Is 27.0gr of Win 748 behind a 53gr bullet too hot out of a .223?  Winchester's load page lists the max at 26.0gr, but that's at 43.5k CUP.  Other loads with the same bullet go to 48-52k CUP, so would 27gr push it in the 50k+ CUP range?

Sierra says 52-53 grain bullet in AR-15---27.5 maximum 2.250" oal-FED case-RP 7 1/2
Sierra                                    bolt gun--26.5 maximum
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Other manuals list loads for 748 just slightly higher than 27 grains but YOU will have to work up loads from below 26-27 grains to be sure they are safe in your rifle. Don't know what the pressure would be but I do know 748 is temperature sensitive so I wouldn't push the limit. For 55 grain bullets I consider 26.4 to be as high a load as I will load using Win 748.

Say, your topic got my curiosity, so I looked up the maximum load in my
Hornady Handbook of Cartridge Reloading, Rifle Pistol Vol. II (Circa 1973).

Under 223 Remington it lists 53gr HP / Win 748 / Regular primer / MAX 27.2grs
Min 24.7 (3100 and 2700 fps)

I was just looking for something to go plinking with.  I didn’t want to waste my
50gr Moly V-Max’s on plinking.   So I reloaded some 53gr HP Sierra Match #1400
(had laying around for years), various Military head-stamp brass found at the range,
with the Win 748 I had on hand (another reload that I had done with Win 748 showed
promise as being accurate).

Here’s what I’m starting with, 53gr HP / Win 748, 25.4grs / CCI 400 SR / various Mil cases.
OAL: 2.240 / crimp: very light touch / case length: 1.750 (Max is 1.760).
Barrel on AR15 is 16” NATO 1-9 twist.

Book says 2800 fps (felt that was just right for what I’m doing).   I will chronograph
the reload and see how it performs at 100yds (hopefully this week).

Let me know how your Reloads work out.

My standard load for years was 28.5gr 748 and a Sierra 52gr. MKHP.  Runs 3450 from a 24" bolt gun.  I have used it all my .223's without problem.  Lyman listed 29 or 30 grains as max in my older manual.  This load was very accurate.

One of the pet loads for my Savage .223 is 27gr W748 with a Hornady 52gr BTHP.. Of course work up to it but for me it shoots great out to 300 yards.  

Went out to the shooting range, and test fired my .223 Rem 53gr HP Sierra Match
#1400 reload.

The reload:  53gr HP / Win 748, 25.4grs / CCI 400 SR / various Mil cases.
OAL: 2.240 / crimp: very light touch / case OAL: 1.750 (Max is 1.760).

Rifle:  High Standard AR15 Model HSTX6551 Flat Top Carbine.
Cartridge:  5.56mm NATO / .223 Remington Cartridge.
Barrel/Chamber:  16 inches long, marked “5.56 NATO 1 - 9”
Sights/Scope: Burris Short Mag 3-9 power, Ballistic Plex
Scope Rings: Warne 1” Maxima Quick Detachable (Weaver/Picatinny)
Trigger:  Timney Trigger, AR-15 Item #664-S, Small Pin .154, 4 Lbs. Pull.
(skeletonized trigger)

I shot with the hand guard resting on Sand bags, towel under hand grip (used to
pinch material to bring on target).

Results  100yds, group to the right of center 1-1/2”.
3 shots;  two 2 holes touching, one hole to the right opening group to 1-1/4”
Looks promising for an accurate reload.

Observation:  Primers starting to flatten, a little radius on the edge.
I didn’t get a chance to set up chronograph.

Carbine cycled and ejected well.  Functioned without any problems.
All reloads were clean burning.   Barrel looked clean when viewed through the
chamber or muzzle.   Bolt Carrier Assembly had the usual carbon build up,
nothing out of the ordinary.

Just an update, thanks for reading my Field Report.   Date: 28Jul08 1700, no wind,
overcast, 90F


Discussion before
Say, your topic got my curiosity, so I looked up the maximum load in my
Hornady Handbook of Cartridge Reloading, Rifle Pistol Vol. II (Circa 1973).
Under 223 Remington it lists 53gr HP / Win 748 / Regular primer / MAX 27.2grs
Min 24.7 (3100 and 2700 fps)
I was just looking for something to go plinking with.  I didn’t want to waste my
50gr V-Max’s on plinking.   So I reloaded some 53gr HP Sierra Match #1400
(had laying around for years), various Military head-stamp brass found at the range,
with the Win 748 I had on hand (another reload that I had done with Win 748 showed
promise as being accurate).
Here’s what I’m starting with, 53gr HP / Win 748, 25.4grs / CCI 400 SR / various Mil cases.
OAL: 2.240 / crimp: very light touch / case length: 1.750 (Max is 1.760).
Barrel on AR15 is 16” NATO 1-9 twist.
Book says 2800 fps (felt that was just right for what I’m doing).   I will chronograph
the reload and see how it performs at 100yds (hopefully this week).
Let me know how your Reloads work out.

In the Sierra book, they state the accuracy load for that bullet (shot from a Colt 20" NATO chamber 1-7 twist) @ 2900fps.  So I substitued 25.7 of 748.  I found this load very accurate in my 20" NATO chambered 1-9 twist Oly.  10 rounds in .75".  

Quoted: In the Sierra book, they state the accuracy load for that bullet (shot from a Colt 20" NATO chamber 1-7 twist) @ 2900fps.  So I substitued 25.7 of 748.  I found this load very accurate in my 20" NATO chambered 1-9 twist Oly.  10 rounds in .75".

And I use 26.0gr of W748 behind both Speer and Sierra 52gr HPBT match bullets with CCI400 primers, very good accuracy load.

Update to reload:  .223 Rem 53gr HP / Win 748, 25.4grs / CCI 400 SR / various
Mil cases.  OAL: 2.240 / crimp: very light touch / case OAL: 1.750 (Max is 1.760).
Varmint load .223 Rem
Bullet:  53gr HP Sierra Match #1400
Powder:  Win 748, 25.4grs.      Primer:   CCI 400 Small Rifle.
Cartridges:   various Mil cases.
OAL: 2.240 / crimp: very light touch / case OAL: 1.750 (Max is 1.760).
Velocity:  Chronographed at 2750fps (Avg.).
Results  40yds, group all fit 4”(no bench rest, kneeling and corner of pickup
tailgate).    Still looks promising for an accurate reload.

Observation:  Primers starting to flatten, a little radius on the edge.

Carbine cycled and ejected well.  Functioned without any problems.

Rifle:  High Standard AR15 Model HSTX6551 Flat Top Carbine.
Cartridge:  5.56mm NATO / .223 Remington Cartridge.
Barrel/Chamber:  16 inches long, marked “5.56 NATO 1 - 9”
Sights/Scope: Burris Short Mag 3-9 power, Ballistic Plex
Scope Rings: Warne 1” Maxima Quick Detachable (Weaver/Picatinny).
Trigger:  Timney Trigger, AR-15 Item #664-S, Small Pin .154, 4 Lbs. Pull.
(skeletonized trigger).
Black Bag Shell Catcher attached (Velcro/rod frame assembly fastened to hand guard).

Just an update, thanks for reading my Field Report.   Date: Thu 20Aug08 1720,
wind 1-5mph, clear, 90F.

Sounds tobe a little on the "Warm side"
I use 26grs of H335 behind a 55gr bullet. And 25grs behide a 62gr bullet. In my AR that is.