pressed in barrel is a lot more trouble -- I know people sometimes use coaxial cutters and dies with bore fitting pilots, but this will never match the quality and concentricity you can get with a good lathe and 4-jaw chuck.

So I'd suggest getting the barrel you really want and have it threaded before you install it.

OP, I don't see that as a problem

Check out RRA NM 20" barrel with Wylde chamber. At least as accurate as their bull barrel and saves about 1# weight. My first build was an 18" bull. Wish I'd gotten the RRA NM barrel instead. (and it is threaded)

https://www.adcofirearms.com/itemdetails_q.cfm?inventorynumber=67

Arizona_Mike said:

Thanks MErl. A picture really is worth 1000 words and matches what I was picturing in my mind except for the steepness (the M4 cuts seem to be the same slope but go deeper toward the chamber).

I'm not going to find a threaded .223 Wylde varmint bull contour so I think I'm going to go with the Squad Designated Marksman (SDM) Contour: Fluted bull to the gas port and .730 for the last 8". This will still allow me to use an adjustable gas block to tame the extra long gas pulse (esp with a suppressor).

Mike

Click to expand...

Having been a SDM I can say this setup is great. Not terribly heavy and still really accurate.

Back to the M4 feedramps: I recently bought a 5.56 barrel from a company called Sota barrels. Had previously bought a .300 Blackout barrel from them and like it.

On their website, they claim that all their barrels have M4 feedramps. Having no reason to verify that my new barrel had M4 ramps, I went ahead and installed it on an upper with M4 ramps. Got to the range and ran into a plethora of feeding problems...lots of setbacks.

One eyeballing of the extension-to-receiver mating revealed the aforementioned "ledge" caused by a non-M4 barrel extension mated with an M4 receiver.

Removed the barrel and took a good macro pic of the feed ramps, which were obviously not M4. Sent the pic via e-mail to Sota. Got an e-mail back saying that they couldn't tell from the pic if they were M4 feedramps or not, and that they'd need a side view of the barrel. I suspected right then that they didn't know an M4 feedramp from an elephant's butt.

Sent that barrel back and they sent me another, which they assured me would have M4 ramps. Didn't even bother to install the replacement, as it obviously didn't have M4 ramps.

Sold the new bad barrel to a friend of mine at a loss. He had a friendly gunsmith recut the ramps into M4 ramps.

Never heard back from Sota when I notified them about the second barrel. Worst customer service of any company with which I've ever done business...including Botach!

Here's a pic of the second barrel, simply mated, but not installed. Looks just like the "bad" illustration in post #5, doesn't it?

Here is a couple pics of my SDM-R I had in 05. Very accurate with M262 and could easily hit a man sized target out to 800 meters. Only thing really holding it back at range was the ACOG. They are AWESOME scopes but not made for real long range precision.

I have a H buffer out of my 6920 if you want to give that a try? Where are you in Az?