Tightening up an AR

velocette · April 25, 2014, 10:41 AM

I use my AR .223 rifle for target shooting. Its fitted with a Shilen 20" match barrel, Geissele trigger and a good scope. Looking at any possible way to tighten up my groups, I checked the fit of the upper to the lower. I found the front takedown / pivot had .006" of side to side play / clearance.
SO, I looked about and found at McMaster Carr, round stainless steel shims in various thicknesses. 380MC018 for .003" thick X 1/4" ID & 3/8" OD;
380MC034 for .005" thick x 1/4" ID & 3/8" OD. I tried to install two .003" shims, one each side of the front lug of the upper & found it virtually impossible to get both in. So I installed an .005" shim on the left side. No slop wobble or wiggle.
A little more slop taken out will very slightly improve consistency shot to shot, and that's what wins matches.

Roger

CowTowner · April 25, 2014, 01:09 PM

Have you considered something like this?
http://www.midwayusa.com/product/339...tainless-steel

FrankenMauser · April 25, 2014, 01:35 PM

You could try cutting your own shims from some 'plastic' shim stock.
At McMasters Carr, the thicknesses you would need are under "color coded plastic shim stock".
They don't specify on the website, but it's likely to be nylon or delrin sheet. Either would be fine in a firearm.

velocette · April 25, 2014, 02:33 PM

Cowtowner;
That JP pin is on its way from Midway. I ordered it at the same time I ordered the shims from McMaster Carr. McM was MUCH faster shipping though.
I'm looking to get 10 round groups under 1/2",

Roger

April 25, 2014, 10:41 AM	#1
velocette Senior Member Join Date: May 25, 2007 Location: South Florida Posts: 924	Tightening up an AR I use my AR .223 rifle for target shooting. Its fitted with a Shilen 20" match barrel, Geissele trigger and a good scope. Looking at any possible way to tighten up my groups, I checked the fit of the upper to the lower. I found the front takedown / pivot had .006" of side to side play / clearance. SO, I looked about and found at McMaster Carr, round stainless steel shims in various thicknesses. 380MC018 for .003" thick X 1/4" ID & 3/8" OD; 380MC034 for .005" thick x 1/4" ID & 3/8" OD. I tried to install two .003" shims, one each side of the front lug of the upper & found it virtually impossible to get both in. So I installed an .005" shim on the left side. No slop wobble or wiggle. A little more slop taken out will very slightly improve consistency shot to shot, and that's what wins matches. Roger __________________ Trigger control + Breath control + Sight alignment = Gun Control. http://www.hrpclub.info/ NRA Smallbore Prone Master, High Power Master

April 25, 2014, 01:09 PM	#2
CowTowner Senior Member Join Date: October 17, 2007 Location: Cowtown of course! Posts: 1,747	Have you considered something like this? http://www.midwayusa.com/product/339...tainless-steel __________________ NRA Chief Range Safety Officer, Home Firearms Safety, Pistol and Rifle Instructor *“Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life......”* President John F. Kennedy

April 25, 2014, 01:35 PM	#3
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	You could try cutting your own shims from some 'plastic' shim stock. At McMasters Carr, the thicknesses you would need are under "color coded plastic shim stock". They don't specify on the website, but it's likely to be nylon or delrin sheet. Either would be fine in a firearm. __________________ Don't even try it. It's even worse than the internet would lead you to believe.

April 25, 2014, 02:33 PM	#4
velocette Senior Member Join Date: May 25, 2007 Location: South Florida Posts: 924	Cowtowner; That JP pin is on its way from Midway. I ordered it at the same time I ordered the shims from McMaster Carr. McM was MUCH faster shipping though. I'm looking to get 10 round groups under 1/2", Roger __________________ Trigger control + Breath control + Sight alignment = Gun Control. http://www.hrpclub.info/ NRA Smallbore Prone Master, High Power Master