Built a 6 arc upper using a shaw barrel and a bcm blem upper. Getting a pretty nasty cold bore flyer so trying to go back through it. Wanted to try lapping the receiver face and was wondering if anyone had a lapping tool that would work for the bcm that they would loan out. Only bcm I own.
BCM Receiver and Lapping
- Thread starter Flyn289
- Start date
Pacific tool & gauge sells an undersized ar15 lapping tool that will fit in thermofit uppers.
I also had a recent build on a bcm demo upper and it had very poor accuracy with a lot of fliers. I switched the barrel to a SOLGW forged upper with Sons M89 rail but haven’t been able to test it yet. I have a feeling these demo uppers are fine for run & gun but maybe not precision builds? I noticed on one of the 2 bcm demo uppers I have the feed ramps have little chunks taken out of them…they are demos so YMMV
Saw pacific tool has them. Was hoping someone had one to lend out instead of buy one for one barrel. Not sure if it'll help my issue or not. Cold bore flyer then stack the rest in the same hole. Let gun cool down and it repeats. Been going through the gun and only thing I have found is rear scope ring screws were a little loose. Not sure how that was cause my issue though. Seems like it wouldn't group at all with the scope ring in mind
You never know, you may end up using the tool again in a few yrs. From my understanding lapping would mainly fix something like you having to adjust your scope an extreme amount U/D or L/R in order to sight it in. If you’re getting random flyers as your barrel heats and cools then something like adding a shim or bedding the barrel with high temp silicone, loctite 620, etc could help. Id also get an enhanced bolt carrier that prevents carrier tilt to rule that out as a variable (you can get an enhanced bcg from midwest industries for around $130).
All that being said if you’re going to bed/shim the barrel you may as well lap the receiver
I have a Wheeler lapping tool; lapped lots of BCM uppers, never had a need for a "special" reduced diameter tool.
But I've never measured the diameter of the tool either..............................works fine on every upper of numerous makes, that I've used it on.
MM
But I've never measured the diameter of the tool either..............................works fine on every upper of numerous makes, that I've used it on.
MM
You never know, you may end up using the tool again in a few yrs. From my understanding lapping would mainly fix something like you having to adjust your scope an extreme amount U/D or L/R in order to sight it in. If you’re getting random flyers as your barrel heats and cools then something like adding a shim or bedding the barrel with high temp silicone, loctite 620, etc could help. Id also get an enhanced bolt carrier that prevents carrier tilt to rule that out as a variable (you can get an enhanced bcg from midwest industries for around $130).
All that being said if you’re going to bed/shim the barrel you may as well lap the receiver
May have to look into that then. Had read some say they wouldn't work on the bcm thermofit stuff . Others said they are pretty loose on regular uppers. Who knows
FWIW I have the wheeler tool (purchased a few months ago) and it doesn’t fit in my bcm demo upper.
I have a Wheeler lapping tool; lapped lots of BCM uppers, never had a need for a "special" reduced diameter.
But I've never measured the diameter of the tool either..............................works fine on every upper of numerous makes, that I've used it on.
MM
And it does work on BCM's, with oil on the body & paying attention to getting it in absolutely straight.
Sorry for the mis-info..........may bad.
MM
But I've never measured the diameter of the tool either..............................works fine on every upper of numerous makes, that I've used it on.
MM
Your comment made me go & check mine, & it is NOT a Wheeler..............it is a Brownell's tool, several years old.
And it does work on BCM's, with oil on the body & paying attention to getting it in absolutely straight.
Sorry for the mis-info..........may bad.
MM
