6.5 Grendel Forum
Brownells 6.5 Grendel BCG...???? - Printable Version

+- 6.5 Grendel Forum (https://65grendel.com)
+-- Forum: 6.5 GRENDEL DISCUSSION FORUMS (https://65grendel.com/forumdisplay.php?fid=3)
+--- Forum: 6.5 Grendel Build-It-Yourself & Custom Builds (https://65grendel.com/forumdisplay.php?fid=9)
+--- Thread: Brownells 6.5 Grendel BCG...???? (/showthread.php?tid=20634)

Pages: 1 2

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-16-2020

Bought a Brownells 6.5 Grendel Type 11 BCG for my WC barreled build. Read a couple of threads on this BCG with too short a bolt. <2.820. Measured this bolt and sure enough the bolt is 2.793 long ( measured 3 times) with a firing pin length of 3.265.

My Monster bolt is 2.820 of course with a firing pin length of 3.282 using a Bravo Co. Ion Bonded BCG with the 5.56 bolt replaced with the MONSTER Bolt matched with a MONSTER GB 16 in. barrel and everything plays well together.

What are the ramifications of using the Brownells Grendel BCG as is with my WC barrel?? Should I return the Brownells BCG and either purchase a Wilson Combat Grendel BCG ($225,00 and out of stock). Or get another MONSTER Bolt and get a different carrier group? I have not heard good things about Tool Craft BCGs but have no experience with them.

I have not fired this weapon yet as I just finished (I thought) building it.

Any info and advise/recommendations are appreciated. I have gotten so much great info and advise from other members and obviously have much to learn.

Thanks to all

Brownells 6.5 Grendel BCG...???? - VASCAR2 - 02-16-2020

I contacted Brownell’s technical and discussed the 2.800 inch bolt and firing pin lengths. The technician I spoke was unaware of the 6.5 Grendel bolt overall length from the tail to the face of the lugs being 2.8100 plus or minus .001. I explained how AR-15 5.56/223 bolts measured 2.800 and used firing pins of approximately 3.279-3.280 or shorter within -.009 inches tolerance. The specification for firing pin protrusion is .028 to .036 inches or .008 inch tolerance in variation of bolt or firing pin length. Alexander Arms added .01 inch length to the 6.5 Grendel bolt to account for the .136 bolt face depth compared to the 5.56/223 bolt face depth of .125 inch. This permitted the use of standard milspec firing pins in the 6.5 Grendel. Brownell’s said they do not sell shorter firing pins for their 6.5 Grendel bolt/BCG.

I suspect the manufacturer of the Brownell’s 6.5 Grendel BCG uses a firing pin protrusion gauge to test their FP protrusion. If you don’t have a firing pin protrusion gauge you can kind of do a work around. Add 2.800 bolt to 3.269 inch length firing pin equals 6.068. Add your bolt 2.793 plus FP length 3.265 equals 6.058. There is .008 tolerance in firing pin protrusion and I suspect your firing pin has excessive protrusion by .002.

Without having a firing pin protrusion gauge you really won’t be 100% sure. Whether .002 will create problem I can’t say. I wish Brownell’s used 2.810 length bolts but they don’t. You could remove .002 inches from the firing pin tip or you could call Brownell’s who will try to resolve this issue. I’d be surprised if you have a firing pin shorter than 3.265 inches. I compared my eight AR-15 firing pins and my shortest FP was 3.274 and my longest was 3.280 inches. From my research there is more emphasis on firing pin protrusion and being within tolerance for bolt length and bolt face depth. My three 5.56/223 bolts overall length were 2.798, 2.7965 and 2.799. All my AR-15 BCG and FP are in spec.

My major concern is someone mixing their firing pins between different AR-15 firearms. A person could easily have an in-spec BCG but by switching FP have an out of spec BCG. The problem is compounded by the 2.800 6.5 Grendel length bolt.


https://www.brownells.com/gunsmith-tools-supplies/measuring-tools/firing-pin-protrusion-gauges/firing-pin-protrusion-gauge-prod26477.aspx


You could buy a Monster bolt and firing pin to use in Brownell’s carrier and keep the Brownell’s bolt for a spare. You could buy a stainless steel firing pin and shorten it to be in spec with the Brownell’s bolt. You could also shorten your brownell’s firing pin but it might be chrome plated thereby going through the plating. I wouldn’t buy a Wilson Combat (WC) BCG at $225 but I’m to cheap.

The latest Toolcraft 6.5 Grendel BCG have been in-spec. You could return your out of spec Brownell’s BCG and buy a Toolcraft or other BCG. I’ve bought PSA Premium 5.56/223 BCG saved the 5.56 bolt and used Monster bolt in a couple of my 6.5 Grendel builds. I try to keep at least one or two spare AR-15 bolts, whether 5.56 or 6.5 Grendel.

Really depends on what you want to do. If it were me I would call Brownell’s and explain their liable to get sued if they ever get a slam fire with one of their out of spec BCG and someone gets hurt. I’d also explain to them AGAIN why they need to wise up and use 2.810 length 6.5 Grendel bolt.

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-16-2020

Thank you....I too am too cheap for the WC BCG......I am going to remeasure my bolts and firing pins tomorrow when my eyes aren't tired and reverify everything...then I am going to call Brownells Monday morning (I have had a vendor account with them for almost 20 years) and get it straightened out, get the Monster bolt and a stainless FP and make everything in spec. plus measure all my other 5.56 bolts and FP's and make some notes in my journal.

I don't ever tear down more than one BCG at a time...won't even have 2 on the bench at the same time so I don't have an old fart brain freeze and get any critical components bass akwards…..too easy to make simple dumb mistakes.

I will post an update when I am straightened out

Thanks again

I am sure I noted the wrong length down for my MONSTER bolt

Brownells 6.5 Grendel BCG...???? - VASCAR2 - 02-16-2020

One thing I failed to mention is how accurate are our calipers. I suspect my calipers are good to within .002 maybe a little less accurate (or how repeatable). You throw in all the variables and you see how tolerances can stack and create issues. It just bugs me a manufacturer would continue to manufacture a 2.800 inch long 6.5 Grendel bolt.

Odin Works was the first to experience pierced primers which was traced to excessive FP penetration and 2.800 length bolts. The first Toolcraft 6.5 Grendel bolts were 2.800 but they quickly changed to 2.8100 length. There were one or two other companies that had an initial run of 2.800 length 6.5 Grendel bolts but switched to 2.810 length bolts.

Like I mentioned in my previous post. Your Brownell’s BCG is very close and the only way I’d know for sure is to check the protrusion with a gauge. When I figured your BCG might be .002 long I was using the figure of 3.279 for firing pin length. The specification for FP length is vague but lets say spec is 3.279 +or- .001. A FP length of 3.280 like one of mine might pass. To many variables in the thousandths of an inch to know for sure.

In all my research most sources indicate AR-15 firing pin length is 3.279. One source listed FP length of 3.279 with a tolerance of -.009. Other sources listed different FP lengths + or - .001. Most sources refer to bolt length, bolt face depth and FP protrusion more than FP length. There doesn’t appear to be an accepted manufacturing tolerance for bolt FP as long as protrusion is in spec. With mass produced products it kind of makes sense to use the FP protrusion to account for variations in the manufacturing process.

Brownells 6.5 Grendel BCG...???? - drykilned - 02-16-2020

I bought and installed a Brownells 6.5 Grendel Type II BCG last year and installed in my BCA Barreled Anderson upper. Had multiple failure to lock into battery causing jams requiring one to mortar the BCG in order to correct the jam. Did that only with mag in place and chambering a round from the mag. Worked fine single loading through chamber by hand. I returned the BCG to Brownells and bought another BCA bcg for almost half the cost of the Brownells. Worked just fine. Have built two 18" SS BCA barreled uppers, both now with Anderson receivers and lowers. one with velocity 3# trigger and one with CMMG premium lower parts kit and trigger. Long story short, BCA bcg works, Brownells did not.

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-17-2020

I was on the phone with Brownells tech support for about 20 minutes and they assured me this bolt would be fine even though the bolt length (tail is short) the FP has been shortened to accommodate the bolt length. If I return it the reimbursement would be a gift card for Brownells
Option 0: Pay $225.00 plus shipping to Wilson Combat for their Grendel type 2 BCG to match my WC barrel
Option 1: Pay more for a Faxon BCG
Option 2: Pay more for an Odin works BCG
Option 3: Use the Brownells BCG and hope it doesn't malfunction
Option 4: Get a Monster bolt and FP from SixFiveArms and use the Brownells carrier
Option 5: Take the gift card (and use for something else above) and spend additional cash for an Alexander Arms BCG or another from another source
Tool Craft etc>

what would the HOARD do???

Brownells 6.5 Grendel BCG...???? - BCHunter - 02-17-2020

Just run it,...brownell sources these products from various manufacturers. Most likely a Toolcraft.
If it doesn't work for some reason, you can return it and pursue other options.

Of your options
#2 Odins works are short same as your brownells
#4 option is just the bolt you have to buy a standard firing pin, from another source,...usually people buy a 5.56 bcg. Switch out the bolt with the monster bolt and reuse the firing pin.

Check other sites for prices on bcg. Joe bob outfitters, armor alley, palmetto state arms, should have bcg around 100.00ish

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-17-2020

I took option 4 on my last build Group Buy 16" Monster barrel and bolt and used a BCM 5.56 BCG and just swapped out the bolt and it runs great

Thanks

Brownells 6.5 Grendel BCG...???? - VASCAR2 - 02-17-2020

As long as you know Brownell’s uses a shorter bolt and requires a shorter firing pin I think you can safely test the BCG. If the firing pin protrusion is on the edge of being in spec you might not experience any issue but I wouldn’t use standard small rifle primers with thinner cups. I use CCI 450 or CCI 41 primers (thicker primer cups) in my AR-15’s just to be on the safe side.

I have three Monster bolts IIRC and they are very good bolts. I’d have no hesitation using the Brownell’s bolt carrier and a Monster bolt with milspec firing pin.

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-17-2020

Good call Vascar2...….I have only 1 case of cci 400 (1000) I will sell and switch to 450s I already gota hold of John and am getting another MONSTER bolt and mil spec FP...…..will package up this Brownells bolt and firing pin and mark them well......back bottom of one of the safes

thanks

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-17-2020

I only have $94.00 in the Brownells BCG...I have a vendors account with them and caught it on sale before xmas…..so with the MONSTER bolt and a FP say $70.00 for both and shipping really a little less than I have in my Bravo Co BCG and other MONSTER bolt.

Really a great learning experience here $165.00 plus all the gained knowledge.....Hope this helps someone else that comes to the forum!!

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-17-2020

I have a good assortment of carriers from AP, BCM and a lower end one from Ruger in my other rifles and carbines.....the Sig is out as it is a piston drive.

Brownells 6.5 Grendel BCG...???? - Lastrites - 02-17-2020

My fairly recent ToolCraft works well, correct spec's and a bargain at $79.

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-17-2020

that's good.....was it 6.5 G when you got it or did you add a Monster bolt in it??

Brownells 6.5 Grendel BCG...???? - FLshooter - 02-18-2020

I have purchased several PSA Toolcraft bolts and complete BCG.I find them to be great quality and the price is good.$72 for a bolt,hundred dollars for the complete BCG.

Brownells 6.5 Grendel BCG...???? - A5BLASTER - 02-18-2020

All this mess right here is why I build my own grendel bcg's and only use bolts from AA,PF and sixfivearms.

Never a problem with them and the fireing pins I get off joebobs. Everything just works like it should.

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-18-2020

Yes a mess.....my fault for not exploring this site further prior to ordering that BCG..learned a great lesson and now have more info in my mental toolbox. You use Lt. wt. bolt carriers don't you? I was reading your posts concerning those but couldn't find exactly what you were writing about. I have a 12 inch or so build in the works and want to follow your lead on this one. Monster bolt and FP from joebobs and build up the carriers you prefer

I haven't had any issues with my Superlative adj. gas block and hope I don't with the SLR adj. on this build.....I have a simple AP lo profile GB in my build box to use on the PF short barrel I have planned for this spring. I only used the SLR because it was the recommended GB by Wilson for this barrel.

Brownells 6.5 Grendel BCG...???? - A5BLASTER - 02-19-2020

Chance-dg Wrote:Yes a mess.....my fault for not exploring this site further prior to ordering that BCG..learned a great lesson and now have more info in my mental toolbox. You use Lt. wt. bolt carriers don't you? I was reading your posts concerning those but couldn't find exactly what you were writing about. I have a 12 inch or so build in the works and want to follow your lead on this one. Monster bolt and FP from joebobs and build up the carriers you prefer

I haven't had any issues with my Superlative adj. gas block and hope I don't with the SLR adj. on this build.....I have a simple AP lo profile GB in my build box to use on the PF short barrel I have planned for this spring. I only used the SLR because it was the recommended GB by Wilson for this barrel.

I have a spare lowmass stripped bcg I will trade you for your full weight stripped bcg.

I need a full weight bcg for some wildcat cartridge testing.

Throw in your low profile non adjustable gas block and I will send you a slr adjustable gas block to replace it as well.

Brownells 6.5 Grendel BCG...???? - Chance-dg - 02-19-2020

Alright....I will do both the stripped auto Bolt Carrier (never fired) and the new in package AP Lo profile GB for your Stripped Lo mass carrier and the SLR gas block

I am going to use the lo mass and a Monster Bolt with this WC barrel set up I have and the SLR GB on a 12.5 PF mid length gas barrel which I still need to get bought thru Mark.

Will you walk me thru the Lo mass Bolt carrier when I build it and start breaking it in please

Brownells 6.5 Grendel BCG...???? - A5BLASTER - 02-19-2020

Chance-dg Wrote:Alright....I will do both the stripped auto Bolt Carrier (never fired) and the new in package AP Lo profile GB for your Stripped Lo mass carrier and the SLR gas block

I am going to use the lo mass and a Monster Bolt with this WC barrel set up I have and the SLR GB on a 12.5 PF mid length gas barrel which I still need to get bought thru Mark.

Will you walk me thru the Lo mass Bolt carrier when I build it and start breaking it in please

Nothing to it just put in the bolt,cam pin, fireing pin and fireing pin retaining pin just like you would in any bcg.

All the parts fit the same in the same places. The bcg is just cut so it is lighter in weight.

Just so we are clear I'm trading you a stripped bcg. Meaning it's not going to have a bolt, cam pin, fireing pin or fireing pin retaining pin when you get it.