George, will you forgive me? GAP 10 breakin

[308sako]

I dropped one, Mea Culpa Mea Culpa

Left target was FL sized Winchester cases averaging 158 grains in weight unloaded, right side was New Winchester brass averaging 162 grains in weight unloaded.

Barrel clean and cold at beginning, sequence of firing was upper most left 1st, the upper most right, target top right second in, bottom right, bottom right second in, lft paper top right, left paper bottom right, bottom left left target.

All loads functioned 100% today including lock back after magazine was empty. Lubricant remains SLIP 2000 EWL only.

It would appear there is hope as yet. I still think that the barrel would prefer IMR 4895 for it's most precise attempts, but velocity remains behind with it.

One question remains as the Switchblock refuses to move, why was a Noveske wrench not supplied?

 

[Pilky01]

Looks great! Nice shooting. What dies are you using to size? Trying to get things together to start reloading for mine.


Sent from my iPhone using Tapatalk

 

[308sako]

I am doing this sequence to make the brass fit this tight chamber; RCBS - FL 1975 vintage '06 die to the cam over, this gives me about .0015" greater squish on the head portion of the case, sort of small base sizing. Unfortunately it also gets the body of the case a little more than I would like, but the feeding benefits out weight any other issue at this point. Then I use a Redding bushing FL with the .339 bushing to bump the shoulder back about .003" at which point I then change the bushing out for a .333 bushing which allows me a finished neck diameter of .3355" or so with my Winchester cases.

Measure everything you can, and especially the differences between new brass and that same brass fired in the rifle. It will tell you what you need to address.

Good luck and please post your findings.

 

[steppenwolf]

All loads functioned 100% today including lock back after magazine was empty. Lubricant remains SLIP 2000 EWL only.

Nice groups. Glad to hear it's running w/o a hitch now.

I've been following this and your other thread very closely, as I have a GAP-10 on order and was worried about having the reliability issue you described and then having to incur the expense and hassle of returning it to George and Co for tuning.

Until I have more time to reload (as in retirement), I'll be shooting mostly factory match ammo supplemented by what handloading I'm able to do.

By way of contrast, I've now got just under 200-rds of various .308 factory thru my recently received LMT LM8 ("slickside") MRP. It came w/ the 16" C/L barrel but I had also ordered the 18" SS 1/11.25 tube, received it, and that's what I've been shooting with. It's scoped w/ a Leupy 1x-6x Mk6 (w/the illumin TMR reticle) and I installed a Geissele SSA-E.

Started w/ breaking in the 18" barrel and, this being my first AR in 7.62/.308, getting settled in and used to how it shoots. I've got a lot of trigger time w/ M1As but this animal is different. Anyway, initial 5-shot groups w/ 168 FGMM were right at or just over 1 MOA @ 100yds, proned out and using a bipod and rear bag. Last outing, after cleaning and re-torquing the SS barrel (which included removing and cleaning both barrel screws), groups with that ammo were .90-to-.75MOA. The best group was with Hornady 155gn AMAX which printed a .60MOA @ 100yds, and I'm still getting used to this rifle. And, FWIW, since receiving the LM8 I have NOT had one FTF, FTE or other malf w/ any ammo, including some several boxes of PMC 308 147gn FMJ that I shot on one of the first outings.

For the money you invest in these top tier .308 ARs, I don't think you should have to settle for getting either "precision" (or "match"-type) accuracy or 100% reliability but not both, certainly with quality factory loads, as a poster in the other thread suggested.

And accuracy aside, I don't think reloading for them with the expectation that they'll function properly should, within reason, be so difficult that you'll have to go through a hundred handloads just to find one that will work.

Still looking forward to my GAP-10; this is just my 2-cents on the issue. Thanks for your posts.

 

[lte82]

For the money you invest in these top tier .308 ARs, I don't think you should have to settle for getting either "precision" (or "match"-type) accuracy or 100% reliability but not both, certainly with quality factory loads, as a poster in the other thread suggested.

While I agree, I have to disagree, kind of. Check out this thread.

http://www.snipershide.com/shooting...les/93301-gap-precision-chamber-question.html

If in fact the GAP-10's are min-spec SAAMI 308 dimensions, with an even tighter neck, that would explain them being "picky". Min-spec 223 chambers suffer from the same problem. IE, they like to be fed min-spec SAAMI dimensioned brass (ie, small base sized).

I'll also go as far to say that if you take some several times fired brass that has been fired in a loose chamber, that has essentially been work hardened and semi-permanently stretched to fit the loose chamber (and can't be un-sprung *completely* back to saami min-spec dimensions), you *may still* has some issues running it in a min-spec chamber after small base sizing.

If you are using a min-spec / tight chamber, start with new brass or at least brass that has been fired in a tight chamber, and FL size it with an SB die.

 

[Shoottothrill]

I would find out what dies Copper Creek is using to reload the Gas Gun Load they sell and I'm sure it would just be a one step deal. Seems like your working too hard to reload for your Gap-10.

 

[308sako]

I would find out what dies Copper Creek is using to reload the Gas Gun Load they sell and I'm sure it would just be a one step deal. Seems like your working too hard to reload for your Gap-10.

It's not hard work, it is a learning process about what is required to make this work. Sorry if I make it sound that way.

The dimensions are so small that like SAMMI tolerances, one die might differ significantly from another. My dies apparently are a bit on the loose side, where I needed a die on the tight side.

 

[tipper]

If you send some fire formed brass to Reloading Tools | Gunsmithing Tools | Reloading Press | Reloading Dies | 3-in-1 Cutter, & tell them what you would like to size it to, they will match up a die to do the job.

 

[308sako]

If you send some fire formed brass to Reloading Tools | Gunsmithing Tools | Reloading Press | Reloading Dies | 3-in-1 Cutter, & tell them what you would like to size it to, they will match up a die to do the job.

I appreciate the link, but having 2 sets of .308 dies already it just seemed wrong to look for a third.

 

[bp7178]

Why not just set your FL die to bump size your brass that has been once fired through that rifle?

 

[The Gump]

You could order a set of custom dies. They are fucking expensive. I ordered a set for my 6 Creedmoor from Bob Green. They ran me $400. I sent him the reamer drawing for my chamber and he sent me a FL sizing die that is exactly .002 smaller than my chamber reamer so everything should chamber perfect up without any slop. The set I ordered uses Redding/ Wilson bushings and the seater is cut to my chamber and has a Mitutoyo micrometer seater. There is zero guess work.

 

[Cornholeo]

RCBS small base dies, IMR4064 behind 175gr SMKs in Lapua brass is what my GAP10 loves. IMR4064 seems to be a little easier to get as well. I have plenty of the 175s but want to try the AMAXs and some 155 Senars at some point. The rifle will out shoot me and lives up to its name GnatsAssPrecision-10.
The only box ammo ever fed through it was FGMM and some SW ammo. It is a tight chamber that loves hand loads and the small base dies have been spot on for me.

 

[308sako]

Why not just set your FL die to bump size your brass that has been once fired through that rifle?

That was the original approach, however the Redding bushing FL die would not size the head portion of the case sufficiently to allow for consistent feeding/extraction at the point where the headspace was correctly bumped.

 

[jaycoux]

You seem to be a guy that is well-versed in reloading. What shell holders are you using?

 

[tipper]

I just don't see how you can bump the shoulder in a FL die, if you run it in only part way it may size the body & make the case grow But it will not touch the shoulder.

 

[308sako]

I just don't see how you can bump the shoulder in a FL die, if you run it in only part way it may size the body & make the case grow But it will not touch the shoulder.

What you are saying is partially true. You do not always need to cam over or touch the shell holder in order to bump the shoulder back on a fired case.

If I did what you are suggesting with my Redding die and RCBS shellholder I would effectively create an additional .008" of headspace which I have absolutely no use for!

My first step is to run the fired cases into the Redding bushing FL die with a .338" bushing. Reason is Redding claims that to work the neck more than .006" in one pass is counter productive to extreme accuracy and or bass life. I size the case and then rotate the case 180 degrees, and size it again. Next stop is the .358 Winchester FL die now, used as though I was going to partial size the brass. Yes it only works on the body and yes it can lengthen the case. I do this to achieve something of the effects of using a small base die. I don't own a small base sizer, nor do I wish to, now I don't need to either. Step three for me is to then go back to the Redding FL bushing die with a .334 bushing for the Winchester brass I have. Yes resize the necks all the way now. I now have concentric proper for my chamber sized cases, which need to be trimmed and chamfered, and the primer pockets cleaned.

jaycoux; I use RCBS shellholders, and either an RCBS Rockchucker or a Big Max press. Been reloading and shooting for 51 years, and I still have all my fingers and both eyes.

Appreciate the comments and questions.

 

[308sako]

Dbl tap

 

[Notso]

My first step is to run the fired cases into the Redding bushing FL die with a .338" bushing. Reason is Redding claims that to work the neck more than .006" in one pass is counter productive to extreme accuracy and or bass life. I size the case and then rotate the case 180 degrees, and size it again. Next stop is the .358 Winchester FL die now, used as though I was going to partial size the brass. Yes it only works on the body and yes it can lengthen the case. I do this to achieve something of the effects of using a small base die. I don't own a small base sizer, nor do I wish to, now I don't need to either. Step three for me is to then go back to the Redding FL bushing die with a .334 bushing for the Winchester brass I have. Yes resize the necks all the way now. I now have concentric proper for my chamber sized cases, which need to be trimmed and chamfered, and the primer pockets cleaned.

Hey Sako, can you elaborate some more what the middle sizing step for? I'm not sure I understand what that step does? How does partial sizing act like a SB die? I thought the SB die mainly works on the case head. It just appears to this novice that its just an step that is working the brass for an unknown reason.

However, I defer to your 51 years of reloading experience and all 10 fingers

 

[308sako]

Hey Sako, can you elaborate some more what the middle sizing step for? I'm not sure I understand what that step does? How does partial sizing act like a SB die? I thought the SB die mainly works on the case head. It just appears to this novice that its just an step that is working the brass for an unknown reason.

However, I defer to your 51 years of reloading experience and all 10 fingers

It's really fairly simple, the .358 Winchester die I am using has a slightly different taper to the body causing a tighter sizing of the head portion while not excessively changing the mid body and shoulder dimensions. I also tried a .30-06 Ackley FL die that I have initially, looking to only size the head portion, but that die came up about .001" short of what is needed.

These are extremely small differences, just that they allow what is needed in this case without over working the brass. The head portion gains approximately .002" of correction, or .001" per side of the case.

 

[Notso]

Got it, thanks. Makes sense now.