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Old October 17th, 2018, 07:32 PM #1
lazarus lazarus is offline
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Bolt impact on accuracy

So question, on AR-15s, how much impact does the bolt have on accuracy? My 20” HBAR has been shooting 75gr PPU just fine, about 1MOA 5 shot groups. Sometimes a little more or a little less. I took it to the range to sight in my ML again. At least that went well.

Anyway, the one box I brought with me (brand new batch from anything I’ve shot before. I’ve got about 10-12 boxes from at least 3-4 batches) the best 5 shot group I managed was 1.5MOA. I was mostly shooting during calm winds, though it was gusting a lot. I am willing to blame a little drift on that, but not 1.5-2MOA groups.

The barrel was pretty heated up by then, but heat hasn’t seemed to seriously impact my group sizes before.

A few months back I got a Brownell’s nitrided BCG for a song on sale. It head spaces, but I have no way to check exact head space other than “it passes”. I swapped the new BCG in for the PSA parkarized BCG which I dropped in my 16” upper, which was without a BCG. I haven’t really shot my 20” much since swapping BCGs.

Is this more likely just a bad box/batch of ammo (the M193 and freedom reloads I was shooting were turning in typical results of 2MOA for the M193 and closer to 3MOA for the freedom reloads)? Or could the BCG be the perpetrator?

I ordered a few boxes of Hornady to test some of that out as I’ve never run .223/5.56 Hornady ammo. Ordered a box of 75gr steel case match, 73gr ELD custom, 68gr BTHP frontier and 75gr BTHP Black. I have 69 and 75gr PPU on hand as well as 69gr and 77gr IMI. At least the testing I’ve doje before my 1:8 twist barrel seems to oiirnthe mid weight rounds the best, with 62-69gr usually shooting about .1-.2” smaller groups.

I was thinking of trying some accuracy tests of both ammo and BCGs side by side.

Thoughts?

PS barrel has maybe 1000 rounds down the tube, so I doubt it has suddenly started to show the signs of excessive wear.

PPS I checked scope base and ring screws to ensure they aren’t loose.
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Old October 17th, 2018, 08:53 PM #2
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If you are looking for that sub-MOA accuracy, you may want to consider a barrel with a matched and headspaced bolt, or doing the reloading thing and finding the load that your barrel really likes.

If you want to check headspace, I have a set of go-no go gauges we can use to check it out. I also have to get that scope to you too.
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Old October 17th, 2018, 09:58 PM #3
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Quote:
Originally Posted by DaemonAssassin View Post
If you are looking for that sub-MOA accuracy, you may want to consider a barrel with a matched and headspaced bolt, or doing the reloading thing and finding the load that your barrel really likes.

If you want to check headspace, I have a set of go-no go gauges we can use to check it out. I also have to get that scope to you too.
Lol, true. I wouldnít mind as accurate as possible. I am more concerned that accuracy suddenly seems significantly lower than it has proved to be in the past. Though maybe that is the issue with PPU. They might make a decent product, but if QC or tooling budgets arenít there, batch to batch (or within batch) variation could be wildly off. Though Iíve generally had good results with them.

I guess really I should have just figured on checking it out the next time I go to the range before I just blindly ordered several boxes of ammo.

My November looks a bit freer than this month, though it really might slip to December before I have a bunch of free time. Maybe I can twist your arm in to helping me lap my upper also (or a couple of uppers) while we are hanging out.

I do finally have reloading gear. Just lacking dies and some spare time to set it up and work up loads. Soon I hope. Iíve got close to 2 weeks off around Christmas.
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Old October 18th, 2018, 01:08 AM #4
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Lol, true. I wouldnít mind as accurate as possible. I am more concerned that accuracy suddenly seems significantly lower than it has proved to be in the past. Though maybe that is the issue with PPU. They might make a decent product, but if QC or tooling budgets arenít there, batch to batch (or within batch) variation could be wildly off. Though Iíve generally had good results with them.

I guess really I should have just figured on checking it out the next time I go to the range before I just blindly ordered several boxes of ammo.

My November looks a bit freer than this month, though it really might slip to December before I have a bunch of free time. Maybe I can twist your arm in to helping me lap my upper also (or a couple of uppers) while we are hanging out.

I do finally have reloading gear. Just lacking dies and some spare time to set it up and work up loads. Soon I hope. Iíve got close to 2 weeks off around Christmas.
PPU generally makes good stuff. It might be variations in temp and also wind that might be affecting you too.

Bear in mind that their powder drops may be slightly different that the lots you used before. Tooling issues would show with the brass not chambering or other factors.

No need to twist my arm, all you have to do is say something and we'll get those bad boys lapped up.

Did you drink the blue Kool-Aid for a press?
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Old October 19th, 2018, 11:53 PM #5
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Quote:
Originally Posted by DaemonAssassin View Post
PPU generally makes good stuff. It might be variations in temp and also wind that might be affecting you too.

Bear in mind that their powder drops may be slightly different that the lots you used before. Tooling issues would show with the brass not chambering or other factors.

No need to twist my arm, all you have to do is say something and we'll get those bad boys lapped up.

Did you drink the blue Kool-Aid for a press?
Lyman press that my wifeís uncle had sitting around he got from a friend years ago and never used. I just havenít had the time to get it out and get dies. I finally have a .38 revolver, so Iíll get those dies to try out first with it. I probably wonít have time till I am off for Christmas to assemble everything and try my hand at some reloading.
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Old October 20th, 2018, 12:03 AM #6
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Lyman press that my wifeís uncle had sitting around he got from a friend years ago and never used. I just havenít had the time to get it out and get dies. I finally have a .38 revolver, so Iíll get those dies to try out first with it. I probably wonít have time till I am off for Christmas to assemble everything and try my hand at some reloading.
Single stage, turret, or progressive?

PM me when you know what your schedule looks like as it gets closer and we'll make a plan to get the uppers done and head down to the Dungeon of Despair (reloading room/Man Cave) if you want some pointers.

I'll be fixing my 550 powder measure this weekend, so that I can run off about 900 rounds for a friend.

Hogdgon Reloading on the web will be your best friend for load data, beyond the books that are published by Sierra, Lyman, Hornady, Speer, Nosler, Barnes, and the others I am forgetting. If you are using projectiles from a company like Lehigh Defense, they should have load data available on their website for you to print out. I know that Lehigh publishes load data fro their projectiles and has it available for free on their website.

Just an example for Lehigh Defense and their own published load data for theri projectiles.
https://www.lehighdefense.com/pages/...d-data-library
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Old October 20th, 2018, 04:28 AM #7
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If you are getting 1-1/2" groups at 100 yards with your PPU, you're doing fine. Making small headspace adjustmentsnad/or looking for a bolt with squared lugs and bolt face is not going to affect this sort of precision.

If good quality match ammo (Federal, Hornady) is shooting to 3/4", then a good quality bolt (square and not necessarily "matched") might shave your groups down to 1/2".

if you're not using some sort of magnified optic with a fine enough reticle for precision holds, you'll never see it and your money is better spent on ammo.

The term "matching the bolt" is so overused and not actually descriptive. Poorly made bolts will suffer uneven lug contact, out of square lugs and/or bolt face. Good quality bolts are made to a higher standard with lugs and bolt face perpendicular to the bore. In turn, the barrel extension locking lug recesses also need to be square and perpendicular to the bore. THIS is what we actually need for precision, not some magical "match" of crappy bolt to crappy barrel. Once headspace is correct, any "matching" of bolt to barrel is done and it's the quality/precision that really matters. You can vary headspace from minimum to maximum and will not see any difference in precision until we get to ignition failures.
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Old October 20th, 2018, 02:20 PM #8
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My biggest concern is that my group sizes seem to have opened up about half an inch “suddenly” and the only thing I can really identify is a different bolt. It was windy that day, but I was shooting at slack wind.

I should have some selections of Hornady match ammo on hand shortly to go with my PPU and IMI. At least when I did have some, PPU 75gr was shooting to about the same group size as GMM. About .9MOA 5 shot groups for an entire box for PPU and about .8MOA for GMM. I’ve only shot one box of GMM in this rifle, but I’ve run 5 or 6 boxes of PPU 75gr and they consistently done right about 1MOA or a slight bit under or a slight bit over.

I am running a Bushnell 3-9x40 Engage rifle scope at 9x. It has a very fine reticle (not a typical hunting reticle).
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Old October 20th, 2018, 02:24 PM #9
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To get your answer: shoot groups with BOTH bolts and compare.
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Old October 20th, 2018, 03:06 PM #10
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Take both bolts to shoot and compare
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