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Posted: 8/19/2004 8:06:13 PM EST
Can anyone tell me if RR ar's have a sear block in the reciever?

Just for info, Also my Department has purchesed RR M4's and they have a new feature that I'm new to in the upper receiver there are two notches that have been machined out. If you notice on a regular AR you may have feeding problems with rounds striking the upper reciever just above the magizine well my bushmaster has two points of impact that you can see the finish has worn where the rounds are double stacked in the magizine and strike every now and then its not a big problem for FMJ's but if you use lead nose soft points you will have problems well getting back to the topic they have machined the two strike points out and made a "feeding ramp" it looks like it will work let me know if Rock River isnt the only one doing this
Link Posted: 8/19/2004 9:35:12 PM EST
you mean like this?



But, if you buy the stripped upper, it doesn't come with them machined, you get to Dremel them in yourself! Who hasn't always wanted to dremel their gun!

Link Posted: 8/20/2004 5:28:46 AM EST
[Last Edit: 8/20/2004 5:34:56 AM EST by zrxc77]

Originally Posted By jmboom:

...they have machined the two strike points out and made a "feeding ramp" it looks like it will work let me know if Rock River isnt the only one doing this



Take a gander at THE thread on M4 feed ramps and all your questions will be answered.

ETA - Regarding your question about sear blocks: Yes, RRA lower receivers have a high shelf.
Link Posted: 8/20/2004 5:40:05 AM EST
no sear block, and M4 cuts are not really needed
Link Posted: 8/20/2004 5:54:04 AM EST

Originally Posted By Leisure_Shoot:
Who hasn't always wanted to dremel their gun!



While Dremels definitely have their place in a good gunsmith's hands, I share your sentiment on the potential overuse/abuse of Dremels that has been shown occasionally on these forums.
Link Posted: 8/26/2004 5:49:29 PM EST
Ok thanks for the info on the feed ramp but on the sear block do the new RR's have them because bushmaster doesnt do they? is colt the only one adding those now adays
Link Posted: 8/26/2004 7:16:26 PM EST
Well, comparing my RRA's lower to the pictures on quarterbore.com, I thought the RRA had a high shelf, but maybe I was wrong. So, I will just post pictures and let you decide.

Here is an overall view into an RRA lower purchased this May:



Here is the depth of the shelf:



Due to some parallax caused by the thickness of the ruler and the angle of the camera, the dimensions are a little tricky to read. The actual dimension from the shelf to the bottom of the take-down pin hole is 1/8". The dimension from the shelf to the top edge of the receiver is 1/2".

Here is the width of the shelf:



And although your question about the feed ramps has already been answered, here is another picture of the dremmel feed ramps:



I hope this helps.
Link Posted: 8/27/2004 8:13:49 AM EST
The pics are of a high shelf reciever. Most current makers have adopted the high shelf as a quick and easy way to prevent use of a DIAS. Bushie and DPMS are still using the thick right wall bump as a (totally useless) DIAS impediment. A couple of the smaller producers have also gone to this mathod, to improve sales, I guess.
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