I have two BCG: One is a lightly used Colt, the other is a brand new G&R group. I am thinking of using one or the other in a new BCM upper with only 100 rounds through it.
Since the Colt bolt is probably superior to G&R, does it make sense to go with it even though it’s used?
Here are the photos of Colt BCG:
Any idea how many rounds have been through the Colt? Personally I am a fan of HP/ MPI inspected bolts but I think either of them would be good to go.
I PREFER USEING A NEW BOLT ON A NEW UPPER. but WTF do I know anyway .
Since its a new upper and BCG I would just drop the G&R BCG in and check headspace…and run it.Save the used Colt bolt as a backup/spare.
I think a couple of hundred rounds through the bolt and 100 rounds through the upper.
I cant get your pictures to load…probably my old computer.
If the Colt bolt has that little amount of wear/use on it ,I’d certainly headspace check and run it.Like Iraqgunz,I also much prefer known manufacture HPT/MPI bolts.
That being said. I would go with the Colt bolt and use the other for a spare. I encourage you to do a headspace check with the proper gage. Chances are it’s not necessary, and since I have gages it’s easy for me to say. But, I don’t like leaving things like that to chance.
Exactly… If they were both brand new it’d be easy. Whenever using a used bolt and/or used barrel you always want to check headspace to be safe.
Just received M16 maximum headspace gauge from Bill Ricca. The Colt bolt would NOT close on the gauge. So the rifle / bolt combo is good to go!
Also tested my other rifles, none of them would close either. Does the chamber have to be 5.56 for the gauge to be valid? Would it work with a Wylde or a .223 chamber as well.
Another thing that got me thinking - what could cause improper headspace when using a used bolt with a new upper?
Thanks.
Headspace dimensions are the same for any 5.56 or .223 chamber. The only differences between chamber dimensions in .223, 5.56, Wylde, etc are in the throat area.
I am no technical genius but I have seen Colt M4 carbines here in country being used by a large company fail when they used .223 commercial gages and pass when they used a GI headspace gage. YMMV.
There are dimensional differences between civilian and military headspace gauges. In my opinion the absolute best gauge to use for most of us users who aren’t cutting chambers but assembling parts, as taught in a Dean Caputo AR Operator Diagnostic class which I took, is the Colt dimensioned Field or Field II gauge. You can get an equivalent one at Brownells part number 319-418-033. With the Colt gauge, if you rifle will not close on it, you have a serviceable rifle. If it closes on a Colt gauge you have an unsafe rifle. I will trust Colt’s dimensions (made from the TDP) more than Clymer’s interpretation.
The following attachment is a chart by Randall Rausch of AR15barrels.com which lists all of the headspace dimensions of different civilian and military gauges. You can see that the dimensions are different between military and civilian, and even different between military M16 and M249 SAW gauges. You can see that a civilian field gauge is 1.4700" and the Colt Field II gauge is 1.4736", you could have a rifle the closes on the civilian gauge but won’t on the Colt Field II gauge. Such a rifle would be perfectly safe to shoot.
m1match: Is the gauge you listed by the Brownell’s part number the same gauge you used in the class? I’ve been looking for one of these and if it is, I’ll be placing an order.
Also, what is the difference in the Field gauges?
I just use a MILSPEC headspace gage to avoid the drama.
Swatcop,
BillRicca.com had them for 30.00 on his website. If you don’t find it, just call him. I bought 3 of them and they are identical to the MIL ones I used.
I got one from Bill a few weeks ago when you mentioned he had them.
Have to say it was the best $30.00 I have ever spent.Heck of alot easier to use for sure.
By the way thanks for the tip IG.
I also got the gauge from Bill Ricca thanks to Iraqgunz’s suggestion. The nice thing about the gauges he sells - no need to remove extractor or ejector. The gauge is relieved for them.
Swatcop,
My understanding of what Dean Caputo was teaching us was that the Colt Field and Field II gauges would be sufficient for us users. The other gauges would be appropriate for an armorer who also wants to check for insufficient headspace. The military gauges, which are harder to find are the ones you want. He said we would be well served if we only had the Colt Field or Field II gauges, and the Brownells part number I listed is made to the same dimension as the Colt Field II gauge, he said that’s the one we want because if your rifle closes on that one, you’ve got excessive headspace and an unsafe rifle. Bill Ricca’s gauges are good to go and he’s one of the few open market sources for the true military gauges.
Excellent info m1match! Just what I needed.
Thanks,
Slugger
I sent my Colt gauge to Ned Christiansen and for $10, he relieved my gauge. Great deal as I already had the Colt from Brownells.